encodedstream.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_ENCODEDSTREAM_H_
#define RAPIDJSON_ENCODEDSTREAM_H_

#include "rapidjson.h"

#ifdef __GNUC__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(effc++)
#endif

RAPIDJSON_NAMESPACE_BEGIN


template <typename Encoding, typename InputByteStream>
class EncodedInputStream {
 RAPIDJSON_STATIC_ASSERT(sizeof(typename InputByteStream::Ch) == 1);
public:
 typedef typename Encoding::Ch Ch;

 EncodedInputStream(InputByteStream& is) : is_(is) { 
 current_ = Encoding::TakeBOM(is_);
 }

 Ch Peek() const { return current_; }
 Ch Take() { Ch c = current_; current_ = Encoding::Take(is_); return c; }
 size_t Tell() const { return is_.Tell(); }

 // 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; }

private:
 EncodedInputStream(const EncodedInputStream&);
 EncodedInputStream& operator=(const EncodedInputStream&);

 InputByteStream& is_;
 Ch current_;
};


template <typename Encoding, typename OutputByteStream>
class EncodedOutputStream {
 RAPIDJSON_STATIC_ASSERT(sizeof(typename OutputByteStream::Ch) == 1);
public:
 typedef typename Encoding::Ch Ch;

 EncodedOutputStream(OutputByteStream& os, bool putBOM = true) : os_(os) { 
 if (putBOM)
 Encoding::PutBOM(os_);
 }

 void Put(Ch c) { Encoding::Put(os_, c); }
 void Flush() { os_.Flush(); }

 // Not implemented
 Ch Peek() const { RAPIDJSON_ASSERT(false); }
 Ch Take() { RAPIDJSON_ASSERT(false); }
 size_t Tell() const { RAPIDJSON_ASSERT(false); return 0; }
 Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
 size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }

private:
 EncodedOutputStream(const EncodedOutputStream&);
 EncodedOutputStream& operator=(const EncodedOutputStream&);

 OutputByteStream& os_;
};

#define RAPIDJSON_ENCODINGS_FUNC(x) UTF8<Ch>::x, UTF16LE<Ch>::x, UTF16BE<Ch>::x, UTF32LE<Ch>::x, UTF32BE<Ch>::x


template <typename CharType, typename InputByteStream>
class AutoUTFInputStream {
 RAPIDJSON_STATIC_ASSERT(sizeof(typename InputByteStream::Ch) == 1);
public:
 typedef CharType Ch;


 AutoUTFInputStream(InputByteStream& is, UTFType type = kUTF8) : is_(&is), type_(type), hasBOM_(false) {
 RAPIDJSON_ASSERT(type >= kUTF8 && type <= kUTF32BE); 
 DetectType();
 static const TakeFunc f[] = { RAPIDJSON_ENCODINGS_FUNC(Take) };
 takeFunc_ = f[type_];
 current_ = takeFunc_(*is_);
 }

 UTFType GetType() const { return type_; }
 bool HasBOM() const { return hasBOM_; }

 Ch Peek() const { return current_; }
 Ch Take() { Ch c = current_; current_ = takeFunc_(*is_); return c; }
 size_t Tell() const { return is_->Tell(); }

 // 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; }

private:
 AutoUTFInputStream(const AutoUTFInputStream&);
 AutoUTFInputStream& operator=(const AutoUTFInputStream&);

 // Detect encoding type with BOM or RFC 4627
 void DetectType() {
 // BOM (Byte Order Mark):
 // 00 00 FE FF UTF-32BE
 // FF FE 00 00 UTF-32LE
 // FE FF UTF-16BE
 // FF FE UTF-16LE
 // EF BB BF UTF-8

 const unsigned char* c = (const unsigned char *)is_->Peek4();
 if (!c)
 return;

 unsigned bom = c[0] | (c[1] << 8) | (c[2] << 16) | (c[3] << 24);
 hasBOM_ = false;
 if (bom == 0xFFFE0000) { type_ = kUTF32BE; hasBOM_ = true; is_->Take(); is_->Take(); is_->Take(); is_->Take(); }
 else if (bom == 0x0000FEFF) { type_ = kUTF32LE; hasBOM_ = true; is_->Take(); is_->Take(); is_->Take(); is_->Take(); }
 else if ((bom & 0xFFFF) == 0xFFFE) { type_ = kUTF16BE; hasBOM_ = true; is_->Take(); is_->Take(); }
 else if ((bom & 0xFFFF) == 0xFEFF) { type_ = kUTF16LE; hasBOM_ = true; is_->Take(); is_->Take(); }
 else if ((bom & 0xFFFFFF) == 0xBFBBEF) { type_ = kUTF8; hasBOM_ = true; is_->Take(); is_->Take(); is_->Take(); }

 // RFC 4627: Section 3
 // "Since the first two characters of a JSON text will always be ASCII
 // characters [RFC0020], it is possible to determine whether an octet
 // stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking
 // at the pattern of nulls in the first four octets."
 // 00 00 00 xx UTF-32BE
 // 00 xx 00 xx UTF-16BE
 // xx 00 00 00 UTF-32LE
 // xx 00 xx 00 UTF-16LE
 // xx xx xx xx UTF-8

 if (!hasBOM_) {
 unsigned pattern = (c[0] ? 1 : 0) | (c[1] ? 2 : 0) | (c[2] ? 4 : 0) | (c[3] ? 8 : 0);
 switch (pattern) {
 case 0x08: type_ = kUTF32BE; break;
 case 0x0A: type_ = kUTF16BE; break;
 case 0x01: type_ = kUTF32LE; break;
 case 0x05: type_ = kUTF16LE; break;
 case 0x0F: type_ = kUTF8; break;
 default: break; // Use type defined by user.
 }
 }

 // Runtime check whether the size of character type is sufficient. It only perform checks with assertion.
 if (type_ == kUTF16LE || type_ == kUTF16BE) RAPIDJSON_ASSERT(sizeof(Ch) >= 2);
 if (type_ == kUTF32LE || type_ == kUTF32BE) RAPIDJSON_ASSERT(sizeof(Ch) >= 4);
 }

 typedef Ch (*TakeFunc)(InputByteStream& is);
 InputByteStream* is_;
 UTFType type_;
 Ch current_;
 TakeFunc takeFunc_;
 bool hasBOM_;
};


template <typename CharType, typename OutputByteStream>
class AutoUTFOutputStream {
 RAPIDJSON_STATIC_ASSERT(sizeof(typename OutputByteStream::Ch) == 1);
public:
 typedef CharType Ch;


 AutoUTFOutputStream(OutputByteStream& os, UTFType type, bool putBOM) : os_(&os), type_(type) {
 RAPIDJSON_ASSERT(type >= kUTF8 && type <= kUTF32BE);

 // Runtime check whether the size of character type is sufficient. It only perform checks with assertion.
 if (type_ == kUTF16LE || type_ == kUTF16BE) RAPIDJSON_ASSERT(sizeof(Ch) >= 2);
 if (type_ == kUTF32LE || type_ == kUTF32BE) RAPIDJSON_ASSERT(sizeof(Ch) >= 4);

 static const PutFunc f[] = { RAPIDJSON_ENCODINGS_FUNC(Put) };
 putFunc_ = f[type_];

 if (putBOM)
 PutBOM();
 }

 UTFType GetType() const { return type_; }

 void Put(Ch c) { putFunc_(*os_, c); }
 void Flush() { os_->Flush(); } 

 // Not implemented
 Ch Peek() const { RAPIDJSON_ASSERT(false); }
 Ch Take() { RAPIDJSON_ASSERT(false); }
 size_t Tell() const { RAPIDJSON_ASSERT(false); return 0; }
 Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
 size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }

private:
 AutoUTFOutputStream(const AutoUTFOutputStream&);
 AutoUTFOutputStream& operator=(const AutoUTFOutputStream&);

 void PutBOM() { 
 typedef void (*PutBOMFunc)(OutputByteStream&);
 static const PutBOMFunc f[] = { RAPIDJSON_ENCODINGS_FUNC(PutBOM) };
 f[type_](*os_);
 }

 typedef void (*PutFunc)(OutputByteStream&, Ch);

 OutputByteStream* os_;
 UTFType type_;
 PutFunc putFunc_;
};

#undef RAPIDJSON_ENCODINGS_FUNC

RAPIDJSON_NAMESPACE_END

#ifdef __GNUC__
RAPIDJSON_DIAG_POP
#endif

#endif // RAPIDJSON_FILESTREAM_H_