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_inspect_iovec()
298 * enif_free_iovec()
300 Typical usage when writing to a file descriptor looks like this:
302 int writeiovec(ErlNifEnv *env, ERL_NIF_TERM term, ERL_NIF_TERM *tail,
304 ErlNifIOQueue *q, int fd) {
305 ErlNifIOVec vec, *iovec = &vec;
307 SysIOVec *sysiovec;
308 int saved_errno;
309 int iovcnt, n;
310 if (!enif_inspect_iovec(env, 64, term, tail, &iovec))
312 return -2;
313 if (enif_ioq_size(q) > 0) {
315 /* If the I/O queue contains data we enqueue the iovec and
316 then peek the data to write out of the queue. */
317 if (!enif_ioq_enqv(q, iovec, 0))
318 return -3;
319 sysiovec = enif_ioq_peek(q, &iovcnt);
321 } else {
322 /* If the I/O queue is empty we skip the trip through it. */
323 iovcnt = iovec->iovcnt;
324 sysiovec = iovec->iov;
325 }
326 /* Attempt to write the data */
328 n = writev(fd, sysiovec, iovcnt);
329 saved_errno = errno;
330 if (enif_ioq_size(q) == 0) {
332 /* If the I/O queue was initially empty we enqueue any
333 remaining data into the queue for writing later. */
334 if (n >= 0 && !enif_ioq_enqv(q, iovec, n))
335 return -3;
336 } else {
337 /* Dequeue any data that was written from the queue. */
338 if (n > 0 && !enif_ioq_deq(q, n, NULL))
339 return -4;
340 }
341 /* return n, which is either number of bytes written or -1 if
343 some error happened */
344 errno = saved_errno;
345 return n;
346 }
347 Long-running NIFs:
349 As mentioned in the warning text at the beginning of this manual
350 page, it is of vital importance that a native function returns rel‐
351 atively fast. It is difficult to give an exact maximum amount of
352 time that a native function is allowed to work, but usually a well-
353 behaving native function is to return to its caller within 1 mil‐
354 lisecond. This can be achieved using different approaches. If you
355 have full control over the code to execute in the native function,
356 the best approach is to divide the work into multiple chunks of
357 work and call the native function multiple times. This is, however,
358 not always possible, for example when calling third-party
359 libraries.
360 The enif_consume_timeslice() function can be used to inform the
362 runtime system about the length of the NIF call. It is typically
363 always to be used unless the NIF executes very fast.
364 If the NIF call is too lengthy, this must be handled in one of the
366 following ways to avoid degraded responsiveness, scheduler load
367 balancing problems, and other strange behaviors:
368 Yielding NIF:
370 If the functionality of a long-running NIF can be split so that
371 its work can be achieved through a series of shorter NIF calls,
372 the application has two options:
373 * Make that series of NIF calls from the Erlang level.
375 * Call a NIF that first performs a chunk of the work, then
377 invokes the enif_schedule_nif function to schedule another NIF
378 call to perform the next chunk. The final call scheduled in
379 this manner can then return the overall result.
380 Breaking up a long-running function in this manner enables the VM
382 to regain control between calls to the NIFs.
383 This approach is always preferred over the other alternatives
385 described below. This both from a performance perspective and a
386 system characteristics perspective.
387 Threaded NIF:
389 This is accomplished by dispatching the work to another thread
390 managed by the NIF library, return from the NIF, and wait for the
391 result. The thread can send the result back to the Erlang process
392 using enif_send. Information about thread primitives is provided
393 below.
394 Dirty NIF:
396 Note:
399 Dirty NIF support is available only when the emulator is configured
400 with dirty scheduler support. As of ERTS version 9.0, dirty sched‐
401 uler support is enabled by default on the runtime system with SMP
402 support. The Erlang runtime without SMP support does not support
403 dirty schedulers even when the dirty scheduler support is explic‐
404 itly enabled. To check at runtime for the presence of dirty sched‐
405 uler threads, code can use the enif_system_info() API function.
406 A NIF that cannot be split and cannot execute in a millisecond or
409 less is called a "dirty NIF", as it performs work that the ordi‐
410 nary schedulers of the Erlang runtime system cannot handle
411 cleanly. Applications that make use of such functions must indi‐
412 cate to the runtime that the functions are dirty so they can be
413 handled specially. This is handled by executing dirty jobs on a
414 separate set of schedulers called dirty schedulers. A dirty NIF
415 executing on a dirty scheduler does not have the same duration
416 restriction as a normal NIF.
417 It is important to classify the dirty job correct. An I/O bound
419 job should be classified as such, and a CPU bound job should be
420 classified as such. If you should classify CPU bound jobs as I/O
421 bound jobs, dirty I/O schedulers might starve ordinary sched‐
422 ulers. I/O bound jobs are expected to either block waiting for
423 I/O, and/or spend a limited amount of time moving data.
424 To schedule a dirty NIF for execution, the application has two
426 options:
427 * Set the appropriate flags value for the dirty NIF in its Erl‐
429 NifFunc entry.
430 * Call enif_schedule_nif, pass to it a pointer to the dirty NIF
432 to be executed, and indicate with argument flags whether it
433 expects the operation to be CPU-bound or I/O-bound.
434 A job that alternates between I/O bound and CPU bound can be
436 reclassified and rescheduled using enif_schedule_nif so that it
437 executes on the correct type of dirty scheduler at all times. For
438 more information see the documentation of the erl(1) command line
439 arguments +SDcpu, and +SDio.
440 While a process executes a dirty NIF, some operations that commu‐
442 nicate with it can take a very long time to complete. Suspend or
443 garbage collection of a process executing a dirty NIF cannot be
444 done until the dirty NIF has returned. Thus, other processes
445 waiting for such operations to complete might have to wait for a
446 very long time. Blocking multi-scheduling, that is, calling
447 erlang:system_flag(multi_scheduling, block), can also take a very
448 long time to complete. This becaue all ongoing dirty operations
449 on all dirty schedulers must complete before the block operation
450 can complete.
451 Many operations communicating with a process executing a dirty
453 NIF can, however, complete while it executes the dirty NIF. For
454 example, retrieving information about it through
455 erlang:process_info, setting its group leader, register/unregis‐
456 ter its name, and so on.
457 Termination of a process executing a dirty NIF can only be com‐
459 pleted up to a certain point while it executes the dirty NIF. All
460 Erlang resources, such as its registered name and its ETS tables,
461 are released. All links and monitors are triggered. The execution
462 of the NIF is, however, not stopped. The NIF can safely continue
463 execution, allocate heap memory, and so on, but it is of course
464 better to stop executing as soon as possible. The NIF can check
465 whether a current process is alive using enif_is_cur‐
466 rent_process_alive. Communication using enif_send and
467 enif_port_command is also dropped when the sending process is not
468 alive. Deallocation of certain internal resources, such as
469 process heap and process control block, is delayed until the
470 dirty NIF has completed.
471
473 ERL_NIF_INIT(MODULE, ErlNifFunc funcs[], load, NULL, upgrade,
474 unload):
475 This is the magic macro to initialize a NIF library. It is to be
476 evaluated in global file scope.
477 MODULE is the name of the Erlang module as an identifier without
479 string quotations. It is stringified by the macro.
480 funcs is a static array of function descriptors for all the imple‐
482 mented NIFs in this library.
483 load, upgrade and unload are pointers to functions. One of load or
485 upgrade is called to initialize the library. unload is called to
486 release the library. All are described individually below.
487 The fourth argument NULL is ignored. It was earlier used for the
489 deprectated reload callback which is no longer supported since OTP
490 20.
491 If compiling a NIF for static inclusion through --enable-static-
493 nifs, you must define STATIC_ERLANG_NIF before the ERL_NIF_INIT
494 declaration.
495 int (*load)(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM
497 load_info):
498 load is called when the NIF library is loaded and no previously
499 loaded library exists for this module.
500 *priv_data can be set to point to some private data if the library
502 needs to keep a state between NIF calls. enif_priv_data returns
503 this pointer. *priv_data is initialized to NULL when load is
504 called.
505 load_info is the second argument to erlang:load_nif/2.
507 The library fails to load if load returns anything other than 0.
509 load can be NULL if initialization is not needed.
510 int (*upgrade)(ErlNifEnv* env, void** priv_data, void**
512 old_priv_data, ERL_NIF_TERM load_info):
513 upgrade is called when the NIF library is loaded and there is old
514 code of this module with a loaded NIF library.
515 Works as load, except that *old_priv_data already contains the
517 value set by the last call to load or upgrade for the old module
518 code. *priv_data is initialized to NULL when upgrade is called. It
519 is allowed to write to both *priv_data and *old_priv_data.
520 The library fails to load if upgrade returns anything other than 0
522 or if upgrade is NULL.
523 void (*unload)(ErlNifEnv* env, void* priv_data):
525 unload is called when the module code that the NIF library belongs
526 to is purged as old. New code of the same module may or may not
527 exist.
528
530 ERL_NIF_TERM:
531 Variables of type ERL_NIF_TERM can refer to any Erlang term. This
532 is an opaque type and values of it can only by used either as argu‐
533 ments to API functions or as return values from NIFs. All
534 ERL_NIF_TERMs belong to an environment (ErlNifEnv). A term cannot
535 be destructed individually, it is valid until its environment is
536 destructed.
537 ErlNifEnv:
539 ErlNifEnv represents an environment that can host Erlang terms. All
540 terms in an environment are valid as long as the environment is
541 valid. ErlNifEnv is an opaque type; pointers to it can only be
542 passed on to API functions. Two types of environments exist:
543 Process-bound environment:
545 Passed as the first argument to all NIFs. All function arguments
546 passed to a NIF belong to that environment. The return value from
547 a NIF must also be a term belonging to the same environment.
548 A process-bound environment contains transient information about
550 the calling Erlang process. The environment is only valid in the
551 thread where it was supplied as argument until the NIF returns.
552 It is thus useless and dangerous to store pointers to process-
553 bound environments between NIF calls.
554 Process-independent environment:
556 Created by calling enif_alloc_env. This environment can be used
557 to store terms between NIF calls and to send terms with
558 enif_send. A process-independent environment with all its terms
559 is valid until you explicitly invalidate it with enif_free_env or
560 enif_send.
561 All contained terms of a list/tuple/map must belong to the same
563 environment as the list/tuple/map itself. Terms can be copied
564 between environments with enif_make_copy.
565 ErlNifFunc:
567 typedef struct {
570 const char* name;
571 unsigned arity;
572 ERL_NIF_TERM (*fptr)(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
573 unsigned flags;
574 } ErlNifFunc;
575 Describes a NIF by its name, arity, and implementation.
577 fptr:
579 A pointer to the function that implements the NIF.
580 argv:
582 Contains the function arguments passed to the NIF.
583 argc:
585 The array length, that is, the function arity. argv[N-1] thus
586 denotes the Nth argument to the NIF. Notice that the argument
587 argc allows for the same C function to implement several Erlang
588 functions with different arity (but probably with the same name).
589 flags:
591 Is 0 for a regular NIF (and so its value can be omitted for stat‐
592 ically initialized ErlNifFunc instances).
593 flags can be used to indicate that the NIF is a dirty NIF that is
595 to be executed on a dirty scheduler thread.
596 If the dirty NIF is expected to be CPU-bound, its flags field is
598 to be set to ERL_NIF_DIRTY_JOB_CPU_BOUND or
599 ERL_NIF_DIRTY_JOB_IO_BOUND.
600 Note:
602 If one of the ERL_NIF_DIRTY_JOB_*_BOUND flags is set, and the run‐
603 time system has no support for dirty schedulers, the runtime system
604 refuses to load the NIF library.
605 ErlNifBinary:
608 typedef struct {
611 unsigned size;
612 unsigned char* data;
613 } ErlNifBinary;
614 ErlNifBinary contains transient information about an inspected
616 binary term. data is a pointer to a buffer of size bytes with the
617 raw content of the binary.
618 Notice that ErlNifBinary is a semi-opaque type and you are only
620 allowed to read fields size and data.
621 ErlNifBinaryToTerm:
623 An enumeration of the options that can be specified to
624 enif_binary_to_term. For default behavior, use value 0.
625 When receiving data from untrusted sources, use option
627 ERL_NIF_BIN2TERM_SAFE.
628 ErlNifMonitor:
630 This is an opaque data type that identifies a monitor.
631 The nif writer is to provide the memory for storing the monitor
633 when calling enif_monitor_process. The address of the data is not
634 stored by the runtime system, so ErlNifMonitor can be used as any
635 other data, it can be copied, moved in memory, forgotten, and so
636 on. To compare two monitors, enif_compare_monitors must be used.
637 ErlNifPid:
639 A process identifier (pid). In contrast to pid terms (instances of
640 ERL_NIF_TERM), ErlNifPids are self-contained and not bound to any
641 environment. ErlNifPid is an opaque type.
642 ErlNifPort:
644 A port identifier. In contrast to port ID terms (instances of
645 ERL_NIF_TERM), ErlNifPorts are self-contained and not bound to any
646 environment. ErlNifPort is an opaque type.
647 ErlNifResourceType:
649 Each instance of ErlNifResourceType represents a class of memory-
650 managed resource objects that can be garbage collected. Each
651 resource type has a unique name and a destructor function that is
652 called when objects of its type are released.
653 ErlNifResourceTypeInit:
655 typedef struct {
658 ErlNifResourceDtor* dtor;
659 ErlNifResourceStop* stop;
660 ErlNifResourceDown* down;
661 } ErlNifResourceTypeInit;
662 Initialization structure read by enif_open_resource_type_x.
664 ErlNifResourceDtor:
666 typedef void ErlNifResourceDtor(ErlNifEnv* env, void* obj);
669 The function prototype of a resource destructor function.
671 The obj argument is a pointer to the resource. The only allowed use
673 for the resource in the destructor is to access its user data one
674 final time. The destructor is guaranteed to be the last callback
675 before the resource is deallocated.
676 ErlNifResourceDown:
678 typedef void ErlNifResourceDown(ErlNifEnv* env, void* obj, const ErlNifPid* pid, const ErlNifMonitor* mon);
681 The function prototype of a resource down function, called on the
683 behalf of enif_monitor_process. obj is the resource, pid is the
684 identity of the monitored process that is exiting, and mon is the
685 identity of the monitor.
686 ErlNifResourceStop:
688 typedef void ErlNifResourceStop(ErlNifEnv* env, void* obj, ErlNifEvent event, int is_direct_call);
691 The function prototype of a resource stop function, called on the
693 behalf of enif_select. obj is the resource, event is OS event,
694 is_direct_call is true if the call is made directly from
695 enif_select or false if it is a scheduled call (potentially from
696 another thread).
697 ErlNifCharEncoding:
699 typedef enum {
702 ERL_NIF_LATIN1
703 }ErlNifCharEncoding;
704 The character encoding used in strings and atoms. The only sup‐
706 ported encoding is ERL_NIF_LATIN1 for ISO Latin-1 (8-bit ASCII).
707 ErlNifSysInfo:
709 Used by enif_system_info to return information about the runtime
710 system. Contains the same content as ErlDrvSysInfo.
711 ErlNifSInt64:
713 A native signed 64-bit integer type.
714 ErlNifUInt64:
716 A native unsigned 64-bit integer type.
717 ErlNifTime:
719 A signed 64-bit integer type for representation of time.
720 ErlNifTimeUnit:
722 An enumeration of time units supported by the NIF API:
723 ERL_NIF_SEC:
725 Seconds
726 ERL_NIF_MSEC:
728 Milliseconds
729 ERL_NIF_USEC:
731 Microseconds
732 ERL_NIF_NSEC:
734 Nanoseconds
735 ErlNifUniqueInteger:
737 An enumeration of the properties that can be requested from
738 enif_unique_integer. For default properties, use value 0.
739 ERL_NIF_UNIQUE_POSITIVE:
741 Return only positive integers.
742 ERL_NIF_UNIQUE_MONOTONIC:
744 Return only strictly monotonically increasing integer corre‐
745 sponding to creation time.
746 ErlNifHash:
748 An enumeration of the supported hash types that can be generated
749 using enif_hash.
750 ERL_NIF_INTERNAL_HASH:
752 Non-portable hash function that only guarantees the same hash for
753 the same term within one Erlang VM instance.
754 It takes 32-bit salt values and generates hashes within
756 0..2^32-1.
757 ERL_NIF_PHASH2:
759 Portable hash function that gives the same hash for the same
760 Erlang term regardless of machine architecture and ERTS version.
761 It ignores salt values and generates hashes within 0..2^27-1.
763 Slower than ERL_NIF_INTERNAL_HASH. It corresponds to
765 erlang:phash2/1.
766 SysIOVec:
768 A system I/O vector, as used by writev on Unix and WSASend on
769 Win32. It is used in ErlNifIOVec and by enif_ioq_peek.
770 ErlNifIOVec:
772 typedef struct {
775 int iovcnt;
776 size_t size;
777 SysIOVec* iov;
778 } ErlNifIOVec;
779 An I/O vector containing iovcnt SysIOVecs pointing to the data. It
781 is used by enif_inspect_iovec and enif_ioq_enqv.
782 ErlNifIOQueueOpts:
784 Options to configure a ErlNifIOQueue.
785 ERL_NIF_IOQ_NORMAL:
787 Create a normal I/O Queue
788
790 void *enif_alloc(size_t size)
791 Allocates memory of size bytes.
793 Returns NULL if the allocation fails.
795 The returned pointer is suitably aligned for any built-in type
797 that fit in the allocated memory.
798 int enif_alloc_binary(size_t size, ErlNifBinary* bin)
800 Allocates a new binary of size size bytes. Initializes the
802 structure pointed to by bin to refer to the allocated binary.
803 The binary must either be released by enif_release_binary or
804 ownership transferred to an Erlang term with enif_make_binary.
805 An allocated (and owned) ErlNifBinary can be kept between NIF
806 calls.
807 Returns true on success, or false if allocation fails.
809 ErlNifEnv *enif_alloc_env()
811 Allocates a new process-independent environment. The environment
813 can be used to hold terms that are not bound to any process.
814 Such terms can later be copied to a process environment with
815 enif_make_copy or be sent to a process as a message with
816 enif_send.
817 Returns pointer to the new environment.
819 void *enif_alloc_resource(ErlNifResourceType*
821 type, unsigned size)
822 Allocates a memory-managed resource object of type type and size
824 size bytes.
825 size_t enif_binary_to_term(ErlNifEnv *env,
827 const unsigned char* data, size_t size, ERL_NIF_TERM *term,
828 ErlNifBinaryToTerm opts)
829 Creates a term that is the result of decoding the binary data at
831 data, which must be encoded according to the Erlang external
832 term format. No more than size bytes are read from data. Argu‐
833 ment opts corresponds to the second argument to
834 erlang:binary_to_term/2 and must be either 0 or
835 ERL_NIF_BIN2TERM_SAFE.
836 On success, stores the resulting term at *term and returns the
838 number of bytes read. Returns 0 if decoding fails or if opts is
839 invalid.
840 See also ErlNifBinaryToTerm, erlang:binary_to_term/2, and
842 enif_term_to_binary.
843 void enif_clear_env(ErlNifEnv* env)
845 Frees all terms in an environment and clears it for reuse. The
847 environment must have been allocated with enif_alloc_env.
848 int enif_compare(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)
850 Returns an integer < 0 if lhs < rhs, 0 if lhs = rhs, and > 0 if
852 lhs > rhs. Corresponds to the Erlang operators ==, /=, =<, <,
853 >=, and > (but not =:= or =/=).
854 int enif_compare_monitors(const ErlNifMonitor
856 *monitor1, const ErlNifMonitor *monitor2)
857 Compares two ErlNifMonitors. Can also be used to imply some
859 artificial order on monitors, for whatever reason.
860 Returns 0 if monitor1 and monitor2 are equal, < 0 if monitor1 <
862 monitor2, and > 0 if monitor1 > monitor2.
863 void enif_cond_broadcast(ErlNifCond *cnd)
865 Same as erl_drv_cond_broadcast.
867 ErlNifCond *enif_cond_create(char *name)
869 Same as erl_drv_cond_create.
871 void enif_cond_destroy(ErlNifCond *cnd)
873 Same as erl_drv_cond_destroy.
875 void enif_cond_signal(ErlNifCond *cnd)
877 Same as erl_drv_cond_signal.
879 void enif_cond_wait(ErlNifCond *cnd, ErlNifMutex *mtx)
881 Same as erl_drv_cond_wait.
883 int enif_consume_timeslice(ErlNifEnv *env, int percent)
885 Gives the runtime system a hint about how much CPU time the cur‐
887 rent NIF call has consumed since the last hint, or since the
888 start of the NIF if no previous hint has been specified. The
889 time is specified as a percent of the timeslice that a process
890 is allowed to execute Erlang code until it can be suspended to
891 give time for other runnable processes. The scheduling timeslice
892 is not an exact entity, but can usually be approximated to about
893 1 millisecond.
894 Notice that it is up to the runtime system to determine if and
896 how to use this information. Implementations on some platforms
897 can use other means to determine consumed CPU time. Lengthy NIFs
898 should regardless of this frequently call enif_consume_timeslice
899 to determine if it is allowed to continue execution.
900 Argument percent must be an integer between 1 and 100. This
902 function must only be called from a NIF-calling thread, and
903 argument env must be the environment of the calling process.
904 Returns 1 if the timeslice is exhausted, otherwise 0. If 1 is
906 returned, the NIF is to return as soon as possible in order for
907 the process to yield.
908 This function is provided to better support co-operative sched‐
910 uling, improve system responsiveness, and make it easier to pre‐
911 vent misbehaviors of the VM because of a NIF monopolizing a
912 scheduler thread. It can be used to divide length work into a
913 number of repeated NIF calls without the need to create threads.
914 See also the warning text at the beginning of this manual page.
916 ErlNifTime enif_convert_time_unit(ErlNifTime
918 val, ErlNifTimeUnit from, ErlNifTimeUnit to)
919 Converts the val value of time unit from to the corresponding
921 value of time unit to. The result is rounded using the floor
922 function.
923 val:
925 Value to convert time unit for.
926 from:
928 Time unit of val.
929 to:
931 Time unit of returned value.
932 Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
934 argument.
935 See also ErlNifTime and ErlNifTimeUnit.
937 ERL_NIF_TERM enif_cpu_time(ErlNifEnv *)
939 Returns the CPU time in the same format as erlang:timestamp().
941 The CPU time is the time the current logical CPU has spent exe‐
942 cuting since some arbitrary point in the past. If the OS does
943 not support fetching this value, enif_cpu_time invokes
944 enif_make_badarg.
945 int enif_demonitor_process(ErlNifEnv* env, void* obj,
947 const ErlNifMonitor* mon)
948 Cancels a monitor created earlier with enif_monitor_process.
950 Argument obj is a pointer to the resource holding the monitor
951 and *mon identifies the monitor.
952 Returns 0 if the monitor was successfully identified and
954 removed. Returns a non-zero value if the monitor could not be
955 identified, which means it was either
956 * never created for this resource
958 * already cancelled
960 * already triggered
962 * just about to be triggered by a concurrent thread
964 This function is only thread-safe when the emulator with SMP
966 support is used. It can only be used in a non-SMP emulator from
967 a NIF-calling thread.
968 int enif_equal_tids(ErlNifTid tid1, ErlNifTid tid2)
970 Same as erl_drv_equal_tids.
972 void enif_free(void* ptr)
974 Frees memory allocated by enif_alloc.
976 void enif_free_env(ErlNifEnv* env)
978 Frees an environment allocated with enif_alloc_env. All terms
980 created in the environment are freed as well.
981 void enif_free_iovec(ErlNifIOvec* iov)
983 Frees an io vector returned from enif_inspect_iovec. This is
985 needed only if a NULL environment is passed to
986 enif_inspect_iovec.
987 ErlNifIOVec *iovec = NULL;
989 size_t max_elements = 128;
990 ERL_NIF_TERM tail;
991 if (!enif_inspect_iovec(NULL, max_elements, term, &tail, iovec))
992 return 0;
993 // Do things with the iovec
995 /* Free the iovector, possibly in another thread or nif function call */
997 enif_free_iovec(iovec);
998 int enif_get_atom(ErlNifEnv* env, ERL_NIF_TERM
1000 term, char* buf, unsigned size, ErlNifCharEncoding encode)
1001 Writes a NULL-terminated string in the buffer pointed to by buf
1003 of size size, consisting of the string representation of the
1004 atom term with encoding encode.
1005 Returns the number of bytes written (including terminating NULL
1007 character) or 0 if term is not an atom with maximum length of
1008 size-1.
1009 int enif_get_atom_length(ErlNifEnv* env,
1011 ERL_NIF_TERM term, unsigned* len, ErlNifCharEncoding encode)
1012 Sets *len to the length (number of bytes excluding terminating
1014 NULL character) of the atom term with encoding encode.
1015 Returns true on success, or false if term is not an atom.
1017 int enif_get_double(ErlNifEnv* env,
1019 ERL_NIF_TERM term, double* dp)
1020 Sets *dp to the floating-point value of term.
1022 Returns true on success, or false if term is not a float.
1024 int enif_get_int(ErlNifEnv* env, ERL_NIF_TERM
1026 term, int* ip)
1027 Sets *ip to the integer value of term.
1029 Returns true on success, or false if term is not an integer or
1031 is outside the bounds of type int.
1032 int enif_get_int64(ErlNifEnv* env, ERL_NIF_TERM
1034 term, ErlNifSInt64* ip)
1035 Sets *ip to the integer value of term.
1037 Returns true on success, or false if term is not an integer or
1039 is outside the bounds of a signed 64-bit integer.
1040 int enif_get_local_pid(ErlNifEnv* env,
1042 ERL_NIF_TERM term, ErlNifPid* pid)
1043 If term is the pid of a node local process, this function ini‐
1045 tializes the pid variable *pid from it and returns true. Other‐
1046 wise returns false. No check is done to see if the process is
1047 alive.
1048 int enif_get_local_port(ErlNifEnv* env,
1050 ERL_NIF_TERM term, ErlNifPort* port_id)
1051 If term identifies a node local port, this function initializes
1053 the port variable *port_id from it and returns true. Otherwise
1054 returns false. No check is done to see if the port is alive.
1055 int enif_get_list_cell(ErlNifEnv* env,
1057 ERL_NIF_TERM list, ERL_NIF_TERM* head, ERL_NIF_TERM* tail)
1058 Sets *head and *tail from list list.
1060 Returns true on success, or false if it is not a list or the
1062 list is empty.
1063 int enif_get_list_length(ErlNifEnv* env,
1065 ERL_NIF_TERM term, unsigned* len)
1066 Sets *len to the length of list term.
1068 Returns true on success, or false if term is not a proper list.
1070 int enif_get_long(ErlNifEnv* env, ERL_NIF_TERM
1072 term, long int* ip)
1073 Sets *ip to the long integer value of term.
1075 Returns true on success, or false if term is not an integer or
1077 is outside the bounds of type long int.
1078 int enif_get_map_size(ErlNifEnv* env,
1080 ERL_NIF_TERM term, size_t *size)
1081 Sets *size to the number of key-value pairs in the map term.
1083 Returns true on success, or false if term is not a map.
1085 int enif_get_map_value(ErlNifEnv* env,
1087 ERL_NIF_TERM map, ERL_NIF_TERM key, ERL_NIF_TERM* value)
1088 Sets *value to the value associated with key in the map map.
1090 Returns true on success, or false if map is not a map or if map
1092 does not contain key.
1093 int enif_get_resource(ErlNifEnv* env,
1095 ERL_NIF_TERM term, ErlNifResourceType* type, void** objp)
1096 Sets *objp to point to the resource object referred to by term.
1098 Returns true on success, or false if term is not a handle to a
1100 resource object of type type.
1101 int enif_get_string(ErlNifEnv* env,
1103 ERL_NIF_TERM list, char* buf, unsigned size,
1104 ErlNifCharEncoding encode)
1105 Writes a NULL-terminated string in the buffer pointed to by buf
1107 with size size, consisting of the characters in the string list.
1108 The characters are written using encoding encode.
1109 Returns one of the following:
1111 * The number of bytes written (including terminating NULL
1113 character)
1114 * -size if the string was truncated because of buffer space
1116 * 0 if list is not a string that can be encoded with encode or
1118 if size was < 1.
1119 The written string is always NULL-terminated, unless buffer size
1121 is < 1.
1122 int enif_get_tuple(ErlNifEnv* env, ERL_NIF_TERM
1124 term, int* arity, const ERL_NIF_TERM** array)
1125 If term is a tuple, this function sets *array to point to an
1127 array containing the elements of the tuple, and sets *arity to
1128 the number of elements. Notice that the array is read-only and
1129 (*array)[N-1] is the Nth element of the tuple. *array is unde‐
1130 fined if the arity of the tuple is zero.
1131 Returns true on success, or false if term is not a tuple.
1133 int enif_get_uint(ErlNifEnv* env, ERL_NIF_TERM
1135 term, unsigned int* ip)
1136 Sets *ip to the unsigned integer value of term.
1138 Returns true on success, or false if term is not an unsigned
1140 integer or is outside the bounds of type unsigned int.
1141 int enif_get_uint64(ErlNifEnv* env,
1143 ERL_NIF_TERM term, ErlNifUInt64* ip)
1144 Sets *ip to the unsigned integer value of term.
1146 Returns true on success, or false if term is not an unsigned
1148 integer or is outside the bounds of an unsigned 64-bit integer.
1149 int enif_get_ulong(ErlNifEnv* env, ERL_NIF_TERM
1151 term, unsigned long* ip)
1152 Sets *ip to the unsigned long integer value of term.
1154 Returns true on success, or false if term is not an unsigned
1156 integer or is outside the bounds of type unsigned long.
1157 int enif_getenv(const char* key, char* value,
1159 size_t *value_size)
1160 Same as erl_drv_getenv.
1162 int enif_has_pending_exception(ErlNifEnv* env,
1164 ERL_NIF_TERM* reason)
1165 Returns true if a pending exception is associated with the envi‐
1167 ronment env. If reason is a NULL pointer, ignore it. Otherwise,
1168 if a pending exception associated with env exists, set *reason
1169 to the value of the exception term. For example, if
1170 enif_make_badarg is called to set a pending badarg exception, a
1171 later call to enif_has_pending_exception(env, &reason) sets
1172 *reason to the atom badarg, then return true.
1173 See also enif_make_badarg and enif_raise_exception.
1175 ErlNifUInt64 enif_hash(ErlNifHash type, ERL_NIF_TERM term, ErlNifUInt64
1177 salt)
1178 Hashes term according to the specified ErlNifHash type.
1180 Ranges of taken salt (if any) and returned value depend on the
1182 hash type.
1183 int enif_inspect_binary(ErlNifEnv* env,
1185 ERL_NIF_TERM bin_term, ErlNifBinary* bin)
1186 Initializes the structure pointed to by bin with information
1188 about binary term bin_term.
1189 Returns true on success, or false if bin_term is not a binary.
1191 int enif_inspect_iolist_as_binary(ErlNifEnv*
1193 env, ERL_NIF_TERM term, ErlNifBinary* bin)
1194 Initializes the structure pointed to by bin with a continuous
1196 buffer with the same byte content as iolist. As with
1197 inspect_binary, the data pointed to by bin is transient and does
1198 not need to be released.
1199 Returns true on success, or false if iolist is not an iolist.
1201 int enif_inspect_iovec(ErlNifEnv*
1203 env, size_t max_elements, ERL_NIF_TERM iovec_term,
1204 ERL_NIF_TERM* tail,
1205 ErlNifIOVec** iovec)
1206 Fills iovec with the list of binaries provided in iovec_term.
1208 The number of elements handled in the call is limited to
1209 max_elements, and tail is set to the remainder of the list. Note
1210 that the output may be longer than max_elements on some plat‐
1211 forms.
1212 To create a list of binaries from an arbitrary iolist, use
1214 erlang:iolist_to_iovec/1.
1215 When calling this function, iovec should contain a pointer to
1217 NULL or a ErlNifIOVec structure that should be used if possible.
1218 e.g.
1219 /* Don't use a pre-allocated structure */
1221 ErlNifIOVec *iovec = NULL;
1222 enif_inspect_iovec(env, max_elements, term, &tail, &iovec);
1223 /* Use a stack-allocated vector as an optimization for vectors with few elements */
1225 ErlNifIOVec vec, *iovec = &vec;
1226 enif_inspect_iovec(env, max_elements, term, &tail, &iovec);
1227 The contents of the iovec is valid until the called nif function
1230 returns. If the iovec should be valid after the nif call
1231 returns, it is possible to call this function with a NULL envi‐
1232 ronment. If no environment is given the iovec owns the data in
1233 the vector and it has to be explicitly freed using
1234 enif_free_iovec.
1235 Returns true on success, or false if iovec_term not an iovec.
1237 ErlNifIOQueue *enif_ioq_create(ErlNifIOQueueOpts opts)
1239 Create a new I/O Queue that can be used to store data. opts has
1241 to be set to ERL_NIF_IOQ_NORMAL.
1242 void enif_ioq_destroy(ErlNifIOQueue *q)
1244 Destroy the I/O queue and free all of it's contents
1246 int enif_ioq_deq(ErlNifIOQueue *q, size_t count, size_t *size)
1248 Dequeue count bytes from the I/O queue. If size is not NULL, the
1250 new size of the queue is placed there.
1251 Returns true on success, or false if the I/O does not contain
1253 count bytes. On failure the queue is left un-altered.
1254 int enif_ioq_enq_binary(ErlNifIOQueue *q, ErlNifBinary *bin, size_t
1256 skip)
1257 Enqueue the bin into q skipping the first skip bytes.
1259 Returns true on success, or false if skip is greater than the
1261 size of bin. Any ownership of the binary data is transferred to
1262 the queue and bin is to be considered read-only for the rest of
1263 the NIF call and then as released.
1264 int enif_ioq_enqv(ErlNifIOQueue *q, ErlNifIOVec *iovec, size_t skip)
1266 Enqueue the iovec into q skipping the first skip bytes.
1268 Returns true on success, or false if skip is greater than the
1270 size of iovec.
1271 SysIOVec *enif_ioq_peek(ErlNifIOQueue *q, int *iovlen)
1273 Get the I/O queue as a pointer to an array of SysIOVecs. It also
1275 returns the number of elements in iovlen. This is the only way
1276 to get data out of the queue.
1277 Nothing is removed from the queue by this function, that must be
1279 done with enif_ioq_deq.
1280 The returned array is suitable to use with the Unix system call
1282 writev.
1283 size_t enif_ioq_size(ErlNifIOQueue *q)
1285 Get the size of q.
1287 int enif_is_atom(ErlNifEnv* env, ERL_NIF_TERM term)
1289 Returns true if term is an atom.
1291 int enif_is_binary(ErlNifEnv* env, ERL_NIF_TERM term)
1293 Returns true if term is a binary.
1295 int enif_is_current_process_alive(ErlNifEnv* env)
1297 Returns true if the currently executing process is currently
1299 alive, otherwise false.
1300 This function can only be used from a NIF-calling thread, and
1302 with an environment corresponding to currently executing pro‐
1303 cesses.
1304 int enif_is_empty_list(ErlNifEnv* env,
1306 ERL_NIF_TERM term)
1307 Returns true if term is an empty list.
1309 int enif_is_exception(ErlNifEnv* env,
1311 ERL_NIF_TERM term)
1312 Return true if term is an exception.
1314 int enif_is_fun(ErlNifEnv* env, ERL_NIF_TERM
1316 term)
1317 Returns true if term is a fun.
1319 int enif_is_identical(ERL_NIF_TERM lhs,
1321 ERL_NIF_TERM rhs)
1322 Returns true if the two terms are identical. Corresponds to the
1324 Erlang operators =:= and =/=.
1325 int enif_is_list(ErlNifEnv* env, ERL_NIF_TERM term)
1327 Returns true if term is a list.
1329 int enif_is_map(ErlNifEnv* env, ERL_NIF_TERM
1331 term)
1332 Returns true if term is a map, otherwise false.
1334 int enif_is_number(ErlNifEnv* env, ERL_NIF_TERM
1336 term)
1337 Returns true if term is a number.
1339 int enif_is_pid(ErlNifEnv* env, ERL_NIF_TERM term)
1341 Returns true if term is a pid.
1343 int enif_is_port(ErlNifEnv* env, ERL_NIF_TERM term)
1345 Returns true if term is a port.
1347 int enif_is_port_alive(ErlNifEnv* env,
1349 ErlNifPort *port_id)
1350 Returns true if port_id is alive.
1352 This function is only thread-safe when the emulator with SMP
1354 support is used. It can only be used in a non-SMP emulator from
1355 a NIF-calling thread.
1356 int enif_is_process_alive(ErlNifEnv* env,
1358 ErlNifPid *pid)
1359 Returns true if pid is alive.
1361 This function is only thread-safe when the emulator with SMP
1363 support is used. It can only be used in a non-SMP emulator from
1364 a NIF-calling thread.
1365 int enif_is_ref(ErlNifEnv* env, ERL_NIF_TERM term)
1367 Returns true if term is a reference.
1369 int enif_is_tuple(ErlNifEnv* env, ERL_NIF_TERM term)
1371 Returns true if term is a tuple.
1373 int enif_keep_resource(void* obj)
1375 Adds a reference to resource object obj obtained from
1377 enif_alloc_resource. Each call to enif_keep_resource for an
1378 object must be balanced by a call to enif_release_resource
1379 before the object is destructed.
1380 ERL_NIF_TERM enif_make_atom(ErlNifEnv* env, const char* name)
1382 Creates an atom term from the NULL-terminated C-string name with
1384 ISO Latin-1 encoding. If the length of name exceeds the maximum
1385 length allowed for an atom (255 characters), enif_make_atom
1386 invokes enif_make_badarg.
1387 ERL_NIF_TERM enif_make_atom_len(ErlNifEnv* env,
1389 const char* name, size_t len)
1390 Create an atom term from the string name with length len. NULL
1392 characters are treated as any other characters. If len exceeds
1393 the maximum length allowed for an atom (255 characters),
1394 enif_make_atom invokes enif_make_badarg.
1395 ERL_NIF_TERM enif_make_badarg(ErlNifEnv* env)
1397 Makes a badarg exception to be returned from a NIF, and asso‐
1399 ciates it with environment env. Once a NIF or any function it
1400 calls invokes enif_make_badarg, the runtime ensures that a
1401 badarg exception is raised when the NIF returns, even if the NIF
1402 attempts to return a non-exception term instead.
1403 The return value from enif_make_badarg can be used only as the
1405 return value from the NIF that invoked it (directly or indi‐
1406 rectly) or be passed to enif_is_exception, but not to any other
1407 NIF API function.
1408 See also enif_has_pending_exception and enif_raise_exception.
1410 Note:
1412 Before ERTS 7.0 (Erlang/OTP 18), the return value from
1413 enif_make_badarg had to be returned from the NIF. This require‐
1414 ment is now lifted as the return value from the NIF is ignored
1415 if enif_make_badarg has been invoked.
1416 ERL_NIF_TERM enif_make_binary(ErlNifEnv* env, ErlNifBinary* bin)
1419 Makes a binary term from bin. Any ownership of the binary data
1421 is transferred to the created term and bin is to be considered
1422 read-only for the rest of the NIF call and then as released.
1423 ERL_NIF_TERM enif_make_copy(ErlNifEnv* dst_env,
1425 ERL_NIF_TERM src_term)
1426 Makes a copy of term src_term. The copy is created in environ‐
1428 ment dst_env. The source term can be located in any environment.
1429 ERL_NIF_TERM enif_make_double(ErlNifEnv* env, double d)
1431 Creates a floating-point term from a double. If argument double
1433 is not finite or is NaN, enif_make_double invokes
1434 enif_make_badarg.
1435 int enif_make_existing_atom(ErlNifEnv* env,
1437 const char* name, ERL_NIF_TERM* atom, ErlNifCharEncoding
1438 encode)
1439 Tries to create the term of an already existing atom from the
1441 NULL-terminated C-string name with encoding encode.
1442 If the atom already exists, this function stores the term in
1444 *atom and returns true, otherwise false. Also returns false if
1445 the length of name exceeds the maximum length allowed for an
1446 atom (255 characters).
1447 int enif_make_existing_atom_len(ErlNifEnv* env,
1449 const char* name, size_t len, ERL_NIF_TERM* atom, ErlNifCharEn‐
1450 coding
1451 encoding)
1452 Tries to create the term of an already existing atom from the
1454 string name with length len and encoding encode. NULL characters
1455 are treated as any other characters.
1456 If the atom already exists, this function stores the term in
1458 *atom and returns true, otherwise false. Also returns false if
1459 len exceeds the maximum length allowed for an atom (255 charac‐
1460 ters).
1461 ERL_NIF_TERM enif_make_int(ErlNifEnv* env, int i)
1463 Creates an integer term.
1465 ERL_NIF_TERM enif_make_int64(ErlNifEnv* env, ErlNifSInt64 i)
1467 Creates an integer term from a signed 64-bit integer.
1469 ERL_NIF_TERM enif_make_list(ErlNifEnv* env, unsigned cnt, ...)
1471 Creates an ordinary list term of length cnt. Expects cnt number
1473 of arguments (after cnt) of type ERL_NIF_TERM as the elements of
1474 the list.
1475 Returns an empty list if cnt is 0.
1477 ERL_NIF_TERM enif_make_list1(ErlNifEnv* env, ERL_NIF_TERM e1)
1479 ERL_NIF_TERM enif_make_list2(ErlNifEnv* env,
1480 ERL_NIF_TERM e1, ERL_NIF_TERM e2)
1481 ERL_NIF_TERM enif_make_list3(ErlNifEnv* env,
1482 ERL_NIF_TERM e1, ERL_NIF_TERM e2, ERL_NIF_TERM e3)
1483 ERL_NIF_TERM enif_make_list4(ErlNifEnv* env,
1484 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)
1485 ERL_NIF_TERM enif_make_list5(ErlNifEnv* env,
1486 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)
1487 ERL_NIF_TERM enif_make_list6(ErlNifEnv* env,
1488 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)
1489 ERL_NIF_TERM enif_make_list7(ErlNifEnv* env,
1490 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)
1491 ERL_NIF_TERM enif_make_list8(ErlNifEnv* env,
1492 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)
1493 ERL_NIF_TERM enif_make_list9(ErlNifEnv* env,
1494 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)
1495 Creates an ordinary list term with length indicated by the func‐
1497 tion name. Prefer these functions (macros) over the variadic
1498 enif_make_list to get a compile-time error if the number of
1499 arguments does not match.
1500 ERL_NIF_TERM enif_make_list_cell(ErlNifEnv*
1502 env, ERL_NIF_TERM head, ERL_NIF_TERM tail)
1503 Creates a list cell [head | tail].
1505 ERL_NIF_TERM enif_make_list_from_array(ErlNifEnv* env, const
1507 ERL_NIF_TERM
1508 arr[], unsigned cnt)
1509 Creates an ordinary list containing the elements of array arr of
1511 length cnt.
1512 Returns an empty list if cnt is 0.
1514 ERL_NIF_TERM enif_make_long(ErlNifEnv* env, long int i)
1516 Creates an integer term from a long int.
1518 int enif_make_map_put(ErlNifEnv* env,
1520 ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM value,
1521 ERL_NIF_TERM* map_out)
1522 Makes a copy of map map_in and inserts key with value. If key
1524 already exists in map_in, the old associated value is replaced
1525 by value.
1526 If successful, this function sets *map_out to the new map and
1528 returns true. Returns false if map_in is not a map.
1529 The map_in term must belong to environment env.
1531 int enif_make_map_remove(ErlNifEnv* env,
1533 ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM* map_out)
1534 If map map_in contains key, this function makes a copy of map_in
1536 in *map_out, and removes key and the associated value. If map
1537 map_in does not contain key, *map_out is set to map_in.
1538 Returns true on success, or false if map_in is not a map.
1540 The map_in term must belong to environment env.
1542 int enif_make_map_update(ErlNifEnv* env,
1544 ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM new_value,
1545 ERL_NIF_TERM* map_out)
1546 Makes a copy of map map_in and replace the old associated value
1548 for key with new_value.
1549 If successful, this function sets *map_out to the new map and
1551 returns true. Returns false if map_in is not a map or if it does
1552 not contain key.
1553 The map_in term must belong to environment env.
1555 unsigned char *enif_make_new_binary(ErlNifEnv*
1557 env, size_t size, ERL_NIF_TERM* termp)
1558 Allocates a binary of size size bytes and creates an owning
1560 term. The binary data is mutable until the calling NIF returns.
1561 This is a quick way to create a new binary without having to use
1562 ErlNifBinary. The drawbacks are that the binary cannot be kept
1563 between NIF calls and it cannot be reallocated.
1564 Returns a pointer to the raw binary data and sets *termp to the
1566 binary term.
1567 ERL_NIF_TERM enif_make_new_map(ErlNifEnv* env)
1569 Makes an empty map term.
1571 ERL_NIF_TERM enif_make_pid(ErlNifEnv* env, const ErlNifPid* pid)
1573 Makes a pid term from *pid.
1575 ERL_NIF_TERM enif_make_ref(ErlNifEnv* env)
1577 Creates a reference like erlang:make_ref/0.
1579 ERL_NIF_TERM enif_make_resource(ErlNifEnv* env, void* obj)
1581 Creates an opaque handle to a memory-managed resource object
1583 obtained by enif_alloc_resource. No ownership transfer is done,
1584 as the resource object still needs to be released by
1585 enif_release_resource. However, notice that the call to
1586 enif_release_resource can occur immediately after obtaining the
1587 term from enif_make_resource, in which case the resource object
1588 is deallocated when the term is garbage collected. For more
1589 details, see the example of creating and returning a resource
1590 object in the User's Guide.
1591 Note:
1593 Since ERTS 9.0 (OTP-20.0), resource terms have a defined behav‐
1594 ior when compared and serialized through term_to_binary or
1595 passed between nodes.
1596 * Two resource terms will compare equal iff they would yield
1598 the same resource object pointer when passed to
1599 enif_get_resource.
1600 * A resoure term can be serialized with term_to_binary and
1602 later be fully recreated if the resource object is still
1603 alive when binary_to_term is called. A stale resource term
1604 will be returned from binary_to_term if the resource object
1605 has been deallocated. enif_get_resource will return false
1606 for stale resource terms.
1607 The same principles of serialization apply when passing
1609 resource terms in messages to remote nodes and back again. A
1610 resource term will act stale on all nodes except the node
1611 where its resource object is still alive in memory.
1612 Before ERTS 9.0 (OTP-20.0), all resource terms did compare equal
1614 to each other and to empty binaries (<<>>). If serialized, they
1615 would be recreated as plain empty binaries.
1616 ERL_NIF_TERM enif_make_resource_binary(ErlNifEnv* env, void* obj, const
1619 void* data, size_t size)
1620 Creates a binary term that is memory-managed by a resource
1622 object obj obtained by enif_alloc_resource. The returned binary
1623 term consists of size bytes pointed to by data. This raw binary
1624 data must be kept readable and unchanged until the destructor of
1625 the resource is called. The binary data can be stored external
1626 to the resource object, in which case the destructor is respon‐
1627 sible for releasing the data.
1628 Several binary terms can be managed by the same resource object.
1630 The destructor is not called until the last binary is garbage
1631 collected. This can be useful to return different parts of a
1632 larger binary buffer.
1633 As with enif_make_resource, no ownership transfer is done. The
1635 resource still needs to be released with enif_release_resource.
1636 int enif_make_reverse_list(ErlNifEnv* env, ERL_NIF_TERM list_in,
1638 ERL_NIF_TERM *list_out)
1639 Sets *list_out to the reverse list of the list list_in and
1641 returns true, or returns false if list_in is not a list.
1642 This function is only to be used on short lists, as a copy is
1644 created of the list, which is not released until after the NIF
1645 returns.
1646 The list_in term must belong to environment env.
1648 ERL_NIF_TERM enif_make_string(ErlNifEnv* env,
1650 const char* string, ErlNifCharEncoding encoding)
1651 Creates a list containing the characters of the NULL-terminated
1653 string string with encoding encoding.
1654 ERL_NIF_TERM enif_make_string_len(ErlNifEnv*
1656 env, const char* string, size_t len, ErlNifCharEncoding
1657 encoding)
1658 Creates a list containing the characters of the string string
1660 with length len and encoding encoding. NULL characters are
1661 treated as any other characters.
1662 ERL_NIF_TERM enif_make_sub_binary(ErlNifEnv*
1664 env, ERL_NIF_TERM bin_term, size_t pos, size_t size)
1665 Makes a subbinary of binary bin_term, starting at zero-based
1667 position pos with a length of size bytes. bin_term must be a
1668 binary or bitstring. pos+size must be less or equal to the num‐
1669 ber of whole bytes in bin_term.
1670 ERL_NIF_TERM enif_make_tuple(ErlNifEnv* env,
1672 unsigned cnt, ...)
1673 Creates a tuple term of arity cnt. Expects cnt number of argu‐
1675 ments (after cnt) of type ERL_NIF_TERM as the elements of the
1676 tuple.
1677 ERL_NIF_TERM enif_make_tuple1(ErlNifEnv* env,
1679 ERL_NIF_TERM e1)
1680 ERL_NIF_TERM enif_make_tuple2(ErlNifEnv* env,
1681 ERL_NIF_TERM e1, ERL_NIF_TERM e2)
1682 ERL_NIF_TERM enif_make_tuple3(ErlNifEnv* env,
1683 ERL_NIF_TERM e1, ERL_NIF_TERM e2, ERL_NIF_TERM e3)
1684 ERL_NIF_TERM enif_make_tuple4(ErlNifEnv* env,
1685 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)
1686 ERL_NIF_TERM enif_make_tuple5(ErlNifEnv* env,
1687 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)
1688 ERL_NIF_TERM enif_make_tuple6(ErlNifEnv* env,
1689 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)
1690 ERL_NIF_TERM enif_make_tuple7(ErlNifEnv* env,
1691 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)
1692 ERL_NIF_TERM enif_make_tuple8(ErlNifEnv* env,
1693 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)
1694 ERL_NIF_TERM enif_make_tuple9(ErlNifEnv* env,
1695 ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)
1696 Creates a tuple term with length indicated by the function name.
1698 Prefer these functions (macros) over the variadic
1699 enif_make_tuple to get a compile-time error if the number of
1700 arguments does not match.
1701 ERL_NIF_TERM enif_make_tuple_from_array(ErlNifEnv* env, const
1703 ERL_NIF_TERM
1704 arr[], unsigned cnt)
1705 Creates a tuple containing the elements of array arr of length
1707 cnt.
1708 ERL_NIF_TERM enif_make_uint(ErlNifEnv* env, unsigned int i)
1710 Creates an integer term from an unsigned int.
1712 ERL_NIF_TERM enif_make_uint64(ErlNifEnv* env, ErlNifUInt64 i)
1714 Creates an integer term from an unsigned 64-bit integer.
1716 ERL_NIF_TERM enif_make_ulong(ErlNifEnv* env, unsigned long i)
1718 Creates an integer term from an unsigned long int.
1720 ERL_NIF_TERM enif_make_unique_integer(ErlNifEnv
1722 *env, ErlNifUniqueInteger properties)
1723 Returns a unique integer with the same properties as specified
1725 by erlang:unique_integer/1.
1726 env is the environment to create the integer in.
1728 ERL_NIF_UNIQUE_POSITIVE and ERL_NIF_UNIQUE_MONOTONIC can be
1730 passed as the second argument to change the properties of the
1731 integer returned. They can be combined by OR:ing the two values
1732 together.
1733 See also ErlNifUniqueInteger.
1735 int enif_map_iterator_create(ErlNifEnv *env,
1737 ERL_NIF_TERM map, ErlNifMapIterator *iter, ErlNifMapIteratorEn‐
1738 try
1739 entry)
1740 Creates an iterator for the map map by initializing the struc‐
1742 ture pointed to by iter. Argument entry determines the start
1743 position of the iterator: ERL_NIF_MAP_ITERATOR_FIRST or
1744 ERL_NIF_MAP_ITERATOR_LAST.
1745 Returns true on success, or false if map is not a map.
1747 A map iterator is only useful during the lifetime of environment
1749 env that the map belongs to. The iterator must be destroyed by
1750 calling enif_map_iterator_destroy:
1751 ERL_NIF_TERM key, value;
1753 ErlNifMapIterator iter;
1754 enif_map_iterator_create(env, my_map, &iter, ERL_NIF_MAP_ITERATOR_FIRST);
1755 while (enif_map_iterator_get_pair(env, &iter, &key, &value)) {
1757 do_something(key,value);
1758 enif_map_iterator_next(env, &iter);
1759 }
1760 enif_map_iterator_destroy(env, &iter);
1761 Note:
1763 The key-value pairs of a map have no defined iteration order.
1764 The only guarantee is that the iteration order of a single map
1765 instance is preserved during the lifetime of the environment
1766 that the map belongs to.
1767 void enif_map_iterator_destroy(ErlNifEnv *env,
1770 ErlNifMapIterator *iter)
1771 Destroys a map iterator created by enif_map_iterator_create.
1773 int enif_map_iterator_get_pair(ErlNifEnv *env,
1775 ErlNifMapIterator *iter, ERL_NIF_TERM *key, ERL_NIF_TERM
1776 *value)
1777 Gets key and value terms at the current map iterator position.
1779 On success, sets *key and *value and returns true. Returns false
1781 if the iterator is positioned at head (before first entry) or
1782 tail (beyond last entry).
1783 int enif_map_iterator_is_head(ErlNifEnv *env,
1785 ErlNifMapIterator *iter)
1786 Returns true if map iterator iter is positioned before the first
1788 entry.
1789 int enif_map_iterator_is_tail(ErlNifEnv *env,
1791 ErlNifMapIterator *iter)
1792 Returns true if map iterator iter is positioned after the last
1794 entry.
1795 int enif_map_iterator_next(ErlNifEnv *env,
1797 ErlNifMapIterator *iter)
1798 Increments map iterator to point to the next key-value entry.
1800 Returns true if the iterator is now positioned at a valid key-
1802 value entry, or false if the iterator is positioned at the tail
1803 (beyond the last entry).
1804 int enif_map_iterator_prev(ErlNifEnv *env,
1806 ErlNifMapIterator *iter)
1807 Decrements map iterator to point to the previous key-value
1809 entry.
1810 Returns true if the iterator is now positioned at a valid key-
1812 value entry, or false if the iterator is positioned at the head
1813 (before the first entry).
1814 int enif_monitor_process(ErlNifEnv* env, void* obj,
1816 const ErlNifPid* target_pid, ErlNifMonitor* mon)
1817 Starts monitoring a process from a resource. When a process is
1819 monitored, a process exit results in a call to the provided down
1820 callback associated with the resource type.
1821 Argument obj is pointer to the resource to hold the monitor and
1823 *target_pid identifies the local process to be monitored.
1824 If mon is not NULL, a successful call stores the identity of the
1826 monitor in the ErlNifMonitor struct pointed to by mon. This
1827 identifier is used to refer to the monitor for later removal
1828 with enif_demonitor_process or compare with enif_compare_moni‐
1829 tors. A monitor is automatically removed when it triggers or
1830 when the resource is deallocated.
1831 Returns 0 on success, < 0 if no down callback is provided, and >
1833 0 if the process is no longer alive.
1834 This function is only thread-safe when the emulator with SMP
1836 support is used. It can only be used in a non-SMP emulator from
1837 a NIF-calling thread.
1838 ErlNifTime enif_monotonic_time(ErlNifTimeUnit time_unit)
1840 Returns the current Erlang monotonic time. Notice that it is
1842 not uncommon with negative values.
1843 time_unit is the time unit of the returned value.
1845 Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
1847 argument, or if called from a thread that is not a scheduler
1848 thread.
1849 See also ErlNifTime and ErlNifTimeUnit.
1851 ErlNifMutex *enif_mutex_create(char *name)
1853 Same as erl_drv_mutex_create.
1855 void enif_mutex_destroy(ErlNifMutex *mtx)
1857 Same as erl_drv_mutex_destroy.
1859 void enif_mutex_lock(ErlNifMutex *mtx)
1861 Same as erl_drv_mutex_lock.
1863 int enif_mutex_trylock(ErlNifMutex *mtx)
1865 Same as erl_drv_mutex_trylock.
1867 void enif_mutex_unlock(ErlNifMutex *mtx)
1869 Same as erl_drv_mutex_unlock.
1871 ERL_NIF_TERM enif_now_time(ErlNifEnv *env)
1873 Returns an erlang:now() time stamp.
1875 This function is deprecated.
1877 ErlNifResourceType *enif_open_resource_type(ErlNifEnv* env, const char*
1879 module_str, const char* name, ErlNifResourceDtor* dtor,
1880 ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
1881 Creates or takes over a resource type identified by the string
1883 name and gives it the destructor function pointed to by dtor.
1884 Argument flags can have the following values:
1885 ERL_NIF_RT_CREATE:
1887 Creates a new resource type that does not already exist.
1888 ERL_NIF_RT_TAKEOVER:
1890 Opens an existing resource type and takes over ownership of
1891 all its instances. The supplied destructor dtor is called
1892 both for existing instances and new instances not yet cre‐
1893 ated by the calling NIF library.
1894 The two flag values can be combined with bitwise OR. The
1896 resource type name is local to the calling module. Argument mod‐
1897 ule_str is not (yet) used and must be NULL. dtor can be NULL if
1898 no destructor is needed.
1899 On success, the function returns a pointer to the resource type
1901 and *tried is set to either ERL_NIF_RT_CREATE or
1902 ERL_NIF_RT_TAKEOVER to indicate what was done. On failure,
1903 returns NULL and sets *tried to flags. It is allowed to set
1904 tried to NULL.
1905 Notice that enif_open_resource_type is only allowed to be called
1907 in the two callbacks load and upgrade.
1908 See also enif_open_resource_type_x.
1910 ErlNifResourceType *enif_open_resource_type_x(ErlNifEnv* env, const
1912 char* name, const ErlNifResourceTypeInit* init,
1913 ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
1914 Same as enif_open_resource_type except it accepts additional
1916 callback functions for resource types that are used together
1917 with enif_select and enif_monitor_process.
1918 Argument init is a pointer to an ErlNifResourceTypeInit struc‐
1920 ture that contains the function pointers for destructor, down
1921 and stop callbacks for the resource type.
1922 int enif_port_command(ErlNifEnv* env, const
1924 ErlNifPort* to_port, ErlNifEnv *msg_env, ERL_NIF_TERM msg)
1925 Works as erlang:port_command/2, except that it is always com‐
1927 pletely asynchronous.
1928 env:
1930 The environment of the calling process. Must not be NULL.
1931 *to_port:
1933 The port ID of the receiving port. The port ID is to refer
1934 to a port on the local node.
1935 msg_env:
1937 The environment of the message term. Can be a process-inde‐
1938 pendent environment allocated with enif_alloc_env or NULL.
1939 msg:
1941 The message term to send. The same limitations apply as on
1942 the payload to erlang:port_command/2.
1943 Using a msg_env of NULL is an optimization, which groups
1945 together calls to enif_alloc_env, enif_make_copy, enif_port_com‐
1946 mand, and enif_free_env into one call. This optimization is only
1947 useful when a majority of the terms are to be copied from env to
1948 msg_env.
1949 Returns true if the command is successfully sent. Returns false
1951 if the command fails, for example:
1952 * *to_port does not refer to a local port.
1954 * The currently executing process (that is, the sender) is not
1956 alive.
1957 * msg is invalid.
1959 See also enif_get_local_port.
1961 void *enif_priv_data(ErlNifEnv* env)
1963 Returns the pointer to the private data that was set by load or
1965 upgrade.
1966 ERL_NIF_TERM enif_raise_exception(ErlNifEnv*
1968 env, ERL_NIF_TERM reason)
1969 Creates an error exception with the term reason to be returned
1971 from a NIF, and associates it with environment env. Once a NIF
1972 or any function it calls invokes enif_raise_exception, the run‐
1973 time ensures that the exception it creates is raised when the
1974 NIF returns, even if the NIF attempts to return a non-exception
1975 term instead.
1976 The return value from enif_raise_exception can only be used as
1978 the return value from the NIF that invoked it (directly or indi‐
1979 rectly) or be passed to enif_is_exception, but not to any other
1980 NIF API function.
1981 See also enif_has_pending_exception and enif_make_badarg.
1983 void *enif_realloc(void* ptr, size_t size)
1985 Reallocates memory allocated by enif_alloc to size bytes.
1987 Returns NULL if the reallocation fails.
1989 The returned pointer is suitably aligned for any built-in type
1991 that fit in the allocated memory.
1992 int enif_realloc_binary(ErlNifBinary* bin, size_t size)
1994 Changes the size of a binary bin. The source binary can be read-
1996 only, in which case it is left untouched and a mutable copy is
1997 allocated and assigned to *bin.
1998 Returns true on success, or false if memory allocation failed.
2000 void enif_release_binary(ErlNifBinary* bin)
2002 Releases a binary obtained from enif_alloc_binary.
2004 void enif_release_resource(void* obj)
2006 Removes a reference to resource object obj obtained from
2008 enif_alloc_resource. The resource object is destructed when the
2009 last reference is removed. Each call to enif_release_resource
2010 must correspond to a previous call to enif_alloc_resource or
2011 enif_keep_resource. References made by enif_make_resource can
2012 only be removed by the garbage collector.
2013 ErlNifRWLock *enif_rwlock_create(char *name)
2015 Same as erl_drv_rwlock_create.
2017 void enif_rwlock_destroy(ErlNifRWLock *rwlck)
2019 Same as erl_drv_rwlock_destroy.
2021 void enif_rwlock_rlock(ErlNifRWLock *rwlck)
2023 Same as erl_drv_rwlock_rlock.
2025 void enif_rwlock_runlock(ErlNifRWLock *rwlck)
2027 Same as erl_drv_rwlock_runlock.
2029 void enif_rwlock_rwlock(ErlNifRWLock *rwlck)
2031 Same as erl_drv_rwlock_rwlock.
2033 void enif_rwlock_rwunlock(ErlNifRWLock *rwlck)
2035 Same as erl_drv_rwlock_rwunlock.
2037 int enif_rwlock_tryrlock(ErlNifRWLock *rwlck)
2039 Same as erl_drv_rwlock_tryrlock.
2041 int enif_rwlock_tryrwlock(ErlNifRWLock *rwlck)
2043 Same as erl_drv_rwlock_tryrwlock.
2045 ERL_NIF_TERM enif_schedule_nif(ErlNifEnv* env,
2047 const char* fun_name, int flags, ERL_NIF_TERM (*fp)(ErlNifEnv*
2048 env, int
2049 argc, const ERL_NIF_TERM argv[]), int argc, const ERL_NIF_TERM
2050 argv[])
2051 Schedules NIF fp to execute. This function allows an application
2053 to break up long-running work into multiple regular NIF calls or
2054 to schedule a dirty NIF to execute on a dirty scheduler thread.
2055 fun_name:
2057 Provides a name for the NIF that is scheduled for execution.
2058 If it cannot be converted to an atom, enif_schedule_nif
2059 returns a badarg exception.
2060 flags:
2062 Must be set to 0 for a regular NIF. If the emulator was
2063 built with dirty scheduler support enabled, flags can be set
2064 to either ERL_NIF_DIRTY_JOB_CPU_BOUND if the job is expected
2065 to be CPU-bound, or ERL_NIF_DIRTY_JOB_IO_BOUND for jobs that
2066 will be I/O-bound. If dirty scheduler threads are not avail‐
2067 able in the emulator, an attempt to schedule such a job
2068 results in a notsup exception.
2069 argc and argv:
2071 Can either be the originals passed into the calling NIF, or
2072 can be values created by the calling NIF.
2073 The calling NIF must use the return value of enif_schedule_nif
2075 as its own return value.
2076 Be aware that enif_schedule_nif, as its name implies, only
2078 schedules the NIF for future execution. The calling NIF does not
2079 block waiting for the scheduled NIF to execute and return. This
2080 means that the calling NIF cannot expect to receive the sched‐
2081 uled NIF return value and use it for further operations.
2082 int enif_select(ErlNifEnv* env, ErlNifEvent event, enum ErlNifSelect‐
2084 Flags mode, void* obj, const ErlNifPid* pid, ERL_NIF_TERM ref)
2085 This function can be used to receive asynchronous notifications
2087 when OS-specific event objects become ready for either read or
2088 write operations.
2089 Argument event identifies the event object. On Unix systems, the
2091 functions select/poll are used. The event object must be a
2092 socket, pipe or other file descriptor object that select/poll
2093 can use.
2094 Argument mode describes the type of events to wait for. It can
2096 be ERL_NIF_SELECT_READ, ERL_NIF_SELECT_WRITE or a bitwise OR
2097 combination to wait for both. It can also be ERL_NIF_SELECT_STOP
2098 which is described further below. When a read or write event is
2099 triggerred, a notification message like this is sent to the
2100 process identified by pid:
2101 {select, Obj, Ref, ready_input | ready_output}
2103 ready_input or ready_output indicates if the event object is
2105 ready for reading or writing.
2106 Argument pid may be NULL to indicate the calling process.
2108 Argument obj is a resource object obtained from
2110 enif_alloc_resource. The purpose of the resource objects is as a
2111 container of the event object to manage its state and lifetime.
2112 A handle to the resource is received in the notification message
2113 as Obj.
2114 Argument ref must be either a reference obtained from
2116 erlang:make_ref/0 or the atom undefined. It will be passed as
2117 Ref in the notifications. If a selective receive statement is
2118 used to wait for the notification then a reference created just
2119 before the receive will exploit a runtime optimization that
2120 bypasses all earlier received messages in the queue.
2121 The notifications are one-shot only. To receive further notifi‐
2123 cations of the same type (read or write), repeated calls to
2124 enif_select must be made after receiving each notification.
2125 Use ERL_NIF_SELECT_STOP as mode in order to safely close an
2127 event object that has been passed to enif_select. The stop call‐
2128 back of the resource obj will be called when it is safe to close
2129 the event object. This safe way of closing event objects must be
2130 used even if all notifications have been received and no further
2131 calls to enif_select have been made.
2132 The first call to enif_select for a specific OS event will
2134 establish a relation between the event object and the containing
2135 resource. All subsequent calls for an event must pass its con‐
2136 taining resource as argument obj. The relation is dissolved when
2137 enif_select has been called with mode as ERL_NIF_SELECT_STOP and
2138 the corresponding stop callback has returned. A resource can
2139 contain several event objects but one event object can only be
2140 contained within one resource. A resource will not be destructed
2141 until all its contained relations have been dissolved.
2142 Note:
2144 Use enif_monitor_process together with enif_select to detect
2145 failing Erlang processes and prevent them from causing permanent
2146 leakage of resources and their contained OS event objects.
2147 Returns a non-negative value on success where the following bits
2150 can be set:
2151 ERL_NIF_SELECT_STOP_CALLED:
2153 The stop callback was called directly by enif_select.
2154 ERL_NIF_SELECT_STOP_SCHEDULED:
2156 The stop callback was scheduled to run on some other thread
2157 or later by this thread.
2158 Returns a negative value if the call failed where the follwing
2160 bits can be set:
2161 ERL_NIF_SELECT_INVALID_EVENT:
2163 Argument event is not a valid OS event object.
2164 ERL_NIF_SELECT_FAILED:
2166 The system call failed to add the event object to the poll
2167 set.
2168 Note:
2170 Use bitwise AND to test for specific bits in the return vaue.
2171 New significant bits may be added in future releases to give
2172 more detailed information for both failed and successful calls.
2173 Do NOT use equallity tests like ==, as that may cause your
2174 application to stop working.
2175 Example:
2177 retval = enif_select(env, fd, ERL_NIF_SELECT_STOP, resource, ref);
2179 if (retval < 0) {
2180 /* handle error */
2181 }
2182 /* Success! */
2183 if (retval & ERL_NIF_SELECT_STOP_CALLED) {
2184 /* ... */
2185 }
2186 ErlNifPid *enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)
2190 Initializes the ErlNifPid variable at *pid to represent the
2192 calling process.
2193 Returns pid if successful, or NULL if caller_env is not a
2195 process-bound environment.
2196 int enif_send(ErlNifEnv* env, ErlNifPid* to_pid,
2198 ErlNifEnv* msg_env, ERL_NIF_TERM msg)
2199 Sends a message to a process.
2201 env:
2203 The environment of the calling process. Must be NULL only if
2204 calling from a created thread.
2205 *to_pid:
2207 The pid of the receiving process. The pid is to refer to a
2208 process on the local node.
2209 msg_env:
2211 The environment of the message term. Must be a process-inde‐
2212 pendent environment allocated with enif_alloc_env or NULL.
2213 msg:
2215 The message term to send.
2216 Returns true if the message is successfully sent. Returns false
2218 if the send operation fails, that is:
2219 * *to_pid does not refer to an alive local process.
2221 * The currently executing process (that is, the sender) is not
2223 alive.
2224 The message environment msg_env with all its terms (including
2226 msg) is invalidated by a successful call to enif_send. The envi‐
2227 ronment is to either be freed with enif_free_env of cleared for
2228 reuse with enif_clear_env.
2229 If msg_env is set to NULL, the msg term is copied and the origi‐
2231 nal term and its environemt is still valid after the call.
2232 This function is only thread-safe when the emulator with SMP
2234 support is used. It can only be used in a non-SMP emulator from
2235 a NIF-calling thread.
2236 Note:
2238 Passing msg_env as NULL is only supported as from ERTS 8.0
2239 (Erlang/OTP 19).
2240 unsigned enif_sizeof_resource(void* obj)
2243 Gets the byte size of resource object obj obtained by
2245 enif_alloc_resource.
2246 int enif_snprintf(char *str, size_t size, const
2248 char *format, ...)
2249 Similar to snprintf but this format string also accepts "%T",
2251 which formats Erlang terms.
2252 void enif_system_info(ErlNifSysInfo
2254 *sys_info_ptr, size_t size)
2255 Same as driver_system_info.
2257 int enif_term_to_binary(ErlNifEnv *env,
2259 ERL_NIF_TERM term, ErlNifBinary *bin)
2260 Allocates a new binary with enif_alloc_binary and stores the
2262 result of encoding term according to the Erlang external term
2263 format.
2264 Returns true on success, or false if the allocation fails.
2266 See also erlang:term_to_binary/1 and enif_binary_to_term.
2268 int enif_thread_create(char *name,ErlNifTid
2270 *tid,void * (*func)(void *),void *args,ErlNifThreadOpts
2271 *opts)
2272 Same as erl_drv_thread_create.
2274 void enif_thread_exit(void *resp)
2276 Same as erl_drv_thread_exit.
2278 int enif_thread_join(ErlNifTid, void **respp)
2280 Same as erl_drv_thread_join.
2282 ErlNifThreadOpts *enif_thread_opts_create(char *name)
2284 Same as erl_drv_thread_opts_create.
2286 void enif_thread_opts_destroy(ErlNifThreadOpts *opts)
2288 Same as erl_drv_thread_opts_destroy.
2290 ErlNifTid enif_thread_self(void)
2292 Same as erl_drv_thread_self.
2294 int enif_thread_type(void)
2296 Determine the type of currently executing thread. A positive
2298 value indicates a scheduler thread while a negative value or
2299 zero indicates another type of thread. Currently the following
2300 specific types exist (which may be extended in the future):
2301 ERL_NIF_THR_UNDEFINED:
2303 Undefined thread that is not a scheduler thread.
2304 ERL_NIF_THR_NORMAL_SCHEDULER:
2306 A normal scheduler thread.
2307 ERL_NIF_THR_DIRTY_CPU_SCHEDULER:
2309 A dirty CPU scheduler thread.
2310 ERL_NIF_THR_DIRTY_IO_SCHEDULER:
2312 A dirty I/O scheduler thread.
2313 ErlNifTime enif_time_offset(ErlNifTimeUnit time_unit)
2315 Returns the current time offset between Erlang monotonic time
2317 and Erlang system time converted into the time_unit passed as
2318 argument.
2319 time_unit is the time unit of the returned value.
2321 Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
2323 argument or if called from a thread that is not a scheduler
2324 thread.
2325 See also ErlNifTime and ErlNifTimeUnit.
2327 void *enif_tsd_get(ErlNifTSDKey key)
2329 Same as erl_drv_tsd_get.
2331 int enif_tsd_key_create(char *name, ErlNifTSDKey *key)
2333 Same as erl_drv_tsd_key_create.
2335 void enif_tsd_key_destroy(ErlNifTSDKey key)
2337 Same as erl_drv_tsd_key_destroy.
2339 void enif_tsd_set(ErlNifTSDKey key, void *data)
2341 Same as erl_drv_tsd_set.
2343 int enif_whereis_pid(ErlNifEnv *env,
2345 ERL_NIF_TERM name, ErlNifPid *pid)
2346 Looks up a process by its registered name.
2348 env:
2350 The environment of the calling process. Must be NULL only if
2351 calling from a created thread.
2352 name:
2354 The name of a registered process, as an atom.
2355 *pid:
2357 The ErlNifPid in which the resolved process id is stored.
2358 On success, sets *pid to the local process registered with name
2360 and returns true. If name is not a registered process, or is not
2361 an atom, false is returned and *pid is unchanged.
2362 Works as erlang:whereis/1, but restricted to processes. See
2364 enif_whereis_port to resolve registered ports.
2365 int enif_whereis_port(ErlNifEnv *env,
2367 ERL_NIF_TERM name, ErlNifPort *port)
2368 Looks up a port by its registered name.
2370 env:
2372 The environment of the calling process. Must be NULL only if
2373 calling from a created thread.
2374 name:
2376 The name of a registered port, as an atom.
2377 *port:
2379 The ErlNifPort in which the resolved port id is stored.
2380 On success, sets *port to the port registered with name and
2382 returns true. If name is not a registered port, or is not an
2383 atom, false is returned and *port is unchanged.
2384 Works as erlang:whereis/1, but restricted to ports. See
2386 enif_whereis_pid to resolve registered processes.
2387
2389 erlang:load_nif/2
2390Ericsson AB erts 9.3.3.10 erl_nif(3)