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#include <errno.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>
/*
* These functions find the absolute path to the current working directory.
*
* They don't use malloc or large amounts of stack space.
*/
static char * recurser(); /* Routine to go up tree */
static char * search_dir(); /* Routine to find the step back down */
static char * path_buf;
static int path_size;
static dev_t root_dev;
static ino_t root_ino;
static struct stat st;
char *
getcwd(buf, size)
char * buf;
int size;
{
path_buf = buf;
path_size = size;
if( size < 3 ) { errno = ERANGE; return 0; }
strcpy(path_buf, ".");
if( stat("/", &st) < 0 ) return 0;
root_dev = st.st_dev;
root_ino = st.st_ino;
return recurser();
}
static char *
recurser()
{
dev_t this_dev;
ino_t this_ino;
if( stat(path_buf, &st) < 0 ) return 0;
this_dev = st.st_dev;
this_ino = st.st_ino;
if( this_dev == root_dev && this_ino == root_ino )
{
strcpy(path_buf, "/");
return path_buf;
}
if( strlen(path_buf) + 4 > path_size ) { errno = ERANGE; return 0; }
strcat(path_buf, "/..");
if( recurser() == 0 ) return 0;
return search_dir(this_dev, this_ino);
}
static char *
search_dir(this_dev, this_ino)
dev_t this_dev;
ino_t this_ino;
{
DIR * dp;
struct dirent * d;
char * ptr;
int slen;
/* The test is for ELKS lib 0.0.9, this should be fixed in the real kernel*/
int slow_search = (sizeof(ino_t) != sizeof(d->d_ino));
if( stat(path_buf, &st) < 0 ) return 0;
if( this_dev != st.st_dev ) slow_search = 1;
slen = strlen(path_buf);
ptr = path_buf + slen -1;
if( *ptr != '/' )
{
if( slen + 2 > path_size ) { errno = ERANGE; return 0; }
strcpy(++ptr, "/");
slen++;
}
slen++;
dp = opendir(path_buf);
if( dp == 0 ) return 0;
while( (d=readdir(dp)) != 0 )
{
if( slow_search || this_ino == d->d_ino )
{
if( slen + strlen(d->d_name) > path_size )
{ errno = ERANGE; return 0; }
strcpy(ptr+1, d->d_name);
if( stat(path_buf, &st) < 0 )
continue;
if( st.st_ino == this_ino && st.st_dev == this_dev )
{
closedir(dp);
return path_buf;
}
}
}
closedir(dp);
errno = ENOENT;
return 0;
}
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