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/* libjodycode: path manipulation
*
* Copyright (C) 2014-2026 by Jody Bruchon <jody@jodybruchon.com>
* Released under The MIT License
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "likely_unlikely.h"
#include "libjodycode.h"
/* Collapse dot-dot and single dot path components
* This code MUST be passed a full file pathname (starting with '/') */
int jc_collapse_dotdot(char * const path)
{
char *p; /* string copy input */
char *out; /* string copy output */
unsigned int i = 0;
if (unlikely(*path != '/')) return JC_ENULL;
p = path; out = path;
while (*p != '\0') {
/* Abort if we're too close to the end of the buffer */
if (unlikely(i >= (JC_PATHBUF_SIZE - 3))) return JC_ECDOTDOT;
/* Skip repeated slashes */
while (*p == '/' && *(p + 1) == '/') {
p++; i++;
}
/* Scan for '/./', '/..', '/.\0' combinations */
if (*p == '/' && *(p + 1) == '.'
&& (*(p + 2) == '.' || *(p + 2) == '/' || *(p + 2) == '\0')) {
/* Check for '../' or terminal '..' */
if (*(p + 2) == '.' && (*(p + 3) == '/' || *(p + 3) == '\0')) {
/* Found a dot-dot; pull everything back to the previous directory */
p += 3; i += 3;
/* If already at root, skip over the dot-dot */
if (i == 0) continue;
/* Don't seek back past the first character */
if ((uintptr_t)out == (uintptr_t)path) continue;
out--;
while (*out != '/') out--;
if (*p == '\0') break;
continue;
} else if (*(p + 2) == '/' || *(p + 2) == '\0') {
/* Found a single dot; seek input ptr past it */
p += 2; i += 2;
if (*p == '\0') break;
continue;
}
/* Fall through: not a dot or dot-dot, just a slash */
}
/* Copy all remaining text */
*out = *p;
p++; out++; i++;
}
/* If only a root slash remains, be sure to keep it */
if ((uintptr_t)out == (uintptr_t)path) {
*out = '/';
out++;
}
/* Output must always be terminated properly */
*out = '\0';
return 0;
}
/* Create a relative symbolic link path for a destination file */
int jc_make_relative_link_name(const char * const src, const char * const dest, char * rel_path)
{
char *p1, *p2;
char *sp, *dp, *ss;
int retval;
if (unlikely(!src || !dest)) return JC_ENULL;
p1 = (char *)malloc(JC_PATHBUF_SIZE + 8);
if (unlikely(p1 == NULL)) return JC_ENOMEM;
p2 = (char *)malloc(JC_PATHBUF_SIZE + 8);
if (unlikely(p2 == NULL)) { free(p1); return JC_ENOMEM; }
/* Get working directory path and prefix to pathnames if needed */
if (*src != '/' || *dest != '/') {
jc_errno = 0;
if (!jc_getcwd(p1, JC_PATHBUF_SIZE)) {
retval = jc_errno;
goto finish;
}
*(p1 + JC_PATHBUF_SIZE - 1) = '\0';
#ifdef ON_WINDOWS
strncat_s(p1, JC_PATHBUF_SIZE, "/", JC_PATHBUF_SIZE - 1);
strncpy_s(p2, JC_PATHBUF_SIZE, p1, JC_PATHBUF_SIZE);
#else
strncat(p1, "/", JC_PATHBUF_SIZE - 1);
strncpy(p2, p1, JC_PATHBUF_SIZE);
#endif
}
/* If an absolute path is provided, use it as-is */
if (*src == '/') *p1 = '\0';
if (*dest == '/') *p2 = '\0';
/* Concatenate working directory to relative paths */
#ifdef ON_WINDOWS
strncat_s(p1, JC_PATHBUF_SIZE, src, JC_PATHBUF_SIZE);
strncat_s(p2, JC_PATHBUF_SIZE, dest, JC_PATHBUF_SIZE);
#else
strncat(p1, src, JC_PATHBUF_SIZE);
strncat(p2, dest, JC_PATHBUF_SIZE);
#endif
/* Collapse . and .. path components */
if (unlikely(jc_collapse_dotdot(p1) != 0 || jc_collapse_dotdot(p2) != 0)) {
retval = JC_ECDOTDOT;
goto finish;
}
/* Find where paths differ, remembering each slash along the way */
sp = p1; dp = p2; ss = p1;
while (*sp == *dp && *sp != '\0' && *dp != '\0') {
if (*sp == '/') ss = sp;
sp++; dp++;
}
/* If paths are 100% identical then the files are the same file */
if (*sp == '\0' && *dp == '\0') {
retval = 1;
goto finish;
}
/* Replace dirs in destination path with dot-dot */
while (*dp != '\0') {
if (*dp == '/') {
*rel_path++ = '.'; *rel_path++ = '.'; *rel_path++ = '/';
}
dp++;
}
/* Copy the file name into rel_path and return */
ss++;
while (unlikely(*ss != '\0')) *rel_path++ = *ss++;
/* . and .. dirs at end are invalid */
if (*(rel_path - 1) == '.')
if (*(rel_path - 2) == '/' || (*(rel_path - 2) == '.' && *(rel_path - 3) == '/') || unlikely(*(rel_path - 1) == '/')) {
retval = JC_EGRNEND;
}
*rel_path = '\0';
finish:
free(p1); free(p2);
return retval;
}
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