freopen.c

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/*
 * freopen.c - open a file and associate a stream with it
 */
/* $Header: /opt/proj/minix/cvsroot/src/lib/stdio/freopen.c,v 1.4 2006/02/02 16:59:07 beng Exp $ */

#if     defined(_POSIX_SOURCE)
#include        <sys/types.h>
#endif
#include        <stdio.h>
#include        <stdlib.h>
#include        "loc_incl.h"
#include        <sys/stat.h>

#define PMODE           0666

/* Do not "optimize" this file to use the open with O_CREAT if the file
 * does not exist. The reason is given in fopen.c.
 */
#define O_RDONLY        0
#define O_WRONLY        1
#define O_RDWR          2

#define O_CREAT         0x010
#define O_TRUNC         0x020
#define O_APPEND        0x040

int _open(const char *path, int flags);
int _creat(const char *path, _mnx_Mode_t mode);
int _close(int d);

FILE *
freopen(const char *name, const char *mode, FILE *stream)
{
        register int i;
        struct stat st;
        int rwmode = 0, rwflags = 0;
        int fd, flags = stream->_flags & (_IONBF | _IOFBF | _IOLBF | _IOMYBUF);

        (void) fflush(stream);                          /* ignore errors */
        (void) _close(fileno(stream));

        switch(*mode++) {
        case 'r':
                flags |= _IOREAD;       
                rwmode = O_RDONLY;
                break;
        case 'w':
                flags |= _IOWRITE;
                rwmode = O_WRONLY;
                rwflags = O_CREAT | O_TRUNC;
                break;
        case 'a': 
                flags |= _IOWRITE | _IOAPPEND;
                rwmode = O_WRONLY;
                rwflags |= O_APPEND | O_CREAT;
                break;         
        default:
                goto loser;
        }

        while (*mode) {
                switch(*mode++) {
                case 'b':
                        continue;
                case '+':
                        rwmode = O_RDWR;
                        flags |= _IOREAD | _IOWRITE;
                        continue;
                /* The sequence may be followed by aditional characters */
                default:
                        break;
                }
                break;
        }

        if ((rwflags & O_TRUNC)
            || (((fd = _open(name, rwmode)) < 0)
                    && (rwflags & O_CREAT))) {
                if (((fd = _creat(name, PMODE)) < 0) && flags | _IOREAD) {
                        (void) _close(fd);
                        fd = _open(name, rwmode);
                }
        }

        if (fd < 0) {
                goto loser;
        }

        if ( fstat( fd, &st ) == 0 ) {
                if ( S_ISFIFO(st.st_mode) ) flags |= _IOFIFO;
        } else {
                goto loser;
        }
        
        stream->_count = 0;
        stream->_fd = fd;
        stream->_flags = flags;
        return stream;

loser:
        for( i = 0; i < FOPEN_MAX; i++) {
                if (stream == __iotab[i]) {
                        __iotab[i] = 0;
                        break;
                }
        }
        if (stream != stdin && stream != stdout && stream != stderr)
                free((void *)stream);
        return (FILE *)NULL;    
}

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