include/rapidjson/memorystream.h

0001 // Tencent is pleased to support the open source community by making RapidJSON available.
0002 //
0003 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip.
0004 //
0005 // Licensed under the MIT License (the "License"); you may not use this file except
0006 // in compliance with the License. You may obtain a copy of the License at
0007 //
0008 // http://opensource.org/licenses/MIT
0009 //
0010 // Unless required by applicable law or agreed to in writing, software distributed
0011 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
0012 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
0013 // specific language governing permissions and limitations under the License.
0014
0015 #ifndef RAPIDJSON_MEMORYSTREAM_H_
0016 #define RAPIDJSON_MEMORYSTREAM_H_
0017
0018 #include "stream.h"
0019
0020 #ifdef __clang__
0021 RAPIDJSON_DIAG_PUSH
0022 RAPIDJSON_DIAG_OFF(unreachable-code)
0023 RAPIDJSON_DIAG_OFF(missing-noreturn)
0024 #endif
0025
0026 RAPIDJSON_NAMESPACE_BEGIN
0027
0028 //! Represents an in-memory input byte stream.
0029 /*!
0030     This class is mainly for being wrapped by EncodedInputStream or AutoUTFInputStream.
0031
0032     It is similar to FileReadBuffer but the source is an in-memory buffer instead of a file.
0033
0034     Differences between MemoryStream and StringStream:
0035     1. StringStream has encoding but MemoryStream is a byte stream.
0036     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.
0037     3. MemoryStream supports Peek4() for encoding detection. StringStream is specified with an encoding so it should not have Peek4().
0038     \note implements Stream concept
0039 */
0040 struct MemoryStream {
0041     typedef char Ch; // byte
0042
0043     MemoryStream(const Ch *src, size_t size) : src_(src), begin_(src), end_(src + size), size_(size) {}
0044
0045     Ch Peek() const { return RAPIDJSON_UNLIKELY(src_ == end_) ? '\0' : *src_; }
0046     Ch Take() { return RAPIDJSON_UNLIKELY(src_ == end_) ? '\0' : *src_++; }
0047     size_t Tell() const { return static_cast<size_t>(src_ - begin_); }
0048
0049     Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
0050     void Put(Ch) { RAPIDJSON_ASSERT(false); }
0051     void Flush() { RAPIDJSON_ASSERT(false); }
0052     size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
0053
0054     // For encoding detection only.
0055     const Ch* Peek4() const {
0056         return Tell() + 4 <= size_ ? src_ : 0;
0057     }
0058
0059     const Ch* src_;     //!< Current read position.
0060     const Ch* begin_;   //!< Original head of the string.
0061     const Ch* end_;     //!< End of stream.
0062     size_t size_;       //!< Size of the stream.
0063 };
0064
0065 RAPIDJSON_NAMESPACE_END
0066
0067 #ifdef __clang__
0068 RAPIDJSON_DIAG_POP
0069 #endif
0070
0071 #endif // RAPIDJSON_MEMORYBUFFER_H_