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| 1 | //===-- memmem implementation -----------------------------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_INLINE_MEMMEM_H |
| 10 | #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_INLINE_MEMMEM_H |
| 11 | |
| 12 | #include "src/__support/macros/attributes.h" // LIBC_INLINE |
| 13 | #include "src/__support/macros/config.h" // LIBC_NAMESPACE_DECL |
| 14 | |
| 15 | #include <stddef.h> |
| 16 | |
| 17 | namespace LIBC_NAMESPACE_DECL { |
| 18 | |
| 19 | template <typename Comp> |
| 20 | LIBC_INLINE constexpr static void * |
| 21 | inline_memmem(const void *haystack, size_t haystack_len, const void *needle, |
| 22 | size_t needle_len, Comp &&comp) { |
| 23 | // TODO: simple brute force implementation. This can be |
| 24 | // improved upon using well known string matching algorithms. |
| 25 | if (!needle_len) |
| 26 | return const_cast<void *>(haystack); |
| 27 | |
| 28 | if (needle_len > haystack_len) |
| 29 | return nullptr; |
| 30 | |
| 31 | const unsigned char *h = static_cast<const unsigned char *>(haystack); |
| 32 | const unsigned char *n = static_cast<const unsigned char *>(needle); |
| 33 | for (size_t i = 0; i <= (haystack_len - needle_len); ++i) { |
| 34 | size_t j = 0; |
| 35 | for (; j < needle_len && !comp(h[i + j], n[j]); ++j) |
| 36 | ; |
| 37 | if (j == needle_len) |
| 38 | return const_cast<unsigned char *>(h + i); |
| 39 | } |
| 40 | return nullptr; |
| 41 | } |
| 42 | |
| 43 | } // namespace LIBC_NAMESPACE_DECL |
| 44 | |
| 45 | #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_INLINE_MEMMEM_H |
| 46 |
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