如何使用protobuf对多个可区分项目进行背靠背编码

How to encode multiple distinguishable items back to back with protobuf?

本文关键字：项目 背靠背 编码 可区分 何使用 protobuf      更新时间：2023-10-16

因此，我进行了一个单元测试，试图确保编码和解码是正确的。基本上，我希望能够将多个不同的C++对象序列化为一个字符串，然后将该字符串写入一个文件。这就是我目前所拥有的：

这是我的.proto文件：

message Register {
    required string regname = 1;
    required uint64 regvalue = 2;
}
message RegisterContext {
    repeated Register elem = 1;
}
message MemoryRegion {
    repeated bytes elem = 1;
}
message Image {
    required string imgName = 1;
    required MemoryRegion Memory = 2;
    required uint64 MemStart = 3;
    required uint64 MemEnd = 4;
    required bool isMain = 5;
}
message MemoryRegions {
    repeated Image elem = 1;
}
message MemoryDump {
    required RegisterContext context = 1;
    required MemoryRegions state = 2;
}

我有语言白话风格的表示对象，可以帮助我像平时一样使用它们：

//name, value
using reg=std::tuple<std::string, uint64_t>;
using reg_context=std::list<reg >;
using mem_region=std::string;
//name, memory, start, end, ismain
using image=std::tuple<std::string, mem_region, uint64_t, uint64_t, bool>;
using mem_region_set=std::list<image >;
using memory_dump=std::tuple<reg_context, mem_region_set>;

以下是失败的测试：

TEST(SerializationTests, test_contiguous_memory_differentiated) {
  mem_region region="x25x26x27";
  image i1{std::make_tuple(std::string("img1"), region, 0, 1, false)},
    i2{std::make_tuple(std::string("img2"), region+"x28", 0, 1, false)},
      i3{std::make_tuple(std::string("img3"), region+"x29", 0, 1, false)};
  mem_region_set regions1{i1, i2, i3}, regions2{i1, i3};
  auto serialized_regions1=serialize_memory_regions(regions1);
  auto serialized_regions2=serialize_memory_regions(regions2);
  std::stringstream ss;
  ss << *serialized_regions1 << *serialized_regions2;
  auto concatenated=ss.str();
  auto deserialized_region1=unpack_memory_regions(concatenated);
  ASSERT_EQ(deserialized_region1, regions1);
  auto deserialized_region2=unpack_memory_regions(concatenated);
  ASSERT_EQ(deserialized_region2, regions2);
}

如何序列化多个对象，以便无论我将它们放入字符串流还是ofstream，它们都会作为distict返回我在这里运行的测试结果是反序列化区域1/2，每个区域总共有5个图像，只有i1、i2、i3、i1、i3

一种可能的方法是在每个protobuf对象之前写入固定的32字节整数。当你需要用多个对象解析缓冲区或文件时，你可以先读取消息长度，然后读取length字节长的消息体并进行解析。例如，你的消息MemoryDump将被编译为class MemoryDump。你可以这样包装：

MemoryDump memoryDump;
fillData(memoryDump); // put data in it somehow
auto size = memoryDump.ByteSize(); // return space that it needs to be packed
std::string buffer;
StringOutputStream stream(&buffer);
CodedOutputStream coded(&stream);
coded.WriteLittleEndian32(size);
memoryDump.SerializeToCodedStream(&coded);
coded.WriteLittleEndian32(size);
memoryDump.SerializeToCodedStream(&coded);

然后当你打开数据包时，你可以做：

MemoryDump memoryDump1;
MemoryDump memoryDump2;
std::string buffer;
readBuffer(buffer);
StringInputStream stream(&buffer);
CodedInputStream coded(&stream);
int size;
coded.ReadLittleEndian32(&size);
memoryDump1.ParseFromBoundedZeroCopyStream(&stream, size);
coded.ReadLittleEndian32(&size);
memoryDump1.ParseFromBoundedZeroCopyStream(&stream, size);
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