2015-02-26 22:04:14 +01:00
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/*
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2016-02-10 00:12:00 +01:00
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* Copyright (c) 2011-present, Facebook, Inc.
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2015-02-26 22:04:14 +01:00
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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*/
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/*
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* This file defines FbsonWriterT (template) and FbsonWriter.
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*
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* FbsonWriterT is a template class which implements an FBSON serializer.
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* Users call various write functions of FbsonWriterT object to write values
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* directly to FBSON packed bytes. All write functions of value or key return
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* the number of bytes written to FBSON, or 0 if there is an error. To write an
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* object, an array, or a string, you must call writeStart[..] before writing
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* values or key, and call writeEnd[..] after finishing at the end.
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*
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* By default, an FbsonWriterT object creates an output stream buffer.
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* Alternatively, you can also pass any output stream object to a writer, as
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* long as the stream object implements some basic functions of std::ostream
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* (such as FbsonOutStream, see FbsonStream.h).
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*
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* FbsonWriter specializes FbsonWriterT with FbsonOutStream type (see
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* FbsonStream.h). So unless you want to provide own a different output stream
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* type, use FbsonParser object.
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*
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* @author Tian Xia <tianx@fb.com>
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*/
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#ifndef FBSON_FBSONWRITER_H
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#define FBSON_FBSONWRITER_H
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#include <stack>
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#include "FbsonDocument.h"
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#include "FbsonStream.h"
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namespace fbson {
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template <class OS_TYPE>
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class FbsonWriterT {
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public:
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FbsonWriterT()
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: alloc_(true), hasHdr_(false), kvState_(WS_Value), str_pos_(0) {
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os_ = new OS_TYPE();
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}
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explicit FbsonWriterT(OS_TYPE& os)
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: os_(&os),
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alloc_(false),
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hasHdr_(false),
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kvState_(WS_Value),
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str_pos_(0) {}
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~FbsonWriterT() {
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if (alloc_) {
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delete os_;
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}
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}
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void reset() {
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os_->clear();
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os_->seekp(0);
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hasHdr_ = false;
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kvState_ = WS_Value;
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for (; !stack_.empty(); stack_.pop())
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;
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}
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// write a key string (or key id if an external dict is provided)
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uint32_t writeKey(const char* key,
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uint8_t len,
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hDictInsert handler = nullptr) {
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if (len && !stack_.empty() && verifyKeyState()) {
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int key_id = -1;
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if (handler) {
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key_id = handler(key, len);
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}
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uint32_t size = sizeof(uint8_t);
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if (key_id < 0) {
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os_->put(len);
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os_->write(key, len);
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size += len;
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} else if (key_id <= FbsonKeyValue::sMaxKeyId) {
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FbsonKeyValue::keyid_type idx = key_id;
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os_->put(0);
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os_->write((char*)&idx, sizeof(FbsonKeyValue::keyid_type));
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size += sizeof(FbsonKeyValue::keyid_type);
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} else { // key id overflow
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assert(0);
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return 0;
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}
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kvState_ = WS_Key;
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return size;
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}
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return 0;
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}
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// write a key id
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uint32_t writeKey(FbsonKeyValue::keyid_type idx) {
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if (!stack_.empty() && verifyKeyState()) {
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os_->put(0);
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os_->write((char*)&idx, sizeof(FbsonKeyValue::keyid_type));
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kvState_ = WS_Key;
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return sizeof(uint8_t) + sizeof(FbsonKeyValue::keyid_type);
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}
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return 0;
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}
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uint32_t writeNull() {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Null);
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kvState_ = WS_Value;
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return sizeof(FbsonValue);
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}
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return 0;
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}
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uint32_t writeBool(bool b) {
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if (!stack_.empty() && verifyValueState()) {
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if (b) {
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os_->put((FbsonTypeUnder)FbsonType::T_True);
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} else {
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os_->put((FbsonTypeUnder)FbsonType::T_False);
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}
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kvState_ = WS_Value;
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return sizeof(FbsonValue);
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}
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return 0;
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}
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uint32_t writeInt8(int8_t v) {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Int8);
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os_->put(v);
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kvState_ = WS_Value;
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return sizeof(Int8Val);
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}
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return 0;
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}
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uint32_t writeInt16(int16_t v) {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Int16);
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os_->write((char*)&v, sizeof(int16_t));
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kvState_ = WS_Value;
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return sizeof(Int16Val);
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}
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return 0;
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}
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uint32_t writeInt32(int32_t v) {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Int32);
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os_->write((char*)&v, sizeof(int32_t));
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kvState_ = WS_Value;
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return sizeof(Int32Val);
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}
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return 0;
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}
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uint32_t writeInt64(int64_t v) {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Int64);
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os_->write((char*)&v, sizeof(int64_t));
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kvState_ = WS_Value;
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return sizeof(Int64Val);
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}
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return 0;
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}
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uint32_t writeDouble(double v) {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Double);
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os_->write((char*)&v, sizeof(double));
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kvState_ = WS_Value;
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return sizeof(DoubleVal);
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}
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return 0;
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}
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// must call writeStartString before writing a string val
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bool writeStartString() {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_String);
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str_pos_ = os_->tellp();
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// fill the size bytes with 0 for now
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uint32_t size = 0;
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os_->write((char*)&size, sizeof(uint32_t));
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kvState_ = WS_String;
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return true;
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}
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return false;
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}
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// finish writing a string val
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bool writeEndString() {
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if (kvState_ == WS_String) {
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std::streampos cur_pos = os_->tellp();
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int32_t size = (int32_t)(cur_pos - str_pos_ - sizeof(uint32_t));
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assert(size >= 0);
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os_->seekp(str_pos_);
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os_->write((char*)&size, sizeof(uint32_t));
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os_->seekp(cur_pos);
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kvState_ = WS_Value;
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return true;
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}
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return false;
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}
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uint32_t writeString(const char* str, uint32_t len) {
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if (kvState_ == WS_String) {
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os_->write(str, len);
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return len;
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}
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return 0;
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}
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uint32_t writeString(char ch) {
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if (kvState_ == WS_String) {
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os_->put(ch);
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return 1;
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}
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return 0;
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}
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// must call writeStartBinary before writing a binary val
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bool writeStartBinary() {
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if (!stack_.empty() && verifyValueState()) {
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os_->put((FbsonTypeUnder)FbsonType::T_Binary);
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str_pos_ = os_->tellp();
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// fill the size bytes with 0 for now
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uint32_t size = 0;
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os_->write((char*)&size, sizeof(uint32_t));
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kvState_ = WS_Binary;
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return true;
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}
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return false;
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}
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// finish writing a binary val
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bool writeEndBinary() {
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if (kvState_ == WS_Binary) {
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std::streampos cur_pos = os_->tellp();
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int32_t size = (int32_t)(cur_pos - str_pos_ - sizeof(uint32_t));
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assert(size >= 0);
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os_->seekp(str_pos_);
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os_->write((char*)&size, sizeof(uint32_t));
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os_->seekp(cur_pos);
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kvState_ = WS_Value;
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return true;
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}
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return false;
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}
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uint32_t writeBinary(const char* bin, uint32_t len) {
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if (kvState_ == WS_Binary) {
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os_->write(bin, len);
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return len;
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}
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return 0;
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}
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// must call writeStartObject before writing an object val
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bool writeStartObject() {
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if (stack_.empty() || verifyValueState()) {
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if (stack_.empty()) {
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// if this is a new FBSON, write the header
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if (!hasHdr_) {
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writeHeader();
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} else
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return false;
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}
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os_->put((FbsonTypeUnder)FbsonType::T_Object);
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// save the size position
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stack_.push(WriteInfo({WS_Object, os_->tellp()}));
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// fill the size bytes with 0 for now
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uint32_t size = 0;
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os_->write((char*)&size, sizeof(uint32_t));
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kvState_ = WS_Value;
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return true;
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}
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return false;
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}
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// finish writing an object val
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bool writeEndObject() {
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if (!stack_.empty() && stack_.top().state == WS_Object &&
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kvState_ == WS_Value) {
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WriteInfo& ci = stack_.top();
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std::streampos cur_pos = os_->tellp();
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int32_t size = (int32_t)(cur_pos - ci.sz_pos - sizeof(uint32_t));
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assert(size >= 0);
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os_->seekp(ci.sz_pos);
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os_->write((char*)&size, sizeof(uint32_t));
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os_->seekp(cur_pos);
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stack_.pop();
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return true;
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}
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return false;
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}
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// must call writeStartArray before writing an array val
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bool writeStartArray() {
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if (stack_.empty() || verifyValueState()) {
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if (stack_.empty()) {
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// if this is a new FBSON, write the header
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if (!hasHdr_) {
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writeHeader();
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} else
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return false;
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}
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os_->put((FbsonTypeUnder)FbsonType::T_Array);
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// save the size position
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stack_.push(WriteInfo({WS_Array, os_->tellp()}));
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// fill the size bytes with 0 for now
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uint32_t size = 0;
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os_->write((char*)&size, sizeof(uint32_t));
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kvState_ = WS_Value;
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return true;
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}
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return false;
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}
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// finish writing an array val
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bool writeEndArray() {
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if (!stack_.empty() && stack_.top().state == WS_Array &&
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kvState_ == WS_Value) {
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WriteInfo& ci = stack_.top();
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std::streampos cur_pos = os_->tellp();
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int32_t size = (int32_t)(cur_pos - ci.sz_pos - sizeof(uint32_t));
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assert(size >= 0);
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os_->seekp(ci.sz_pos);
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os_->write((char*)&size, sizeof(uint32_t));
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os_->seekp(cur_pos);
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stack_.pop();
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return true;
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}
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return false;
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}
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OS_TYPE* getOutput() { return os_; }
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private:
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// verify we are in the right state before writing a value
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bool verifyValueState() {
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assert(!stack_.empty());
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return (stack_.top().state == WS_Object && kvState_ == WS_Key) ||
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(stack_.top().state == WS_Array && kvState_ == WS_Value);
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}
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// verify we are in the right state before writing a key
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bool verifyKeyState() {
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assert(!stack_.empty());
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return stack_.top().state == WS_Object && kvState_ == WS_Value;
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|
}
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|
|
void writeHeader() {
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|
|
os_->put(FBSON_VER);
|
|
|
|
hasHdr_ = true;
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|
|
|
}
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private:
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|
|
enum WriteState {
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WS_NONE,
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|
WS_Array,
|
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|
|
WS_Object,
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|
|
WS_Key,
|
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|
|
WS_Value,
|
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|
|
WS_String,
|
|
|
|
WS_Binary,
|
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|
|
};
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|
|
|
struct WriteInfo {
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|
|
|
WriteState state;
|
|
|
|
std::streampos sz_pos;
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|
|
|
};
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|
|
private:
|
|
|
|
OS_TYPE* os_;
|
|
|
|
bool alloc_;
|
|
|
|
bool hasHdr_;
|
|
|
|
WriteState kvState_; // key or value state
|
|
|
|
std::streampos str_pos_;
|
|
|
|
std::stack<WriteInfo> stack_;
|
|
|
|
};
|
|
|
|
|
|
|
|
typedef FbsonWriterT<FbsonOutStream> FbsonWriter;
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|
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|
|
} // namespace fbson
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|
#endif // FBSON_FBSONWRITER_H
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