Buffer(3)

NAME
Buffer - Extensible string buffers.

Module
Module Buffer

Documentation

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 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 .