text: // Copyright 2015 Google Inc. All rights reserved
  //
  // 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
  //
  //      http://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.
  
  // Copyright (c) 2011 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  // Copied from strings/stringpiece.cc with modifications
  
  // +build ignore
  
  #include <ctype.h>
  #include <limits.h>
  #include <stdint.h>
  
  #include <algorithm>
  #include <ostream>
  
  #include "string_piece.h"
  
  typedef StringPiece::size_type size_type;
  
  bool operator==(const StringPiece& x, const StringPiece& y) {
    if (x.size() != y.size())
      return false;
    size_t len = x.size();
    if (len >= sizeof(uint64_t)) {
      len -= sizeof(uint64_t);
      uint64_t xt = *reinterpret_cast<const uint64_t*>(x.data() + len);
      uint64_t yt = *reinterpret_cast<const uint64_t*>(y.data() + len);
      if (xt != yt)
        return false;
    }
    return StringPiece::wordmemcmp(x.data(), y.data(), len) == 0;
  }
  
  void StringPiece::CopyToString(std::string* target) const {
    target->assign(!empty() ? data() : "", size());
  }
  
  void StringPiece::AppendToString(std::string* target) const {
    if (!empty())
      target->append(data(), size());
  }
  
  size_type StringPiece::copy(char* buf, size_type n, size_type pos) const {
    size_type ret = std::min(length_ - pos, n);
    memcpy(buf, ptr_ + pos, ret);
    return ret;
  }
  
  size_type StringPiece::find(const StringPiece& s, size_type pos) const {
    if (pos > length_)
      return npos;
  
    const char* result = std::search(ptr_ + pos, ptr_ + length_,
                                     s.ptr_, s.ptr_ + s.length_);
    const size_type xpos = result - ptr_;
    return xpos + s.length_ <= length_ ? xpos : npos;
  }
  
  size_type StringPiece::find(char c, size_type pos) const {
    if (pos >= length_)
      return npos;
  
    const char* result = std::find(ptr_ + pos, ptr_ + length_, c);
    return result != ptr_ + length_ ? static_cast<size_t>(result - ptr_) : npos;
  }
  
  size_type StringPiece::rfind(const StringPiece& s, size_type pos) const {
    if (length_ < s.length_)
      return npos;
  
    if (s.empty())
      return std::min(length_, pos);
  
    const char* last = ptr_ + std::min(length_ - s.length_, pos) + s.length_;
    const char* result = std::find_end(ptr_, last, s.ptr_, s.ptr_ + s.length_);
    return result != last ? static_cast<size_t>(result - ptr_) : npos;
  }
  
  size_type StringPiece::rfind(char c, size_type pos) const {
    if (length_ == 0)
      return npos;
  
    for (size_type i = std::min(pos, length_ - 1); ; --i) {
      if (ptr_[i] == c)
        return i;
      if (i == 0)
        break;
    }
    return npos;
  }
  
  // For each character in characters_wanted, sets the index corresponding
  // to the ASCII code of that character to 1 in table.  This is used by
  // the find_.*_of methods below to tell whether or not a character is in
  // the lookup table in constant time.
  // The argument `table' must be an array that is large enough to hold all
  // the possible values of an unsigned char.  Thus it should be be declared
  // as follows:
  //   bool table[UCHAR_MAX + 1]
  static inline void BuildLookupTable(const StringPiece& characters_wanted,
                                      bool* table) {
    const size_type length = characters_wanted.length();
    const char* const data = characters_wanted.data();
    for (size_type i = 0; i < length; ++i) {
      table[static_cast<unsigned char>(data[i])] = true;
    }
  }
  
  size_type StringPiece::find_first_of(const StringPiece& s,
                                       size_type pos) const {
    if (length_ == 0 || s.length_ == 0)
      return npos;
  
    // Avoid the cost of BuildLookupTable() for a single-character search.
    if (s.length_ == 1)
      return find_first_of(s.ptr_[0], pos);
  
    bool lookup[UCHAR_MAX + 1] = { false };
    BuildLookupTable(s, lookup);
    for (size_type i = pos; i < length_; ++i) {
      if (lookup[static_cast<unsigned char>(ptr_[i])]) {
        return i;
      }
    }
    return npos;
  }
  
  size_type StringPiece::find_first_not_of(const StringPiece& s,
                                           size_type pos) const {
    if (length_ == 0)
      return npos;
  
    if (s.length_ == 0)
      return 0;
  
    // Avoid the cost of BuildLookupTable() for a single-character search.
    if (s.length_ == 1)
      return find_first_not_of(s.ptr_[0], pos);
  
    bool lookup[UCHAR_MAX + 1] = { false };
    BuildLookupTable(s, lookup);
    for (size_type i = pos; i < length_; ++i) {
      if (!lookup[static_cast<unsigned char>(ptr_[i])]) {
        return i;
      }
    }
    return npos;
  }
  
  size_type StringPiece::find_first_not_of(char c, size_type pos) const {
    if (length_ == 0)
      return npos;
  
    for (; pos < length_; ++pos) {
      if (ptr_[pos] != c) {
        return pos;
      }
    }
    return npos;
  }
  
  size_type StringPiece::find_last_of(const StringPiece& s, size_type pos) const {
    if (length_ == 0 || s.length_ == 0)
      return npos;
  
    // Avoid the cost of BuildLookupTable() for a single-character search.
    if (s.length_ == 1)
      return find_last_of(s.ptr_[0], pos);
  
    bool lookup[UCHAR_MAX + 1] = { false };
    BuildLookupTable(s, lookup);
    for (size_type i = std::min(pos, length_ - 1); ; --i) {
      if (lookup[static_cast<unsigned char>(ptr_[i])])
        return i;
      if (i == 0)
        break;
    }
    return npos;
  }
  
  size_type StringPiece::find_last_not_of(const StringPiece& s,
                                          size_type pos) const {
    if (length_ == 0)
      return npos;
  
    size_type i = std::min(pos, length_ - 1);
    if (s.length_ == 0)
      return i;
  
    // Avoid the cost of BuildLookupTable() for a single-character search.
    if (s.length_ == 1)
      return find_last_not_of(s.ptr_[0], pos);
  
    bool lookup[UCHAR_MAX + 1] = { false };
    BuildLookupTable(s, lookup);
    for (; ; --i) {
      if (!lookup[static_cast<unsigned char>(ptr_[i])])
        return i;
      if (i == 0)
        break;
    }
    return npos;
  }
  
  size_type StringPiece::find_last_not_of(char c, size_type pos) const {
    if (length_ == 0)
      return npos;
  
    for (size_type i = std::min(pos, length_ - 1); ; --i) {
      if (ptr_[i] != c)
        return i;
      if (i == 0)
        break;
    }
    return npos;
  }
  
  StringPiece StringPiece::substr(size_type pos, size_type n) const {
    if (pos > length_) pos = length_;
    if (n > length_ - pos) n = length_ - pos;
    return StringPiece(ptr_ + pos, n);
  }
  
  const StringPiece::size_type StringPiece::npos = size_type(-1);
  