1Stdlib.Bytes(3) OCaml library Stdlib.Bytes(3)
2
6 Stdlib.Bytes - no description
7
9 Module Stdlib.Bytes
10
12 Module Bytes
13 : (module Stdlib__bytes)
14 val length : bytes -> int
23 Return the length (number of bytes) of the argument.
25 val get : bytes -> int -> char
29 get s n returns the byte at index n in argument s .
32 Raise Invalid_argument if n is not a valid index in s .
34 val set : bytes -> int -> char -> unit
38 set s n c modifies s in place, replacing the byte at index n with c .
41 Raise Invalid_argument if n is not a valid index in s .
43 val create : int -> bytes
47 create n returns a new byte sequence of length n . The sequence is
50 uninitialized and contains arbitrary bytes.
51 Raise Invalid_argument if n < 0 or n > Sys.max_string_length .
53 val make : int -> char -> bytes
57 make n c returns a new byte sequence of length n , filled with the byte
60 c .
61 Raise Invalid_argument if n < 0 or n > Sys.max_string_length .
63 val init : int -> (int -> char) -> bytes
67 Bytes.init n f returns a fresh byte sequence of length n , with charac‐
70 ter i initialized to the result of f i (in increasing index order).
71 Raise Invalid_argument if n < 0 or n > Sys.max_string_length .
73 val empty : bytes
77 A byte sequence of size 0.
79 val copy : bytes -> bytes
83 Return a new byte sequence that contains the same bytes as the argu‐
85 ment.
86 val of_string : string -> bytes
90 Return a new byte sequence that contains the same bytes as the given
92 string.
93 val to_string : bytes -> string
97 Return a new string that contains the same bytes as the given byte
99 sequence.
100 val sub : bytes -> int -> int -> bytes
104 sub s start len returns a new byte sequence of length len , containing
107 the subsequence of s that starts at position start and has length len .
108 Raise Invalid_argument if start and len do not designate a valid range
110 of s .
111 val sub_string : bytes -> int -> int -> string
115 Same as sub but return a string instead of a byte sequence.
117 val extend : bytes -> int -> int -> bytes
121 extend s left right returns a new byte sequence that contains the bytes
124 of s , with left uninitialized bytes prepended and right uninitialized
125 bytes appended to it. If left or right is negative, then bytes are
126 removed (instead of appended) from the corresponding side of s .
127 Raise Invalid_argument if the result length is negative or longer than
129 Sys.max_string_length bytes.
130 val fill : bytes -> int -> int -> char -> unit
134 fill s start len c modifies s in place, replacing len characters with c
137 , starting at start .
138 Raise Invalid_argument if start and len do not designate a valid range
140 of s .
141 val blit : bytes -> int -> bytes -> int -> int -> unit
145 blit src srcoff dst dstoff len copies len bytes from sequence src ,
148 starting at index srcoff , to sequence dst , starting at index dstoff .
149 It works correctly even if src and dst are the same byte sequence, and
150 the source and destination intervals overlap.
151 Raise Invalid_argument if srcoff and len do not designate a valid range
153 of src , or if dstoff and len do not designate a valid range of dst .
154 val blit_string : string -> int -> bytes -> int -> int -> unit
158 blit_string src srcoff dst dstoff len copies len bytes from string src
161 , starting at index srcoff , to byte sequence dst , starting at index
162 dstoff .
163 Raise Invalid_argument if srcoff and len do not designate a valid range
165 of src , or if dstoff and len do not designate a valid range of dst .
166 val concat : bytes -> bytes list -> bytes
170 concat sep sl concatenates the list of byte sequences sl , inserting
173 the separator byte sequence sep between each, and returns the result as
174 a new byte sequence.
175 Raise Invalid_argument if the result is longer than
177 Sys.max_string_length bytes.
178 val cat : bytes -> bytes -> bytes
182 cat s1 s2 concatenates s1 and s2 and returns the result as new byte
185 sequence.
186 Raise Invalid_argument if the result is longer than
188 Sys.max_string_length bytes.
189 val iter : (char -> unit) -> bytes -> unit
193 iter f s applies function f in turn to all the bytes of s . It is
196 equivalent to f (get s 0); f (get s 1); ...; f (get s
197 (length s - 1)); () .
198 val iteri : (int -> char -> unit) -> bytes -> unit
202 Same as Bytes.iter , but the function is applied to the index of the
204 byte as first argument and the byte itself as second argument.
205 val map : (char -> char) -> bytes -> bytes
209 map f s applies function f in turn to all the bytes of s (in increasing
212 index order) and stores the resulting bytes in a new sequence that is
213 returned as the result.
214 val mapi : (int -> char -> char) -> bytes -> bytes
218 mapi f s calls f with each character of s and its index (in increasing
221 index order) and stores the resulting bytes in a new sequence that is
222 returned as the result.
223 val trim : bytes -> bytes
227 Return a copy of the argument, without leading and trailing whitespace.
229 The bytes regarded as whitespace are the ASCII characters ' ' , '\012'
230 , '\n' , '\r' , and '\t' .
231 val escaped : bytes -> bytes
235 Return a copy of the argument, with special characters represented by
237 escape sequences, following the lexical conventions of OCaml. All
238 characters outside the ASCII printable range (32..126) are escaped, as
239 well as backslash and double-quote.
240 Raise Invalid_argument if the result is longer than
242 Sys.max_string_length bytes.
243 val index : bytes -> char -> int
247 index s c returns the index of the first occurrence of byte c in s .
250 Raise Not_found if c does not occur in s .
252 val index_opt : bytes -> char -> int option
256 index_opt s c returns the index of the first occurrence of byte c in s
259 or None if c does not occur in s .
260 Since 4.05
263 val rindex : bytes -> char -> int
267 rindex s c returns the index of the last occurrence of byte c in s .
270 Raise Not_found if c does not occur in s .
272 val rindex_opt : bytes -> char -> int option
276 rindex_opt s c returns the index of the last occurrence of byte c in s
279 or None if c does not occur in s .
280 Since 4.05
283 val index_from : bytes -> int -> char -> int
287 index_from s i c returns the index of the first occurrence of byte c in
290 s after position i . Bytes.index s c is equivalent to Bytes.index_from
291 s 0 c .
292 Raise Invalid_argument if i is not a valid position in s . Raise
294 Not_found if c does not occur in s after position i .
295 val index_from_opt : bytes -> int -> char -> int option
299 index_from_opt s i c returns the index of the first occurrence of byte
302 c in s after position i or None if c does not occur in s after position
303 i . Bytes.index_opt s c is equivalent to Bytes.index_from_opt s 0 c .
304 Raise Invalid_argument if i is not a valid position in s .
306 Since 4.05
309 val rindex_from : bytes -> int -> char -> int
313 rindex_from s i c returns the index of the last occurrence of byte c in
316 s before position i+1 . rindex s c is equivalent to rindex_from s
317 (Bytes.length s - 1) c .
318 Raise Invalid_argument if i+1 is not a valid position in s . Raise
320 Not_found if c does not occur in s before position i+1 .
321 val rindex_from_opt : bytes -> int -> char -> int option
325 rindex_from_opt s i c returns the index of the last occurrence of byte
328 c in s before position i+1 or None if c does not occur in s before
329 position i+1 . rindex_opt s c is equivalent to rindex_from s
330 (Bytes.length s - 1) c .
331 Raise Invalid_argument if i+1 is not a valid position in s .
333 Since 4.05
336 val contains : bytes -> char -> bool
340 contains s c tests if byte c appears in s .
343 val contains_from : bytes -> int -> char -> bool
347 contains_from s start c tests if byte c appears in s after position
350 start . contains s c is equivalent to contains_from
351 s 0 c .
352 Raise Invalid_argument if start is not a valid position in s .
354 val rcontains_from : bytes -> int -> char -> bool
358 rcontains_from s stop c tests if byte c appears in s before position
361 stop+1 .
362 Raise Invalid_argument if stop < 0 or stop+1 is not a valid position in
364 s .
365 val uppercase : bytes -> bytes
369 Deprecated. Functions operating on Latin-1 character set are depre‐
371 cated.
372 Return a copy of the argument, with all lowercase letters translated to
375 uppercase, including accented letters of the ISO Latin-1 (8859-1) char‐
376 acter set.
377 val lowercase : bytes -> bytes
381 Deprecated. Functions operating on Latin-1 character set are depre‐
383 cated.
384 Return a copy of the argument, with all uppercase letters translated to
387 lowercase, including accented letters of the ISO Latin-1 (8859-1) char‐
388 acter set.
389 val capitalize : bytes -> bytes
393 Deprecated. Functions operating on Latin-1 character set are depre‐
395 cated.
396 Return a copy of the argument, with the first character set to upper‐
399 case, using the ISO Latin-1 (8859-1) character set..
400 val uncapitalize : bytes -> bytes
404 Deprecated. Functions operating on Latin-1 character set are depre‐
406 cated.
407 Return a copy of the argument, with the first character set to lower‐
410 case, using the ISO Latin-1 (8859-1) character set..
411 val uppercase_ascii : bytes -> bytes
415 Return a copy of the argument, with all lowercase letters translated to
417 uppercase, using the US-ASCII character set.
418 Since 4.03.0
421 val lowercase_ascii : bytes -> bytes
425 Return a copy of the argument, with all uppercase letters translated to
427 lowercase, using the US-ASCII character set.
428 Since 4.03.0
431 val capitalize_ascii : bytes -> bytes
435 Return a copy of the argument, with the first character set to upper‐
437 case, using the US-ASCII character set.
438 Since 4.03.0
441 val uncapitalize_ascii : bytes -> bytes
445 Return a copy of the argument, with the first character set to lower‐
447 case, using the US-ASCII character set.
448 Since 4.03.0
451 type t = bytes
454 An alias for the type of byte sequences.
457 val compare : t -> t -> int
461 The comparison function for byte sequences, with the same specification
463 as compare . Along with the type t , this function compare allows the
464 module Bytes to be passed as argument to the functors Set.Make and
465 Map.Make .
466 val equal : t -> t -> bool
470 The equality function for byte sequences.
472 Since 4.03.0
475 Unsafe conversions (for advanced users)
480 This section describes unsafe, low-level conversion functions between
481 bytes and string . They do not copy the internal data; used improperly,
482 they can break the immutability invariant on strings provided by the
483 -safe-string option. They are available for expert library authors, but
484 for most purposes you should use the always-correct Bytes.to_string and
485 Bytes.of_string instead.
486 val unsafe_to_string : bytes -> string
488 Unsafely convert a byte sequence into a string.
490 To reason about the use of unsafe_to_string , it is convenient to con‐
492 sider an "ownership" discipline. A piece of code that manipulates some
493 data "owns" it; there are several disjoint ownership modes, including:
494 -Unique ownership: the data may be accessed and mutated
496 -Shared ownership: the data has several owners, that may only access
498 it, not mutate it.
499 Unique ownership is linear: passing the data to another piece of code
501 means giving up ownership (we cannot write the data again). A unique
502 owner may decide to make the data shared (giving up mutation rights on
503 it), but shared data may not become uniquely-owned again.
504 unsafe_to_string s can only be used when the caller owns the byte
507 sequence s -- either uniquely or as shared immutable data. The caller
508 gives up ownership of s , and gains ownership of the returned string.
509 There are two valid use-cases that respect this ownership discipline:
511 1. Creating a string by initializing and mutating a byte sequence that
513 is never changed after initialization is performed.
514 let string_init len f : string =
517 let s = Bytes.create len in
518 for i = 0 to len - 1 do Bytes.set s i (f i) done;
519 Bytes.unsafe_to_string s
520 This function is safe because the byte sequence s will never be
523 accessed or mutated after unsafe_to_string is called. The string_init
524 code gives up ownership of s , and returns the ownership of the result‐
525 ing string to its caller.
526 Note that it would be unsafe if s was passed as an additional parameter
528 to the function f as it could escape this way and be mutated in the
529 future -- string_init would give up ownership of s to pass it to f ,
530 and could not call unsafe_to_string safely.
531 We have provided the String.init , String.map and String.mapi functions
533 to cover most cases of building new strings. You should prefer those
534 over to_string or unsafe_to_string whenever applicable.
535 2. Temporarily giving ownership of a byte sequence to a function that
537 expects a uniquely owned string and returns ownership back, so that we
538 can mutate the sequence again after the call ended.
539 let bytes_length (s : bytes) =
542 String.length (Bytes.unsafe_to_string s)
543 In this use-case, we do not promise that s will never be mutated after
546 the call to bytes_length s . The String.length function temporarily
547 borrows unique ownership of the byte sequence (and sees it as a string
548 ), but returns this ownership back to the caller, which may assume that
549 s is still a valid byte sequence after the call. Note that this is only
550 correct because we know that String.length does not capture its argu‐
551 ment -- it could escape by a side-channel such as a memoization combi‐
552 nator.
553 The caller may not mutate s while the string is borrowed (it has tempo‐
555 rarily given up ownership). This affects concurrent programs, but also
556 higher-order functions: if String.length returned a closure to be
557 called later, s should not be mutated until this closure is fully
558 applied and returns ownership.
559 val unsafe_of_string : string -> bytes
563 Unsafely convert a shared string to a byte sequence that should not be
565 mutated.
566 The same ownership discipline that makes unsafe_to_string correct
568 applies to unsafe_of_string : you may use it if you were the owner of
569 the string value, and you will own the return bytes in the same mode.
570 In practice, unique ownership of string values is extremely difficult
572 to reason about correctly. You should always assume strings are shared,
573 never uniquely owned.
574 For example, string literals are implicitly shared by the compiler, so
576 you never uniquely own them.
577 let incorrect = Bytes.unsafe_of_string "hello"
580 let s = Bytes.of_string "hello"
581 The first declaration is incorrect, because the string literal "hello"
584 could be shared by the compiler with other parts of the program, and
585 mutating incorrect is a bug. You must always use the second version,
586 which performs a copy and is thus correct.
587 Assuming unique ownership of strings that are not string literals, but
589 are (partly) built from string literals, is also incorrect. For exam‐
590 ple, mutating unsafe_of_string ("foo" ^ s) could mutate the shared
591 string "foo" -- assuming a rope-like representation of strings. More
592 generally, functions operating on strings will assume shared ownership,
593 they do not preserve unique ownership. It is thus incorrect to assume
594 unique ownership of the result of unsafe_of_string .
595 The only case we have reasonable confidence is safe is if the produced
597 bytes is shared -- used as an immutable byte sequence. This is possibly
598 useful for incremental migration of low-level programs that manipulate
599 immutable sequences of bytes (for example Marshal.from_bytes ) and pre‐
600 viously used the string type for this purpose.
601 Iterators
606 val to_seq : t -> char Seq.t
607 Iterate on the string, in increasing index order. Modifications of the
609 string during iteration will be reflected in the iterator.
610 Since 4.07
613 val to_seqi : t -> (int * char) Seq.t
617 Iterate on the string, in increasing order, yielding indices along
619 chars
620 Since 4.07
623 val of_seq : char Seq.t -> t
627 Create a string from the generator
629 Since 4.07
632 Binary encoding/decoding of integers
637 The functions in this section binary encode and decode integers to and
638 from byte sequences.
639 All following functions raise Invalid_argument if the space needed at
641 index i to decode or encode the integer is not available.
642 Little-endian (resp. big-endian) encoding means that least (resp. most)
644 significant bytes are stored first. Big-endian is also known as net‐
645 work byte order. Native-endian encoding is either little-endian or
646 big-endian depending on Sys.big_endian .
647 32-bit and 64-bit integers are represented by the int32 and int64
649 types, which can be interpreted either as signed or unsigned numbers.
650 8-bit and 16-bit integers are represented by the int type, which has
652 more bits than the binary encoding. These extra bits are handled as
653 follows:
654 -Functions that decode signed (resp. unsigned) 8-bit or 16-bit integers
656 represented by int values sign-extend (resp. zero-extend) their result.
657 -Functions that encode 8-bit or 16-bit integers represented by int val‐
659 ues truncate their input to their least significant bytes.
660 val get_uint8 : bytes -> int -> int
663 get_uint8 b i is b 's unsigned 8-bit integer starting at byte index i .
666 Since 4.08
669 val get_int8 : bytes -> int -> int
673 get_int8 b i is b 's signed 8-bit integer starting at byte index i .
676 Since 4.08
679 val get_uint16_ne : bytes -> int -> int
683 get_uint16_ne b i is b 's native-endian unsigned 16-bit integer start‐
686 ing at byte index i .
687 Since 4.08
690 val get_uint16_be : bytes -> int -> int
694 get_uint16_be b i is b 's big-endian unsigned 16-bit integer starting
697 at byte index i .
698 Since 4.08
701 val get_uint16_le : bytes -> int -> int
705 get_uint16_le b i is b 's little-endian unsigned 16-bit integer start‐
708 ing at byte index i .
709 Since 4.08
712 val get_int16_ne : bytes -> int -> int
716 get_int16_ne b i is b 's native-endian signed 16-bit integer starting
719 at byte index i .
720 Since 4.08
723 val get_int16_be : bytes -> int -> int
727 get_int16_be b i is b 's big-endian signed 16-bit integer starting at
730 byte index i .
731 Since 4.08
734 val get_int16_le : bytes -> int -> int
738 get_int16_le b i is b 's little-endian signed 16-bit integer starting
741 at byte index i .
742 Since 4.08
745 val get_int32_ne : bytes -> int -> int32
749 get_int32_ne b i is b 's native-endian 32-bit integer starting at byte
752 index i .
753 Since 4.08
756 val get_int32_be : bytes -> int -> int32
760 get_int32_be b i is b 's big-endian 32-bit integer starting at byte
763 index i .
764 Since 4.08
767 val get_int32_le : bytes -> int -> int32
771 get_int32_le b i is b 's little-endian 32-bit integer starting at byte
774 index i .
775 Since 4.08
778 val get_int64_ne : bytes -> int -> int64
782 get_int64_ne b i is b 's native-endian 64-bit integer starting at byte
785 index i .
786 Since 4.08
789 val get_int64_be : bytes -> int -> int64
793 get_int64_be b i is b 's big-endian 64-bit integer starting at byte
796 index i .
797 Since 4.08
800 val get_int64_le : bytes -> int -> int64
804 get_int64_le b i is b 's little-endian 64-bit integer starting at byte
807 index i .
808 Since 4.08
811 val set_uint8 : bytes -> int -> int -> unit
815 set_uint8 b i v sets b 's unsigned 8-bit integer starting at byte index
818 i to v .
819 Since 4.08
822 val set_int8 : bytes -> int -> int -> unit
826 set_int8 b i v sets b 's signed 8-bit integer starting at byte index i
829 to v .
830 Since 4.08
833 val set_uint16_ne : bytes -> int -> int -> unit
837 set_uint16_ne b i v sets b 's native-endian unsigned 16-bit integer
840 starting at byte index i to v .
841 Since 4.08
844 val set_uint16_be : bytes -> int -> int -> unit
848 set_uint16_be b i v sets b 's big-endian unsigned 16-bit integer start‐
851 ing at byte index i to v .
852 Since 4.08
855 val set_uint16_le : bytes -> int -> int -> unit
859 set_uint16_le b i v sets b 's little-endian unsigned 16-bit integer
862 starting at byte index i to v .
863 Since 4.08
866 val set_int16_ne : bytes -> int -> int -> unit
870 set_int16_ne b i v sets b 's native-endian signed 16-bit integer start‐
873 ing at byte index i to v .
874 Since 4.08
877 val set_int16_be : bytes -> int -> int -> unit
881 set_int16_be b i v sets b 's big-endian signed 16-bit integer starting
884 at byte index i to v .
885 Since 4.08
888 val set_int16_le : bytes -> int -> int -> unit
892 set_int16_le b i v sets b 's little-endian signed 16-bit integer start‐
895 ing at byte index i to v .
896 Since 4.08
899 val set_int32_ne : bytes -> int -> int32 -> unit
903 set_int32_ne b i v sets b 's native-endian 32-bit integer starting at
906 byte index i to v .
907 Since 4.08
910 val set_int32_be : bytes -> int -> int32 -> unit
914 set_int32_be b i v sets b 's big-endian 32-bit integer starting at byte
917 index i to v .
918 Since 4.08
921 val set_int32_le : bytes -> int -> int32 -> unit
925 set_int32_le b i v sets b 's little-endian 32-bit integer starting at
928 byte index i to v .
929 Since 4.08
932 val set_int64_ne : bytes -> int -> int64 -> unit
936 set_int64_ne b i v sets b 's native-endian 64-bit integer starting at
939 byte index i to v .
940 Since 4.08
943 val set_int64_be : bytes -> int -> int64 -> unit
947 set_int64_be b i v sets b 's big-endian 64-bit integer starting at byte
950 index i to v .
951 Since 4.08
954 val set_int64_le : bytes -> int -> int64 -> unit
958 set_int64_le b i v sets b 's little-endian 64-bit integer starting at
961 byte index i to v .
962 Since 4.08
965OCamldoc 2020-02-27 Stdlib.Bytes(3)