From 0b74748a0d7e4a1d07db59d948fdd23361b7b4fd Mon Sep 17 00:00:00 2001
From: NukeBird <nukebird.dev@gmail.com>
Date: Tue, 2 Dec 2025 17:16:04 +0300
Subject: [PATCH] axl_strstr

---
 axl_string.c      |  26 ++++++++++
 axl_string.h      |   2 +-
 axl_string_test.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 145 insertions(+), 1 deletion(-)

diff --git a/axl_string.c b/axl_string.c
index 7fafcd0..1cc060a 100644
--- a/axl_string.c
+++ b/axl_string.c
@@ -1,4 +1,5 @@
 #include "axl_string.h"
+#include "axl_memory.h"
 
 u32 axl_strlen(const i8* s)
 {
@@ -139,3 +140,28 @@ const i8* axl_strchr(const i8* str, i8 c)
     
     return (c == '\0') ? str : NULL;
 }
+
+i8* axl_strstr(const i8* str, const i8* substr)
+{
+    if(!str || !substr)
+    {
+        return NULL;
+    }
+
+    if(*substr == '\0')
+    {
+        return (i8*)str;
+    }
+
+    u32 n = axl_strlen(substr);
+
+    while(*str)
+    {
+        if(!axl_memcmp(str++, substr, n))
+        {
+            return (i8*)(str - 1);
+        }
+    }
+
+    return NULL;
+}
diff --git a/axl_string.h b/axl_string.h
index 5c65cb2..7ea2da2 100644
--- a/axl_string.h
+++ b/axl_string.h
@@ -11,5 +11,5 @@ i8*       axl_strncat(i8* dst, const i8* src, u32 n);
 i32       axl_strcmp(const i8* s1, const i8* s2);
 i32       axl_strncmp(const i8* s1, const i8* s2, u32 n);
 const i8* axl_strchr(const i8* str, i8 c);
-
+i8*       axl_strstr(const i8* str, const i8* substr);
 #endif // AXL_STRING
diff --git a/axl_string_test.c b/axl_string_test.c
index 6019c7d..c6f7bcf 100644
--- a/axl_string_test.c
+++ b/axl_string_test.c
@@ -322,6 +322,124 @@ KOAN(strchr_returns_proper_ptr)
     ASSERT_PTR_EQ(str + 7, axl_strchr(str, '\0'));
 }
 
+KOAN(strstr_null_pointer)
+{
+    ASSERT_NULL(axl_strstr(NULL, "test"));
+    ASSERT_NULL(axl_strstr("test", NULL));
+    ASSERT_NULL(axl_strstr(NULL, NULL));
+}
+
+KOAN(strstr_empty_string)
+{
+    i8 str[] = "";
+    ASSERT_NULL(axl_strstr(str, "test"));
+    ASSERT_PTR_EQ(str, axl_strstr(str, ""));
+}
+
+KOAN(strstr_empty_substring)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str, axl_strstr(str, ""));
+}
+
+KOAN(strstr_exact_match)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str, axl_strstr(str, "hello world"));
+}
+
+KOAN(strstr_prefix_match)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str, axl_strstr(str, "hello"));
+}
+
+KOAN(strstr_suffix_match)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str + 6, axl_strstr(str, "world"));
+}
+
+KOAN(strstr_middle_match)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str + 2, axl_strstr(str, "llo"));
+}
+
+KOAN(strstr_single_char_match)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str + 4, axl_strstr(str, "o"));
+}
+
+KOAN(strstr_multiple_occurrences)
+{
+    i8 str[] = "hello world";
+    ASSERT_PTR_EQ(str + 4, axl_strstr(str, "o"));
+}
+
+KOAN(strstr_not_found)
+{
+    i8 str[] = "hello world";
+    ASSERT_NULL(axl_strstr(str, "xyz"));
+    ASSERT_NULL(axl_strstr(str, "hello!"));
+    ASSERT_NULL(axl_strstr(str, "world!"));
+}
+
+KOAN(strstr_partial_match_but_not_full)
+{
+    i8 str[] = "hello world";
+    ASSERT_NULL(axl_strstr(str, "helloo"));
+    ASSERT_NULL(axl_strstr(str, "worldd"));
+}
+
+KOAN(strstr_case_sensitive)
+{
+    i8 str[] = "Hello World";
+    ASSERT_NULL(axl_strstr(str, "hello"));
+    ASSERT_NULL(axl_strstr(str, "world"));
+    ASSERT_PTR_EQ(str, axl_strstr(str, "Hello"));
+    ASSERT_PTR_EQ(str + 6, axl_strstr(str, "World"));
+}
+
+KOAN(strstr_with_null_bytes)
+{
+    i8 str[] = "ab\0cde";
+    ASSERT_PTR_EQ(str, axl_strstr(str, "ab"));
+    ASSERT_NULL(axl_strstr(str, "cde"));
+}
+
+KOAN(strstr_longer_substring_than_string)
+{
+    i8 str[] = "short";
+    ASSERT_NULL(axl_strstr(str, "longer string"));
+}
+
+KOAN(strstr_repeated_pattern)
+{
+    i8 str[] = "ababab";
+    ASSERT_PTR_EQ(str, axl_strstr(str, "ab"));
+    ASSERT_PTR_EQ(str + 1, axl_strstr(str, "baba"));
+}
+
+KOAN(strstr_overlapping_match)
+{
+    i8 str[] = "aaaaa";
+    ASSERT_PTR_EQ(str, axl_strstr(str, "aa"));
+    ASSERT_PTR_EQ(str, axl_strstr(str, "aaa"));
+    ASSERT_PTR_EQ(str, axl_strstr(str, "aaaa"));
+    ASSERT_PTR_EQ(str, axl_strstr(str, "aaaaa"));
+}
+
+KOAN(strstr_special_chars)
+{
+    i8 str[] = "hello\tworld\n";
+    ASSERT_PTR_EQ(str, axl_strstr(str, "hello"));
+    ASSERT_PTR_EQ(str + 6, axl_strstr(str, "world"));
+    ASSERT_PTR_EQ(str + 5, axl_strstr(str, "\t"));
+    ASSERT_PTR_EQ(str + 11, axl_strstr(str, "\n"));
+}
+
 int main(void)
 {
     axl_init();