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|
; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Mike Sperber
; Character/string encodings
; We abstract over the primitive encode-char/decode-char characters to
; get two sets of procedures, one going through the general
; text-encoding infrastructure, and the other making use of the VM
; instructions.
(define-syntax define-coding-procs
(syntax-rules ()
((define-coding-procs
(do-encode-char do-decode-char)
char-encoding-length
string-encoding-length
encode-char
encode-string
string->bytes-n
string->bytes
decode-char
bytes-string-size
decode-string
bytes->string
bytes->string-n)
(begin
(define (char-encoding-length enc c)
(call-with-values
(lambda ()
(do-encode-char enc c empty-buffer 0 0))
(lambda (ok? count)
count)))
(define (string-encoding-length enc s start-index count)
(let loop ((enc-length 0)
(char-index 0))
(if (>= char-index count)
enc-length
(loop (+ enc-length
(char-encoding-length enc (string-ref s (+ start-index char-index))))
(+ 1 char-index)))))
; returns byte count of the encoding
(define (encode-char enc c target target-start)
(call-with-values
(lambda ()
(do-encode-char enc
c target target-start
(- (byte-vector-length target) target-start)))
(lambda (ok? count)
count)))
; Will only produce complete encodings
; returns three values:
; - encoding status
; - # characters consumed
; - # bytes decoded
(define (encode-string enc source source-start source-count
target target-start target-count)
(let loop ((source-index 0)
(target-index 0))
(cond
((>= source-index source-count)
(values (enum encoding-status complete)
source-index
target-index))
((>= target-index target-count)
(values (enum encoding-status insufficient)
source-index
target-index))
(else
(let ((c (string-ref source (+ source-start source-index))))
(call-with-values
(lambda ()
(do-encode-char enc
c
target (+ target-start target-index)
(max 0 (- target-count target-index))))
(lambda (ok? count)
(if (not ok?)
(values (enum encoding-status insufficient)
source-index
target-index)
(loop (+ source-index 1) (+ target-index count))))))))))
(define (string->bytes-n enc s start count)
(let* ((size (string-encoding-length enc s 0 count))
(result (make-byte-vector size 0)))
(encode-string enc s 0 count result 0 size)
result))
(define (string->bytes enc s)
(string->bytes-n enc s 0 (string-length s)))
; Decoding
; Returns three values:
; - decoding status
; - character if status is COMPLETE, else #f
; - # bytes consumed if COMPLETE or INCOMPLETE, else #f
(define (decode-char enc bytes start-index count)
(call-with-values
(lambda ()
(do-decode-char enc
bytes start-index
count))
(lambda (maybe-char count)
(cond
(maybe-char
(values (enum decoding-status complete)
maybe-char
count))
(count
(values (enum decoding-status incomplete)
#f
count))
(else
(values (enum decoding-status invalid)
#f
#f))))))
; If STOP-AT-INVALID? is #f, we'll skip an invalid byte, and pretend
; it generated one character.
; Returns three values:
; - :DECODING-STATUS object
; - # bytes consumed
; - # characters decoded
(define (bytes-string-size enc bytes start count stop-at-invalid?)
(let loop ((index 0)
(target-index 0))
(if (>= index count)
(values (enum decoding-status complete)
index target-index)
(call-with-values
(lambda ()
(do-decode-char enc
bytes
(+ start index)
(- count index)))
(lambda (char count)
(cond
(char
(loop (+ index count) (+ target-index 1)))
(count
(values (enum decoding-status incomplete)
index target-index))
(stop-at-invalid?
(values (enum decoding-status invalid)
index target-index))
(else
(loop (+ 1 index) (+ 1 target-index)))))))))
; Returns three values:
; - :DECODING-STATUS object
; - # bytes consumed
; - # characters decoded
(define (decode-string enc
bytes start count
target target-start target-count
maybe-error-char)
(let loop ((index 0)
(target-index 0))
(cond
((>= index count)
(values (enum decoding-status complete)
index
target-index))
((>= target-index target-count)
(values (enum decoding-status insufficient)
index target-index))
(else
(call-with-values
(lambda ()
(do-decode-char enc
bytes
(+ start index)
(- count index)))
(lambda (char count)
(cond
(char
(string-set! target (+ target-start target-index) char)
(loop (+ index count) (+ target-index 1)))
(count
(values (enum decoding-status incomplete)
index target-index))
(maybe-error-char
(string-set! target (+ target-start target-index) maybe-error-char)
(loop (+ 1 index) (+ 1 target-index)))
(else
(values (enum decoding-status invalid)
index target-index)))))))))
; may be slightly faster because of REVERSE-LIST->STRING
; If MAYBE-ERROR-CHAR is #f, we'll raise an error upon an invalid encoding
; If it's a character, it will be used at invalid *and incomplete* encodings
(define (bytes->string enc source maybe-error-char)
(bytes->string-n enc source 0 (byte-vector-length source) maybe-error-char))
(define (bytes->string-n enc source start source-count maybe-error-char)
(let loop ((rev-chars '())
(char-count 0)
(source-index 0))
(if (>= source-index source-count)
(reverse-list->string rev-chars char-count)
(call-with-values
(lambda ()
(do-decode-char enc
source
(+ start source-index)
(- source-count source-index)))
(lambda (char count)
(cond
(char
(loop (cons char rev-chars)
(+ 1 char-count)
(+ count source-index)))
(maybe-error-char
(loop (cons maybe-error-char rev-chars)
(+ 1 char-count)
(+ 1 source-index)))
(count
(decoding-error enc ; ####
"incomplete encoding"
source (+ start source-index)))
(else
(decoding-error enc ; ####
"invalid encoding"
source (+ start source-index)))))))))
))))
(define-coding-procs (char->utf utf->char)
char-encoding-length/encoding
string-encoding-length/encoding
encode-char/encoding
encode-string/encoding
string->bytes-n/encoding
string->bytes/encoding
decode-char/encoding
bytes-string-size/encoding
decode-string/encoding
bytes->string/encoding
bytes->string-n/encoding)
(define-syntax primitive-encode-char/text-codec
(syntax-rules ()
((encode-char/text-codec enc ch buffer start count)
(atomically
((text-codec-encode-char-proc enc) ch buffer start count)))))
(define-syntax primitive-decode-char/text-codec
(syntax-rules ()
((decode-char/text-codec enc buffer start count)
(atomically
((text-codec-decode-char-proc enc) buffer start count)))))
(define-coding-procs (primitive-encode-char/text-codec primitive-decode-char/text-codec)
char-encoding-length/text-codec
string-encoding-length/text-codec
encode-char/text-codec
encode-string/text-codec
string->bytes-n/text-codec
string->bytes/text-codec
decode-char/text-codec
bytes-string-size/text-codec
decode-string/text-codec
bytes->string/text-codec
bytes->string-n/text-codec)
(define-syntax define-text-codec-proc
(syntax-rules ()
((define-text-codec-proc (?name ?arg ...) ?name/codec ?name/encoding)
(define (?name codec ?arg ...)
(let ((spec (text-codec->spec codec)))
(if (text-codec? spec)
(?name/codec spec ?arg ...)
(?name/encoding spec ?arg ...)))))))
(define-text-codec-proc (char-encoding-length c)
char-encoding-length/text-codec char-encoding-length/encoding)
(define-text-codec-proc (string-encoding-length s start-index count)
string-encoding-length/text-codec string-encoding-length/encoding)
(define-text-codec-proc (encode-char c target target-start)
encode-char/text-codec encode-char/encoding)
(define-text-codec-proc (encode-string source source-start source-count
target target-start target-count)
encode-string/text-codec encode-string/encoding)
(define-text-codec-proc (string->bytes-n s start count)
string->bytes-n/text-codec string->bytes-n/encoding)
(define-text-codec-proc (string->bytes s)
string->bytes/text-codec string->bytes/encoding)
(define-text-codec-proc (decode-char bytes start-index count)
decode-char/text-codec decode-char/encoding)
(define-text-codec-proc (bytes-string-size bytes start count stop-at-invalid?)
bytes-string-size/text-codec bytes-string-size/encoding)
(define-text-codec-proc (decode-string bytes start count
target target-start target-count
maybe-error-char)
decode-string/text-codec decode-string/encoding)
(define-text-codec-proc (bytes->string source maybe-error-char)
bytes->string/text-codec bytes->string/encoding)
(define-text-codec-proc (bytes->string-n source start source-count maybe-error-char)
bytes->string-n/text-codec bytes->string-n/encoding)
;; Utilities
(define empty-buffer (make-byte-vector 0 0))
(define-enumeration encoding-status
(complete insufficient))
(define (decoding-error encoding-name
message
bytes start)
(raise
(make-message-condition
(string-append "error while decoding " encoding-name ": " message))
(make-decoding-error encoding-name
bytes start)))
(define-enumeration decoding-status
(complete incomplete insufficient invalid))
;; UTF-8
(define (char-encoding-length/utf-8 c)
(char-encoding-length/encoding (enum text-encoding-option utf-8) c))
(define (string-encoding-length/utf-8 s start-index count)
(string-encoding-length/encoding (enum text-encoding-option utf-8)
s start-index count))
(define (encode-char/utf-8 c target target-start)
(encode-char/encoding (enum text-encoding-option utf-8) c target target-start))
(define (encode-string/utf-8 source source-start source-count
target target-start target-count)
(encode-string/encoding (enum text-encoding-option utf-8)
source source-start source-count
target target-start target-count))
(define (string->utf-8-n s start count)
(string->bytes-n/encoding (enum text-encoding-option utf-8) s start count))
(define (string->utf-8 s)
(string->bytes/encoding (enum text-encoding-option utf-8) s))
(define (decode-char/utf-8 bytes start-index count)
(decode-char/encoding (enum text-encoding-option utf-8) bytes start-index count))
(define (bytes-string-size/utf-8 bytes start count stop-at-invalid?)
(bytes-string-size/encoding (enum text-encoding-option utf-8)
bytes start count stop-at-invalid?))
(define (decode-string/utf-8 bytes start count
target target-start target-count
maybe-error-char)
(decode-string/encoding (enum text-encoding-option utf-8)
bytes start count
target target-start target-count
maybe-error-char))
(define (utf-8->string source maybe-error-char)
(bytes->string/encoding (enum text-encoding-option utf-8)
source maybe-error-char))
(define (utf-8->string-n source start source-count maybe-error-char)
(bytes->string-n/encoding (enum text-encoding-option utf-8)
source start source-count maybe-error-char))
|
