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#lang scheme/base
;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; PARSEQ.PLT
;; A Parser Combinator library.
;;
;; Bonzai Lab, LLC. All rights reserved.
;;
;; Licensed under LGPL.
;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; input.ss - holds the abstraction of the input object...
;; yc 12/31/2009 - first version
;; yc 1/8/2009 - fix build-input & Input/c
(require scheme/contract)
;; state
;; the struct that abstracts the input
;; currently this holds an input-port + the position on the port
;; in the future this can be used to hold string, list, vector, etc.
(define-struct input (source pos) #:prefab)
;; input
;; an utility for converting source into input state.
(define (build-input v (pos 0))
(define (helper v)
(cond ((input-port? v) v)
((string? v) (open-input-string v))
((bytes? v) (open-input-bytes v))))
(if (input? v)
(new-input v pos)
(make-input (helper v) pos)))
;; new-input
;; make a new input based on the old input and a new position...
(define (new-input input incr)
(make-input (input-source input)
(+ incr (input-pos input))))
;; peek-bytes*
;; return a funtion that will make a particular amount of reading based on
;; the requested size...
(define (peek-bytes* size)
(lambda (in)
(peek-bytes size (input-pos in) (input-source in))))
;; peek-string*
;; return a function that will read a particular size of string...
;; this can fail since it is expected to be using utf-8 as the input size...
(define (peek-string* size)
(lambda (in)
(peek-string size (input-pos in) (input-source in))))
;; peek-byte*
;; peek a single byte
(define (peek-byte* in)
(peek-byte (input-source in) (input-pos in)))
;; peek-char*
;; peek a single char
(define (peek-char* in)
(peek-char (input-source in) (input-pos in)))
;; read-bytes*
;; read out the bytes based on the size of the input...
(define (read-bytes* in)
(read-bytes (input-pos in) (input-source in)))
(define Input/c (or/c input? bytes? string? input-port?))
(define Parser/c (-> Input/c (values any/c Input/c)))
(provide input
input?
input-source
input-pos
(rename-out (build-input make-input))
new-input
peek-bytes*
peek-string*
peek-byte*
peek-char*
read-bytes*
Input/c
Parser/c
)
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