106 lines
3.5 KiB
Scheme
106 lines
3.5 KiB
Scheme
;;; Basic read and write
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;;; Copyright (c) 1993 by Olin Shivers.
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;;; Note: read ops should check to see if their string args are mutable.
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(define (bogus-substring-spec? s start end)
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(or (< start 0)
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(< (string-length s) end)
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(< end start)))
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;;; Best-effort/forward-progress reading
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (read-string!/partial s . args)
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(let-optionals args ((fd/port (current-input-port))
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(start 0)
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(end (string-length s)))
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(cond ((integer? fd/port)
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(let ((port (fdes->inport fd/port)))
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(set-port-buffering port bufpol/block (max (- end start) 0))
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(read-string!/partial port start end)))
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(else ; no differnce between fd/ports and s48 ports
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(let* ((buffer (make-string (- end start)))
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(needed (if (> (byte-vector-length (port-buffer fd/port)) 1)
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'any 'immediate)) ;bufpol/none may return with 0
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(len (read-block buffer 0 needed fd/port)))
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(if (eof-object? len)
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#f
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(begin
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(copy-bytes! buffer 0 s start len)
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len)))))))
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(define (read-string/partial len . maybe-fd/port)
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(let* ((s (make-string len))
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(fd/port (:optional maybe-fd/port (current-input-port)))
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(nread (read-string!/partial s fd/port 0 len)))
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(cond ((not nread) #f) ; EOF
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((= nread len) s)
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(else (substring s 0 nread)))))
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;;; Persistent reading
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;
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;;; Operation on ports is easy, since we can use read-block
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(define (read-string! s . args)
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(let-optionals args ((fd/port (current-input-port))
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(start 0)
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(end (string-length s)))
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(cond ((integer? fd/port)
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(let ((port (fdes->inport fd/port)))
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(set-port-buffering port bufpol/block (max (- end start) 0))
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(read-string! port start end)))
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(else ; no differnce between fd/port and s48 ports
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(let ((nbytes/eof (read-block s start (- end start) fd/port)))
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(if (eof-object? nbytes/eof)
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#f
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nbytes/eof))))))
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(define (read-string len . maybe-fd/port)
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(let* ((s (make-string len))
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(fd/port (:optional maybe-fd/port (current-input-port)))
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(nread (read-string! s fd/port 0 len)))
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(cond ((not nread) #f) ; EOF
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((= nread len) s)
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(else (substring s 0 nread)))))
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;;; Best-effort/forward-progress writing
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Non-blocking output to a buffered port is not defined.
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(define (write-string/partial s . args)
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(let-optionals args ((fd/port (current-output-port))
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(start 0)
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(end (string-length s)))
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(cond ((integer? fd/port)
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(let ((port (fdes->outport fd/port)))
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(set-port-buffering port bufpol/block (max (- end start) 0))
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(write-string/partial s port start end)))
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(else
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;; the only way to implement this, would be to use
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;; channel-maybe-write. But this is an VM-instruction which is not
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;; exported. Since we now have threads this shouldn;t matter.
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(error "write-string/parital is currently dereleased.
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See the RELEASE file for details")))))
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;;; Persistent writing
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (write-string s . args)
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(let-optionals args ((fd/port (current-output-port))
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(start 0)
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(end (string-length s)))
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(cond ((integer? fd/port)
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(let ((port (fdes->outport fd/port)))
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(set-port-buffering port bufpol/block (max (- end start) 0))
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(write-string s port start end)))
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(else (write-block s start (- end start) fd/port)))))
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