1// Tencent is pleased to support the open source community by making RapidJSON available.
 2// 
 3// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
 4//
 5// Licensed under the MIT License (the "License"); you may not use this file except
 6// in compliance with the License. You may obtain a copy of the License at
 7//
 8// http://opensource.org/licenses/MIT
 9//
10// Unless required by applicable law or agreed to in writing, software distributed 
11// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 
12// CONDITIONS OF ANY KIND, either express or implied. See the License for the 
13// specific language governing permissions and limitations under the License.
14
15#ifndef RAPIDJSON_MEMORYSTREAM_H_
16#define RAPIDJSON_MEMORYSTREAM_H_
17
18#include "stream.h"
19
20#ifdef __clang__
21RAPIDJSON_DIAG_PUSH
22RAPIDJSON_DIAG_OFF(unreachable-code)
23RAPIDJSON_DIAG_OFF(missing-noreturn)
24#endif
25
26RAPIDJSON_NAMESPACE_BEGIN
27
28//! Represents an in-memory input byte stream.
29/*!
30    This class is mainly for being wrapped by EncodedInputStream or AutoUTFInputStream.
31
32    It is similar to FileReadBuffer but the source is an in-memory buffer instead of a file.
33
34    Differences between MemoryStream and StringStream:
35    1. StringStream has encoding but MemoryStream is a byte stream.
36    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.
37    3. MemoryStream supports Peek4() for encoding detection. StringStream is specified with an encoding so it should not have Peek4().
38    \note implements Stream concept
39*/
40struct MemoryStream {
41    typedef char Ch; // byte
42
43    MemoryStream(const Ch *src, size_t size) : src_(src), begin_(src), end_(src + size), size_(size) {}
44
45    Ch Peek() const { return RAPIDJSON_UNLIKELY(src_ == end_) ? '\0' : *src_; }
46    Ch Take() { return RAPIDJSON_UNLIKELY(src_ == end_) ? '\0' : *src_++; }
47    size_t Tell() const { return static_cast<size_t>(src_ - begin_); }
48
49    Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
50    void Put(Ch) { RAPIDJSON_ASSERT(false); }
51    void Flush() { RAPIDJSON_ASSERT(false); }
52    size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
53
54    // For encoding detection only.
55    const Ch* Peek4() const {
56        return Tell() + 4 <= size_ ? src_ : 0;
57    }
58
59    const Ch* src_;     //!< Current read position.
60    const Ch* begin_;   //!< Original head of the string.
61    const Ch* end_;     //!< End of stream.
62    size_t size_;       //!< Size of the stream.
63};
64
65RAPIDJSON_NAMESPACE_END
66
67#ifdef __clang__
68RAPIDJSON_DIAG_POP
69#endif
70
71#endif // RAPIDJSON_MEMORYBUFFER_H_