2 files changed, 68 insertions, 0 deletions
diff --git a/src/shared/include/camellia/path.h b/src/shared/include/camellia/path.h
index ba6bccf..8efa0d4 100644
--- a/src/shared/include/camellia/path.h
+++ b/src/shared/include/camellia/path.h
@@ -1,3 +1,10 @@
 #pragma once
+#include <stddef.h>
 
 #define PATH_MAX 512
+
+/** Reduce a path to its simplest form.
+ *
+ * @return length of the string in *out, always less than len. Negative if the path was invalid.
+ */
+int path_simplify(const char *in, char *out, size_t len);
diff --git a/src/shared/path.c b/src/shared/path.c
new file mode 100644
index 0000000..9d2eda3
--- /dev/null
+++ b/src/shared/path.c
@@ -0,0 +1,61 @@
+#include <camellia/path.h>
+#include <shared/mem.h>
+#include <stdbool.h>
+
+// TODO shared assert
+#define assert(...)
+
+int path_simplify(const char *in, char *out, size_t len) {
+	if (len == 0)     return -1; // empty paths are invalid
+	if (in[0] != '/') return -1; // so are relative paths
+
+	int seg_len; // the length of the current path segment
+	int out_pos = 0;
+	bool directory = 0;
+
+	for (size_t i = 0; i < len; i += seg_len + 1) {
+		assert(in[i] == '/');
+
+		seg_len = 0;
+		directory = false;
+		for (size_t j = i + 1; j < len; j++) {
+			if (in[j] == '/') {
+				directory = true;
+				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] == '.')) {
+			/*  // or /./  */
+			directory = true;
+		} else if (seg_len == 2 && in[i + 1] == '.' && in[i + 2] == '.') {
+			/*  /../  */
+			directory = true;
+
+			/* try to backtrack to the last slash */
+			while (--out_pos >= 0 && out[out_pos] != '/');
+			if (out_pos < 0) return -1;
+		} else {
+			/* a normal segment, e.g. /asdf/ */
+			out[out_pos] = '/';
+			memcpy(&out[out_pos + 1], &in[i + 1], seg_len);
+			out_pos += seg_len + 1;
+		}
+
+	}
+
+	/* paths to directories should have a trailing slash */
+	if (directory) out[out_pos++] = '/';
+
+	return out_pos;
+}