Module Buffer

module Buffer: sig .. end
Extensible string buffers.

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

type t
The abstract type of buffers.
val create : int -> t
create n returns a fresh buffer, initially empty. The n parameter is the initial size of the internal string that holds the buffer contents. That string 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.
val contents : t -> string
Return a copy of the current contents of the buffer. The buffer itself is unchanged.
val sub : t -> int -> int -> string
Buffer.sub b off len returns (a copy of) the substring of the current contents of the buffer b starting at offset off of length len bytes. May raise Invalid_argument if out of bounds request. The buffer itself is unaffected.
val blit : t -> int -> string -> 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 string dst, starting at character dstoff.

Raise Invalid_argument if srcoff and len do not designate a valid substring of src, or if dstoff and len do not designate a valid substring of dst.
Since 3.11.2
val nth : t -> int -> char
get the n-th character of the buffer. Raise Invalid_argument if index out of bounds
val length : t -> int
Return the number of characters currently contained in the buffer.
val clear : t -> unit
Empty the buffer.
val reset : t -> unit
Empty the buffer and deallocate the internal string holding the buffer contents, replacing it with the initial internal string 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.
val add_char : t -> char -> unit
add_char b c appends the character c at the end of the buffer b.
val add_string : t -> string -> unit
add_string b s appends the string s at the end of the buffer b.
val 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 the buffer b.
val add_substitute : t -> (string -> string) -> string -> unit
add_substitute b f s appends the string pattern s at the end of the buffer b with substitution. The substitution process looks for variables into the pattern and substitutes each variable name by its value, as obtained by applying the mapping f to the variable name. Inside the string pattern, a variable name immediately follows a non-escaped $ character and 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; it then stands for a plain $. Raise Not_found if the closing character of a parenthesized variable cannot be found.

val 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.
val add_channel : t -> Pervasives.in_channel -> int -> unit
add_channel b ic n reads exactly n character from the input channel ic and stores them at the end of buffer b. Raise End_of_file if the channel contains fewer than n characters.
val output_buffer : Pervasives.out_channel -> t -> unit
output_buffer oc b writes the current contents of buffer b on the output channel oc.