Module Stdlib.BufferSource

Extensible buffers.

This module implements buffers that automatically expand as necessary. It provides accumulative concatenation of strings in linear time (instead of quadratic time when strings are concatenated pairwise). For example:

let concat_strings ss =
  let b = Buffer.create 16 in
    List.iter (Buffer.add_string b) ss;
    Buffer.contents b

Unsynchronized accesses

Unsynchronized accesses to a buffer may lead to an invalid buffer state. Thus, concurrent accesses to a buffer must be synchronized (for instance with a Mutex.t).

Sourcetype t

The abstract type of buffers.

Sourceval create : int -> t

create n returns a fresh buffer, initially empty. The n parameter is the initial size of the internal byte sequence that holds the buffer contents. That byte sequence is automatically reallocated when more than n characters are stored in the buffer, but shrinks back to n characters when reset is called. For best performance, n should be of the same order of magnitude as the number of characters that are expected to be stored in the buffer (for instance, 80 for a buffer that holds one output line). Nothing bad will happen if the buffer grows beyond that limit, however. In doubt, take n = 16 for instance. If n is not between 1 and Sys.max_string_length, it will be clipped to that interval.

Sourceval contents : t -> string

Return a copy of the current contents of the buffer. The buffer itself is unchanged.

Sourceval to_bytes : t -> bytes

Return a copy of the current contents of the buffer. The buffer itself is unchanged.

  • since 4.02
Sourceval sub : t -> int -> int -> string

Buffer.sub b off len returns a copy of len bytes from the current contents of the buffer b, starting at offset off.

Sourceval blit : t -> int -> bytes -> int -> int -> unit

Buffer.blit src srcoff dst dstoff len copies len characters from the current contents of the buffer src, starting at offset srcoff to dst, starting at character dstoff.

  • raises Invalid_argument

    if srcoff and len do not designate a valid range of src, or if dstoff and len do not designate a valid range of dst.

  • since 3.11.2
Sourceval nth : t -> int -> char

Get the n-th character of the buffer.

Sourceval length : t -> int

Return the number of characters currently contained in the buffer.

Sourceval clear : t -> unit

Empty the buffer.

Sourceval reset : t -> unit

Empty the buffer and deallocate the internal byte sequence holding the buffer contents, replacing it with the initial internal byte sequence of length n that was allocated by Buffer.create n. For long-lived buffers that may have grown a lot, reset allows faster reclamation of the space used by the buffer.

Sourceval output_buffer : out_channel -> t -> unit

output_buffer oc b writes the current contents of buffer b on the output channel oc.

Sourceval truncate : t -> int -> unit

truncate b len truncates the length of b to len Note: the internal byte sequence is not shortened.

  • since 4.05

Appending

Note: all add_* operations can raise Failure if the internal byte sequence of the buffer would need to grow beyond Sys.max_string_length.

Sourceval add_char : t -> char -> unit

add_char b c appends the character c at the end of buffer b.

Sourceval add_utf_8_uchar : t -> Uchar.t -> unit

add_utf_8_uchar b u appends the UTF-8 encoding of u at the end of buffer b.

  • since 4.06
Sourceval add_utf_16le_uchar : t -> Uchar.t -> unit

add_utf_16le_uchar b u appends the UTF-16LE encoding of u at the end of buffer b.

  • since 4.06
Sourceval add_utf_16be_uchar : t -> Uchar.t -> unit

add_utf_16be_uchar b u appends the UTF-16BE encoding of u at the end of buffer b.

  • since 4.06
Sourceval add_string : t -> string -> unit

add_string b s appends the string s at the end of buffer b.

Sourceval add_bytes : t -> bytes -> unit

add_bytes b s appends the byte sequence s at the end of buffer b.

  • since 4.02
Sourceval add_substring : t -> string -> int -> int -> unit

add_substring b s ofs len takes len characters from offset ofs in string s and appends them at the end of buffer b.

Sourceval add_subbytes : t -> bytes -> int -> int -> unit

add_subbytes b s ofs len takes len characters from offset ofs in byte sequence s and appends them at the end of buffer b.

  • since 4.02
Sourceval add_substitute : t -> (string -> string) -> string -> unit

add_substitute b f s appends the string pattern s at the end of buffer b with substitution. The substitution process looks for variable references in the pattern and substitutes each variable reference with its value, as obtained by applying the mapping f to the variable name. Inside the string pattern, a variable reference is a non-escaped $ immediately followed by a variable name, which is one of the following:

  • a non empty sequence of alphanumeric or _ characters,
  • an arbitrary sequence of characters enclosed by a pair of matching parentheses or curly brackets. An escaped $ character is a $ that immediately follows a backslash character; the two characters together stand for a plain $.
Sourceval add_buffer : t -> t -> unit

add_buffer b1 b2 appends the current contents of buffer b2 at the end of buffer b1. b2 is not modified.

Sourceval add_channel : t -> in_channel -> int -> unit

add_channel b ic n reads at most n characters from the input channel ic and stores them at the end of buffer b.

  • raises End_of_file

    if the channel contains fewer than n characters. In this case, the characters are still added to the buffer, so as to avoid loss of data.

Buffers and Sequences

Sourceval to_seq : t -> char Seq.t

Iterate on the buffer, in increasing order.

The behavior is not specified if the buffer is modified during iteration.

  • since 4.07
Sourceval to_seqi : t -> (int * char) Seq.t

Iterate on the buffer, in increasing order, yielding indices along chars.

The behavior is not specified if the buffer is modified during iteration.

  • since 4.07
Sourceval add_seq : t -> char Seq.t -> unit

Add chars to the buffer

  • since 4.07
Sourceval of_seq : char Seq.t -> t

Create a buffer from the generator

  • since 4.07

Binary encoding of integers

The functions in this section append binary encodings of integers to buffers.

Little-endian (resp. big-endian) encoding means that least (resp. most) significant bytes are stored first. Big-endian is also known as network byte order. Native-endian encoding is either little-endian or big-endian depending on Sys.big_endian.

32-bit and 64-bit integers are represented by the int32 and int64 types, which can be interpreted either as signed or unsigned numbers.

8-bit and 16-bit integers are represented by the int type, which has more bits than the binary encoding. Functions that encode these values truncate their inputs to their least significant bytes.

Sourceval add_uint8 : t -> int -> unit

add_uint8 b i appends a binary unsigned 8-bit integer i to b.

  • since 4.08
Sourceval add_int8 : t -> int -> unit

add_int8 b i appends a binary signed 8-bit integer i to b.

  • since 4.08
Sourceval add_uint16_ne : t -> int -> unit

add_uint16_ne b i appends a binary native-endian unsigned 16-bit integer i to b.

  • since 4.08
Sourceval add_uint16_be : t -> int -> unit

add_uint16_be b i appends a binary big-endian unsigned 16-bit integer i to b.

  • since 4.08
Sourceval add_uint16_le : t -> int -> unit

add_uint16_le b i appends a binary little-endian unsigned 16-bit integer i to b.

  • since 4.08
Sourceval add_int16_ne : t -> int -> unit

add_int16_ne b i appends a binary native-endian signed 16-bit integer i to b.

  • since 4.08
Sourceval add_int16_be : t -> int -> unit

add_int16_be b i appends a binary big-endian signed 16-bit integer i to b.

  • since 4.08
Sourceval add_int16_le : t -> int -> unit

add_int16_le b i appends a binary little-endian signed 16-bit integer i to b.

  • since 4.08
Sourceval add_int32_ne : t -> int32 -> unit

add_int32_ne b i appends a binary native-endian 32-bit integer i to b.

  • since 4.08
Sourceval add_int32_be : t -> int32 -> unit

add_int32_be b i appends a binary big-endian 32-bit integer i to b.

  • since 4.08
Sourceval add_int32_le : t -> int32 -> unit

add_int32_le b i appends a binary little-endian 32-bit integer i to b.

  • since 4.08
Sourceval add_int64_ne : t -> int64 -> unit

add_int64_ne b i appends a binary native-endian 64-bit integer i to b.

  • since 4.08
Sourceval add_int64_be : t -> int64 -> unit

add_int64_be b i appends a binary big-endian 64-bit integer i to b.

  • since 4.08
Sourceval add_int64_le : t -> int64 -> unit

add_int64_ne b i appends a binary little-endian 64-bit integer i to b.

  • since 4.08