From cb8c1a0d7073eee491d000b35a62bb91d39de414 Mon Sep 17 00:00:00 2001
From: Bastian Dehn <hhaalo@arcor.de>
Date: Mon, 2 Mar 2026 21:24:00 +0100
Subject: [PATCH] add replace function

---
 src/rename.c         | 33 +++++++++++++++++++++++++++++++++
 src/rename.h         |  2 ++
 tests/rename_tests.c | 13 +++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/src/rename.c b/src/rename.c
index 13ac556..35d6646 100644
--- a/src/rename.c
+++ b/src/rename.c
@@ -177,4 +177,37 @@ void rename_revert(const char* src, char* dst)
 			dst[dst_count++] = src[i];
 		}
 	}
+}
+
+char* replace(const char* src, const char* pattern, const char* replace_str)
+{
+	const size_t len = strlen(src);
+	const size_t plen = strlen(pattern);
+
+	uint32_t count = 0;
+	for (uint32_t i = 0; i < len; i++) {
+		if (strncmp(&src[i], pattern, plen) == 0)
+			count++;
+	}
+
+	const size_t rlen = strlen(replace_str);
+	const size_t difflen = count * (rlen - plen);
+	const size_t outlen = len + difflen + 1;
+	char* output = malloc(outlen);
+	if (output == NULL)
+		return NULL;
+	memset(output, 0, outlen);
+
+	uint32_t outi = 0;
+	for (uint32_t i = 0; i < len; i++) {
+		if (strncmp(&src[i], pattern, plen) == 0) {
+			memcpy(&output[outi], replace_str, rlen);
+			i += plen - 1;
+			outi += rlen;
+		} else {
+			output[outi++] = src[i];
+		}
+	}
+
+	return output;
 }
\ No newline at end of file
diff --git a/src/rename.h b/src/rename.h
index 76334eb..90c2f19 100644
--- a/src/rename.h
+++ b/src/rename.h
@@ -40,4 +40,6 @@ void rename_lower(const char* src, char* dst);
 void rename_string(const char* src, char* dst);
 void rename_revert(const char* src, char* dst);
 
+char* replace(const char* src, const char* pattern, const char* replace_str);
+
 #endif
\ No newline at end of file
diff --git a/tests/rename_tests.c b/tests/rename_tests.c
index 346db23..a6e052c 100644
--- a/tests/rename_tests.c
+++ b/tests/rename_tests.c
@@ -267,6 +267,18 @@ void four_byte_wide_character()
 	assert_int_equal(length, 3);
 }
 
+void replace_string()
+{
+	const char* input = "Hello Max!";
+
+	char* output = replace(input, "Max", "World");
+
+	assert_string_equal(output, "Hello World!");
+
+	free(output);
+	output = NULL;
+}
+
 int main()
 {
 	const struct CMUnitTest tests[] = {
@@ -294,6 +306,7 @@ int main()
 		cmocka_unit_test(two_byte_wide_character),
 		cmocka_unit_test(three_byte_wide_character),
 		cmocka_unit_test(four_byte_wide_character),
+		cmocka_unit_test(replace_string)
 	};
 
 	return cmocka_run_group_tests(tests, setup_group, teardown_group);
-- 
2.47.3