compilers/linux86-0.16.17/libc/misc/getcwd.c

   1
   2 #include <errno.h>
   3 #include <sys/stat.h>
   4 #include <dirent.h>
   5 #include <string.h>
   6 /*
   7  * These functions find the absolute path to the current working directory.
   8  *
   9  * They don't use malloc or large amounts of stack space.
  10  */
  11
  12 static char * recurser();       /* Routine to go up tree */
  13 static char * search_dir();     /* Routine to find the step back down */
  14 static char * path_buf;
  15 static int    path_size;
  16
  17 static dev_t root_dev;
  18 static ino_t root_ino;
  19
  20 static struct stat st;
  21
  22 char *
  23 getcwd(buf, size)
  24 char * buf;
  25 int size;
  26 {
  27    path_buf = buf;
  28    path_size = size;
  29
  30    if( size < 3 ) { errno = ERANGE; return 0; }
  31    strcpy(path_buf, ".");
  32
  33    if( stat("/", &st) < 0 ) return 0;
  34
  35    root_dev = st.st_dev;
  36    root_ino = st.st_ino;
  37
  38    return recurser();
  39 }
  40
  41 static char *
  42 recurser()
  43 {
  44    dev_t this_dev;
  45    ino_t this_ino;
  46    if( stat(path_buf, &st) < 0 ) return 0;
  47    this_dev = st.st_dev;
  48    this_ino = st.st_ino;
  49    if( this_dev == root_dev && this_ino == root_ino )
  50    {
  51       strcpy(path_buf, "/");
  52       return path_buf;
  53    }
  54    if( strlen(path_buf) + 4 > path_size ) { errno = ERANGE; return 0; }
  55    strcat(path_buf, "/..");
  56    if( recurser() == 0 ) return 0;
  57
  58    return search_dir(this_dev, this_ino);
  59 }
  60
  61 static char *
  62 search_dir(this_dev, this_ino)
  63 dev_t this_dev;
  64 ino_t this_ino;
  65 {
  66    DIR * dp;
  67    struct dirent * d;
  68    char * ptr;
  69    int slen;
  70    /* The test is for ELKS lib 0.0.9, this should be fixed in the real kernel*/
  71    int slow_search = (sizeof(ino_t) != sizeof(d->d_ino));
  72
  73    if( stat(path_buf, &st) < 0 ) return 0;
  74    if( this_dev != st.st_dev ) slow_search = 1;
  75
  76    slen = strlen(path_buf);
  77    ptr = path_buf + slen -1;
  78    if( *ptr != '/' )
  79    {
  80       if( slen + 2 > path_size ) { errno = ERANGE; return 0; }
  81       strcpy(++ptr, "/");
  82       slen++;
  83    }
  84    slen++;
  85
  86    dp = opendir(path_buf);
  87    if( dp == 0 ) return 0;
  88
  89    while( (d=readdir(dp)) != 0 )
  90    {
  91       if( slow_search || this_ino == d->d_ino )
  92       {
  93          if( slen + strlen(d->d_name) > path_size )
  94             { errno = ERANGE; return 0; }
  95          strcpy(ptr+1, d->d_name);
  96          if( stat(path_buf, &st) < 0 )
  97             continue;
  98          if( st.st_ino == this_ino && st.st_dev == this_dev )
  99          {
 100             closedir(dp);
 101             return path_buf;
 102          }
 103       }
 104    }
 105
 106    closedir(dp);
 107    errno = ENOENT;
 108    return 0;
 109 }