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#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>
/* #undef FAST_DIR_SEARCH_POSSIBLE on Linux */
/* These functions find the absolute path to the current working directory. */
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( char *buf, int size)
{
path_size = size;
if (size < 3) {
__set_errno(ERANGE);
return NULL;
}
if (buf != NULL)
path_buf = buf;
else
{
path_buf = malloc (size);
if (path_buf == NULL)
return NULL;
}
strcpy(path_buf, ".");
if (stat("/", &st) < 0)
return NULL;
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) {
__set_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;
#ifdef FAST_DIR_SEARCH_POSSIBLE
/* 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));
#endif
if (stat(path_buf, &st) < 0)
return 0;
#ifdef FAST_DIR_SEARCH_POSSIBLE
if (this_dev != st.st_dev)
slow_search = 1;
#endif
slen = strlen(path_buf);
ptr = path_buf + slen - 1;
if (*ptr != '/') {
if (slen + 2 > path_size) {
__set_errno(ERANGE);
return 0;
}
strcpy(++ptr, "/");
slen++;
}
slen++;
dp = opendir(path_buf);
if (dp == 0)
return 0;
while ((d = readdir(dp)) != 0) {
#ifdef FAST_DIR_SEARCH_POSSIBLE
if (slow_search || this_ino == d->d_ino) {
#endif
if (slen + strlen(d->d_name) > path_size) {
__set_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;
}
#ifdef FAST_DIR_SEARCH_POSSIBLE
}
#endif
}
closedir(dp);
__set_errno(ENOENT);
return 0;
}
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