| //===-- memmem implementation -----------------------------------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMMEM_IMPLEMENTATIONS_H |
| #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMMEM_IMPLEMENTATIONS_H |
| |
| #include <stddef.h> |
| |
| namespace __llvm_libc { |
| |
| template <typename Comp> |
| constexpr static void * |
| memmem_implementation(const void *haystack, size_t haystack_len, |
| const void *needle, size_t needle_len, Comp &&comp) { |
| // TODO: simple brute force implementation. This can be |
| // improved upon using well known string matching algorithms. |
| if (!needle_len) |
| return const_cast<void *>(haystack); |
| |
| if (needle_len > haystack_len) |
| return nullptr; |
| |
| const unsigned char *h = static_cast<const unsigned char *>(haystack); |
| const unsigned char *n = static_cast<const unsigned char *>(needle); |
| for (size_t i = 0; i <= (haystack_len - needle_len); ++i) { |
| size_t j = 0; |
| for (; j < needle_len && !comp(h[i + j], n[j]); ++j) |
| ; |
| if (j == needle_len) |
| return const_cast<unsigned char *>(h + i); |
| } |
| return nullptr; |
| } |
| |
| } // namespace __llvm_libc |
| |
| #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_MEMMEM_IMPLEMENTATIONS_H |