A position-based interface to character streams.
The streams are optimized for applications that mostly read a stream sequentially and occasionally backtrack over a bounded distance, which is a common usage pattern of backtracking parsers.
The characters in a character stream provided by this module are accessed based on their position in the stream. A position pos is valid in the stream s if it satisfies 0 <= pos < length s. Character streams can be created from input channels and from strings.
val from_string : string -> tfrom_string s creates a character stream that contains the characters of the string s.
val from_channel :
?block_size:int ->
?block_overlap:int ->
?min_rspace:int ->
in_channel ->
tfrom_channel ?block_size ?block_overlap ?min_rspace chn creates a character stream that contains the characters of the input channel chn. The behavior of the stream is undefined if the channel is modified subsequently.
When a character stream is created from an input channel, the characters in this channel are read in overlapping blocks, where block_size and block_overlap determine the size of a block and the amount of overlap. If the length of the channel is not greater than the block size, the whole channel is read at once. Otherwise, only a single block of the channel is kept in memory at a time. Whenever the current stream position leaves the part that is currently kept in memory, a new block is read from the channel. The channel must support seeking (i.e., must be created from a regular file) to enable this. If possible, blocks are read with the specified amount of overlap to minimize the re-reading of blocks due to backtracking. min_rspace specifies the minimum number of characters a regular expression is matched against (if possible) by match_regexp.
val length : t -> intlength s returns the number of characters in the stream s.
val seek : t -> int -> unitseek s pos prepares the stream for reading from position pos. If pos is outside the block currently held in memory, a block containing pos is read, replacing the old block.
val read_char : t -> int -> char optionread_char s pos returns Some c if c is the character at position pos in s, or None if this position is not a valid position in s.
val read_string : t -> int -> int -> stringread_string s pos maxlen returns a string containing the next n characters in s, where n is the minimum of maxlen and the number of characters remaining from position pos. If pos is not a valid position in s, the empty string is returned.
val match_char : t -> int -> char -> boolmatch_char s pos c is equivalent to read_char s pos = Some c.
val match_string : t -> int -> string -> boolmatch_string s pos str is equivalent to read_string s pos
(String.length str) = str.
module MakeRegexp (Regexp : MParser_Sig.Regexp) : sig ... end