memorystream.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. 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_MEMORYSTREAM_H_
#define RAPIDJSON_MEMORYSTREAM_H_
 
#include "stream.h"
 
#ifdef __clang__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(unreachable-code)
RAPIDJSON_DIAG_OFF(missing-noreturn)
#endif
 
RAPIDJSON_NAMESPACE_BEGIN
 
//! Represents an in-memory input byte stream.
/*!
    This class is mainly for being wrapped by EncodedInputStream or AutoUTFInputStream.
 
    It is similar to FileReadBuffer but the source is an in-memory buffer instead of a file.
 
    Differences between MemoryStream and StringStream:
    1. StringStream has encoding but MemoryStream is a byte stream.
    2. MemoryStream needs size of the source buffer and the buffer don't need to be null terminated. StringStream assume null-terminated string as source.
    3. MemoryStream supports Peek4() for encoding detection. StringStream is specified with an encoding so it should not have Peek4().
    \note implements Stream concept
*/
struct MemoryStream {
    typedef char Ch; // byte
 
    MemoryStream(const Ch *src, size_t size) : src_(src), begin_(src), end_(src + size), size_(size) {}
 
    Ch Peek() const { return RAPIDJSON_UNLIKELY(src_ == end_) ? '\0' : *src_; }
    Ch Take() { return RAPIDJSON_UNLIKELY(src_ == end_) ? '\0' : *src_++; }
    size_t Tell() const { return static_cast<size_t>(src_ - begin_); }
 
    Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
    void Put(Ch) { RAPIDJSON_ASSERT(false); }
    void Flush() { RAPIDJSON_ASSERT(false); }
    size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
 
    // For encoding detection only.
    const Ch* Peek4() const {
        return Tell() + 4 <= size_ ? src_ : 0;
    }
 
    const Ch* src_;     //!< Current read position.
    const Ch* begin_;   //!< Original head of the string.
    const Ch* end_;     //!< End of stream.
    size_t size_;       //!< Size of the stream.
};
 
RAPIDJSON_NAMESPACE_END
 
#ifdef __clang__
RAPIDJSON_DIAG_POP
#endif
 
#endif // RAPIDJSON_MEMORYBUFFER_H_