scsh-0.6/scsh/next/stdio_dep.c

92 lines
2.0 KiB
C

/* Copyright (c) 1994 by Olin Shivers.
** Copyright (c) 1994-1995 by Brian D. Carlstrom.
**
** This file implements the char-ready? procedure for file descriptors
** and Scsh's fdports. It is not Posix, so it must be implemented for
** each OS to which scsh is ported.
**
** This version assumes two things:
** - the existence of select to tell if there is data
** available for the file descriptor.
** - the existence of the _cnt field in the stdio FILE struct, telling
** if there is any buffered input in the struct.
**
** Most Unixes have these things, so this file should work for them.
** However, Your Mileage May Vary.
**
** You could also replace the select() with a iotctl(FIONREAD) call, if you
** had one but not the other.
** -Olin&Brian
*/
#include <sys/types.h>
#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
#include "libcig.h"
#include <errno.h>
#include "stdio_dep.h" /* Make sure the .h interface agrees with the code. */
/* These two procs return #t if data ready, #f data not ready,
** and errno if error.
*/
s48_value char_ready_fdes(int fd)
{
fd_set readfds;
struct timeval timeout;
int result;
FD_ZERO(&readfds);
FD_SET(fd,&readfds);
timeout.tv_sec=0;
timeout.tv_usec=0;
result=select(fd+1, &readfds, NULL, NULL, &timeout);
if(result == -1 )
return(s48_enter_fixnum(errno));
if(result)
return(S48_TRUE);
return(S48_FALSE);
}
s48_value stream_char_readyp(FILE *f)
{
int fd = fileno(f);
return f->_cnt > 0 ? S48_TRUE : char_ready_fdes(fd);
}
void setfileno(FILE *fs, int fd)
{
fileno(fs) = fd;
}
int fbufcount(FILE* fs)
{
return fs->_cnt;
}
/* Returns true if there is no buffered data in stream FS
** (or there is no buffering, period.)
*/
int ibuf_empty(FILE *fs)
{
return fs->_cnt <= 0;
}
/* Returns true if the buffer in stream FS is full
** (or there is no buffering, period).
*/
int obuf_full(FILE *fs)
{
return (fs->_flag & _IOLBF) ? (- fs->_cnt >= fs->_bufsiz-1)
: (fs->_cnt <= 0);
}