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"
13 #include "src/__support/macros/config.h"
14
15 #include <stddef.h>
16
17 namespace LIBC_NAMESPACE_DECL {
18
19 template <typename Comp>
20 LIBC_INLINE constexpr static void *
inline_memmem(const void * haystack,size_t haystack_len,const void * needle,size_t needle_len,Comp && comp)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