92 lines
2.0 KiB
C
92 lines
2.0 KiB
C
/* Copyright (c) 1994 by Olin Shivers.
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** Copyright (c) 1994-1995 by Brian D. Carlstrom.
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**
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** This file implements the char-ready? procedure for file descriptors
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** and Scsh's fdports. It is not Posix, so it must be implemented for
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** each OS to which scsh is ported.
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**
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** This version assumes two things:
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** - the existence of select to tell if there is data
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** available for the file descriptor.
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** - the existence of the _cnt field in the stdio FILE struct, telling
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** if there is any buffered input in the struct.
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**
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** Most Unixes have these things, so this file should work for them.
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** However, Your Mileage May Vary.
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**
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** You could also replace the select() with a iotctl(FIONREAD) call, if you
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** had one but not the other.
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** -Olin&Brian
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*/
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#include <sys/types.h>
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#include <sys/time.h>
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#include <stdio.h>
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#include <unistd.h>
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#include "libcig.h"
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#include <errno.h>
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#include "stdio_dep.h" /* Make sure the .h interface agrees with the code. */
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/* These two procs return #t if data ready, #f data not ready,
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** and errno if error.
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*/
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scheme_value char_ready_fdes(int fd)
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{
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fd_set readfds;
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struct timeval timeout;
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int result;
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FD_ZERO(&readfds);
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FD_SET(fd,&readfds);
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timeout.tv_sec=0;
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timeout.tv_usec=0;
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result=select(fd+1, &readfds, NULL, NULL, &timeout);
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if(result == -1 )
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return(ENTER_FIXNUM(errno));
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if(result)
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return(SCHTRUE);
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return(SCHFALSE);
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}
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scheme_value stream_char_readyp(FILE *f)
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{
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int fd = fileno(f);
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return f->_cnt > 0 ? SCHTRUE : char_ready_fdes(fd);
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}
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void setfileno(FILE *fs, int fd)
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{
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fileno(fs) = fd;
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}
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int fbufcount(FILE* fs)
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{
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return fs->_cnt;
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}
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/* Returns true if there is no buffered data in stream FS
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** (or there is no buffering, period.)
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*/
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int ibuf_empty(FILE *fs)
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{
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return fs->_cnt <= 0;
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}
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/* Returns true if the buffer in stream FS is full
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** (or there is no buffering, period).
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*/
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int obuf_full(FILE *fs)
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{
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return (fs->_flag & _IOLBF) ? (- fs->_cnt >= fs->_bufsiz-1)
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: (fs->_cnt <= 0);
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}
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