fopen.c

来自「操作系统SunOS 4.1.3版本的源码」· C语言 代码 · 共 75 行

#if !defined(lint) && defined(SCCSIDS)
static	char sccsid[] = "@(#)fopen.c 1.1 92/07/30 SMI"; /* from S5R2 1.8 */
#endif

/*LINTLIBRARY*/
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

extern int open(), fclose();
extern FILE *_findiop(), *_endopen();

FILE *
fopen(file, mode)
char	*file, *mode;
{
	return (_endopen(file, mode, _findiop()));
}

FILE *
freopen(file, mode, iop)
char	*file, *mode;
register FILE *iop;
{
	(void) fclose(iop); /* doesn't matter if this fails */
	return (_endopen(file, mode, iop));
}

static FILE *
_endopen(file, mode, iop)
char	*file, *mode;
register FILE *iop;
{
	register int	plus, oflag, fd;

	if (iop == NULL || file == NULL || file[0] == '\0') {
#ifdef POSIX
		errno = ENOENT;
#endif POSIX
		return (NULL);
	}
	plus = (mode[1] == '+');
	switch (mode[0]) {
	case 'w':
		oflag = (plus ? O_RDWR : O_WRONLY) | O_TRUNC | O_CREAT;
		break;
	case 'a':
		oflag = (plus ? O_RDWR : O_WRONLY) | O_APPEND | O_CREAT;
		break;
	case 'r':
		oflag = plus ? O_RDWR : O_RDONLY;
		break;
	default:
		return (NULL);
	}
	if ((fd = open(file, oflag, 0666)) < 0)
		return (NULL);
	iop->_cnt = 0;
	iop->_file = fd;
	iop->_flag = plus ? _IORW : (mode[0] == 'r') ? _IOREAD : _IOWRT;
	if (mode[0] == 'a')   {
		if (!plus)  {
			/* if update only mode, move file pointer to the end
			   of the file */
			if ((lseek(fd,0L,2)) < 0)  {
				(void) close(fd);
				return NULL;
			}
		}
	}
	iop->_base = iop->_ptr = NULL;
	iop->_bufsiz = 0;
	return (iop);
}