Module Make.Bytes

Byte sequence operations.

A byte sequence is a mutable data structure that contains a fixed-length sequence of bytes. Each byte can be indexed in constant time for reading or writing.

Given a byte sequence s of length l, we can access each of the l bytes of s via its index in the sequence. Indexes start at 0, and we will call an index valid in s if it falls within the range [0...l-1] (inclusive). A position is the point between two bytes or at the beginning or end of the sequence. We call a position valid in s if it falls within the range [0...l] (inclusive). Note that the byte at index n is between positions n and n+1.

Two parameters start and len are said to designate a valid range of s if len >= 0 and start and start+len are valid positions in s.

Byte sequences can be modified in place, for instance via the set and blit functions described below. See also strings (module String), which are almost the same data structure, but cannot be modified in place.

Bytes are represented by the OCaml type char.

The labeled version of this module can be used as described in the StdLabels module.

val length : bytes -> int

Return the length (number of bytes) of the argument.

val get : bytes -> int -> char

get s n returns the byte at index n in argument s.

  • raises Invalid_argument

    if n is not a valid index in s.

val set : bytes -> int -> char -> unit

set s n c modifies s in place, replacing the byte at index n with c.

  • raises Invalid_argument

    if n is not a valid index in s.

val make : int -> char -> bytes

make n c returns a new byte sequence of length n, filled with the byte c.

  • raises Invalid_argument

    if n < 0 or n > Sys.max_string_length.

val init : int -> (int -> char) -> bytes

init n f returns a fresh byte sequence of length n, with character i initialized to the result of f i (in increasing index order).

  • raises Invalid_argument

    if n < 0 or n > Sys.max_string_length.

val empty : bytes

A byte sequence of size 0.

val copy : bytes -> bytes

Return a new byte sequence that contains the same bytes as the argument.

val of_string : string -> bytes

Return a new byte sequence that contains the same bytes as the given string.

val to_string : bytes -> string

Return a new string that contains the same bytes as the given byte sequence.

val sub : bytes -> int -> int -> bytes

sub s pos len returns a new byte sequence of length len, containing the subsequence of s that starts at position pos and has length len.

  • raises Invalid_argument

    if pos and len do not designate a valid range of s.

val sub_string : bytes -> int -> int -> string

Same as sub but return a string instead of a byte sequence.

val extend : bytes -> int -> int -> bytes

extend s left right returns a new byte sequence that contains the bytes of s, with left uninitialized bytes prepended and right uninitialized bytes appended to it. If left or right is negative, then bytes are removed (instead of appended) from the corresponding side of s.

  • raises Invalid_argument

    if the result length is negative or longer than Sys.max_string_length bytes.

  • since 4.05.0 in BytesLabels
val fill : bytes -> int -> int -> char -> unit

fill s pos len c modifies s in place, replacing len characters with c, starting at pos.

  • raises Invalid_argument

    if pos and len do not designate a valid range of s.

val blit : bytes -> int -> bytes -> int -> int -> unit

blit src src_pos dst dst_pos len copies len bytes from sequence src, starting at index src_pos, to sequence dst, starting at index dst_pos. It works correctly even if src and dst are the same byte sequence, and the source and destination intervals overlap.

  • raises Invalid_argument

    if src_pos and len do not designate a valid range of src, or if dst_pos and len do not designate a valid range of dst.

val blit_string : string -> int -> bytes -> int -> int -> unit

blit src src_pos dst dst_pos len copies len bytes from string src, starting at index src_pos, to byte sequence dst, starting at index dst_pos.

  • raises Invalid_argument

    if src_pos and len do not designate a valid range of src, or if dst_pos and len do not designate a valid range of dst.

  • since 4.05.0 in BytesLabels
val concat : bytes -> bytes list -> bytes

concat sep sl concatenates the list of byte sequences sl, inserting the separator byte sequence sep between each, and returns the result as a new byte sequence.

  • raises Invalid_argument

    if the result is longer than Sys.max_string_length bytes.

val cat : bytes -> bytes -> bytes

cat s1 s2 concatenates s1 and s2 and returns the result as a new byte sequence.

  • raises Invalid_argument

    if the result is longer than Sys.max_string_length bytes.

  • since 4.05.0 in BytesLabels
val iter : (char -> unit) -> bytes -> unit

iter f s applies function f in turn to all the bytes of s. It is equivalent to f (get s 0); f (get s 1); ...; f (get s (length s - 1)); ().

val iteri : (int -> char -> unit) -> bytes -> unit

Same as iter, but the function is applied to the index of the byte as first argument and the byte itself as second argument.

val map : (char -> char) -> bytes -> bytes

map f s applies function f in turn to all the bytes of s (in increasing index order) and stores the resulting bytes in a new sequence that is returned as the result.

val mapi : (int -> char -> char) -> bytes -> bytes

mapi f s calls f with each character of s and its index (in increasing index order) and stores the resulting bytes in a new sequence that is returned as the result.

val trim : bytes -> bytes

Return a copy of the argument, without leading and trailing whitespace. The bytes regarded as whitespace are the ASCII characters ' ', '\012', '\n', '\r', and '\t'.

val escaped : bytes -> bytes

Return a copy of the argument, with special characters represented by escape sequences, following the lexical conventions of OCaml. All characters outside the ASCII printable range (32..126) are escaped, as well as backslash and double-quote.

  • raises Invalid_argument

    if the result is longer than Sys.max_string_length bytes.

val index_opt : bytes -> char -> int option

index_opt s c returns the index of the first occurrence of byte c in s or None if c does not occur in s.

  • since 4.05
val rindex_opt : bytes -> char -> int option

rindex_opt s c returns the index of the last occurrence of byte c in s or None if c does not occur in s.

  • since 4.05
val index_from_opt : bytes -> int -> char -> int option

index_from_opt s i c returns the index of the first occurrence of byte c in s after position i or None if c does not occur in s after position i. index_opt s c is equivalent to index_from_opt s 0 c.

  • raises Invalid_argument

    if i is not a valid position in s.

  • since 4.05
val rindex_from_opt : bytes -> int -> char -> int option

rindex_from_opt s i c returns the index of the last occurrence of byte c in s before position i+1 or None if c does not occur in s before position i+1. rindex_opt s c is equivalent to rindex_from s (length s - 1) c.

  • raises Invalid_argument

    if i+1 is not a valid position in s.

  • since 4.05
val contains : bytes -> char -> bool

contains s c tests if byte c appears in s.

val contains_from : bytes -> int -> char -> bool

contains_from s start c tests if byte c appears in s after position start. contains s c is equivalent to contains_from s 0 c.

  • raises Invalid_argument

    if start is not a valid position in s.

val rcontains_from : bytes -> int -> char -> bool

rcontains_from s stop c tests if byte c appears in s before position stop+1.

  • raises Invalid_argument

    if stop < 0 or stop+1 is not a valid position in s.

val uppercase_ascii : bytes -> bytes

Return a copy of the argument, with all lowercase letters translated to uppercase, using the US-ASCII character set.

  • since 4.03.0 (4.05.0 in BytesLabels)
val lowercase_ascii : bytes -> bytes

Return a copy of the argument, with all uppercase letters translated to lowercase, using the US-ASCII character set.

  • since 4.03.0 (4.05.0 in BytesLabels)
val capitalize_ascii : bytes -> bytes

Return a copy of the argument, with the first character set to uppercase, using the US-ASCII character set.

  • since 4.03.0 (4.05.0 in BytesLabels)
val uncapitalize_ascii : bytes -> bytes

Return a copy of the argument, with the first character set to lowercase, using the US-ASCII character set.

  • since 4.03.0 (4.05.0 in BytesLabels)
type t = bytes

An alias for the type of byte sequences.

val compare : t -> t -> int

The comparison function for byte sequences, with the same specification as Stdlib.compare. Along with the type t, this function compare allows the module Bytes to be passed as argument to the functors Set.Make and Map.Make.

val equal : t -> t -> bool

The equality function for byte sequences.

  • since 4.03.0 (4.05.0 in BytesLabels)
val logand : bytes -> bytes -> bytes

Bitwise AND on bytes.

If the arguments have different lengths, the prefix of the longer bytes is cut to have the same length as the shorter one before taking bitwise AND.

ex. 0xff0f AND 0xff = 0x0f AND 0xff = 0x0f

val logor : bytes -> bytes -> bytes

Bitwise OR on bytes.

If the arguments have different lengths, the shorter bytes is 0-padded on the left to have the same length before taking bitwise OR.

ex. 0xf000 OR 0x0f = 0xf000 OR 0x000f = 0xf00f

val logxor : bytes -> bytes -> bytes

Bitwise XOR on bytes.

If the arguments have different lengths, the shorter bytes is 0-padded on the left to have the same length before taking bitwise XOR.

ex. 0xf0ff XOR 0x0f = 0xf0ff XOR 0x000f = 0xf0f0

val lognot : bytes -> bytes

Bitwise NOT on bytes.

ex. NOT 0xf0f0 = 0x0f0f

val shift_left : bytes -> int -> bytes

Logical shift left on bytes, using big-endian encoding. shift_left bs nbits returns a bytes longer than bs when nbits > 0. It raises Invalid_argument "shift_left" when nbits < 0.

ex. 0x1234 LSL 0 = 0x1234 0x1234 LSL 1 = 0x002468 (not 0x2468) 0x1234 LSL 8 = 0x123400 0x001234 LSL 1 = 0x00002468 (not 0x002468) 0x (empty bytes) LSL 1 = 0x00

val shift_right : bytes -> int -> bytes

Logical shift right on bytes, using big-endian encoding. shift_right bs nbits raises Invalid_argument "shift_right" when nbits < 0.

ex. 0x1234 LSR 0 = 0x1234 0x1234 LSR 1 = 0x091a 0x1234 LSR 8 = 0x12 (not 0x0012) 0x123499 LSR 9 = 0x091a