zbuffer example

[walchko]

Hello! I tried to use the zbuffer to compress my data, but I can't seem to make it work. I modified one of the example programs and replaced stringstream with zbuffer. What am I doing wrong? Also, maybe there could be an example somewhere showing how to do this (assuming I didn't overlook it)?

#include <msgpack.hpp>
#include <msgpack/zbuffer.hpp>
#include <stdio.h>
#include <string>
#include <sstream>
#include <iostream>
#include <cassert>

using namespace std;

class base1 {
public:
   int a;
   MSGPACK_DEFINE(a);
};
class base2 {
public:
   int b;
   MSGPACK_DEFINE(b);
};
class test: public base1, public base2 {
public:
    int c;
    std::string d;
    // You can choose any order. It is represented to the msgpack array elements order.
    MSGPACK_DEFINE(d, MSGPACK_BASE(base2), c, MSGPACK_BASE(base1));
};

int main(){
    test a = {1,3,5,"hello"};
    printf("a: %d %d %d %s\n", a.a, a.b, a.c, a.d.c_str());

    // stringstream ss;
    msgpack::zbuffer ss;
    msgpack::pack(ss, a);
    size_t offset = 0;
    cout << "offset: " << offset << endl;
    {
        // msgpack::object_handle oh = msgpack::unpack(ss.str().data(), ss.str().size(), offset);
        msgpack::object_handle oh = msgpack::unpack(ss.data(), ss.size(), offset);
        msgpack::object obj = oh.get();

        cout << obj << endl;

        test b;
        obj.convert(b);

        assert(a.a == b.a);
        assert(a.b == b.b);
        assert(a.c == b.c);
        assert(a.d == b.d);
        // assert(obj.as<decltype(a)>() == a);
    }

    return 0;
}

Output:

a: 1 3 5 hello
offset: 0
120
libc++abi.dylib: terminating with uncaught exception of type msgpack::v1::type_error: std::bad_cast
Abort trap: 6

I am using osx and my compiler is:

$ g++ --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.4)
Target: x86_64-apple-darwin18.2.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

[redboltz]

@walchko , msgpack-c unpack function cannot recognize the buffer is z-compressed or not. So you need to decompress the buffer by yourself before calling unpack.

        // decompress the compressed buffer ss.data(), ss.size()
        // std::string decompressed = /* deflate using zlib API */;
        // msgpack::object_handle oh = msgpack::unpack(ss.data(), ss.size(), offset);
        msgpack::object_handle oh = msgpack::unpack(decompressed.data(), decompressed.size(), offset);

I think that the following link is helpful.

https://stackoverflow.com/questions/27529570/simple-zlib-c-string-compression-and-decompression