libc/src/string/strstr.cpp

   1 //===-- Implementation of strstr ------------------------------------------===//
   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 #include "src/string/strstr.h"
  10
  11 #include "src/__support/common.h"
  12 #include <stddef.h>
  13
  14 namespace __llvm_libc {
  15
  16 // TODO: This is a simple brute force implementation. This can be
  17 // improved upon using well known string matching algorithms.
  18 char *LLVM_LIBC_ENTRYPOINT(strstr)(const char *haystack, const char *needle) {
  19   for (size_t i = 0; haystack[i]; ++i) {
  20     size_t j;
  21     for (j = 0; haystack[i + j] && haystack[i + j] == needle[j]; ++j)
  22       ;
  23     if (!needle[j])
  24       return const_cast<char *>(haystack + i);
  25   }
  26   return nullptr;
  27 }
  28
  29 } // namespace __llvm_libc