Kernel+LibC: Implement 'memmem'

This commit adds an implementation of memmem, using the Bitap text
search algorithm for needles smaller than 32 bytes, and a naive loop
search for longer needles.

1 files changed, 70 insertions, 0 deletions

diff --git a/Tests/LibC/memmem-tests.cpp b/Tests/LibC/memmem-tests.cpp
new file mode 100644
index 0000000000..87487fcf2c
--- /dev/null
+++ b/Tests/LibC/memmem-tests.cpp
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2020, Ali Mohammad Pur <ali.mpfard@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Types.h>
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+struct TestCase {
+    const u8* haystack;
+    size_t haystack_length;
+    const u8* needle;
+    size_t needle_length;
+    ssize_t matching_offset { -1 };
+};
+
+const static TestCase g_test_cases[] = {
+    { (const u8*) {}, 0u, (const u8*) {}, 0u, 0 },
+    { (const u8[]) { 1, 2, 3 }, 3u, (const u8[]) { 1, 2, 3 }, 3u, 0 },
+    { (const u8[]) { 1, 2, 4 }, 3u, (const u8[]) { 1, 2, 3 }, 3u, -1 },
+    { (const u8*)"abcdef", 6u, (const u8[]) {}, 0u, 0 },
+    { (const u8*)"abcdef", 6u, (const u8*)"de", 2u, 3 },
+    { (const u8[]) { 0, 1, 2, 5, 2, 5 }, 6u, (const u8[]) { 1 }, 1u, 1 },
+    { (const u8[]) { 0, 1, 2, 5, 2, 5 }, 6u, (const u8[]) { 1, 2 }, 2u, 1 },
+    { (const u8[]) { 0, 1, 1, 2 }, 4u, (const u8[]) { 1, 5 }, 2u, -1 },
+    { (const u8[64]) { 0 }, 64u, (const u8[33]) { 0 }, 33u, 0 },
+    { (const u8[64]) { 0, 1, 1, 2 }, 64u, (const u8[33]) { 1, 1 }, 2u, 1 },
+};
+
+int main()
+{
+    bool failed = false;
+    size_t i = 0;
+    for (const auto& test_case : g_test_cases) {
+        auto expected = test_case.matching_offset >= 0 ? test_case.haystack + test_case.matching_offset : nullptr;
+        auto result = memmem(test_case.haystack, test_case.haystack_length, test_case.needle, test_case.needle_length);
+        if (result != expected) {
+            failed = true;
+            fprintf(stderr, "Test %zu FAILED! expected %p, got %p\n", i, expected, result);
+        }
+        ++i;
+    }
+
+    return failed ? 1 : 0;
+}