From 497ed57057438577c8524aa03fe33aa8c05477a6 Mon Sep 17 00:00:00 2001
From: Anna Schumaker <Anna@NoWheyCreamery.com>
Date: Tue, 11 Apr 2017 09:12:17 -0400
Subject: [PATCH] core/string: Add a function for checking if a string is a
 subdirectory

I want to use this to prevent users from adding a subdirectory of a path
that has already been added to the library.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>
---
 core/string.c         | 22 ++++++++++++++++++++++
 include/core/string.h |  3 +++
 tests/core/string.c   | 13 +++++++++++++
 3 files changed, 38 insertions(+)

diff --git a/core/string.c b/core/string.c
index 8c9d0853..90d84553 100644
--- a/core/string.c
+++ b/core/string.c
@@ -81,3 +81,25 @@ bool string_match_token(const gchar *prefix, gchar **tokens)
 
 	return false;
 }
+
+bool string_is_subdir(const gchar *a, const gchar *b)
+{
+	gchar **parent = b ? g_strsplit(b, "/", -1) : NULL;
+	gchar **child  = a ? g_strsplit(a, "/", -1) : NULL;
+	bool    subdir = true;
+	int i;
+
+	if (!parent || !child)
+		return false;
+
+	for (i = 0; parent[i]; i++) {
+		if (!child[i] || g_utf8_collate(parent[i], child[i]) != 0) {
+			subdir = false;
+			break;
+		}
+	}
+
+	g_strfreev(parent);
+	g_strfreev(child);
+	return subdir;
+}
diff --git a/include/core/string.h b/include/core/string.h
index 63f53f9d..79ef417a 100644
--- a/include/core/string.h
+++ b/include/core/string.h
@@ -39,6 +39,9 @@ static inline bool string_match(const gchar *a, const gchar *b)
 /* Returns True if one of the tokens begins with the specified prefix. */
 bool string_match_token(const gchar *, gchar **);
 
+/* Returns True if string a is a subdirectory of string b. */
+bool string_is_subdir(const gchar *, const gchar *);
+
 /* Return the length of the string, with NULL checks */
 static inline int string_length(const gchar *str)
 {
diff --git a/tests/core/string.c b/tests/core/string.c
index 094b1ece..ac7e390f 100644
--- a/tests/core/string.c
+++ b/tests/core/string.c
@@ -108,6 +108,18 @@ void test_match_tokens()
 	g_assert_false(string_match_token("rule", tokens));
 }
 
+void test_subdirectory()
+{
+	g_assert_false(string_is_subdir(NULL,   NULL));
+	g_assert_false(string_is_subdir(NULL,   "/a/b"));
+	g_assert_false(string_is_subdir("/a/b", NULL));
+	g_assert_false(string_is_subdir("/a",   "/a/b"));
+	g_assert_false(string_is_subdir("/a",   "/ab"));
+	g_assert_true( string_is_subdir("/a/b", "/a"));
+	g_assert_true( string_is_subdir("/a/b", "/a/b"));
+	g_assert_true( string_is_subdir("/a/b/c/d", "/a/b"));
+}
+
 void test_length()
 {
 	g_assert_cmpint(string_length(NULL), ==, 0);
@@ -125,6 +137,7 @@ int main(int argc, char **argv)
 	g_test_add_func("/Core/String/Comparison/Tokens", test_compare_tokens);
 	g_test_add_func("/Core/String/Matching", test_match);
 	g_test_add_func("/Core/String/Matching/Tokens", test_match_tokens);
+	g_test_add_func("/Core/String/Subdirectory", test_subdirectory);
 	g_test_add_func("/Core/String/Length", test_length);
 	return g_test_run();
 }