Implement normalize_absolute_path
[git/git.git] / path.c
diff --git a/path.c b/path.c
index b7c24a2..7175a06 100644 (file)
--- a/path.c
+++ b/path.c
@@ -357,3 +357,56 @@ const char *make_absolute_path(const char *path)
 
        return buf;
 }
+
+/*
+ * path = absolute path
+ * buf = buffer of at least max(2, strlen(path)+1) bytes
+ * It is okay if buf == path, but they should not overlap otherwise.
+ *
+ * Performs the following normalizations on path, storing the result in buf:
+ * - Removes trailing slashes.
+ * - Removes empty components.
+ * - Removes "." components.
+ * - Removes ".." components, and the components the precede them.
+ * "" and paths that contain only slashes are normalized to "/".
+ * Returns the length of the output.
+ *
+ * Note that this function is purely textual.  It does not follow symlinks,
+ * verify the existence of the path, or make any system calls.
+ */
+int normalize_absolute_path(char *buf, const char *path)
+{
+       const char *comp_start = path, *comp_end = path;
+       char *dst = buf;
+       int comp_len;
+       assert(buf);
+       assert(path);
+
+       while (*comp_start) {
+               assert(*comp_start == '/');
+               while (*++comp_end && *comp_end != '/')
+                       ; /* nothing */
+               comp_len = comp_end - comp_start;
+
+               if (!strncmp("/",  comp_start, comp_len) ||
+                   !strncmp("/.", comp_start, comp_len))
+                       goto next;
+
+               if (!strncmp("/..", comp_start, comp_len)) {
+                       while (dst > buf && *--dst != '/')
+                               ; /* nothing */
+                       goto next;
+               }
+
+               memcpy(dst, comp_start, comp_len);
+               dst += comp_len;
+       next:
+               comp_start = comp_end;
+       }
+
+       if (dst == buf)
+               *dst++ = '/';
+
+       *dst = '\0';
+       return dst - buf;
+}