2 files changed, 55 insertions, 0 deletions
diff --git a/src/kernel/vfs/path.c b/src/kernel/vfs/path.c
new file mode 100644
index 0000000..8662f03
--- /dev/null
+++ b/src/kernel/vfs/path.c
@@ -0,0 +1,44 @@
+#include <kernel/vfs/path.h>
+#include <kernel/panic.h>
+
+bool path_simplify(const char *in, char *out, size_t len) {
+	if (len == 0)     return false; // empty paths are invalid
+	if (in[0] != '/') return false; // so are relative paths
+
+	int depth = 0;
+	int seg_len; // the length of the current path segment
+
+	for (int i = 0; i < len; i += seg_len + 1) {
+		// TODO implement assert
+		if (in[i] != '/') panic();
+
+		seg_len = 0;
+		for (int j = i + 1; j < len; j++) {
+			if (in[j] == '/') break;
+			seg_len++;
+		}
+
+		/* example iteration, illustrated with terrible ASCII art
+		 *
+		 *          |i=5 |next i = i + seg_len + 1 = 10
+		 *          v    v
+		 *     /some/path/asdf
+		 *           |--|
+		 *           seg_len = 4
+		 *           (segment starts at i+1) */
+
+		if (seg_len == 0 || (seg_len == 1 && in[i + 1] == '.')) {
+			// the segment is // or /./
+			// the depth doesn't change
+		} else if (seg_len == 2 && in[i + 1] == '.' && in[i + 2] == '.') {
+			// the segment is /../
+			if (--depth < 0)
+				return false;
+		} else {
+			// normal segment
+			depth++;
+		}
+	}
+
+	return true;
+}
diff --git a/src/kernel/vfs/path.h b/src/kernel/vfs/path.h
new file mode 100644
index 0000000..22dc754
--- /dev/null
+++ b/src/kernel/vfs/path.h
@@ -0,0 +1,11 @@
+#pragma once
+#include <stdbool.h>
+#include <stddef.h>
+
+/** Reduce a path to its simplest form.
+ * *in and *out can't overlap unless they're equal. Then, the path is modified
+ * in-place.
+ *
+ * @return Was the path valid? If this is false, *out is undefined
+ */
+bool path_simplify(const char *in, char *out, size_t len);