C++ 如何写入多个协议缓冲区';将消息添加到可追加的压缩文件中?
我使用protocol buffers的CodedOutputStream和FileOutputStream将多条消息按顺序序列化为如下文件:C++ 如何写入多个协议缓冲区';将消息添加到可追加的压缩文件中?,c++,protocol-buffers,C++,Protocol Buffers,我使用protocol buffers的CodedOutputStream和FileOutputStream将多条消息按顺序序列化为如下文件: // File is opened using append mode and wrapped into // a FileOutputStream and a CodedOutputStream bool Open(const std::string& filename, int buffer_size = kDefault
// File is opened using append mode and wrapped into
// a FileOutputStream and a CodedOutputStream
bool Open(const std::string& filename,
int buffer_size = kDefaultBufferSize) {
file_ = open(filename.c_str(),
O_WRONLY | O_APPEND | O_CREAT, // open mode
S_IREAD | S_IWRITE | S_IRGRP | S_IROTH | S_ISUID); //file permissions
if (file_ != -1) {
file_ostream_ = new FileOutputStream(file_, buffer_size);
ostream_ = new CodedOutputStream(file_ostream_);
return true;
} else {
return false;
}
}
// Code for append a new message
bool Serialize(const google::protobuf::Message& message) {
ostream_->WriteLittleEndian32(message.ByteSize());
return message.SerializeToCodedStream(ostream_);
}
// Code for reading a message using a FileInputStream
// wrapped into a CodedInputStream
bool Next(google::protobuf::Message *msg) {
google::protobuf::uint32 size;
bool has_next = istream_->ReadLittleEndian32(&size);
if(!has_next) {
return false;
} else {
CodedInputStream::Limit msgLimit = istream_->PushLimit(size);
if ( msg->ParseFromCodedStream(istream_) ) {
istream_->PopLimit(msgLimit);
return true;
}
return false;
}
}
file_ostream_ = new FileOutputStream(file_, buffer_size);
gzip_ostream_ = new GzipOutputStream(file_ostream_);
ostream_ = new CodedOutputStream(gzip_ostream_);
如何使用GzipOutputStream执行相同的操作?gzip压缩文件可以像我使用CodedOutputStream那样重新打开以附加新消息吗?我刚刚意识到我只需要将文件OutputStream包装到另一个GzipOutputStream中,如下所示:
// File is opened using append mode and wrapped into
// a FileOutputStream and a CodedOutputStream
bool Open(const std::string& filename,
int buffer_size = kDefaultBufferSize) {
file_ = open(filename.c_str(),
O_WRONLY | O_APPEND | O_CREAT, // open mode
S_IREAD | S_IWRITE | S_IRGRP | S_IROTH | S_ISUID); //file permissions
if (file_ != -1) {
file_ostream_ = new FileOutputStream(file_, buffer_size);
ostream_ = new CodedOutputStream(file_ostream_);
return true;
} else {
return false;
}
}
// Code for append a new message
bool Serialize(const google::protobuf::Message& message) {
ostream_->WriteLittleEndian32(message.ByteSize());
return message.SerializeToCodedStream(ostream_);
}
// Code for reading a message using a FileInputStream
// wrapped into a CodedInputStream
bool Next(google::protobuf::Message *msg) {
google::protobuf::uint32 size;
bool has_next = istream_->ReadLittleEndian32(&size);
if(!has_next) {
return false;
} else {
CodedInputStream::Limit msgLimit = istream_->PushLimit(size);
if ( msg->ParseFromCodedStream(istream_) ) {
istream_->PopLimit(msgLimit);
return true;
}
return false;
}
}
file_ostream_ = new FileOutputStream(file_, buffer_size);
gzip_ostream_ = new GzipOutputStream(file_ostream_);
ostream_ = new CodedOutputStream(gzip_ostream_);
阅读时,也要这样做:
file_istream_ = new FileInputStream(file_, buffer_size);
gzip_istream_ = new GzipInputStream(file_istream_);
istream_ = new CodedInputStream(gzip_istream_);
关闭并重新打开文件以附加消息也可以正常工作