lib/stdio/freopen.c

   1 /*
   2  * freopen.c - open a file and associate a stream with it
   3  */
   4 /* $Header$ */
   5
   6 #if     defined(_POSIX_SOURCE)
   7 #include        <sys/types.h>
   8 #endif
   9 #include        <stdio.h>
  10 #include        <stdlib.h>
  11 #include        "loc_incl.h"
  12 #include        <sys/stat.h>
  13
  14 #define PMODE           0666
  15
  16 /* Do not "optimize" this file to use the open with O_CREAT if the file
  17  * does not exist. The reason is given in fopen.c.
  18  */
  19 #define O_RDONLY        0
  20 #define O_WRONLY        1
  21 #define O_RDWR          2
  22
  23 #define O_CREAT         0x010
  24 #define O_TRUNC         0x020
  25 #define O_APPEND        0x040
  26
  27 int _open(const char *path, int flags);
  28 int _creat(const char *path, _mnx_Mode_t mode);
  29 int _close(int d);
  30
  31 FILE *
  32 freopen(const char *name, const char *mode, FILE *stream)
  33 {
  34         register int i;
  35         struct stat st;
  36         int rwmode = 0, rwflags = 0;
  37         int fd, flags = stream->_flags & (_IONBF | _IOFBF | _IOLBF | _IOMYBUF);
  38
  39         (void) fflush(stream);                          /* ignore errors */
  40         (void) _close(fileno(stream));
  41
  42         switch(*mode++) {
  43         case 'r':
  44                 flags |= _IOREAD;
  45                 rwmode = O_RDONLY;
  46                 break;
  47         case 'w':
  48                 flags |= _IOWRITE;
  49                 rwmode = O_WRONLY;
  50                 rwflags = O_CREAT | O_TRUNC;
  51                 break;
  52         case 'a':
  53                 flags |= _IOWRITE | _IOAPPEND;
  54                 rwmode = O_WRONLY;
  55                 rwflags |= O_APPEND | O_CREAT;
  56                 break;
  57         default:
  58                 goto loser;
  59         }
  60
  61         while (*mode) {
  62                 switch(*mode++) {
  63                 case 'b':
  64                         continue;
  65                 case '+':
  66                         rwmode = O_RDWR;
  67                         flags |= _IOREAD | _IOWRITE;
  68                         continue;
  69                 /* The sequence may be followed by aditional characters */
  70                 default:
  71                         break;
  72                 }
  73                 break;
  74         }
  75
  76         if ((rwflags & O_TRUNC)
  77             || (((fd = _open(name, rwmode)) < 0)
  78                     && (rwflags & O_CREAT))) {
  79                 if (((fd = _creat(name, PMODE)) < 0) && flags | _IOREAD) {
  80                         (void) _close(fd);
  81                         fd = _open(name, rwmode);
  82                 }
  83         }
  84
  85         if (fd < 0) {
  86                 goto loser;
  87         }
  88
  89         if ( fstat( fd, &st ) == 0 ) {
  90                 if ( S_ISFIFO(st.st_mode) ) flags |= _IOFIFO;
  91         } else {
  92                 goto loser;
  93         }
  94
  95         stream->_count = 0;
  96         stream->_fd = fd;
  97         stream->_flags = flags;
  98         return stream;
  99
 100 loser:
 101         for( i = 0; i < FOPEN_MAX; i++) {
 102                 if (stream == __iotab[i]) {
 103                         __iotab[i] = 0;
 104                         break;
 105                 }
 106         }
 107         if (stream != stdin && stream != stdout && stream != stderr)
 108                 free((void *)stream);
 109         return (FILE *)NULL;
 110 }