v6.2.0

Major networking and RPC enhancements, including JSON RPC 2.0 registry support, zero-copy REPE handling, and a standardized ABI-stable plugin interface for REPE.

Breaking Changes

• Move append_arrays and error_on_const_read options out of glz::opts by @stephenberry in #2110

  • These options are now inheritable options that must be added to a custom options struct.
  • See How to Use Inheritable Options

• WebSocket Client: ctx_ changed to context() method by @stephenberry in #2106

  // Before (won't compile)
  client.ctx_->stop();
  
  // After
  client.context()->stop();

Highlights

JSON RPC 2.0 Registry Support

Added support for JSON RPC 2.0 protocol to the registry, enabling standard JSON-based remote procedure calls alongside REPE.

struct my_api
{
   int counter = 0;
   std::string greet() { return "Hello, World!"; }
   int add(int value) { counter += value; return counter; }
};

// Create a JSON-RPC registry
glz::registry<glz::opts{}, glz::JSONRPC> server{};

my_api api{};
server.on(api);

// Call a function
auto response = server.call(R"({"jsonrpc":"2.0","method":"greet","id":1})");
// Returns: {"jsonrpc":"2.0","result":"Hello, World!","id":1}

// Read a variable
response = server.call(R"({"jsonrpc":"2.0","method":"counter","id":2})");
// Returns: {"jsonrpc":"2.0","result":0,"id":2}

// Call a function with parameters
response = server.call(R"({"jsonrpc":"2.0","method":"add","params":10,"id":3})");
// Returns: {"jsonrpc":"2.0","result":10,"id":3}

• #2098

REPE Plugin Interface

A new standardized plugin interface for REPE enables ABI-stable dynamic plugin systems that work seamlessly with glz::registry and glz::asio_server. This includes:

• Pure C header (plugin.h) for cross-compiler compatibility
• C++ helper (plugin_helper.hpp) for implementing plugins using glz::registry
• Interface versioning for safe plugin loading

extern "C" {
    uint32_t repe_plugin_interface_version() { return REPE_PLUGIN_INTERFACE_VERSION; }
    const char* repe_plugin_name() { return "calculator"; }
    repe_buffer repe_plugin_call(const char* request, uint64_t request_size) {
        return glz::repe::plugin_call(registry, request, request_size);
    }
}

• #2097

Zero-Copy REPE Handling

True zero-copy implementation for the REPE RPC protocol, eliminating unnecessary memory allocations and copies in the hot path:

• parse_request returns views into the original buffer
• response_builder writes directly to output buffer

server.call = [](std::span<const char> request, std::string& response_buffer) {
    auto result = glz::repe::parse_request(request);
    // req.query and req.body are views into request
    registry.call(request, response_buffer);  // Zero-copy
};

• #2108

Indexed rename_key API

A new indexed rename_key API allows transforming JSON keys based on member type information at compile time. This is useful for automatically using enum type names as JSON keys:

template <>
struct glz::meta<AppContext> {
    template <size_t Index>
    static constexpr auto rename_key() {
        using MemberType = glz::member_type_t<AppContext, Index>;

        if constexpr (std::is_enum_v<MemberType>) {
            return glz::name_v<MemberType>;
        } else {
            return glz::member_nameof<Index, AppContext>;
        }
    }
};

Output: {"num":42,"MyEnum":"Second","MyFlag":"Yes"}

• #2083

New Compile Time Options

• skip_null_members_on_read - Skip null values when reading, preserving existing values by @stephenberry in #2086
• skip_self_constraint - Disable self constraint validation via a compile time option by @stephenberry in #2121

Improvements

• asio_server custom call handler for routing and middleware by @stephenberry in #2096
• glz::merge support for the registry by @stephenberry in #2088
• REPE buffer helpers by @stephenberry in #2095
• Simplify REPE plugin initialization by @stephenberry in #2119
• CMake improvements by @stephenberry in #2112
• Use weak_ptr rather than shared_ptr for server lifetime safety by @stephenberry in #2113
• Extract decode_index_unknown_key by @stephenberry in #2111
• std::span serialization tests by @stephenberry in #2109
• Better client socket connection handling by @stephenberry in #2105
• Safer unique_socket, delete copy constructor and assignment by @stephenberry in #2104
• Improve asio client connected() status by @stephenberry in #2103
• repe_plugin_data struct by @stephenberry in #2099

Fixes

• WebSocket Client: Fix shared context and improve lifetime safety by @stephenberry in #2106
• Fix concurrent WebSocket connections (thread-safe write queue, RFC 6455 close handshake) by @stephenberry in #2092
• Fix MSVC with std::uniform_int_distribution<unsigned int> by @stephenberry in #2085
• Fix GCC warnings in tests by @stephenberry in #2094
• Fix Clang build warnings for unit tests and bump asio dependency versions by @stephenberry in #2107
• Don't export -Wno-missing-braces for languages other than C and C++ by @stephenberry in #2076
• Cleanup broken tests by @stephenberry in #2118

Testing

• Test error_on_missing_keys with JSON schema generation by @stephenberry in #2093
• More registry tests by @stephenberry in #2087

Documentation

Extensive documentation added:

• ASIO Setup Guide
• REPE Plugin Interface
• REPE Buffer API
• JSON-RPC Registry
• Rename Keys
• Compile Time Options
• WebSocket client documentation updates

Full Changelog: v6.1.0...v6.2.0