1erl_nif(3) C Library Functions erl_nif(3)
2
6 erl_nif - API functions for an Erlang NIF library.
7
9 A NIF library contains native implementation of some functions of an
10 Erlang module. The native implemented functions (NIFs) are called like
11 any other functions without any difference to the caller. Each NIF must
12 have an implementation in Erlang that is invoked if the function is
13 called before the NIF library is successfully loaded. A typical such
14 stub implementation is to throw an exception. But it can also be used
15 as a fallback implementation if the NIF library is not implemented for
16 some architecture.
17 Warning:
19 Use this functionality with extreme care.
21 A native function is executed as a direct extension of the native code
23 of the VM. Execution is not made in a safe environment. The VM cannot
24 provide the same services as provided when executing Erlang code, such
25 as pre-emptive scheduling or memory protection. If the native function
26 does not behave well, the whole VM will misbehave.
27 * A native function that crash will crash the whole VM.
29 * An erroneously implemented native function can cause a VM internal
31 state inconsistency, which can cause a crash of the VM, or miscel‐
32 laneous misbehaviors of the VM at any point after the call to the
33 native function.
34 * A native function doing lengthy work before returning degrades
36 responsiveness of the VM, and can cause miscellaneous strange
37 behaviors. Such strange behaviors include, but are not limited to,
38 extreme memory usage, and bad load balancing between schedulers.
39 Strange behaviors that can occur because of lengthy work can also
40 vary between Erlang/OTP releases.
41 A minimal example of a NIF library can look as follows:
43 /* niftest.c */
45 #include <erl_nif.h>
46 static ERL_NIF_TERM hello(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
48 {
49 return enif_make_string(env, "Hello world!", ERL_NIF_LATIN1);
50 }
51 static ErlNifFunc nif_funcs[] =
53 {
54 {"hello", 0, hello}
55 };
56 ERL_NIF_INIT(niftest,nif_funcs,NULL,NULL,NULL,NULL)
58 The Erlang module can look as follows:
60 -module(niftest).
62 -export([init/0, hello/0]).
64 init() ->
66 erlang:load_nif("./niftest", 0).
67 hello() ->
69 "NIF library not loaded".
70 Compile and test can look as follows (on Linux):
72 $> gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
74 $> erl
75 1> c(niftest).
77 {ok,niftest}
78 2> niftest:hello().
79 "NIF library not loaded"
80 3> niftest:init().
81 ok
82 4> niftest:hello().
83 "Hello world!"
84 A better solution for a real module is to take advantage of the new
86 directive on_load (see section Running a Function When a Module is
87 Loaded in the Erlang Reference Manual) to load the NIF library automat‐
88 ically when the module is loaded.
89 Note:
91 A NIF does not have to be exported, it can be local to the module. How‐
92 ever, unused local stub functions will be optimized away by the com‐
93 piler, causing loading of the NIF library to fail.
94 Once loaded, a NIF library is persistent. It will not be unloaded until
97 the module code version that it belongs to is purged.
98
100 All interaction between NIF code and the Erlang runtime system is per‐
101 formed by calling NIF API functions. Functions exist for the following
102 functionality:
103 Read and write Erlang terms:
105 Any Erlang terms can be passed to a NIF as function arguments and
106 be returned as function return values. The terms are of C-type
107 ERL_NIF_TERM and can only be read or written using API functions.
108 Most functions to read the content of a term are prefixed enif_get_
109 and usually return true (or false) if the term is of the expected
110 type (or not). The functions to write terms are all prefixed
111 enif_make_ and usually return the created ERL_NIF_TERM. There are
112 also some functions to query terms, like enif_is_atom,
113 enif_is_identical, and enif_compare.
114 All terms of type ERL_NIF_TERM belong to an environment of type
116 ErlNifEnv. The lifetime of a term is controlled by the lifetime of
117 its environment object. All API functions that read or write terms
118 has the environment that the term belongs to as the first function
119 argument.
120 Binaries:
122 Terms of type binary are accessed with the help of struct type Erl‐
123 NifBinary, which contains a pointer (data) to the raw binary data
124 and the length (size) of the data in bytes. Both data and size are
125 read-only and are only to be written using calls to API functions.
126 Instances of ErlNifBinary are, however, always allocated by the
127 user (usually as local variables).
128 The raw data pointed to by data is only mutable after a call to
130 enif_alloc_binary or enif_realloc_binary. All other functions that
131 operate on a binary leave the data as read-only. A mutable binary
132 must in the end either be freed with enif_release_binary or made
133 read-only by transferring it to an Erlang term with
134 enif_make_binary. However, it does not have to occur in the same
135 NIF call. Read-only binaries do not have to be released.
136 enif_make_new_binary can be used as a shortcut to allocate and
138 return a binary in the same NIF call.
139 Binaries are sequences of whole bytes. Bitstrings with an arbitrary
141 bit length have no support yet.
142 Resource objects:
144 The use of resource objects is a safe way to return pointers to
145 native data structures from a NIF. A resource object is only a
146 block of memory allocated with enif_alloc_resource. A handle ("safe
147 pointer") to this memory block can then be returned to Erlang by
148 the use of enif_make_resource. The term returned by
149 enif_make_resource is opaque in nature. It can be stored and passed
150 between processes, but the only real end usage is to pass it back
151 as an argument to a NIF. The NIF can then call enif_get_resource
152 and get back a pointer to the memory block, which is guaranteed to
153 still be valid. A resource object is not deallocated until the last
154 handle term is garbage collected by the VM and the resource is
155 released with enif_release_resource (not necessarily in that
156 order).
157 All resource objects are created as instances of some resource
159 type. This makes resources from different modules to be distin‐
160 guishable. A resource type is created by calling
161 enif_open_resource_type when a library is loaded. Objects of that
162 resource type can then later be allocated and enif_get_resource
163 verifies that the resource is of the expected type. A resource type
164 can have a user-supplied destructor function, which is automati‐
165 cally called when resources of that type are released (by either
166 the garbage collector or enif_release_resource). Resource types are
167 uniquely identified by a supplied name string and the name of the
168 implementing module.
169 The following is a template example of how to create and return a
171 resource object.
172 ERL_NIF_TERM term;
174 MyStruct* obj = enif_alloc_resource(my_resource_type, sizeof(MyStruct));
175 /* initialize struct ... */
177 term = enif_make_resource(env, obj);
179 if (keep_a_reference_of_our_own) {
181 /* store 'obj' in static variable, private data or other resource object */
182 }
183 else {
184 enif_release_resource(obj);
185 /* resource now only owned by "Erlang" */
186 }
187 return term;
188 Notice that once enif_make_resource creates the term to return to
190 Erlang, the code can choose to either keep its own native pointer
191 to the allocated struct and release it later, or release it immedi‐
192 ately and rely only on the garbage collector to deallocate the
193 resource object eventually when it collects the term.
194 Another use of resource objects is to create binary terms with
196 user-defined memory management. enif_make_resource_binary creates a
197 binary term that is connected to a resource object. The destructor
198 of the resource is called when the binary is garbage collected, at
199 which time the binary data can be released. An example of this can
200 be a binary term consisting of data from a mmap'ed file. The
201 destructor can then do munmap to release the memory region.
202 Resource types support upgrade in runtime by allowing a loaded NIF
204 library to take over an already existing resource type and by that
205 "inherit" all existing objects of that type. The destructor of the
206 new library is thereafter called for the inherited objects and the
207 library with the old destructor function can be safely unloaded.
208 Existing resource objects, of a module that is upgraded, must
209 either be deleted or taken over by the new NIF library. The unload‐
210 ing of a library is postponed as long as there exist resource
211 objects with a destructor function in the library.
212 Module upgrade and static data:
214 A loaded NIF library is tied to the Erlang module instance that
215 loaded it. If the module is upgraded, the new module instance needs
216 to load its own NIF library (or maybe choose not to). The new mod‐
217 ule instance can, however, choose to load the exact same NIF
218 library as the old code if it wants to. Sharing the dynamic library
219 means that static data defined by the library is shared as well. To
220 avoid unintentionally shared static data between module instances,
221 each Erlang module version can keep its own private data. This pri‐
222 vate data can be set when the NIF library is loaded and later
223 retrieved by calling enif_priv_data.
224 Threads and concurrency:
226 A NIF is thread-safe without any explicit synchronization as long
227 as it acts as a pure function and only reads the supplied argu‐
228 ments. When you write to a shared state either through static vari‐
229 ables or enif_priv_data, you need to supply your own explicit syn‐
230 chronization. This includes terms in process independent environ‐
231 ments that are shared between threads. Resource objects also
232 require synchronization if you treat them as mutable.
233 The library initialization callbacks load and upgrade are thread-
235 safe even for shared state data.
236 Version Management:
238 When a NIF library is built, information about the NIF API version
239 is compiled into the library. When a NIF library is loaded, the
240 runtime system verifies that the library is of a compatible ver‐
241 sion. erl_nif.h defines the following:
242 ERL_NIF_MAJOR_VERSION:
244 Incremented when NIF library incompatible changes are made to the
245 Erlang runtime system. Normally it suffices to recompile the NIF
246 library when the ERL_NIF_MAJOR_VERSION has changed, but it can,
247 under rare circumstances, mean that NIF libraries must be
248 slightly modified. If so, this will of course be documented.
249 ERL_NIF_MINOR_VERSION:
251 Incremented when new features are added. The runtime system uses
252 the minor version to determine what features to use.
253 The runtime system normally refuses to load a NIF library if the
255 major versions differ, or if the major versions are equal and the
256 minor version used by the NIF library is greater than the one used
257 by the runtime system. Old NIF libraries with lower major versions
258 are, however, allowed after a bump of the major version during a
259 transition period of two major releases. Such old NIF libraries can
260 however fail if deprecated features are used.
261 Time Measurement:
263 Support for time measurement in NIF libraries:
264 * ErlNifTime
266 * ErlNifTimeUnit
268 * enif_monotonic_time()
270 * enif_time_offset()
272 * enif_convert_time_unit()
274 I/O Queues:
276 The Erlang nif library contains function for easily working with
277 I/O vectors as used by the unix system call writev. The I/O Queue
278 is not thread safe, so some other synchronization mechanism has to
279 be used.
280 * SysIOVec
282 * ErlNifIOVec
284 * enif_ioq_create()
286 * enif_ioq_destroy()
288 * enif_ioq_enq_binary()
290 * enif_ioq_enqv()
292 * enif_ioq_deq()
294 * enif_ioq_peek()
296 * enif_ioq_peek_head()
298 * enif_inspect_iovec()
300 * enif_free_iovec()
302 Typical usage when writing to a file descriptor looks like this:
304 int writeiovec(ErlNifEnv *env, ERL_NIF_TERM term, ERL_NIF_TERM *tail,
306 ErlNifIOQueue *q, int fd) {
307 ErlNifIOVec vec, *iovec = &vec;
309 SysIOVec *sysiovec;
310 int saved_errno;
311 int iovcnt, n;
312 if (!enif_inspect_iovec(env, 64, term, tail, &iovec))
314 return -2;
315 if (enif_ioq_size(q) > 0) {
317 /* If the I/O queue contains data we enqueue the iovec and
318 then peek the data to write out of the queue. */
319 if (!enif_ioq_enqv(q, iovec, 0))
320 return -3;
321 sysiovec = enif_ioq_peek(q, &iovcnt);
323 } else {
324 /* If the I/O queue is empty we skip the trip through it. */
325 iovcnt = iovec->iovcnt;
326 sysiovec = iovec->iov;
327 }
328 /* Attempt to write the data */
330 n = writev(fd, sysiovec, iovcnt);
331 saved_errno = errno;
332 if (enif_ioq_size(q) == 0) {
334 /* If the I/O queue was initially empty we enqueue any
335 remaining data into the queue for writing later. */
336 if (n >= 0 && !enif_ioq_enqv(q, iovec, n))
337 return -3;
338 } else {
339 /* Dequeue any data that was written from the queue. */
340 if (n > 0 && !enif_ioq_deq(q, n, NULL))
341 return -4;
342 }
343 /* return n, which is either number of bytes written or -1 if
345 some error happened */
346 errno = saved_errno;
347 return n;
348 }
349 Long-running NIFs:
351 As mentioned in the warning text at the beginning of this manual
352 page, it is of vital importance that a native function returns rel‐
353 atively fast. It is difficult to give an exact maximum amount of
354 time that a native function is allowed to work, but usually a well-
355 behaving native function is to return to its caller within 1 mil‐
356 lisecond. This can be achieved using different approaches. If you
357 have full control over the code to execute in the native function,
358 the best approach is to divide the work into multiple chunks of
359 work and call the native function multiple times. This is, however,
360 not always possible, for example when calling third-party
361 libraries.
362 The enif_consume_timeslice() function can be used to inform the
364 runtime system about the length of the NIF call. It is typically
365 always to be used unless the NIF executes very fast.
366 If the NIF call is too lengthy, this must be handled in one of the
368 following ways to avoid degraded responsiveness, scheduler load
369 balancing problems, and other strange behaviors:
370 Yielding NIF:
372 If the functionality of a long-running NIF can be split so that
373 its work can be achieved through a series of shorter NIF calls,
374 the application has two options:
375 * Make that series of NIF calls from the Erlang level.
377 * Call a NIF that first performs a chunk of the work, then
379 invokes the enif_schedule_nif function to schedule another NIF
380 call to perform the next chunk. The final call scheduled in
381 this manner can then return the overall result.
382 Breaking up a long-running function in this manner enables the VM
384 to regain control between calls to the NIFs.
385 This approach is always preferred over the other alternatives
387 described below. This both from a performance perspective and a
388 system characteristics perspective.
389 Threaded NIF:
391 This is accomplished by dispatching the work to another thread
392 managed by the NIF library, return from the NIF, and wait for the
393 result. The thread can send the result back to the Erlang process
394 using enif_send. Information about thread primitives is provided
395 below.
396 Dirty NIF:
398 Note:
401 Dirty NIF support is available only when the emulator is configured
402 with dirty scheduler support. As of ERTS version 9.0, dirty sched‐
403 uler support is enabled by default on the runtime system with SMP
404 support. The Erlang runtime without SMP support does not support
405 dirty schedulers even when the dirty scheduler support is explic‐
406 itly enabled. To check at runtime for the presence of dirty sched‐
407 uler threads, code can use the enif_system_info() API function.
408 A NIF that cannot be split and cannot execute in a millisecond or
411 less is called a "dirty NIF", as it performs work that the ordi‐
412 nary schedulers of the Erlang runtime system cannot handle
413 cleanly. Applications that make use of such functions must indi‐
414 cate to the runtime that the functions are dirty so they can be
415 handled specially. This is handled by executing dirty jobs on a
416 separate set of schedulers called dirty schedulers. A dirty NIF
417 executing on a dirty scheduler does not have the same duration
418 restriction as a normal NIF.
419 It is important to classify the dirty job correct. An I/O bound
421 job should be classified as such, and a CPU bound job should be
422 classified as such. If you should classify CPU bound jobs as I/O
423 bound jobs, dirty I/O schedulers might starve ordinary sched‐
424 ulers. I/O bound jobs are expected to either block waiting for
425 I/O, and/or spend a limited amount of time moving data.
426 To schedule a dirty NIF for execution, the application has two
428 options:
429 * Set the appropriate flags value for the dirty NIF in its Erl‐
431 NifFunc entry.
432 * Call enif_schedule_nif, pass to it a pointer to the dirty NIF
434 to be executed, and indicate with argument flags whether it
435 expects the operation to be CPU-bound or I/O-bound.
436 A job that alternates between I/O bound and CPU bound can be
438 reclassified and rescheduled using enif_schedule_nif so that it
439 executes on the correct type of dirty scheduler at all times. For
440 more information see the documentation of the erl(1) command line
441 arguments +SDcpu, and +SDio.
442 While a process executes a dirty NIF, some operations that commu‐
444 nicate with it can take a very long time to complete. Suspend or
445 garbage collection of a process executing a dirty NIF cannot be
446 done until the dirty NIF has returned. Thus, other processes
447 waiting for such operations to complete might have to wait for a
448 very long time. Blocking multi-scheduling, that is, calling
449 erlang:system_flag(multi_scheduling, block), can also take a very
450 long time to complete. This is because all ongoing dirty opera‐
451 tions on all dirty schedulers must complete before the block
452 operation can complete.
453 Many operations communicating with a process executing a dirty
455 NIF can, however, complete while it executes the dirty NIF. For
456 example, retrieving information about it through
457 erlang:process_info, setting its group leader, register/unregis‐
458 ter its name, and so on.
459 Termination of a process executing a dirty NIF can only be com‐
461 pleted up to a certain point while it executes the dirty NIF. All
462 Erlang resources, such as its registered name and its ETS tables,
463 are released. All links and monitors are triggered. The execution
464 of the NIF is, however, not stopped. The NIF can safely continue
465 execution, allocate heap memory, and so on, but it is of course
466 better to stop executing as soon as possible. The NIF can check
467 whether a current process is alive using enif_is_cur‐
468 rent_process_alive. Communication using enif_send and
469 enif_port_command is also dropped when the sending process is not
470 alive. Deallocation of certain internal resources, such as
471 process heap and process control block, is delayed until the
472 dirty NIF has completed.
473
475 ERL_NIF_INIT(MODULE, ErlNifFunc funcs[], load, NULL, upgrade,
476 unload):
477 This is the magic macro to initialize a NIF library. It is to be
478 evaluated in global file scope.
479 MODULE is the name of the Erlang module as an identifier without
481 string quotations. It is stringified by the macro.
482 funcs is a static array of function descriptors for all the imple‐
484 mented NIFs in this library.
485 load, upgrade and unload are pointers to functions. One of load or
487 upgrade is called to initialize the library. unload is called to
488 release the library. All are described individually below.
489 The fourth argument NULL is ignored. It was earlier used for the
491 deprecated reload callback which is no longer supported since OTP
492 20.
493 If compiling a NIF for static inclusion through --enable-static-
495 nifs, you must define STATIC_ERLANG_NIF before the ERL_NIF_INIT
496 declaration.
497 int (*load)(ErlNifEnv* caller_env, void** priv_data, ERL_NIF_TERM
499 load_info):
500 load is called when the NIF library is loaded and no previously
501 loaded library exists for this module.
502 *priv_data can be set to point to some private data if the library
504 needs to keep a state between NIF calls. enif_priv_data returns
505 this pointer. *priv_data is initialized to NULL when load is
506 called.
507 load_info is the second argument to erlang:load_nif/2.
509 The library fails to load if load returns anything other than 0.
511 load can be NULL if initialization is not needed.
512 int (*upgrade)(ErlNifEnv* caller_env, void** priv_data, void**
514 old_priv_data, ERL_NIF_TERM load_info):
515 upgrade is called when the NIF library is loaded and there is old
516 code of this module with a loaded NIF library.
517 Works as load, except that *old_priv_data already contains the
519 value set by the last call to load or upgrade for the old module
520 code. *priv_data is initialized to NULL when upgrade is called. It
521 is allowed to write to both *priv_data and *old_priv_data.
522 The library fails to load if upgrade returns anything other than 0
524 or if upgrade is NULL.
525 void (*unload)(ErlNifEnv* caller_env, void* priv_data):
527 unload is called when the module code that the NIF library belongs
528 to is purged as old. New code of the same module may or may not
529 exist.
530
532 ERL_NIF_TERM:
533 Variables of type ERL_NIF_TERM can refer to any Erlang term. This
534 is an opaque type and values of it can only by used either as argu‐
535 ments to API functions or as return values from NIFs. All
536 ERL_NIF_TERMs belong to an environment (ErlNifEnv). A term cannot
537 be destructed individually, it is valid until its environment is
538 destructed.
539 ErlNifEnv:
541 ErlNifEnv represents an environment that can host Erlang terms. All
542 terms in an environment are valid as long as the environment is
543 valid. ErlNifEnv is an opaque type; pointers to it can only be
544 passed on to API functions. Three types of environments exist:
545 Process bound environment:
547 Passed as the first argument to all NIFs. All function arguments
548 passed to a NIF belong to that environment. The return value from
549 a NIF must also be a term belonging to the same environment.
550 A process bound environment contains transient information about
552 the calling Erlang process. The environment is only valid in the
553 thread where it was supplied as argument until the NIF returns.
554 It is thus useless and dangerous to store pointers to process
555 bound environments between NIF calls.
556 Callback environment:
558 Passed as the first argument to all the non-NIF callback func‐
559 tions (load, upgrade, unload, dtor, down and stop). Works like a
560 process bound environment but with a temporary pseudo process
561 that "terminates" when the callback has returned. Terms may be
562 created in this environment but they will only be accessible dur‐
563 ing the callback.
564 Process independent environment:
566 Created by calling enif_alloc_env. This environment can be used
567 to store terms between NIF calls and to send terms with
568 enif_send. A process independent environment with all its terms
569 is valid until you explicitly invalidate it with enif_free_env or
570 enif_send.
571 All contained terms of a list/tuple/map must belong to the same
573 environment as the list/tuple/map itself. Terms can be copied
574 between environments with enif_make_copy.
575 ErlNifFunc:
577 typedef struct {
580 const char* name;
581 unsigned arity;
582 ERL_NIF_TERM (*fptr)(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
583 unsigned flags;
584 } ErlNifFunc;
585 Describes a NIF by its name, arity, and implementation.
587 fptr:
589 A pointer to the function that implements the NIF.
590 argv:
592 Contains the function arguments passed to the NIF.
593 argc:
595 The array length, that is, the function arity. argv[N-1] thus
596 denotes the Nth argument to the NIF. Notice that the argument
597 argc allows for the same C function to implement several Erlang
598 functions with different arity (but probably with the same name).
599 flags:
601 Is 0 for a regular NIF (and so its value can be omitted for stat‐
602 ically initialized ErlNifFunc instances).
603 flags can be used to indicate that the NIF is a dirty NIF that is
605 to be executed on a dirty scheduler thread.
606 If the dirty NIF is expected to be CPU-bound, its flags field is
608 to be set to ERL_NIF_DIRTY_JOB_CPU_BOUND or
609 ERL_NIF_DIRTY_JOB_IO_BOUND.
610 Note:
612 If one of the ERL_NIF_DIRTY_JOB_*_BOUND flags is set, and the run‐
613 time system has no support for dirty schedulers, the runtime system
614 refuses to load the NIF library.
615 ErlNifBinary:
618 typedef struct {
621 unsigned size;
622 unsigned char* data;
623 } ErlNifBinary;
624 ErlNifBinary contains transient information about an inspected
626 binary term. data is a pointer to a buffer of size bytes with the
627 raw content of the binary.
628 Notice that ErlNifBinary is a semi-opaque type and you are only
630 allowed to read fields size and data.
631 ErlNifBinaryToTerm:
633 An enumeration of the options that can be specified to
634 enif_binary_to_term. For default behavior, use value 0.
635 When receiving data from untrusted sources, use option
637 ERL_NIF_BIN2TERM_SAFE.
638 ErlNifMonitor:
640 This is an opaque data type that identifies a monitor.
641 The nif writer is to provide the memory for storing the monitor
643 when calling enif_monitor_process. The address of the data is not
644 stored by the runtime system, so ErlNifMonitor can be used as any
645 other data, it can be copied, moved in memory, forgotten, and so
646 on. To compare two monitors, enif_compare_monitors must be used.
647 ErlNifPid:
649 A process identifier (pid). In contrast to pid terms (instances of
650 ERL_NIF_TERM), ErlNifPids are self-contained and not bound to any
651 environment. ErlNifPid is an opaque type.
652 ErlNifPort:
654 A port identifier. In contrast to port ID terms (instances of
655 ERL_NIF_TERM), ErlNifPorts are self-contained and not bound to any
656 environment. ErlNifPort is an opaque type.
657 ErlNifResourceType:
659 Each instance of ErlNifResourceType represents a class of memory-
660 managed resource objects that can be garbage collected. Each
661 resource type has a unique name and a destructor function that is
662 called when objects of its type are released.
663 ErlNifResourceTypeInit:
665 typedef struct {
668 ErlNifResourceDtor* dtor;
669 ErlNifResourceStop* stop;
670 ErlNifResourceDown* down;
671 } ErlNifResourceTypeInit;
672 Initialization structure read by enif_open_resource_type_x.
674 ErlNifResourceDtor:
676 typedef void ErlNifResourceDtor(ErlNifEnv* caller_env, void* obj);
679 The function prototype of a resource destructor function.
681 The obj argument is a pointer to the resource. The only allowed use
683 for the resource in the destructor is to access its user data one
684 final time. The destructor is guaranteed to be the last callback
685 before the resource is deallocated.
686 ErlNifResourceDown:
688 typedef void ErlNifResourceDown(ErlNifEnv* caller_env, void* obj, ErlNifPid* pid, ErlNifMonitor* mon);
691 The function prototype of a resource down function, called on the
693 behalf of enif_monitor_process. obj is the resource, pid is the
694 identity of the monitored process that is exiting, and mon is the
695 identity of the monitor.
696 ErlNifResourceStop:
698 typedef void ErlNifResourceStop(ErlNifEnv* caller_env, void* obj, ErlNifEvent event, int is_direct_call);
701 The function prototype of a resource stop function, called on the
703 behalf of enif_select. obj is the resource, event is OS event,
704 is_direct_call is true if the call is made directly from
705 enif_select or false if it is a scheduled call (potentially from
706 another thread).
707 ErlNifCharEncoding:
709 typedef enum {
712 ERL_NIF_LATIN1
713 }ErlNifCharEncoding;
714 The character encoding used in strings and atoms. The only sup‐
716 ported encoding is ERL_NIF_LATIN1 for ISO Latin-1 (8-bit ASCII).
717 ErlNifSysInfo:
719 Used by enif_system_info to return information about the runtime
720 system. Contains the same content as ErlDrvSysInfo.
721 ErlNifSInt64:
723 A native signed 64-bit integer type.
724 ErlNifUInt64:
726 A native unsigned 64-bit integer type.
727 ErlNifTime:
729 A signed 64-bit integer type for representation of time.
730 ErlNifTimeUnit:
732 An enumeration of time units supported by the NIF API:
733 ERL_NIF_SEC:
735 Seconds
736 ERL_NIF_MSEC:
738 Milliseconds
739 ERL_NIF_USEC:
741 Microseconds
742 ERL_NIF_NSEC:
744 Nanoseconds
745 ErlNifUniqueInteger:
747 An enumeration of the properties that can be requested from
748 enif_make_unique_integer. For default properties, use value 0.
749 ERL_NIF_UNIQUE_POSITIVE:
751 Return only positive integers.
752 ERL_NIF_UNIQUE_MONOTONIC:
754 Return only strictly monotonically increasing integer corre‐
755 sponding to creation time.
756 ErlNifHash:
758 An enumeration of the supported hash types that can be generated
759 using enif_hash.
760 ERL_NIF_INTERNAL_HASH:
762 Non-portable hash function that only guarantees the same hash for
763 the same term within one Erlang VM instance.
764 It takes 32-bit salt values and generates hashes within
766 0..2^32-1.
767 ERL_NIF_PHASH2:
769 Portable hash function that gives the same hash for the same
770 Erlang term regardless of machine architecture and ERTS version.
771 It ignores salt values and generates hashes within 0..2^27-1.
773 Slower than ERL_NIF_INTERNAL_HASH. It corresponds to
775 erlang:phash2/1.
776 SysIOVec:
778 A system I/O vector, as used by writev on Unix and WSASend on
779 Win32. It is used in ErlNifIOVec and by enif_ioq_peek.
780 ErlNifIOVec:
782 typedef struct {
785 int iovcnt;
786 size_t size;
787 SysIOVec* iov;
788 } ErlNifIOVec;
789 An I/O vector containing iovcnt SysIOVecs pointing to the data. It
791 is used by enif_inspect_iovec and enif_ioq_enqv.
792 ErlNifIOQueueOpts:
794 Options to configure a ErlNifIOQueue.
795 ERL_NIF_IOQ_NORMAL:
797 Create a normal I/O Queue
798
800 void *enif_alloc(size_t size)
801 Allocates memory of size bytes.
803 Returns NULL if the allocation fails.
805 The returned pointer is suitably aligned for any built-in type
807 that fit in the allocated memory.
808 int enif_alloc_binary(size_t size, ErlNifBinary* bin)
810 Allocates a new binary of size size bytes. Initializes the
812 structure pointed to by bin to refer to the allocated binary.
813 The binary must either be released by enif_release_binary or
814 ownership transferred to an Erlang term with enif_make_binary.
815 An allocated (and owned) ErlNifBinary can be kept between NIF
816 calls.
817 If you do not need to reallocate or keep the data alive across
819 NIF calls, consider using enif_make_new_binary instead as it
820 will allocate small binaries on the process heap when possible.
821 Returns true on success, or false if allocation fails.
823 ErlNifEnv *enif_alloc_env()
825 Allocates a new process independent environment. The environment
827 can be used to hold terms that are not bound to any process.
828 Such terms can later be copied to a process environment with
829 enif_make_copy or be sent to a process as a message with
830 enif_send.
831 Returns pointer to the new environment.
833 void *enif_alloc_resource(ErlNifResourceType*
835 type, unsigned size)
836 Allocates a memory-managed resource object of type type and size
838 size bytes.
839 size_t enif_binary_to_term(ErlNifEnv *env,
841 const unsigned char* data, size_t size, ERL_NIF_TERM *term,
842 ErlNifBinaryToTerm opts)
843 Creates a term that is the result of decoding the binary data at
845 data, which must be encoded according to the Erlang external
846 term format. No more than size bytes are read from data. Argu‐
847 ment opts corresponds to the second argument to
848 erlang:binary_to_term/2 and must be either 0 or
849 ERL_NIF_BIN2TERM_SAFE.
850 On success, stores the resulting term at *term and returns the
852 number of bytes read. Returns 0 if decoding fails or if opts is
853 invalid.
854 See also ErlNifBinaryToTerm, erlang:binary_to_term/2, and
856 enif_term_to_binary.
857 void enif_clear_env(ErlNifEnv* env)
859 Frees all terms in an environment and clears it for reuse. The
861 environment must have been allocated with enif_alloc_env.
862 int enif_compare(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)
864 Returns an integer < 0 if lhs < rhs, 0 if lhs = rhs, and > 0 if
866 lhs > rhs. Corresponds to the Erlang operators ==, /=, =<, <,
867 >=, and > (but not =:= or =/=).
868 int enif_compare_monitors(const ErlNifMonitor
870 *monitor1, const ErlNifMonitor *monitor2)
871 Compares two ErlNifMonitors. Can also be used to imply some
873 artificial order on monitors, for whatever reason.
874 Returns 0 if monitor1 and monitor2 are equal, < 0 if monitor1 <
876 monitor2, and > 0 if monitor1 > monitor2.
877 void enif_cond_broadcast(ErlNifCond *cnd)
879 Same as erl_drv_cond_broadcast.
881 ErlNifCond *enif_cond_create(char *name)
883 Same as erl_drv_cond_create.
885 void enif_cond_destroy(ErlNifCond *cnd)
887 Same as erl_drv_cond_destroy.
889 char*enif_cond_name(ErlNifCond* cnd)
891 Same as erl_drv_cond_name.
893 void enif_cond_signal(ErlNifCond *cnd)
895 Same as erl_drv_cond_signal.
897 void enif_cond_wait(ErlNifCond *cnd, ErlNifMutex *mtx)
899 Same as erl_drv_cond_wait.
901 int enif_consume_timeslice(ErlNifEnv *env, int percent)
903 Gives the runtime system a hint about how much CPU time the cur‐
905 rent NIF call has consumed since the last hint, or since the
906 start of the NIF if no previous hint has been specified. The
907 time is specified as a percent of the timeslice that a process
908 is allowed to execute Erlang code until it can be suspended to
909 give time for other runnable processes. The scheduling timeslice
910 is not an exact entity, but can usually be approximated to about
911 1 millisecond.
912 Notice that it is up to the runtime system to determine if and
914 how to use this information. Implementations on some platforms
915 can use other means to determine consumed CPU time. Lengthy NIFs
916 should regardless of this frequently call enif_consume_timeslice
917 to determine if it is allowed to continue execution.
918 Argument percent must be an integer between 1 and 100. This
920 function must only be called from a NIF-calling thread, and
921 argument env must be the environment of the calling process.
922 Returns 1 if the timeslice is exhausted, otherwise 0. If 1 is
924 returned, the NIF is to return as soon as possible in order for
925 the process to yield.
926 This function is provided to better support co-operative sched‐
928 uling, improve system responsiveness, and make it easier to pre‐
929 vent misbehaviors of the VM because of a NIF monopolizing a
930 scheduler thread. It can be used to divide length work into a
931 number of repeated NIF calls without the need to create threads.
932 See also the warning text at the beginning of this manual page.
934 ErlNifTime enif_convert_time_unit(ErlNifTime
936 val, ErlNifTimeUnit from, ErlNifTimeUnit to)
937 Converts the val value of time unit from to the corresponding
939 value of time unit to. The result is rounded using the floor
940 function.
941 val:
943 Value to convert time unit for.
944 from:
946 Time unit of val.
947 to:
949 Time unit of returned value.
950 Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
952 argument.
953 See also ErlNifTime and ErlNifTimeUnit.
955 ERL_NIF_TERM enif_cpu_time(ErlNifEnv *)
957 Returns the CPU time in the same format as erlang:timestamp().
959 The CPU time is the time the current logical CPU has spent exe‐
960 cuting since some arbitrary point in the past. If the OS does
961 not support fetching this value, enif_cpu_time invokes
962 enif_make_badarg.
963 int enif_demonitor_process(ErlNifEnv* caller_env,
965 void* obj, const ErlNifMonitor* mon)
966 Cancels a monitor created earlier with enif_monitor_process.
968 Argument obj is a pointer to the resource holding the monitor
969 and *mon identifies the monitor.
970 Argument caller_env is the environment of the calling process or
972 callback. Must only be NULL if calling from a custom thread.
973 Returns 0 if the monitor was successfully identified and
975 removed. Returns a non-zero value if the monitor could not be
976 identified, which means it was either
977 * never created for this resource
979 * already cancelled
981 * already triggered
983 * just about to be triggered by a concurrent thread
985 This function is only thread-safe when the emulator with SMP
987 support is used. It can only be used in a non-SMP emulator from
988 a NIF-calling thread.
989 int enif_equal_tids(ErlNifTid tid1, ErlNifTid tid2)
991 Same as erl_drv_equal_tids.
993 int enif_fprintf(FILE *stream, const char *format, ...)
995 Similar to fprintf but this format string also accepts "%T",
997 which formats Erlang terms of type ERL_NIF_TERM.
998 This function is primarily intended for debugging purpose. It is
1000 not recommended to print very large terms with %T. The function
1001 may change errno, even if successful.
1002 void enif_free(void* ptr)
1004 Frees memory allocated by enif_alloc.
1006 void enif_free_env(ErlNifEnv* env)
1008 Frees an environment allocated with enif_alloc_env. All terms
1010 created in the environment are freed as well.
1011 void enif_free_iovec(ErlNifIOvec* iov)
1013 Frees an io vector returned from enif_inspect_iovec. This is
1015 needed only if a NULL environment is passed to
1016 enif_inspect_iovec.
1017 ErlNifIOVec *iovec = NULL;
1019 size_t max_elements = 128;
1020 ERL_NIF_TERM tail;
1021 if (!enif_inspect_iovec(NULL, max_elements, term, &tail, &iovec))
1022 return 0;
1023 // Do things with the iovec
1025 /* Free the iovector, possibly in another thread or nif function call */
1027 enif_free_iovec(iovec);
1028 int enif_get_atom(ErlNifEnv* env, ERL_NIF_TERM
1030 term, char* buf, unsigned size, ErlNifCharEncoding encode)
1031 Writes a NULL-terminated string in the buffer pointed to by buf
1033 of size size, consisting of the string representation of the
1034 atom term with encoding encode.
1035 Returns the number of bytes written (including terminating NULL
1037 character) or 0 if term is not an atom with maximum length of
1038 size-1.
1039 int enif_get_atom_length(ErlNifEnv* env,
1041 ERL_NIF_TERM term, unsigned* len, ErlNifCharEncoding encode)
1042 Sets *len to the length (number of bytes excluding terminating
1044 NULL character) of the atom term with encoding encode.
1045 Returns true on success, or false if term is not an atom.
1047 int enif_get_double(ErlNifEnv* env,
1049 ERL_NIF_TERM term, double* dp)
1050 Sets *dp to the floating-point value of term.
1052 Returns true on success, or false if term is not a float.
1054 int enif_get_int(ErlNifEnv* env, ERL_NIF_TERM
1056 term, int* ip)
1057 Sets *ip to the integer value of term.
1059 Returns true on success, or false if term is not an integer or
1061 is outside the bounds of type int.
1062 int enif_get_int64(ErlNifEnv* env, ERL_NIF_TERM
1064 term, ErlNifSInt64* ip)
1065 Sets *ip to the integer value of term.
1067 Returns true on success, or false if term is not an integer or
1069 is outside the bounds of a signed 64-bit integer.
1070 int enif_get_local_pid(ErlNifEnv* env,
1072 ERL_NIF_TERM term, ErlNifPid* pid)
1073 If term is the pid of a node local process, this function ini‐
1075 tializes the pid variable *pid from it and returns true. Other‐
1076 wise returns false. No check is done to see if the process is
1077 alive.
1078 int enif_get_local_port(ErlNifEnv* env,
1080 ERL_NIF_TERM term, ErlNifPort* port_id)
1081 If term identifies a node local port, this function initializes
1083 the port variable *port_id from it and returns true. Otherwise
1084 returns false. No check is done to see if the port is alive.
1085 int enif_get_list_cell(ErlNifEnv* env,
1087 ERL_NIF_TERM list, ERL_NIF_TERM* head, ERL_NIF_TERM* tail)
1088 Sets *head and *tail from list list.
1090 Returns true on success, or false if it is not a list or the
1092 list is empty.
1093 int enif_get_list_length(ErlNifEnv* env,
1095 ERL_NIF_TERM term, unsigned* len)
1096 Sets *len to the length of list term.
1098 Returns true on success, or false if term is not a proper list.
1100 int enif_get_long(ErlNifEnv* env, ERL_NIF_TERM
1102 term, long int* ip)
1103 Sets *ip to the long integer value of term.
1105 Returns true on success, or false if term is not an integer or
1107 is outside the bounds of type long int.
1108 int enif_get_map_size(ErlNifEnv* env,
1110 ERL_NIF_TERM term, size_t *size)
1111 Sets *size to the number of key-value pairs in the map term.
1113 Returns true on success, or false if term is not a map.
1115 int enif_get_map_value(ErlNifEnv* env,
1117 ERL_NIF_TERM map, ERL_NIF_TERM key, ERL_NIF_TERM* value)
1118 Sets *value to the value associated with key in the map map.
1120 Returns true on success, or false if map is not a map or if map
1122 does not contain key.
1123 int enif_get_resource(ErlNifEnv* env,
1125 ERL_NIF_TERM term, ErlNifResourceType* type, void** objp)
1126 Sets *objp to point to the resource object referred to by term.
1128 Returns true on success, or false if term is not a handle to a
1130 resource object of type type.
1131 int enif_get_string(ErlNifEnv* env,
1133 ERL_NIF_TERM list, char* buf, unsigned size,
1134 ErlNifCharEncoding encode)
1135 Writes a NULL-terminated string in the buffer pointed to by buf
1137 with size size, consisting of the characters in the string list.
1138 The characters are written using encoding encode.
1139 Returns one of the following:
1141 * The number of bytes written (including terminating NULL
1143 character)
1144 * -size if the string was truncated because of buffer space
1146 * 0 if list is not a string that can be encoded with encode or
1148 if size was < 1.
1149 The written string is always NULL-terminated, unless buffer size
1151 is < 1.
1152 int enif_get_tuple(ErlNifEnv* env, ERL_NIF_TERM
1154 term, int* arity, const ERL_NIF_TERM** array)
1155 If term is a tuple, this function sets *array to point to an
1157 array containing the elements of the tuple, and sets *arity to
1158 the number of elements. Notice that the array is read-only and
1159 (*array)[N-1] is the Nth element of the tuple. *array is unde‐
1160 fined if the arity of the tuple is zero.
1161 Returns true on success, or false if term is not a tuple.
1163 int enif_get_uint(ErlNifEnv* env, ERL_NIF_TERM
1165 term, unsigned int* ip)
1166 Sets *ip to the unsigned integer value of term.
1168 Returns true on success, or false if term is not an unsigned
1170 integer or is outside the bounds of type unsigned int.
1171 int enif_get_uint64(ErlNifEnv* env,
1173 ERL_NIF_TERM term, ErlNifUInt64* ip)
1174 Sets *ip to the unsigned integer value of term.
1176 Returns true on success, or false if term is not an unsigned
1178 integer or is outside the bounds of an unsigned 64-bit integer.
1179 int enif_get_ulong(ErlNifEnv* env, ERL_NIF_TERM
1181 term, unsigned long* ip)
1182 Sets *ip to the unsigned long integer value of term.
1184 Returns true on success, or false if term is not an unsigned
1186 integer or is outside the bounds of type unsigned long.
1187 int enif_getenv(const char* key, char* value,
1189 size_t *value_size)
1190 Same as erl_drv_getenv.
1192 int enif_has_pending_exception(ErlNifEnv* env,
1194 ERL_NIF_TERM* reason)
1195 Returns true if a pending exception is associated with the envi‐
1197 ronment env. If reason is a NULL pointer, ignore it. Otherwise,
1198 if a pending exception associated with env exists, set *reason
1199 to the value of the exception term. For example, if
1200 enif_make_badarg is called to set a pending badarg exception, a
1201 later call to enif_has_pending_exception(env, &reason) sets
1202 *reason to the atom badarg, then return true.
1203 See also enif_make_badarg and enif_raise_exception.
1205 ErlNifUInt64 enif_hash(ErlNifHash type, ERL_NIF_TERM term, ErlNifUInt64
1207 salt)
1208 Hashes term according to the specified ErlNifHash type.
1210 Ranges of taken salt (if any) and returned value depend on the
1212 hash type.
1213 int enif_inspect_binary(ErlNifEnv* env,
1215 ERL_NIF_TERM bin_term, ErlNifBinary* bin)
1216 Initializes the structure pointed to by bin with information
1218 about binary term bin_term.
1219 Returns true on success, or false if bin_term is not a binary.
1221 int enif_inspect_iolist_as_binary(ErlNifEnv*
1223 env, ERL_NIF_TERM term, ErlNifBinary* bin)
1224 Initializes the structure pointed to by bin with a continuous
1226 buffer with the same byte content as iolist. As with
1227 inspect_binary, the data pointed to by bin is transient and does
1228 not need to be released.
1229 Returns true on success, or false if iolist is not an iolist.
1231 int enif_inspect_iovec(ErlNifEnv*
1233 env, size_t max_elements, ERL_NIF_TERM iovec_term,
1234 ERL_NIF_TERM* tail,
1235 ErlNifIOVec** iovec)
1236 Fills iovec with the list of binaries provided in iovec_term.
1238 The number of elements handled in the call is limited to
1239 max_elements, and tail is set to the remainder of the list. Note
1240 that the output may be longer than max_elements on some plat‐
1241 forms.
1242 To create a list of binaries from an arbitrary iolist, use
1244 erlang:iolist_to_iovec/1.
1245 When calling this function, iovec should contain a pointer to
1247 NULL or a ErlNifIOVec structure that should be used if possible.
1248 e.g.
1249 /* Don't use a pre-allocated structure */
1251 ErlNifIOVec *iovec = NULL;
1252 enif_inspect_iovec(env, max_elements, term, &tail, &iovec);
1253 /* Use a stack-allocated vector as an optimization for vectors with few elements */
1255 ErlNifIOVec vec, *iovec = &vec;
1256 enif_inspect_iovec(env, max_elements, term, &tail, &iovec);
1257 The contents of the iovec is valid until the called nif function
1260 returns. If the iovec should be valid after the nif call
1261 returns, it is possible to call this function with a NULL envi‐
1262 ronment. If no environment is given the iovec owns the data in
1263 the vector and it has to be explicitly freed using
1264 enif_free_iovec.
1265 Returns true on success, or false if iovec_term not an iovec.
1267 ErlNifIOQueue *enif_ioq_create(ErlNifIOQueueOpts opts)
1269 Create a new I/O Queue that can be used to store data. opts has
1271 to be set to ERL_NIF_IOQ_NORMAL.
1272 void enif_ioq_destroy(ErlNifIOQueue *q)
1274 Destroy the I/O queue and free all of it's contents
1276 int enif_ioq_deq(ErlNifIOQueue *q, size_t count, size_t *size)
1278 Dequeue count bytes from the I/O queue. If size is not NULL, the
1280 new size of the queue is placed there.
1281 Returns true on success, or false if the I/O does not contain
1283 count bytes. On failure the queue is left un-altered.
1284 int enif_ioq_enq_binary(ErlNifIOQueue *q, ErlNifBinary *bin, size_t
1286 skip)
1287 Enqueue the bin into q skipping the first skip bytes.
1289 Returns true on success, or false if skip is greater than the
1291 size of bin. Any ownership of the binary data is transferred to
1292 the queue and bin is to be considered read-only for the rest of
1293 the NIF call and then as released.
1294 int enif_ioq_enqv(ErlNifIOQueue *q, ErlNifIOVec *iovec, size_t skip)
1296 Enqueue the iovec into q skipping the first skip bytes.
1298 Returns true on success, or false if skip is greater than the
1300 size of iovec.
1301 SysIOVec *enif_ioq_peek(ErlNifIOQueue *q, int *iovlen)
1303 Get the I/O queue as a pointer to an array of SysIOVecs. It also
1305 returns the number of elements in iovlen.
1306 Nothing is removed from the queue by this function, that must be
1308 done with enif_ioq_deq.
1309 The returned array is suitable to use with the Unix system call
1311 writev.
1312 int enif_ioq_peek_head(ErlNifEnv *env, ErlNifIOQueue *q, size_t *size,
1314 ERL_NIF_TERM *bin_term)
1315 Get the head of the IO Queue as a binary term.
1317 If size is not NULL, the size of the head is placed there.
1319 Nothing is removed from the queue by this function, that must be
1321 done with enif_ioq_deq.
1322 Returns true on success, or false if the queue is empty.
1324 size_t enif_ioq_size(ErlNifIOQueue *q)
1326 Get the size of q.
1328 int enif_is_atom(ErlNifEnv* env, ERL_NIF_TERM term)
1330 Returns true if term is an atom.
1332 int enif_is_binary(ErlNifEnv* env, ERL_NIF_TERM term)
1334 Returns true if term is a binary.
1336 int enif_is_current_process_alive(ErlNifEnv* env)
1338 Returns true if the currently executing process is currently
1340 alive, otherwise false.
1341 This function can only be used from a NIF-calling thread, and
1343 with an environment corresponding to currently executing pro‐
1344 cesses.
1345 int enif_is_empty_list(ErlNifEnv* env,
1347 ERL_NIF_TERM term)
1348 Returns true if term is an empty list.
1350 int enif_is_exception(ErlNifEnv* env,
1352 ERL_NIF_TERM term)
1353 Return true if term is an exception.
1355 int enif_is_fun(ErlNifEnv* env, ERL_NIF_TERM
1357 term)
1358 Returns true if term is a fun.
1360 int enif_is_identical(ERL_NIF_TERM lhs,
1362 ERL_NIF_TERM rhs)
1363 Returns true if the two terms are identical. Corresponds to the
1365 Erlang operators =:= and =/=.
1366 int enif_is_list(ErlNifEnv* env, ERL_NIF_TERM term)
1368 Returns true if term is a list.
1370 int enif_is_map(ErlNifEnv* env, ERL_NIF_TERM
1372 term)
1373 Returns true if term is a map, otherwise false.
1375 int enif_is_number(ErlNifEnv* env, ERL_NIF_TERM
1377 term)
1378 Returns true if term is a number.
1380 int enif_is_pid(ErlNifEnv* env, ERL_NIF_TERM term)
1382 Returns true if term is a pid.
1384 int enif_is_port(ErlNifEnv* env, ERL_NIF_TERM term)
1386 Returns true if term is a port.
1388 int enif_is_port_alive(ErlNifEnv* env,
1390 ErlNifPort *port_id)
1391 Returns true if port_id is alive.
1393 This function is only thread-safe when the emulator with SMP
1395 support is used. It can only be used in a non-SMP emulator from
1396 a NIF-calling thread.
1397 int enif_is_process_alive(ErlNifEnv* env,
1399 ErlNifPid *pid)
1400 Returns true if pid is alive.
1402 This function is only thread-safe when the emulator with SMP
1404 support is used. It can only be used in a non-SMP emulator from
1405 a NIF-calling thread.
1406 int enif_is_ref(ErlNifEnv* env, ERL_NIF_TERM term)
1408 Returns true if term is a reference.
1410 int enif_is_tuple(ErlNifEnv* env, ERL_NIF_TERM term)
1412 Returns true if term is a tuple.
1414 int enif_keep_resource(void* obj)
1416 Adds a reference to resource object obj obtained from
1418 enif_alloc_resource. Each call to enif_keep_resource for an
1419 object must be balanced by a call to enif_release_resource
1420 before the object is destructed.
1421 ERL_NIF_TERM enif_make_atom(ErlNifEnv* env, const char* name)
1423 Creates an atom term from the NULL-terminated C-string name with
1425 ISO Latin-1 encoding. If the length of name exceeds the maximum
1426 length allowed for an atom (255 characters), enif_make_atom
1427 invokes enif_make_badarg.
1428 ERL_NIF_TERM enif_make_atom_len(ErlNifEnv* env,
1430 const char* name, size_t len)
1431 Create an atom term from the string name with length len. NULL
1433 characters are treated as any other characters. If len exceeds
1434 the maximum length allowed for an atom (255 characters),
1435 enif_make_atom invokes enif_make_badarg.
1436 ERL_NIF_TERM enif_make_badarg(ErlNifEnv* env)
1438 Makes a badarg exception to be returned from a NIF, and asso‐
1440 ciates it with environment env. Once a NIF or any function it
1441 calls invokes enif_make_badarg, the runtime ensures that a
1442 badarg exception is raised when the NIF returns, even if the NIF
1443 attempts to return a non-exception term instead.
1444 The return value from enif_make_badarg can be used only as the
1446 return value from the NIF that invoked it (directly or indi‐
1447 rectly) or be passed to enif_is_exception, but not to any other
1448 NIF API function.
1449 See also enif_has_pending_exception and enif_raise_exception.
1451 Note:
1453 Before ERTS 7.0 (Erlang/OTP 18), the return value from
1454 enif_make_badarg had to be returned from the NIF. This require‐
1455 ment is now lifted as the return value from the NIF is ignored
1456 if enif_make_badarg has been invoked.
1457 ERL_NIF_TERM enif_make_binary(ErlNifEnv* env, ErlNifBinary* bin)
1460 Makes a binary term from bin. Any ownership of the binary data
1462 is transferred to the created term and bin is to be considered
1463 read-only for the rest of the NIF call and then as released.
1464 ERL_NIF_TERM enif_make_copy(ErlNifEnv* dst_env,
1466 ERL_NIF_TERM src_term)
1467 Makes a copy of term src_term. The copy is created in environ‐
1469 ment dst_env. The source term can be located in any environment.
1470 ERL_NIF_TERM enif_make_double(ErlNifEnv* env, double d)
1472 Creates a floating-point term from a double. If argument double
1474 is not finite or is NaN, enif_make_double invokes
1475 enif_make_badarg.
1476 int enif_make_existing_atom(ErlNifEnv* env,
1478 const char* name, ERL_NIF_TERM* atom, ErlNifCharEncoding
1479 encode)
1480 Tries to create the term of an already existing atom from the
1482 NULL-terminated C-string name with encoding encode.
1483 If the atom already exists, this function stores the term in
1485 *atom and returns true, otherwise false. Also returns false if
1486 the length of name exceeds the maximum length allowed for an
1487 atom (255 characters).
1488 int enif_make_existing_atom_len(ErlNifEnv* env,
1490 const char* name, size_t len, ERL_NIF_TERM* atom, ErlNifCharEn‐
1491 coding
1492 encoding)
1493 Tries to create the term of an already existing atom from the
1495 string name with length len and encoding encode. NULL characters
1496 are treated as any other characters.
1497 If the atom already exists, this function stores the term in
1499 *atom and returns true, otherwise false. Also returns false if
1500 len exceeds the maximum length allowed for an atom (255 charac‐
1501 ters).
1502 ERL_NIF_TERM enif_make_int(ErlNifEnv* env, int i)
1504 Creates an integer term.
1506 ERL_NIF_TERM enif_make_int64(ErlNifEnv* env, ErlNifSInt64 i)
1508 Creates an integer term from a signed 64-bit integer.
1510 ERL_NIF_TERM enif_make_list(ErlNifEnv* env, unsigned cnt, ...)
1512 Creates an ordinary list term of length cnt. Expects cnt number
1514 of arguments (after cnt) of type ERL_NIF_TERM as the elements of
1515 the list.
1516 Returns an empty list if cnt is 0.
1518 ERL_NIF_TERM enif_make_list1(ErlNifEnv* env, ERL_NIF_TERM e1)
1520 ERL_NIF_TERM enif_make_list2(ErlNifEnv* env,
1521 ERL_NIF_TERM e1, ERL_NIF_TERM e2)
1522 ERL_NIF_TERM enif_make_list3(ErlNifEnv* env,
1523 ERL_NIF_TERM e1, ERL_NIF_TERM e2, ERL_NIF_TERM e3)
1524 ERL_NIF_TERM enif_make_list4(ErlNifEnv* env,
1525 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)
1526 ERL_NIF_TERM enif_make_list5(ErlNifEnv* env,
1527 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)
1528 ERL_NIF_TERM enif_make_list6(ErlNifEnv* env,
1529 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)
1530 ERL_NIF_TERM enif_make_list7(ErlNifEnv* env,
1531 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)
1532 ERL_NIF_TERM enif_make_list8(ErlNifEnv* env,
1533 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)
1534 ERL_NIF_TERM enif_make_list9(ErlNifEnv* env,
1535 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)
1536 Creates an ordinary list term with length indicated by the func‐
1538 tion name. Prefer these functions (macros) over the variadic
1539 enif_make_list to get a compile-time error if the number of
1540 arguments does not match.
1541 ERL_NIF_TERM enif_make_list_cell(ErlNifEnv*
1543 env, ERL_NIF_TERM head, ERL_NIF_TERM tail)
1544 Creates a list cell [head | tail].
1546 ERL_NIF_TERM enif_make_list_from_array(ErlNifEnv* env, const
1548 ERL_NIF_TERM
1549 arr[], unsigned cnt)
1550 Creates an ordinary list containing the elements of array arr of
1552 length cnt.
1553 Returns an empty list if cnt is 0.
1555 ERL_NIF_TERM enif_make_long(ErlNifEnv* env, long int i)
1557 Creates an integer term from a long int.
1559 int enif_make_map_put(ErlNifEnv* env,
1561 ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM value,
1562 ERL_NIF_TERM* map_out)
1563 Makes a copy of map map_in and inserts key with value. If key
1565 already exists in map_in, the old associated value is replaced
1566 by value.
1567 If successful, this function sets *map_out to the new map and
1569 returns true. Returns false if map_in is not a map.
1570 The map_in term must belong to environment env.
1572 int enif_make_map_remove(ErlNifEnv* env,
1574 ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM* map_out)
1575 If map map_in contains key, this function makes a copy of map_in
1577 in *map_out, and removes key and the associated value. If map
1578 map_in does not contain key, *map_out is set to map_in.
1579 Returns true on success, or false if map_in is not a map.
1581 The map_in term must belong to environment env.
1583 int enif_make_map_update(ErlNifEnv* env,
1585 ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM new_value,
1586 ERL_NIF_TERM* map_out)
1587 Makes a copy of map map_in and replace the old associated value
1589 for key with new_value.
1590 If successful, this function sets *map_out to the new map and
1592 returns true. Returns false if map_in is not a map or if it does
1593 not contain key.
1594 The map_in term must belong to environment env.
1596 int enif_make_map_from_arrays(ErlNifEnv* env, ERL_NIF_TERM keys[],
1598 ERL_NIF_TERM values[], size_t cnt, ERL_NIF_TERM *map_out)
1599 Makes a map term from the given keys and values.
1601 If successful, this function sets *map_out to the new map and
1603 returns true. Returns false there are any duplicate keys.
1604 All keys and values must belong to env.
1606 unsigned char *enif_make_new_binary(ErlNifEnv*
1608 env, size_t size, ERL_NIF_TERM* termp)
1609 Allocates a binary of size size bytes and creates an owning
1611 term. The binary data is mutable until the calling NIF returns.
1612 This is a quick way to create a new binary without having to use
1613 ErlNifBinary. The drawbacks are that the binary cannot be kept
1614 between NIF calls and it cannot be reallocated.
1615 Returns a pointer to the raw binary data and sets *termp to the
1617 binary term.
1618 ERL_NIF_TERM enif_make_new_map(ErlNifEnv* env)
1620 Makes an empty map term.
1622 ERL_NIF_TERM enif_make_pid(ErlNifEnv* env, const ErlNifPid* pid)
1624 Makes a pid term from *pid.
1626 ERL_NIF_TERM enif_make_ref(ErlNifEnv* env)
1628 Creates a reference like erlang:make_ref/0.
1630 ERL_NIF_TERM enif_make_resource(ErlNifEnv* env, void* obj)
1632 Creates an opaque handle to a memory-managed resource object
1634 obtained by enif_alloc_resource. No ownership transfer is done,
1635 as the resource object still needs to be released by
1636 enif_release_resource. However, notice that the call to
1637 enif_release_resource can occur immediately after obtaining the
1638 term from enif_make_resource, in which case the resource object
1639 is deallocated when the term is garbage collected. For more
1640 details, see the example of creating and returning a resource
1641 object in the User's Guide.
1642 Note:
1644 Since ERTS 9.0 (OTP-20.0), resource terms have a defined behav‐
1645 ior when compared and serialized through term_to_binary or
1646 passed between nodes.
1647 * Two resource terms will compare equal if and only if they
1649 would yield the same resource object pointer when passed to
1650 enif_get_resource.
1651 * A resource term can be serialized with term_to_binary and
1653 later be fully recreated if the resource object is still
1654 alive when binary_to_term is called. A stale resource term
1655 will be returned from binary_to_term if the resource object
1656 has been deallocated. enif_get_resource will return false
1657 for stale resource terms.
1658 The same principles of serialization apply when passing
1660 resource terms in messages to remote nodes and back again. A
1661 resource term will act stale on all nodes except the node
1662 where its resource object is still alive in memory.
1663 Before ERTS 9.0 (OTP-20.0), all resource terms did compare equal
1665 to each other and to empty binaries (<<>>). If serialized, they
1666 would be recreated as plain empty binaries.
1667 ERL_NIF_TERM enif_make_resource_binary(ErlNifEnv* env, void* obj, const
1670 void* data, size_t size)
1671 Creates a binary term that is memory-managed by a resource
1673 object obj obtained by enif_alloc_resource. The returned binary
1674 term consists of size bytes pointed to by data. This raw binary
1675 data must be kept readable and unchanged until the destructor of
1676 the resource is called. The binary data can be stored external
1677 to the resource object, in which case the destructor is respon‐
1678 sible for releasing the data.
1679 Several binary terms can be managed by the same resource object.
1681 The destructor is not called until the last binary is garbage
1682 collected. This can be useful to return different parts of a
1683 larger binary buffer.
1684 As with enif_make_resource, no ownership transfer is done. The
1686 resource still needs to be released with enif_release_resource.
1687 int enif_make_reverse_list(ErlNifEnv* env, ERL_NIF_TERM list_in,
1689 ERL_NIF_TERM *list_out)
1690 Sets *list_out to the reverse list of the list list_in and
1692 returns true, or returns false if list_in is not a list.
1693 This function is only to be used on short lists, as a copy is
1695 created of the list, which is not released until after the NIF
1696 returns.
1697 The list_in term must belong to environment env.
1699 ERL_NIF_TERM enif_make_string(ErlNifEnv* env,
1701 const char* string, ErlNifCharEncoding encoding)
1702 Creates a list containing the characters of the NULL-terminated
1704 string string with encoding encoding.
1705 ERL_NIF_TERM enif_make_string_len(ErlNifEnv*
1707 env, const char* string, size_t len, ErlNifCharEncoding
1708 encoding)
1709 Creates a list containing the characters of the string string
1711 with length len and encoding encoding. NULL characters are
1712 treated as any other characters.
1713 ERL_NIF_TERM enif_make_sub_binary(ErlNifEnv*
1715 env, ERL_NIF_TERM bin_term, size_t pos, size_t size)
1716 Makes a subbinary of binary bin_term, starting at zero-based
1718 position pos with a length of size bytes. bin_term must be a
1719 binary or bitstring. pos+size must be less or equal to the num‐
1720 ber of whole bytes in bin_term.
1721 ERL_NIF_TERM enif_make_tuple(ErlNifEnv* env,
1723 unsigned cnt, ...)
1724 Creates a tuple term of arity cnt. Expects cnt number of argu‐
1726 ments (after cnt) of type ERL_NIF_TERM as the elements of the
1727 tuple.
1728 ERL_NIF_TERM enif_make_tuple1(ErlNifEnv* env,
1730 ERL_NIF_TERM e1)
1731 ERL_NIF_TERM enif_make_tuple2(ErlNifEnv* env,
1732 ERL_NIF_TERM e1, ERL_NIF_TERM e2)
1733 ERL_NIF_TERM enif_make_tuple3(ErlNifEnv* env,
1734 ERL_NIF_TERM e1, ERL_NIF_TERM e2, ERL_NIF_TERM e3)
1735 ERL_NIF_TERM enif_make_tuple4(ErlNifEnv* env,
1736 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)
1737 ERL_NIF_TERM enif_make_tuple5(ErlNifEnv* env,
1738 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)
1739 ERL_NIF_TERM enif_make_tuple6(ErlNifEnv* env,
1740 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)
1741 ERL_NIF_TERM enif_make_tuple7(ErlNifEnv* env,
1742 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)
1743 ERL_NIF_TERM enif_make_tuple8(ErlNifEnv* env,
1744 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)
1745 ERL_NIF_TERM enif_make_tuple9(ErlNifEnv* env,
1746 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)
1747 Creates a tuple term with length indicated by the function name.
1749 Prefer these functions (macros) over the variadic
1750 enif_make_tuple to get a compile-time error if the number of
1751 arguments does not match.
1752 ERL_NIF_TERM enif_make_tuple_from_array(ErlNifEnv* env, const
1754 ERL_NIF_TERM
1755 arr[], unsigned cnt)
1756 Creates a tuple containing the elements of array arr of length
1758 cnt.
1759 ERL_NIF_TERM enif_make_uint(ErlNifEnv* env, unsigned int i)
1761 Creates an integer term from an unsigned int.
1763 ERL_NIF_TERM enif_make_uint64(ErlNifEnv* env, ErlNifUInt64 i)
1765 Creates an integer term from an unsigned 64-bit integer.
1767 ERL_NIF_TERM enif_make_ulong(ErlNifEnv* env, unsigned long i)
1769 Creates an integer term from an unsigned long int.
1771 ERL_NIF_TERM enif_make_unique_integer(ErlNifEnv
1773 *env, ErlNifUniqueInteger properties)
1774 Returns a unique integer with the same properties as specified
1776 by erlang:unique_integer/1.
1777 env is the environment to create the integer in.
1779 ERL_NIF_UNIQUE_POSITIVE and ERL_NIF_UNIQUE_MONOTONIC can be
1781 passed as the second argument to change the properties of the
1782 integer returned. They can be combined by OR:ing the two values
1783 together.
1784 See also ErlNifUniqueInteger.
1786 int enif_map_iterator_create(ErlNifEnv *env,
1788 ERL_NIF_TERM map, ErlNifMapIterator *iter, ErlNifMapIteratorEn‐
1789 try
1790 entry)
1791 Creates an iterator for the map map by initializing the struc‐
1793 ture pointed to by iter. Argument entry determines the start
1794 position of the iterator: ERL_NIF_MAP_ITERATOR_FIRST or
1795 ERL_NIF_MAP_ITERATOR_LAST.
1796 Returns true on success, or false if map is not a map.
1798 A map iterator is only useful during the lifetime of environment
1800 env that the map belongs to. The iterator must be destroyed by
1801 calling enif_map_iterator_destroy:
1802 ERL_NIF_TERM key, value;
1804 ErlNifMapIterator iter;
1805 enif_map_iterator_create(env, my_map, &iter, ERL_NIF_MAP_ITERATOR_FIRST);
1806 while (enif_map_iterator_get_pair(env, &iter, &key, &value)) {
1808 do_something(key,value);
1809 enif_map_iterator_next(env, &iter);
1810 }
1811 enif_map_iterator_destroy(env, &iter);
1812 Note:
1814 The key-value pairs of a map have no defined iteration order.
1815 The only guarantee is that the iteration order of a single map
1816 instance is preserved during the lifetime of the environment
1817 that the map belongs to.
1818 void enif_map_iterator_destroy(ErlNifEnv *env,
1821 ErlNifMapIterator *iter)
1822 Destroys a map iterator created by enif_map_iterator_create.
1824 int enif_map_iterator_get_pair(ErlNifEnv *env,
1826 ErlNifMapIterator *iter, ERL_NIF_TERM *key, ERL_NIF_TERM
1827 *value)
1828 Gets key and value terms at the current map iterator position.
1830 On success, sets *key and *value and returns true. Returns false
1832 if the iterator is positioned at head (before first entry) or
1833 tail (beyond last entry).
1834 int enif_map_iterator_is_head(ErlNifEnv *env,
1836 ErlNifMapIterator *iter)
1837 Returns true if map iterator iter is positioned before the first
1839 entry.
1840 int enif_map_iterator_is_tail(ErlNifEnv *env,
1842 ErlNifMapIterator *iter)
1843 Returns true if map iterator iter is positioned after the last
1845 entry.
1846 int enif_map_iterator_next(ErlNifEnv *env,
1848 ErlNifMapIterator *iter)
1849 Increments map iterator to point to the next key-value entry.
1851 Returns true if the iterator is now positioned at a valid key-
1853 value entry, or false if the iterator is positioned at the tail
1854 (beyond the last entry).
1855 int enif_map_iterator_prev(ErlNifEnv *env,
1857 ErlNifMapIterator *iter)
1858 Decrements map iterator to point to the previous key-value
1860 entry.
1861 Returns true if the iterator is now positioned at a valid key-
1863 value entry, or false if the iterator is positioned at the head
1864 (before the first entry).
1865 int enif_monitor_process(ErlNifEnv* caller_env,
1867 void* obj, const ErlNifPid* target_pid, ErlNifMonitor* mon)
1868 Starts monitoring a process from a resource. When a process is
1870 monitored, a process exit results in a call to the provided down
1871 callback associated with the resource type.
1872 Argument obj is pointer to the resource to hold the monitor and
1874 *target_pid identifies the local process to be monitored.
1875 If mon is not NULL, a successful call stores the identity of the
1877 monitor in the ErlNifMonitor struct pointed to by mon. This
1878 identifier is used to refer to the monitor for later removal
1879 with enif_demonitor_process or compare with enif_compare_moni‐
1880 tors. A monitor is automatically removed when it triggers or
1881 when the resource is deallocated.
1882 Argument caller_env is the environment of the calling process or
1884 callback. Must only be NULL if calling from a custom thread.
1885 Returns 0 on success, < 0 if no down callback is provided, and >
1887 0 if the process is no longer alive.
1888 This function is only thread-safe when the emulator with SMP
1890 support is used. It can only be used in a non-SMP emulator from
1891 a NIF-calling thread.
1892 ErlNifTime enif_monotonic_time(ErlNifTimeUnit time_unit)
1894 Returns the current Erlang monotonic time. Notice that it is
1896 not uncommon with negative values.
1897 time_unit is the time unit of the returned value.
1899 Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
1901 argument, or if called from a thread that is not a scheduler
1902 thread.
1903 See also ErlNifTime and ErlNifTimeUnit.
1905 ErlNifMutex *enif_mutex_create(char *name)
1907 Same as erl_drv_mutex_create.
1909 void enif_mutex_destroy(ErlNifMutex *mtx)
1911 Same as erl_drv_mutex_destroy.
1913 void enif_mutex_lock(ErlNifMutex *mtx)
1915 Same as erl_drv_mutex_lock.
1917 char*enif_mutex_name(ErlNifMutex* mtx)
1919 Same as erl_drv_mutex_name.
1921 int enif_mutex_trylock(ErlNifMutex *mtx)
1923 Same as erl_drv_mutex_trylock.
1925 void enif_mutex_unlock(ErlNifMutex *mtx)
1927 Same as erl_drv_mutex_unlock.
1929 ERL_NIF_TERM enif_now_time(ErlNifEnv *env)
1931 Returns an erlang:now() time stamp.
1933 This function is deprecated.
1935 ErlNifResourceType *enif_open_resource_type(ErlNifEnv* env, const char*
1937 module_str, const char* name, ErlNifResourceDtor* dtor,
1938 ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
1939 Creates or takes over a resource type identified by the string
1941 name and gives it the destructor function pointed to by dtor.
1942 Argument flags can have the following values:
1943 ERL_NIF_RT_CREATE:
1945 Creates a new resource type that does not already exist.
1946 ERL_NIF_RT_TAKEOVER:
1948 Opens an existing resource type and takes over ownership of
1949 all its instances. The supplied destructor dtor is called
1950 both for existing instances and new instances not yet cre‐
1951 ated by the calling NIF library.
1952 The two flag values can be combined with bitwise OR. The
1954 resource type name is local to the calling module. Argument mod‐
1955 ule_str is not (yet) used and must be NULL. dtor can be NULL if
1956 no destructor is needed.
1957 On success, the function returns a pointer to the resource type
1959 and *tried is set to either ERL_NIF_RT_CREATE or
1960 ERL_NIF_RT_TAKEOVER to indicate what was done. On failure,
1961 returns NULL and sets *tried to flags. It is allowed to set
1962 tried to NULL.
1963 Notice that enif_open_resource_type is only allowed to be called
1965 in the two callbacks load and upgrade.
1966 See also enif_open_resource_type_x.
1968 ErlNifResourceType *enif_open_resource_type_x(ErlNifEnv* env, const
1970 char* name, const ErlNifResourceTypeInit* init,
1971 ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
1972 Same as enif_open_resource_type except it accepts additional
1974 callback functions for resource types that are used together
1975 with enif_select and enif_monitor_process.
1976 Argument init is a pointer to an ErlNifResourceTypeInit struc‐
1978 ture that contains the function pointers for destructor, down
1979 and stop callbacks for the resource type.
1980 int enif_port_command(ErlNifEnv* env, const
1982 ErlNifPort* to_port, ErlNifEnv *msg_env, ERL_NIF_TERM msg)
1983 Works as erlang:port_command/2, except that it is always com‐
1985 pletely asynchronous.
1986 env:
1988 The environment of the calling process. Must not be NULL.
1989 *to_port:
1991 The port ID of the receiving port. The port ID is to refer
1992 to a port on the local node.
1993 msg_env:
1995 The environment of the message term. Can be a process inde‐
1996 pendent environment allocated with enif_alloc_env or NULL.
1997 msg:
1999 The message term to send. The same limitations apply as on
2000 the payload to erlang:port_command/2.
2001 Using a msg_env of NULL is an optimization, which groups
2003 together calls to enif_alloc_env, enif_make_copy, enif_port_com‐
2004 mand, and enif_free_env into one call. This optimization is only
2005 useful when a majority of the terms are to be copied from env to
2006 msg_env.
2007 Returns true if the command is successfully sent. Returns false
2009 if the command fails, for example:
2010 * *to_port does not refer to a local port.
2012 * The currently executing process (that is, the sender) is not
2014 alive.
2015 * msg is invalid.
2017 See also enif_get_local_port.
2019 void *enif_priv_data(ErlNifEnv* env)
2021 Returns the pointer to the private data that was set by load or
2023 upgrade.
2024 ERL_NIF_TERM enif_raise_exception(ErlNifEnv*
2026 env, ERL_NIF_TERM reason)
2027 Creates an error exception with the term reason to be returned
2029 from a NIF, and associates it with environment env. Once a NIF
2030 or any function it calls invokes enif_raise_exception, the run‐
2031 time ensures that the exception it creates is raised when the
2032 NIF returns, even if the NIF attempts to return a non-exception
2033 term instead.
2034 The return value from enif_raise_exception can only be used as
2036 the return value from the NIF that invoked it (directly or indi‐
2037 rectly) or be passed to enif_is_exception, but not to any other
2038 NIF API function.
2039 See also enif_has_pending_exception and enif_make_badarg.
2041 void *enif_realloc(void* ptr, size_t size)
2043 Reallocates memory allocated by enif_alloc to size bytes.
2045 Returns NULL if the reallocation fails.
2047 The returned pointer is suitably aligned for any built-in type
2049 that fit in the allocated memory.
2050 int enif_realloc_binary(ErlNifBinary* bin, size_t size)
2052 Changes the size of a binary bin. The source binary can be read-
2054 only, in which case it is left untouched and a mutable copy is
2055 allocated and assigned to *bin.
2056 Returns true on success, or false if memory allocation failed.
2058 void enif_release_binary(ErlNifBinary* bin)
2060 Releases a binary obtained from enif_alloc_binary.
2062 void enif_release_resource(void* obj)
2064 Removes a reference to resource object obj obtained from
2066 enif_alloc_resource. The resource object is destructed when the
2067 last reference is removed. Each call to enif_release_resource
2068 must correspond to a previous call to enif_alloc_resource or
2069 enif_keep_resource. References made by enif_make_resource can
2070 only be removed by the garbage collector.
2071 ErlNifRWLock *enif_rwlock_create(char *name)
2073 Same as erl_drv_rwlock_create.
2075 void enif_rwlock_destroy(ErlNifRWLock *rwlck)
2077 Same as erl_drv_rwlock_destroy.
2079 char*enif_rwlock_name(ErlNifRWLock* rwlck)
2081 Same as erl_drv_rwlock_name.
2083 void enif_rwlock_rlock(ErlNifRWLock *rwlck)
2085 Same as erl_drv_rwlock_rlock.
2087 void enif_rwlock_runlock(ErlNifRWLock *rwlck)
2089 Same as erl_drv_rwlock_runlock.
2091 void enif_rwlock_rwlock(ErlNifRWLock *rwlck)
2093 Same as erl_drv_rwlock_rwlock.
2095 void enif_rwlock_rwunlock(ErlNifRWLock *rwlck)
2097 Same as erl_drv_rwlock_rwunlock.
2099 int enif_rwlock_tryrlock(ErlNifRWLock *rwlck)
2101 Same as erl_drv_rwlock_tryrlock.
2103 int enif_rwlock_tryrwlock(ErlNifRWLock *rwlck)
2105 Same as erl_drv_rwlock_tryrwlock.
2107 ERL_NIF_TERM enif_schedule_nif(ErlNifEnv* env,
2109 const char* fun_name, int flags, ERL_NIF_TERM (*fp)(ErlNifEnv*
2110 env, int
2111 argc, const ERL_NIF_TERM argv[]), int argc, const ERL_NIF_TERM
2112 argv[])
2113 Schedules NIF fp to execute. This function allows an application
2115 to break up long-running work into multiple regular NIF calls or
2116 to schedule a dirty NIF to execute on a dirty scheduler thread.
2117 fun_name:
2119 Provides a name for the NIF that is scheduled for execution.
2120 If it cannot be converted to an atom, enif_schedule_nif
2121 returns a badarg exception.
2122 flags:
2124 Must be set to 0 for a regular NIF. If the emulator was
2125 built with dirty scheduler support enabled, flags can be set
2126 to either ERL_NIF_DIRTY_JOB_CPU_BOUND if the job is expected
2127 to be CPU-bound, or ERL_NIF_DIRTY_JOB_IO_BOUND for jobs that
2128 will be I/O-bound. If dirty scheduler threads are not avail‐
2129 able in the emulator, an attempt to schedule such a job
2130 results in a notsup exception.
2131 argc and argv:
2133 Can either be the originals passed into the calling NIF, or
2134 can be values created by the calling NIF.
2135 The calling NIF must use the return value of enif_schedule_nif
2137 as its own return value.
2138 Be aware that enif_schedule_nif, as its name implies, only
2140 schedules the NIF for future execution. The calling NIF does not
2141 block waiting for the scheduled NIF to execute and return. This
2142 means that the calling NIF cannot expect to receive the sched‐
2143 uled NIF return value and use it for further operations.
2144 int enif_select(ErlNifEnv* env, ErlNifEvent event, enum ErlNifSelect‐
2146 Flags mode, void* obj, const ErlNifPid* pid, ERL_NIF_TERM ref)
2147 This function can be used to receive asynchronous notifications
2149 when OS-specific event objects become ready for either read or
2150 write operations.
2151 Argument event identifies the event object. On Unix systems, the
2153 functions select/poll are used. The event object must be a
2154 socket, pipe or other file descriptor object that select/poll
2155 can use.
2156 Argument mode describes the type of events to wait for. It can
2158 be ERL_NIF_SELECT_READ, ERL_NIF_SELECT_WRITE or a bitwise OR
2159 combination to wait for both. It can also be ERL_NIF_SELECT_STOP
2160 which is described further below. When a read or write event is
2161 triggered, a notification message like this is sent to the
2162 process identified by pid:
2163 {select, Obj, Ref, ready_input | ready_output}
2165 ready_input or ready_output indicates if the event object is
2167 ready for reading or writing.
2168 Argument pid may be NULL to indicate the calling process.
2170 Argument obj is a resource object obtained from
2172 enif_alloc_resource. The purpose of the resource objects is as a
2173 container of the event object to manage its state and lifetime.
2174 A handle to the resource is received in the notification message
2175 as Obj.
2176 Argument ref must be either a reference obtained from
2178 erlang:make_ref/0 or the atom undefined. It will be passed as
2179 Ref in the notifications. If a selective receive statement is
2180 used to wait for the notification then a reference created just
2181 before the receive will exploit a runtime optimization that
2182 bypasses all earlier received messages in the queue.
2183 The notifications are one-shot only. To receive further notifi‐
2185 cations of the same type (read or write), repeated calls to
2186 enif_select must be made after receiving each notification.
2187 Use ERL_NIF_SELECT_STOP as mode in order to safely close an
2189 event object that has been passed to enif_select. The stop call‐
2190 back of the resource obj will be called when it is safe to close
2191 the event object. This safe way of closing event objects must be
2192 used even if all notifications have been received and no further
2193 calls to enif_select have been made.
2194 The first call to enif_select for a specific OS event will
2196 establish a relation between the event object and the containing
2197 resource. All subsequent calls for an event must pass its con‐
2198 taining resource as argument obj. The relation is dissolved when
2199 enif_select has been called with mode as ERL_NIF_SELECT_STOP and
2200 the corresponding stop callback has returned. A resource can
2201 contain several event objects but one event object can only be
2202 contained within one resource. A resource will not be destructed
2203 until all its contained relations have been dissolved.
2204 Note:
2206 Use enif_monitor_process together with enif_select to detect
2207 failing Erlang processes and prevent them from causing permanent
2208 leakage of resources and their contained OS event objects.
2209 Returns a non-negative value on success where the following bits
2212 can be set:
2213 ERL_NIF_SELECT_STOP_CALLED:
2215 The stop callback was called directly by enif_select.
2216 ERL_NIF_SELECT_STOP_SCHEDULED:
2218 The stop callback was scheduled to run on some other thread
2219 or later by this thread.
2220 Returns a negative value if the call failed where the following
2222 bits can be set:
2223 ERL_NIF_SELECT_INVALID_EVENT:
2225 Argument event is not a valid OS event object.
2226 ERL_NIF_SELECT_FAILED:
2228 The system call failed to add the event object to the poll
2229 set.
2230 Note:
2232 Use bitwise AND to test for specific bits in the return value.
2233 New significant bits may be added in future releases to give
2234 more detailed information for both failed and successful calls.
2235 Do NOT use equality tests like ==, as that may cause your appli‐
2236 cation to stop working.
2237 Example:
2239 retval = enif_select(env, fd, ERL_NIF_SELECT_STOP, resource, ref);
2241 if (retval < 0) {
2242 /* handle error */
2243 }
2244 /* Success! */
2245 if (retval & ERL_NIF_SELECT_STOP_CALLED) {
2246 /* ... */
2247 }
2248 ErlNifPid *enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)
2252 Initializes the ErlNifPid variable at *pid to represent the
2254 calling process.
2255 Returns pid if successful, or NULL if caller_env is not a
2257 process bound environment.
2258 int enif_send(ErlNifEnv* caller_env,
2260 ErlNifPid* to_pid, ErlNifEnv* msg_env, ERL_NIF_TERM msg)
2261 Sends a message to a process.
2263 caller_env:
2265 The environment of the calling process or callback. Must be
2266 NULL only if calling from a custom thread not spawned by
2267 ERTS.
2268 *to_pid:
2270 The pid of the receiving process. The pid is to refer to a
2271 process on the local node.
2272 msg_env:
2274 The environment of the message term. Must be a process inde‐
2275 pendent environment allocated with enif_alloc_env or NULL.
2276 msg:
2278 The message term to send.
2279 Returns true if the message is successfully sent. Returns false
2281 if the send operation fails, that is:
2282 * *to_pid does not refer to an alive local process.
2284 * The currently executing process (that is, the sender) is not
2286 alive.
2287 The message environment msg_env with all its terms (including
2289 msg) is invalidated by a successful call to enif_send. The envi‐
2290 ronment is to either be freed with enif_free_env of cleared for
2291 reuse with enif_clear_env.
2292 If msg_env is set to NULL, the msg term is copied and the origi‐
2294 nal term and its environment is still valid after the call.
2295 This function is only thread-safe when the emulator with SMP
2297 support is used. It can only be used in a non-SMP emulator from
2298 a NIF-calling thread.
2299 Note:
2301 Passing msg_env as NULL is only supported as from ERTS 8.0
2302 (Erlang/OTP 19).
2303 unsigned enif_sizeof_resource(void* obj)
2306 Gets the byte size of resource object obj obtained by
2308 enif_alloc_resource.
2309 int enif_snprintf(char *str, size_t size, const
2311 char *format, ...)
2312 Similar to snprintf but this format string also accepts "%T",
2314 which formats Erlang terms of type ERL_NIF_TERM.
2315 This function is primarily intended for debugging purpose. It is
2317 not recommended to print very large terms with %T. The function
2318 may change errno, even if successful.
2319 void enif_system_info(ErlNifSysInfo
2321 *sys_info_ptr, size_t size)
2322 Same as driver_system_info.
2324 int enif_term_to_binary(ErlNifEnv *env,
2326 ERL_NIF_TERM term, ErlNifBinary *bin)
2327 Allocates a new binary with enif_alloc_binary and stores the
2329 result of encoding term according to the Erlang external term
2330 format.
2331 Returns true on success, or false if the allocation fails.
2333 See also erlang:term_to_binary/1 and enif_binary_to_term.
2335 int enif_thread_create(char *name,ErlNifTid
2337 *tid,void * (*func)(void *),void *args,ErlNifThreadOpts
2338 *opts)
2339 Same as erl_drv_thread_create.
2341 void enif_thread_exit(void *resp)
2343 Same as erl_drv_thread_exit.
2345 int enif_thread_join(ErlNifTid, void **respp)
2347 Same as erl_drv_thread_join.
2349 char*enif_thread_name(ErlNifTid tid)
2351 Same as erl_drv_thread_name.
2353 ErlNifThreadOpts *enif_thread_opts_create(char *name)
2355 Same as erl_drv_thread_opts_create.
2357 void enif_thread_opts_destroy(ErlNifThreadOpts *opts)
2359 Same as erl_drv_thread_opts_destroy.
2361 ErlNifTid enif_thread_self(void)
2363 Same as erl_drv_thread_self.
2365 int enif_thread_type(void)
2367 Determine the type of currently executing thread. A positive
2369 value indicates a scheduler thread while a negative value or
2370 zero indicates another type of thread. Currently the following
2371 specific types exist (which may be extended in the future):
2372 ERL_NIF_THR_UNDEFINED:
2374 Undefined thread that is not a scheduler thread.
2375 ERL_NIF_THR_NORMAL_SCHEDULER:
2377 A normal scheduler thread.
2378 ERL_NIF_THR_DIRTY_CPU_SCHEDULER:
2380 A dirty CPU scheduler thread.
2381 ERL_NIF_THR_DIRTY_IO_SCHEDULER:
2383 A dirty I/O scheduler thread.
2384 ErlNifTime enif_time_offset(ErlNifTimeUnit time_unit)
2386 Returns the current time offset between Erlang monotonic time
2388 and Erlang system time converted into the time_unit passed as
2389 argument.
2390 time_unit is the time unit of the returned value.
2392 Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
2394 argument or if called from a thread that is not a scheduler
2395 thread.
2396 See also ErlNifTime and ErlNifTimeUnit.
2398 void *enif_tsd_get(ErlNifTSDKey key)
2400 Same as erl_drv_tsd_get.
2402 int enif_tsd_key_create(char *name, ErlNifTSDKey *key)
2404 Same as erl_drv_tsd_key_create.
2406 void enif_tsd_key_destroy(ErlNifTSDKey key)
2408 Same as erl_drv_tsd_key_destroy.
2410 void enif_tsd_set(ErlNifTSDKey key, void *data)
2412 Same as erl_drv_tsd_set.
2414 int enif_vfprintf(FILE *stream, const char *format, va_list ap)
2416 Equivalent to enif_fprintf except that its called with a va_list
2419 instead of a variable number of arguments.
2420 int enif_vsnprintf(char *str, size_t size, const char *format, va_list
2422 ap)
2423 Equivalent to enif_snprintf except that its called with a
2426 va_list instead of a variable number of arguments.
2427 int enif_whereis_pid(ErlNifEnv *env,
2429 ERL_NIF_TERM name, ErlNifPid *pid)
2430 Looks up a process by its registered name.
2432 env:
2434 The environment of the calling process. Must be NULL only if
2435 calling from a created thread.
2436 name:
2438 The name of a registered process, as an atom.
2439 *pid:
2441 The ErlNifPid in which the resolved process id is stored.
2442 On success, sets *pid to the local process registered with name
2444 and returns true. If name is not a registered process, or is not
2445 an atom, false is returned and *pid is unchanged.
2446 Works as erlang:whereis/1, but restricted to processes. See
2448 enif_whereis_port to resolve registered ports.
2449 int enif_whereis_port(ErlNifEnv *env,
2451 ERL_NIF_TERM name, ErlNifPort *port)
2452 Looks up a port by its registered name.
2454 env:
2456 The environment of the calling process. Must be NULL only if
2457 calling from a created thread.
2458 name:
2460 The name of a registered port, as an atom.
2461 *port:
2463 The ErlNifPort in which the resolved port id is stored.
2464 On success, sets *port to the port registered with name and
2466 returns true. If name is not a registered port, or is not an
2467 atom, false is returned and *port is unchanged.
2468 Works as erlang:whereis/1, but restricted to ports. See
2470 enif_whereis_pid to resolve registered processes.
2471
2473 erlang:load_nif/2
2474Ericsson AB erts 10.3.5.2 erl_nif(3)