Boost beast send json with byte array to client throw websocket

Question

I have file which is converted from byte array to string

processResultJson.append(reinterpret_cast<const char *const>(im->bits), sizeof(im->bits));
processResultJson.append(reinterpret_cast<const char *const>(im->bits), im_res->bmi->bmiHeader.biSizeImage);

docData.put("Image1", processResultJson);}
boost::property_tree::json_parser::write_json(m_stream, SRegulaDR::docData);
resultString = m_stream.str();

size_t n = net::buffer_copy(buffer_.prepare(resultString.size()), net::buffer(resultString));        buffer_.commit(n);

in this situation i get error_code=2 - End of file and then error_code=995 I/O operation...

How i can send JSON with byte array witch converted to string Thanks!!!

In **what** situation do you get end-of-file? There's no reading code in sight — sehe, Feb 19 '21 at 18:52

score 1 · Accepted Answer · answered Feb 19 '21 at 19:16

Don't use Property Tree as if it's a JSON library. It has well known limitations: https://www.boost.org/doc/libs/1_75_0/doc/html/property_tree/parsers.html#property_tree.parsers.json_parser

Note especially the limitationssurrounding arrays.

Next up, you didn't write an array to begin with, instead writing a string. But since it's binary data, it may be a valid JSON string, and this could be a source of error.

Also, you probably don't need to copy the whole JSON again to put it in a buffer. Instead, boost::asio::buffer(resultString) will work (as long as you make sure that the lifetime of resultString is enough, like with buffer_).

Just testing a little does suggest that characters are being escaped correctly by write_json:

Live On Compiler Explorer

#define BOOST_BIND_GLOBAL_PLACEHOLDERS
#include <boost/property_tree/json_parser.hpp>
#include <iostream>
using namespace std::string_literals;

struct Im { std::array<std::uint64_t, 10> bits; };

int main()
{
    auto im = std::make_unique<Im>(
            Im { 0b0010'1100'1010'0010'0111'1100'0010 });

    std::string_view bitmsg(
        reinterpret_cast<char const*>(&im->bits),
        sizeof(im->bits));

    auto processResultJson = "some binary data: \0 \x10 \xef αβγδ\n"s;
    processResultJson += bitmsg;

    boost::property_tree::ptree docData; 
    docData.put("Image1", processResultJson);
    std::ostringstream oss;
    boost::property_tree::json_parser::write_json(oss, docData);

    std::cout << oss.str();
}

Prints

{ "Image1": "some binary data: \u0000 \u0010 αβγδ\nu0002\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000\u0000" }

Json lint reports it as valid JSON (for what it's worth)

However, consider making doubly sure by

using base64 encoding to encode binary data
using Boost JSON or another proper JSON library

Demo With Boost JSON

1.75.0 introduced a proper JSON library. Let's celebrate.

The straightforward translation is: https://godbolt.org/z/es9jGc

json::object docData;
docData["Image1"] = processResultJson;

std::string resultString = json::serialize(docData);

However, you can now easily use strong-typed, proper arrays: https://godbolt.org/z/K9c6bc

json::object docData;
docData["Image1"] = json::array(im->bits.begin(), im->bits.end());

Printing

{"Image1":[46802882,0,0,0,0,0,0,0,0,0]}

Or you can, in fact, use default conversions with value_from: :

Live On Compiler Explorer

#include <iostream>
#include <boost/json/src.hpp> // for header-only
namespace json = boost::json;

struct Im { std::array<std::uint64_t, 10> bits; };

int main()
{
    auto im = std::make_unique<Im>(
            Im { 0b0010'1100'1010'0010'0111'1100'0010, /*...*/ });

    std::cout << json::object{ {"Image1", json::value_from(im->bits) } };
}

Prints

{"Image1":[46802882,0,0,0,0,0,0,0,0,0]}

I try using boost json and now get another problem. If I include I get LNK2005 errors — Khusayn, Feb 20 '21 at 08:55
I only add #include #include and only implement static class member as boost::json::object and get LNK2005 errors — Khusayn, Feb 20 '21 at 09:02
You can link it or include the source header as well (like I did on computer explorer) — sehe, Feb 20 '21 at 13:33
Hi sehe. I put my question on this link more detailed with codes can you help! https://stackoverflow.com/questions/66298798/why-i-get-lnk2005-errors-on-using-boost-json — Khusayn, Feb 21 '21 at 03:16

Boost beast send json with byte array to client throw websocket

1 Answers1

Demo With Boost JSON