istreamwrapper.h

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// Tencent is pleased to support the open source community by making RapidJSON
// available.
//
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All
// rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file
// except in compliance with the License. You may obtain a copy of the License
// at
//
// http://opensource.org/licenses/MIT
//
// 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.

#ifndef RAPIDJSON_ISTREAMWRAPPER_H_
#define RAPIDJSON_ISTREAMWRAPPER_H_

#include <ios>
#include <iosfwd>
#include "stream.h"

#ifdef __clang__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(padded)
#elif defined(_MSC_VER)
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(4351)  // new behavior: elements of array 'array' will be
                          // default initialized
#endif

RAPIDJSON_NAMESPACE_BEGIN


template <typename StreamType>
class BasicIStreamWrapper {
 public:
  typedef typename StreamType::char_type Ch;


  BasicIStreamWrapper(StreamType &stream)
      : stream_(stream),
        buffer_(peekBuffer_),
        bufferSize_(4),
        bufferLast_(0),
        current_(buffer_),
        readCount_(0),
        count_(0),
        eof_(false) {
    Read();
  }


  BasicIStreamWrapper(StreamType &stream, char *buffer, size_t bufferSize)
      : stream_(stream),
        buffer_(buffer),
        bufferSize_(bufferSize),
        bufferLast_(0),
        current_(buffer_),
        readCount_(0),
        count_(0),
        eof_(false) {
    RAPIDJSON_ASSERT(bufferSize >= 4);
    Read();
  }

  Ch Peek() const { return *current_; }
  Ch Take() {
    Ch c = *current_;
    Read();
    return c;
  }
  size_t Tell() const {
    return count_ + static_cast<size_t>(current_ - buffer_);
  }

  // Not implemented
  void Put(Ch) { RAPIDJSON_ASSERT(false); }
  void Flush() { RAPIDJSON_ASSERT(false); }
  Ch *PutBegin() {
    RAPIDJSON_ASSERT(false);
    return 0;
  }
  size_t PutEnd(Ch *) {
    RAPIDJSON_ASSERT(false);
    return 0;
  }

  // For encoding detection only.
  const Ch *Peek4() const {
    return (current_ + 4 - !eof_ <= bufferLast_) ? current_ : 0;
  }

 private:
  BasicIStreamWrapper();
  BasicIStreamWrapper(const BasicIStreamWrapper &);
  BasicIStreamWrapper &operator=(const BasicIStreamWrapper &);

  void Read() {
    if (current_ < bufferLast_)
      ++current_;
    else if (!eof_) {
      count_ += readCount_;
      readCount_ = bufferSize_;
      bufferLast_ = buffer_ + readCount_ - 1;
      current_ = buffer_;

      if (!stream_.read(buffer_, static_cast<std::streamsize>(bufferSize_))) {
        readCount_ = static_cast<size_t>(stream_.gcount());
        *(bufferLast_ = buffer_ + readCount_) = '\0';
        eof_ = true;
      }
    }
  }

  StreamType &stream_;
  Ch peekBuffer_[4], *buffer_;
  size_t bufferSize_;
  Ch *bufferLast_;
  Ch *current_;
  size_t readCount_;
  size_t count_;  
  bool eof_;
};

typedef BasicIStreamWrapper<std::istream> IStreamWrapper;
typedef BasicIStreamWrapper<std::wistream> WIStreamWrapper;

#if defined(__clang__) || defined(_MSC_VER)
RAPIDJSON_DIAG_POP
#endif

RAPIDJSON_NAMESPACE_END

#endif  // RAPIDJSON_ISTREAMWRAPPER_H_