diff --git a/Kernel/StdLib.cpp b/Kernel/StdLib.cpp index d72b2af4f0..54cb6b109e 100644 --- a/Kernel/StdLib.cpp +++ b/Kernel/StdLib.cpp @@ -39,6 +39,34 @@ String copy_string_from_user(const char* user_str, size_t user_str_size) return String(user_str, length); } +namespace { +const static void* bitap_bitwise(const void* haystack, size_t haystack_length, const void* needle, size_t needle_length) +{ + ASSERT(needle_length < 32); + + u64 lookup = 0xfffffffe; + + constexpr size_t mask_length = (size_t)((u8)-1) + 1; + u64 needle_mask[mask_length]; + + for (size_t i = 0; i < mask_length; ++i) + needle_mask[i] = 0xffffffff; + + for (size_t i = 0; i < needle_length; ++i) + needle_mask[((const u8*)needle)[i]] &= ~(0x00000001 << i); + + for (size_t i = 0; i < haystack_length; ++i) { + lookup |= needle_mask[((const u8*)haystack)[i]]; + lookup <<= 1; + + if (!(lookup & (0x00000001 << needle_length))) + return ((const u8*)haystack) + i - needle_length + 1; + } + + return nullptr; +} +} + extern "C" { void copy_to_user(void* dest_ptr, const void* src_ptr, size_t n) @@ -91,6 +119,31 @@ void* memmove(void* dest, const void* src, size_t n) return dest; } +const void* memmem(const void* haystack, size_t haystack_length, const void* needle, size_t needle_length) +{ + if (needle_length == 0) + return haystack; + + if (haystack_length < needle_length) + return nullptr; + + if (haystack_length == needle_length) + return memcmp(haystack, needle, haystack_length) == 0 ? haystack : nullptr; + + if (needle_length < 32) + return bitap_bitwise(haystack, haystack_length, needle, needle_length); + + // Fallback to a slower search. + auto length_diff = haystack_length - needle_length; + for (size_t i = 0; i < length_diff; ++i) { + const auto* start = ((const u8*)haystack) + i; + if (memcmp(start, needle, needle_length) == 0) + return start; + } + + return nullptr; +} + char* strcpy(char* dest, const char* src) { auto* dest_ptr = dest; diff --git a/Kernel/StdLib.h b/Kernel/StdLib.h index 994c514123..d85deeebb1 100644 --- a/Kernel/StdLib.h +++ b/Kernel/StdLib.h @@ -54,6 +54,7 @@ char* strdup(const char*); int memcmp(const void*, const void*, size_t); char* strrchr(const char* str, int ch); void* memmove(void* dest, const void* src, size_t n); +const void* memmem(const void* haystack, size_t, const void* needle, size_t); inline u16 ntohs(u16 w) { return (w & 0xff) << 8 | ((w >> 8) & 0xff); } inline u16 htons(u16 w) { return (w & 0xff) << 8 | ((w >> 8) & 0xff); } diff --git a/Libraries/LibC/string.cpp b/Libraries/LibC/string.cpp index b159d5d181..b9da8c0a8a 100644 --- a/Libraries/LibC/string.cpp +++ b/Libraries/LibC/string.cpp @@ -189,6 +189,59 @@ void* memmove(void* dest, const void* src, size_t n) return dest; } +namespace { +const static void* bitap_bitwise(const void* haystack, size_t haystack_length, const void* needle, size_t needle_length) +{ + ASSERT(needle_length < 32); + + u64 lookup = 0xfffffffe; + + constexpr size_t mask_length = (size_t)((u8)-1) + 1; + u64 needle_mask[mask_length]; + + for (size_t i = 0; i < mask_length; ++i) + needle_mask[i] = 0xffffffff; + + for (size_t i = 0; i < needle_length; ++i) + needle_mask[((const u8*)needle)[i]] &= ~(0x00000001 << i); + + for (size_t i = 0; i < haystack_length; ++i) { + lookup |= needle_mask[((const u8*)haystack)[i]]; + lookup <<= 1; + + if (!(lookup & (0x00000001 << needle_length))) + return ((const u8*)haystack) + i - needle_length + 1; + } + + return nullptr; +} +} + +const void* memmem(const void* haystack, size_t haystack_length, const void* needle, size_t needle_length) +{ + if (needle_length == 0) + return haystack; + + if (haystack_length < needle_length) + return nullptr; + + if (haystack_length == needle_length) + return memcmp(haystack, needle, haystack_length) == 0 ? haystack : nullptr; + + if (needle_length < 32) + return bitap_bitwise(haystack, haystack_length, needle, needle_length); + + // Fallback to a slower search. + auto length_diff = haystack_length - needle_length; + for (size_t i = 0; i < length_diff; ++i) { + const auto* start = ((const u8*)haystack) + i; + if (memcmp(start, needle, needle_length) == 0) + return start; + } + + return nullptr; +} + char* strcpy(char* dest, const char* src) { char* originalDest = dest; diff --git a/Libraries/LibC/string.h b/Libraries/LibC/string.h index 6e6fb6f457..0d8a0a194a 100644 --- a/Libraries/LibC/string.h +++ b/Libraries/LibC/string.h @@ -41,6 +41,7 @@ int memcmp(const void*, const void*, size_t); void* memcpy(void*, const void*, size_t); void* memmove(void*, const void*, size_t); void* memchr(const void*, int c, size_t); +const void* memmem(const void* haystack, size_t, const void* needle, size_t); void bzero(void*, size_t); void bcopy(const void*, void*, size_t); void* memset(void*, int, size_t); 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 + * 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 +#include +#include +#include +#include +#include + +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; +}