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//===-- 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
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