Implemented my_dirname and added unit tests for it.

2 files changed, 34 insertions, 0 deletions

diff --git a/src/misc.c b/src/misc.c
index c130b86..bb838c7 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -82,6 +82,32 @@ const char *my_basename(const char *path)
         return path;
 }
 
+const char *my_dirname(char *path)
+{
+    if (strcmp(path, ".") == 0) {
+        return "..";
+    } else if (strcmp(path, "/") == 0) {
+        return "/";
+    } else {
+        int len = strlen(path);
+        char *p = path + len - 1;
+        while (p > path) {
+            if (*p == '/') {
+                break;
+            }
+            --p;
+        }
+        if (p > path) {
+            *p = '\0';
+            return path;
+        } else if (*path == '/') {
+            return "/";
+        } else {
+            return ".";
+        }
+    }
+}
+
 void grow_array_impl(void **array, int* capacity, int member_size)
 {
     int new_cap = *capacity;
diff --git a/src/misc.h b/src/misc.h
index 2ef8f6d..8b00f8d 100644
--- a/src/misc.h
+++ b/src/misc.h
@@ -38,6 +38,14 @@ char *strdup_until(const char *s, const char *endchars);
    Returns NULL if path is NULL. */
 const char *my_basename(const char *path);
 
+/* A thread-safe version of dirname, with slightly different behavior.
+   If path is ".", returns "..".
+   If path is "/", returns "/".
+   If path has an initial slash but no other slashes, returns "/".
+   If path contains a slash, replaces the last slash with a '\0' and returns path.
+   Otherwise, returns ".". */
+const char *my_dirname(char *path);
+
 /* Reallocs `*array` (may be NULL) to be at least one larger
    than `*capacity` (may be 0) and stores the new capacity
    in `*capacity`. */