604 lines
18 KiB
Scheme
604 lines
18 KiB
Scheme
; Copyright (c) 1993-1999 by Richard Kelsey and Jonathan Rees. See file COPYING.
|
|
|
|
; Ports and port handlers
|
|
|
|
; See doc/io.txt for a description of the i/o system, including ports,
|
|
; port handlers, and so forth.
|
|
|
|
(define-record-type port-handler :port-handler
|
|
(make-port-handler discloser close buffer-proc)
|
|
port-handler?
|
|
(discloser port-handler-discloser)
|
|
(close port-handler-close)
|
|
(buffer-proc port-handler-buffer-proc))
|
|
|
|
(define (disclose-port port)
|
|
((port-handler-discloser (port-handler port)) (port-data port)))
|
|
|
|
(define-method &disclose ((port :input-port))
|
|
(disclose-port port))
|
|
|
|
(define-method &disclose ((port :output-port))
|
|
(disclose-port port))
|
|
|
|
; The PORT-LOCKED? bit is checked by READ-CHAR, PEEK-CHAR, and WRITE-CHAR
|
|
; which are too simple-minded to understand real locks. The three procedures
|
|
; below ensure that (PORT-LOCKED? <port>) is #t whenever someone has aquired
|
|
; <port>'s lock.
|
|
|
|
(define (obtain-port-lock port)
|
|
(set-port-locked?! port #t)
|
|
(obtain-lock (port-lock port)))
|
|
|
|
(define (maybe-obtain-port-lock port)
|
|
(let ((ints (set-enabled-interrupts! 0)))
|
|
(set-port-locked?! port #t)
|
|
(let ((result (if (maybe-obtain-lock (port-lock port))
|
|
#t
|
|
(begin
|
|
(set-port-locked?! port #f)
|
|
#f))))
|
|
(set-enabled-interrupts! ints)
|
|
result)))
|
|
|
|
(define (release-port-lock port)
|
|
(let ((ints (set-enabled-interrupts! 0)))
|
|
(if (release-lock (port-lock port))
|
|
(set-port-locked?! port #f))
|
|
(set-enabled-interrupts! ints)))
|
|
|
|
; Set up exception handlers for the three unnecessary I/O primitives,
|
|
; READ-CHAR, PEEK-CHAR, and WRITE-CHAR. These do the right thing in
|
|
; the case of buffer overflow or underflow.
|
|
;
|
|
; This is abstracted to avoid a circular module dependency.
|
|
|
|
(define (initialize-i/o-handlers! define-exception-handler signal-exception)
|
|
(define-exception-handler (enum op read-char)
|
|
(one-arg-proc->handler (read-char-handler #t) signal-exception))
|
|
|
|
(define-exception-handler (enum op peek-char)
|
|
(one-arg-proc->handler (read-char-handler #f) signal-exception))
|
|
|
|
(define-exception-handler (enum op write-char)
|
|
(two-arg-proc->handler write-char-handler signal-exception)))
|
|
|
|
; Check the exception and then lock the port.
|
|
|
|
(define (one-arg-proc->handler proc signal-exception)
|
|
(lambda (opcode reason port)
|
|
(if (= reason (enum exception buffer-full/empty))
|
|
(begin
|
|
(obtain-port-lock port)
|
|
(let ((value (proc port)))
|
|
(release-port-lock port)
|
|
value))
|
|
(signal-exception opcode reason port))))
|
|
|
|
; This could combined with on-arg-... if the port were the first argument.
|
|
|
|
(define (two-arg-proc->handler proc signal-exception)
|
|
(lambda (opcode reason arg port)
|
|
(if (= reason (enum exception buffer-full/empty))
|
|
(begin
|
|
(obtain-port-lock port)
|
|
(let ((value (proc arg port)))
|
|
(release-port-lock port)
|
|
value))
|
|
(signal-exception opcode reason arg port))))
|
|
|
|
; If a character is available, use it; if there is an EOF waiting, use that;
|
|
; otherwise fill the buffer and go from there.
|
|
|
|
(define (read-char-handler read?)
|
|
(lambda (port)
|
|
(cond ((< (port-index port) (port-limit port))
|
|
(let ((index (port-index port)))
|
|
(if read?
|
|
(set-port-index! port (+ 1 index)))
|
|
(ascii->char (code-vector-ref (port-buffer port) index))))
|
|
((port-pending-eof? port)
|
|
(if read?
|
|
(set-port-pending-eof?! port #f))
|
|
(eof-object))
|
|
(else
|
|
(let ((got (fill-port-buffer! port 'any)))
|
|
(cond ((or (eof-object? got)
|
|
(= 0 got))
|
|
(if (not read?)
|
|
(set-port-pending-eof?! port #t))
|
|
(eof-object))
|
|
(else
|
|
(set-port-index! port (if read? 1 0))
|
|
(set-port-limit! port got)
|
|
(ascii->char (code-vector-ref (port-buffer port) 0)))))))))
|
|
|
|
(define (fill-port-buffer! port needed)
|
|
((port-handler-buffer-proc (port-handler port))
|
|
(port-data port)
|
|
(port-buffer port)
|
|
0
|
|
needed))
|
|
|
|
; Write the character if there is room, or call the handler if there is
|
|
; no actual buffering. Otherwise use the handler to empty the buffer.
|
|
|
|
(define (write-char-handler char port)
|
|
(cond ((< (port-index port) (port-limit port))
|
|
(code-vector-set! (port-buffer port)
|
|
(port-index port)
|
|
(char->ascii char))
|
|
(set-port-index! port (+ 1 (port-index port))))
|
|
((= 0 (port-limit port))
|
|
((port-handler-buffer-proc (port-handler port)) (port-data port) char))
|
|
(else
|
|
(empty-port-buffer! port)
|
|
(code-vector-set! (port-buffer port) 0 (char->ascii char))
|
|
(set-port-index! port 1)))
|
|
(unspecific))
|
|
|
|
; This may change PORT's buffer.
|
|
|
|
(define (empty-port-buffer! port)
|
|
((port-handler-buffer-proc (port-handler port))
|
|
(port-data port)
|
|
(port-buffer port)
|
|
0
|
|
(port-index port))
|
|
(set-port-index! port 0)
|
|
(set-port-flushed?! port #t))
|
|
|
|
(define port-flushed? port-pending-eof?)
|
|
(define set-port-flushed?! set-port-pending-eof?!)
|
|
|
|
;----------------
|
|
; Closing is done with the appropriate handler.
|
|
; R4RS says that CLOSE-... is idempotent.
|
|
|
|
(define (close-input-port port)
|
|
(if (input-port? port)
|
|
(begin
|
|
(obtain-port-lock port)
|
|
(if (open-input-port? port)
|
|
(begin
|
|
(make-input-port-closed! port)
|
|
((port-handler-close (port-handler port)) (port-data port))))
|
|
(release-port-lock port))
|
|
(call-error "invalid argument" close-input-port port)))
|
|
|
|
(define (close-output-port port)
|
|
(if (output-port? port)
|
|
(begin
|
|
(obtain-port-lock port)
|
|
(if (open-output-port? port)
|
|
(begin
|
|
(really-force-output port)
|
|
(make-output-port-closed! port)
|
|
((port-handler-close (port-handler port)) (port-data port))))
|
|
(release-port-lock port))
|
|
(call-error "invalid argument" close-output-port port)))
|
|
|
|
;----------------
|
|
; Port operations that do not have opcodes. Each of these needs to check its
|
|
; arguments and then lock the port. A macro is used to add the checking and
|
|
; locking code. This has to check that the port is a port before locking it
|
|
; and then check that it is open after locking it.
|
|
|
|
; A macro to handle locking ports and checking that they're open.
|
|
|
|
(define-syntax define-port-op
|
|
(syntax-rules ()
|
|
((define-port-op (?id ?args ...) ?port ?predicate ?body)
|
|
(define (?id ?args ...)
|
|
(if ?predicate ; if args are okay
|
|
(begin
|
|
(obtain-port-lock ?port) ; lock the port
|
|
(if (open-port? ?port) ; check that it's open
|
|
(let ((value ?body)) ; do the work
|
|
(release-port-lock ?port) ; release the lock
|
|
value) ; return
|
|
(begin
|
|
(release-port-lock ?port)
|
|
(call-error "invalid argument" ?id ?args ...))))
|
|
(call-error "invalid argument" ?id ?args ...))))
|
|
|
|
; ?port defaults to the first argument
|
|
((define-port-op (?id ?port ?args ...) ?predicate ?body)
|
|
(define-port-op (?id ?port ?args ...) ?port ?predicate ?body))))
|
|
|
|
;----------------
|
|
; See if there is a character available. CHAR-READY? itself is defined
|
|
; in current-ports.scm as it needs CURRENT-INPUT-PORT when called with
|
|
; no arguments.
|
|
|
|
(define (real-char-ready? port)
|
|
(cond ((not (open-input-port? port))
|
|
(call-error "invalid argument" char-ready? port))
|
|
((not (maybe-obtain-port-lock port))
|
|
#f)
|
|
((not (open-port? port)) ; have to check again after the lock call
|
|
(release-port-lock port)
|
|
(call-error "invalid argument" char-ready? port))
|
|
((or (< (port-index port) (port-limit port))
|
|
(port-pending-eof? port))
|
|
(release-port-lock port)
|
|
#t)
|
|
(else
|
|
(let ((got (fill-port-buffer! port 'immediate)))
|
|
(cond ((eof-object? got)
|
|
(set-port-pending-eof?! port #t)
|
|
(release-port-lock port)
|
|
#t)
|
|
(else
|
|
(set-port-index! port 0)
|
|
(set-port-limit! port got)
|
|
(release-port-lock port)
|
|
(> got 0)))))))
|
|
|
|
;----------------
|
|
; Check the arguments and the state of the buffer. Leave any actual work
|
|
; up to the next procedure.
|
|
;
|
|
; The arguments are the same as those for input port handlers: BUFFER is either
|
|
; a string or a code vector, START is the initial index, and COUNT is either
|
|
; the required number of characters, 'ANY (one or more characters wanted),
|
|
; or 'IMMEDIATE (get what's available, but don't block).
|
|
|
|
(define-port-op (read-block buffer start count port) port
|
|
(and (open-input-port? port)
|
|
(okay-limits? buffer start (if (or (eq? count 'any)
|
|
(eq? count 'immediate))
|
|
1
|
|
count)))
|
|
(cond ((port-pending-eof? port)
|
|
(set-port-pending-eof?! port #f)
|
|
(eof-object))
|
|
((eq? count 0)
|
|
0)
|
|
(else
|
|
(really-read-block buffer start count port))))
|
|
|
|
; If nothing is available, call the port's handler procedure. Otherwise,
|
|
; copy any available characters into the buffer. If more are needed the
|
|
; buffer handler is called.
|
|
|
|
(define (really-read-block buffer start count port)
|
|
(let ((have (- (port-limit port) (port-index port))))
|
|
(if (= have 0)
|
|
((port-handler-buffer-proc (port-handler port))
|
|
(port-data port)
|
|
buffer
|
|
start
|
|
count)
|
|
(let ((move (min have
|
|
(if (symbol? count)
|
|
(- (buffer-length buffer) start)
|
|
count))))
|
|
(copy-bytes! (port-buffer port) (port-index port) buffer start move)
|
|
(set-port-index! port (+ (port-index port) move))
|
|
(if (or (symbol? count)
|
|
(= move count))
|
|
move
|
|
(read-more buffer start count port move))))))
|
|
|
|
(define (buffer-length buffer)
|
|
(if (string? buffer)
|
|
(string-length buffer)
|
|
(code-vector-length buffer)))
|
|
|
|
(define (read-more buffer start count port have)
|
|
(let ((more ((port-handler-buffer-proc (port-handler port))
|
|
(port-data port)
|
|
buffer
|
|
(+ start have)
|
|
(- count have))))
|
|
(if (eof-object? more)
|
|
(if (= 0 have)
|
|
(eof-object)
|
|
(begin
|
|
(set-port-pending-eof?! port #t)
|
|
have))
|
|
(+ more have))))
|
|
|
|
; Check that BUFFER contains COUNT characters starting from START.
|
|
|
|
(define (okay-limits? buffer start count)
|
|
(and (integer? start)
|
|
(exact? start)
|
|
(<= 0 start)
|
|
(integer? count)
|
|
(exact? count)
|
|
(<= 0 count)
|
|
(<= (+ start count)
|
|
(cond ((string? buffer)
|
|
(string-length buffer))
|
|
((code-vector? buffer)
|
|
(code-vector-length buffer))
|
|
(else
|
|
-1)))))
|
|
|
|
;----------------
|
|
; Write the COUNT bytes beginning at START from BUFFER to PORT.
|
|
|
|
(define-port-op (write-block buffer start count port) port
|
|
(and (open-output-port? port)
|
|
(okay-limits? buffer start count))
|
|
(if (= 0 (port-limit port))
|
|
(write-unbuffered-block buffer start count port)
|
|
(write-buffered-block buffer start count port)))
|
|
|
|
; WRITE-STRING is a front for WRITE-BLOCK.
|
|
|
|
(define (write-string string port)
|
|
(write-block string 0 (string-length string) port))
|
|
|
|
; Copy the bytes into the buffer if there is room, otherwise write out anything
|
|
; in the buffer and then write BUFFER.
|
|
|
|
(define (write-buffered-block buffer start count port)
|
|
(let ((space (- (port-limit port) (port-index port))))
|
|
(cond ((>= space count)
|
|
(copy-bytes! buffer start (port-buffer port) (port-index port) count)
|
|
(set-port-index! port (+ (port-index port) count)))
|
|
(else
|
|
(really-force-output port)
|
|
((port-handler-buffer-proc (port-handler port))
|
|
(port-data port) buffer start count)))))
|
|
|
|
; For unbuffered ports we have to call the handler on each character
|
|
; separately.
|
|
|
|
(define (write-unbuffered-block buffer start count port)
|
|
(let ((proc (port-handler-buffer-proc (port-handler port)))
|
|
(data (port-data port))
|
|
(string? (string? buffer)))
|
|
(do ((i 0 (+ i 1)))
|
|
((= i count))
|
|
(proc data (if string?
|
|
(string-ref buffer (+ start i))
|
|
(ascii->char (code-vector-ref buffer (+ start i))))))))
|
|
|
|
;----------------
|
|
; Empty the buffer if it contains anything.
|
|
|
|
(define-port-op (force-output port)
|
|
(open-output-port? port)
|
|
(really-force-output port))
|
|
|
|
(define (really-force-output port)
|
|
(if (< 0 (port-index port))
|
|
(empty-port-buffer! port)))
|
|
|
|
; Used to avoid race conditions elsewhere.
|
|
|
|
(define (force-output-if-open port)
|
|
(if (output-port? port)
|
|
(begin
|
|
(obtain-port-lock port)
|
|
(if (open-output-port? port)
|
|
(really-force-output port))
|
|
(release-port-lock port))
|
|
(call-error "invalid argument" force-output-if-open port)))
|
|
|
|
;----------------
|
|
|
|
(define default-buffer-size 4096) ; should get this from the system
|
|
|
|
;----------------
|
|
; Is PORT open?
|
|
|
|
(define (open-port? port)
|
|
(not (= 0 (bitwise-and open-port-mask (port-status port)))))
|
|
|
|
(define open-port-mask
|
|
(bitwise-ior (arithmetic-shift 1 (enum port-status-options open-for-input))
|
|
(arithmetic-shift 1 (enum port-status-options open-for-output))))
|
|
|
|
;----------------
|
|
; Input ports
|
|
|
|
(define input-port-mask
|
|
(arithmetic-shift 1 (enum port-status-options input)))
|
|
|
|
(define open-input-port-mask
|
|
(arithmetic-shift 1 (enum port-status-options open-for-input)))
|
|
|
|
(define open-input-port-status
|
|
(bitwise-ior input-port-mask open-input-port-mask))
|
|
|
|
(define (open-input-port? port)
|
|
(not (= 0 (bitwise-and open-input-port-mask (port-status port)))))
|
|
|
|
(define (make-input-port-closed! port)
|
|
(set-port-status! port (bitwise-and (port-status port)
|
|
(bitwise-not open-input-port-mask))))
|
|
|
|
(define (make-input-port handler data buffer index limit)
|
|
(if (and (okay-buffer? buffer index limit)
|
|
(port-handler? handler))
|
|
(make-port handler
|
|
(bitwise-ior input-port-mask open-input-port-mask)
|
|
(make-lock)
|
|
#f ; locked?
|
|
data
|
|
buffer
|
|
index
|
|
limit
|
|
#f) ; pending-eof?
|
|
(call-error "invalid argument"
|
|
make-input-port handler data buffer index limit)))
|
|
|
|
(define (okay-buffer? buffer index limit)
|
|
(and (code-vector? buffer)
|
|
(let ((length (code-vector-length buffer)))
|
|
(integer? limit)
|
|
(<= 0 limit)
|
|
(<= limit length)
|
|
(<= index limit)
|
|
(integer? index)
|
|
(<= 0 index)
|
|
(<= index limit))))
|
|
|
|
;----------------
|
|
; Output ports
|
|
|
|
(define output-port-mask
|
|
(arithmetic-shift 1 (enum port-status-options output)))
|
|
|
|
(define open-output-port-mask
|
|
(arithmetic-shift 1 (enum port-status-options open-for-output)))
|
|
|
|
(define open-output-port-status
|
|
(bitwise-ior output-port-mask open-output-port-mask))
|
|
|
|
(define (open-output-port? port)
|
|
(not (= 0 (bitwise-and open-output-port-mask (port-status port)))))
|
|
|
|
(define (make-output-port-closed! port)
|
|
(set-port-status! port (bitwise-and (port-status port)
|
|
(bitwise-not open-output-port-mask))))
|
|
|
|
(define (make-output-port handler data buffer index limit)
|
|
(if (and (okay-buffer? buffer index limit)
|
|
(> limit 0)
|
|
(port-handler? handler))
|
|
(make-port handler
|
|
open-output-port-status
|
|
(make-lock)
|
|
#f ; locked?
|
|
data
|
|
buffer
|
|
index
|
|
limit
|
|
#f) ; pending-eof?
|
|
(call-error "invalid argument"
|
|
make-output-port handler data buffer index limit)))
|
|
|
|
(define (make-unbuffered-output-port handler data)
|
|
(if (port-handler? handler)
|
|
(make-port handler
|
|
open-output-port-status
|
|
(make-lock)
|
|
#f ; locked?
|
|
data
|
|
(make-code-vector 0 0)
|
|
0
|
|
0
|
|
#f) ; pending-eof?
|
|
(call-error "invalid argument"
|
|
make-unbuffered-output-port handler data)))
|
|
|
|
(define null-output-port-handler
|
|
(make-port-handler
|
|
(lambda (ignore)
|
|
(list 'null-output-port))
|
|
(lambda (ignore)
|
|
(unspecific))
|
|
(lambda (channel buffer start need)
|
|
(unspecific))))
|
|
|
|
(define (make-null-output-port)
|
|
(make-port null-output-port-handler
|
|
open-output-port-status
|
|
(make-lock) ; wasted
|
|
#f ; locked?
|
|
(unspecific)
|
|
(make-code-vector 1 0)
|
|
0
|
|
1 ; if 0 it would look unbuffered
|
|
#f)) ; pending-eof?
|
|
|
|
;----------------
|
|
; Code to periodically flush output ports.
|
|
|
|
(define *flush-these-ports* (cons #f '()))
|
|
|
|
(define (initialize-output-port-list!)
|
|
(set! *flush-these-ports* (cons #f '())))
|
|
|
|
(define (periodically-force-output! port)
|
|
(set-cdr! *flush-these-ports*
|
|
(cons (make-weak-pointer port) (cdr *flush-these-ports*))))
|
|
|
|
; Return a list of thunks that will flush the buffer of each open, unlocked
|
|
; port that contains characters that have been there since the last time
|
|
; this was called. The actual i/o is done using separate threads to keep
|
|
; i/o errors from killing anything vital.
|
|
;
|
|
; If USE-FLUSHED?-FLAGS? is true this won't flush buffers that have been
|
|
; flushed by someone else sinse the last call. If it is false then flush
|
|
; all non-empty buffers, because the system has nothing to do and is going
|
|
; to pause while waiting for external events.
|
|
|
|
(define (output-port-forcers use-flushed?-flags?)
|
|
(let loop ((next (cdr *flush-these-ports*))
|
|
(last *flush-these-ports*)
|
|
(thunks '()))
|
|
(if (null? next)
|
|
thunks
|
|
(let ((port (weak-pointer-ref (car next))))
|
|
(cond ((or (not port) ; GCed or closed
|
|
(not (open-output-port? port))) ; so drop it from the list
|
|
(set-cdr! last (cdr next))
|
|
(loop (cdr next) last thunks))
|
|
((not (maybe-obtain-port-lock port)) ; locked
|
|
(loop (cdr next) next thunks))
|
|
((and use-flushed?-flags? ; flushed recently
|
|
(port-flushed? port))
|
|
(set-port-flushed?! port #f)
|
|
(release-port-lock port)
|
|
(loop (cdr next) next thunks))
|
|
((< 0 (port-index port)) ; non-empty
|
|
(release-port-lock port)
|
|
(loop (cdr next) next
|
|
(cons (make-forcing-thunk port)
|
|
thunks)))
|
|
(else ; empty
|
|
(release-port-lock port)
|
|
(loop (cdr next) next thunks)))))))
|
|
|
|
; Returns a list of the current ports that are flushed whenever.
|
|
; This is used to flush channel ports before forking.
|
|
|
|
(define (periodically-flushed-ports)
|
|
(let ((ints (set-enabled-interrupts! 0)))
|
|
(let loop ((next (cdr *flush-these-ports*))
|
|
(last *flush-these-ports*)
|
|
(ports '()))
|
|
(if (null? next)
|
|
(begin
|
|
(set-enabled-interrupts! ints)
|
|
ports)
|
|
(let ((port (weak-pointer-ref (car next))))
|
|
(cond ((or (not port) ; GCed or closed
|
|
(not (open-output-port? port))) ; so drop it from the list
|
|
(set-cdr! last (cdr next))
|
|
(loop (cdr next) last ports))
|
|
(else
|
|
(loop (cdr next)
|
|
next
|
|
(cons port ports)))))))))
|
|
|
|
; Write out PORT's buffer. If a problem occurs it is reported and PORT
|
|
; is closed.
|
|
|
|
(define (make-forcing-thunk port)
|
|
(lambda ()
|
|
(if (and (report-errors-as-warnings
|
|
(lambda ()
|
|
(if (maybe-obtain-port-lock port)
|
|
(begin
|
|
(really-force-output port)
|
|
(release-port-lock port))))
|
|
"error when flushing buffer; closing port"
|
|
port)
|
|
(open-output-port? port))
|
|
(report-errors-as-warnings
|
|
(lambda ()
|
|
(make-output-port-closed! port)
|
|
((port-handler-close (port-handler port)) (port-data port)))
|
|
"error when closing port"
|
|
port))))
|
|
|
|
|