V10/libI77/notused/fopen.5.c

/*	@(#)fopen.c	1.8	*/
/*LINTLIBRARY*/
#include "stdio.h"
#include <fcntl.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')
		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)  {
				return NULL;
			}
		}
	}
	_bufend(iop) = iop->_base = iop->_ptr = NULL;
	return (iop);
}