libc: Implement dirname() and basename()

libs/libc/include/libgen.h

@@ -6,8 +6,13 @@ extern "C"
 {
 #endif
 
-    char* basename(char*); // Not implemented.
-    char* dirname(char*);  // Not implemented.
+    /* Returns the last component of a path. This function is allowed to modify the string passed to it, so it should
+     * probably be a copy of another string. */
+    char* basename(char* path);
+
+    /* Returns the parent directory of a path. This function is allowed to modify the string passed to it, so it should
+     * probably be a copy of another string. */
+    char* dirname(char* path);
 
 #ifdef __cplusplus
 }

libs/libc/src/libgen.cpp

@@ -1,15 +1,51 @@
 #include <libgen.h>
 #include <luna.h>
+#include <string.h>
+
+static char dot[] = ".";
 
 extern "C"
 {
-    char* basename(char*)
+    char* basename(char* path)
     {
-        NOT_IMPLEMENTED("basename");
+        // If path is NULL, or the string's length is 0, return .
+        if (!path) return dot;
+        size_t len = strlen(path);
+        if (!len) return dot;
+
+        // Strip trailing slashes.
+        char* it = path + len - 1;
+        while (*it == '/' && it != path) { it--; }
+        *(it + 1) = 0;
+        if (it == path) return path;
+
+        // Return path from the first character if there are no more slashes, or from the first character after the last
+        // slash.
+        char* beg = strrchr(path, '/');
+        if (!beg) return path;
+        return beg + 1;
     }
 
-    char* dirname(char*)
+    char* dirname(char* path)
     {
-        NOT_IMPLEMENTED("dirname");
+        // If path is NULL, or the string's length is 0, return .
+        if (!path) return dot;
+        size_t len = strlen(path);
+        if (!len) return dot;
+
+        // Strip trailing slashes.
+        char* it = path + len - 1;
+        while (*it == '/' && it != path) { it--; }
+        *(char*)(it + 1) = 0;
+        if (it == path) return path;
+
+        // Search for the last slash. If there is none, return .
+        // Otherwise, we end the string there and return.
+        char* end = strrchr(path, '/');
+        if (!end) return dot;
+        if (end != path) *end = 0;
+        else
+            *(end + 1) = 0;
+        return path;
     }
 }