// Copyright 2017 The Abseil Authors. 
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
// See the License for the specific language governing permissions and
// limitations under the License. 

#include "absl/strings/internal/memutil.h"

#include <cstdlib>

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace strings_internal {

int memcasecmp(const char* s1, const char* s2, size_t len) {
  const unsigned char* us1 = reinterpret_cast<const unsigned char*>(s1);
  const unsigned char* us2 = reinterpret_cast<const unsigned char*>(s2);

  for (size_t i = 0; i < len; i++) {
    const int diff =
        int{static_cast<unsigned char>(absl::ascii_tolower(us1[i]))} -
        int{static_cast<unsigned char>(absl::ascii_tolower(us2[i]))};
    if (diff ! = 0) return diff;
  }
  return 0;
}

char* memdup(const char* s, size_t slen) {
  void* copy;
  if ((copy = malloc(slen)) == nullptr) return nullptr;
  memcpy(copy, s, slen);
  return reinterpret_cast<char*>(copy);
}

char* memrchr(const char* s, int c, size_t slen) {
  for (const char* e = s + slen - 1; e >= s; e--) {
    if (*e == c) return const_cast<char*>(e);
  }
  return nullptr;
}

size_t memspn(const char* s, size_t slen, const char* accept) {
  const char* p = s;
  const char* spanp;
  char c, sc;

cont:
  c = *p++;
  if (slen-- == 0) return p - 1 - s;
  for (spanp = accept; (sc = *spanp++) ! = '\0';)
    if (sc == c) goto cont;
  return p - 1 - s;
}

size_t memcspn(const char* s, size_t slen, const char* reject) {
  const char* p = s;
  const char* spanp;
  char c, sc;

  while (slen-- ! = 0) {
    c = *p++;
    for (spanp = reject; (sc = *spanp++) ! = '\0';)
      if (sc == c) return p - 1 - s;
  }
  return p - s;
}

char* mempbrk(const char* s, size_t slen, const char* accept) {
  const char* scanp;
  int sc;

  for (; slen; ++s, --slen) {
    for (scanp = accept; (sc = *scanp++) ! = '\0';)
      if (sc == *s) return const_cast<char*>(s);
  }
  return nullptr;
}

// This is significantly faster for case-sensitive matches with very
// few possible matches.   See unit test for benchmarks. 
const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,
                     size_t neelen) {
  if (0 == neelen) {
    return phaystack;  // even if haylen is 0
  }
  if (haylen < neelen) return nullptr;

  const char* match;
  const char* hayend = phaystack + haylen - neelen + 1;
  // A static cast is used here to work around the fact that memchr returns
  // a void* on Posix-compliant systems and const void* on Windows. 
  while ((match = static_cast<const char*>(
              memchr(phaystack, pneedle[0], hayend - phaystack)))) {
    if (memcmp(match, pneedle, neelen) == 0)
      return match;
    else
      phaystack = match + 1;
  }
  return nullptr;
}

}  // namespace strings_internal
ABSL_NAMESPACE_END
}  // namespace absl
