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

#if __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_