composable_kernel/include/rapidjson/istreamwrapper.h

// 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.
//
// 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>

#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

//! Wrapper of \c std::basic_istream into RapidJSON's Stream concept.
/*!
    The classes can be wrapped including but not limited to:

    - \c std::istringstream
    - \c std::stringstream
    - \c std::wistringstream
    - \c std::wstringstream
    - \c std::ifstream
    - \c std::fstream
    - \c std::wifstream
    - \c std::wfstream

    \tparam StreamType Class derived from \c std::basic_istream.
*/

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

    //! Constructor.
    /*!
        \param stream stream opened for read.
    */
    BasicIStreamWrapper(StreamType& stream)
        : stream_(stream),
          buffer_(peekBuffer_),
          bufferSize_(4),
          bufferLast_(0),
          current_(buffer_),
          readCount_(0),
          count_(0),
          eof_(false)
    {
        Read();
    }

    //! Constructor.
    /*!
        \param stream stream opened for read.
        \param buffer user-supplied buffer.
        \param bufferSize size of buffer in bytes. Must >=4 bytes.
    */
    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_; //!< Number of characters read
    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_