logos-cpp-sdk

How to Build

Using Nix (Recommended)

The project includes a Nix flake for reproducible builds with a modular structure:

Build Complete SDK (Library + Headers + Generator)

# Build everything (default)
nix build

# Or explicitly
nix build '.#logos-cpp-sdk'
nix build '.#default'

The result will include:

• /bin/logos-cpp-generator - Code generator binary
• /lib/ - SDK libraries
• /include/ - Headers (core/ and cpp/)

Build Individual Components

# Build only the generator binary (outputs to /bin)
nix build '.#logos-cpp-bin'

# Build only the SDK library (outputs to /lib)
nix build '.#logos-cpp-lib'

# Build only the headers (outputs to /include)
nix build '.#logos-cpp-include'

# Legacy alias for generator
nix build '.#cpp-generator'

Development Shell

# Enter development shell with all dependencies
nix develop

Note: In zsh, you need to quote the target (e.g., '.#logos-cpp-sdk') to prevent glob expansion.

If you don't have flakes enabled globally, add experimental flags:

nix build '.#logos-cpp-sdk' --extra-experimental-features 'nix-command flakes'

The compiled artifacts can be found at result/

Modular Architecture

The nix build system is organized into modular files in the /nix directory:

• nix/default.nix - Common configuration (dependencies, flags, metadata)
• nix/bin.nix - Generator binary compilation
• nix/lib.nix - SDK library compilation
• nix/include.nix - Header installation
• nix/tests.nix - Test suite (build + run via nix build '.#tests')

Run Tests

# Build and run all tests (build fails if any test fails)
nix build '.#tests'

The test binaries are available in result/bin/ and can be re-run with filters:

./result/bin/sdk_tests --gtest_filter="LogosResultTest.*"
./result/bin/generator_tests --gtest_filter="*PascalCase*"

Manual Build

Building the C++ SDK

cd cpp
./compile.sh

Building the Code Generator

cd cpp-generator
./compile.sh

The generator binary will be available at build/bin/logos-cpp-generator.

Usage

Code Generator

The logos-cpp-generator tool generates C++ wrapper code for Logos plugins.

Basic Usage

# Generate wrapper for a single plugin (uses default output directory)
logos-cpp-generator /path/to/plugin.dylib

# Specify custom output directory
logos-cpp-generator /path/to/plugin.dylib --output-dir /custom/output/path

# Generate only the module files (no core manager or umbrella headers)
logos-cpp-generator /path/to/plugin.dylib --module-only

# Combine options
logos-cpp-generator /path/to/plugin.dylib --output-dir /custom/output --module-only

Generate from Metadata

# List dependencies from metadata.json
logos-cpp-generator --metadata /path/to/metadata.json

# Generate wrappers for all dependencies
logos-cpp-generator --metadata /path/to/metadata.json --module-dir /path/to/modules

# Generate with custom output directory
logos-cpp-generator --metadata /path/to/metadata.json --module-dir /path/to/modules --output-dir /custom/output

# Generate only module files (no core manager or umbrella headers)
logos-cpp-generator --metadata /path/to/metadata.json --module-dir /path/to/modules --module-only

# Generate only core manager and umbrella files (assumes module files already exist)
logos-cpp-generator --metadata /path/to/metadata.json --general-only

# Generate general files with custom output directory
logos-cpp-generator --metadata /path/to/metadata.json --general-only --output-dir /custom/output

Options

--output-dir /path/to/output

• Default: If not specified, generated files are placed in logos-cpp-sdk/cpp/generated/
• Custom: Specify any directory for the generated files
• The output directory will be created automatically if it doesn't exist

--module-only

• When specified, generates only the requested module's .h and .cpp files
• Skips generation of core_manager_api.* and umbrella headers (logos_sdk.*)
• Useful when you only need wrapper code for specific modules

--general-only

• When specified with --metadata, generates only the core manager and umbrella SDK files
• Assumes module wrapper files already exist in the output directory
• Generates: core_manager_api.h, core_manager_api.cpp, logos_sdk.h, logos_sdk.cpp
• The umbrella headers will include references to all modules listed in the metadata's dependencies array
• For each dependency (e.g., "waku_module"), it will:
  • Include waku_module_api.h in the header
  • Include waku_module_api.cpp in the source
  • Create a WakuModule waku_module; member in the LogosModules struct
• Does not require --module-dir since it doesn't process plugins

Generated Files

By default (without --module-only or --general-only):

• <module>_api.h and <module>_api.cpp - Wrapper code for each module
• core_manager_api.h and core_manager_api.cpp - Core manager wrapper
• logos_sdk.h and logos_sdk.cpp - Umbrella headers including all modules

With --module-only:

• Only <module>_api.h and <module>_api.cpp - Wrapper code for the requested module(s)

With --general-only:

• Only core_manager_api.h and core_manager_api.cpp - Core manager wrapper
• Only logos_sdk.h and logos_sdk.cpp - Umbrella headers that reference existing module files

Typical Workflow

A common workflow is to generate module wrappers separately, then generate the umbrella SDK:

# Step 1: Generate individual module wrappers
logos-cpp-generator /path/to/plugin1.dylib --module-only --output-dir ./generated
logos-cpp-generator /path/to/plugin2.dylib --module-only --output-dir ./generated

# Step 2: Generate core manager and umbrella SDK (references modules from step 1)
logos-cpp-generator --metadata metadata.json --general-only --output-dir ./generated

This approach gives you fine-grained control over which modules to include and allows rebuilding just the umbrella headers without regenerating all module wrappers.

Universal modules: LogosModuleContext

Universal (codegen-driven) modules — those built from a package_xxx_impl.h header rather than a handcrafted QObject plugin — don't see the raw LogosAPI at all. Instead, the codegen-generated provider populates a narrow LogosModuleContext base class with everything an impl typically needs:

• Three host-injected properties exposed as typed getters
• A LogosModules aggregate for calling other modules

An impl opts in by inheriting from LogosModuleContext (defined in logos_module_context.h):

#include <logos_module_context.h>
#include <logos_json.h>
#include "logos_sdk.h"      // generated at build time; defines LogosModules

class MyModuleImpl : public LogosModuleContext {
public:
    LogosMap doWork(const std::string& input) {
        // Cross-module call through the flat LogosModules aggregator.
        // Because this module is `interface: "universal"`, mkLogosModule.nix
        // passed -DLOGOS_API_STYLE=std to the codegen, so every <Dep>
        // wrapper takes/returns std types — no Qt at the call site.
        std::string reply = modules().some_dep.echo(input);
        // ...
    }

protected:
    void onContextReady() override {
        // One-time setup: the getters below are now readable.
        // Fires exactly once, before any method dispatch.
        std::string dataDir = instancePersistencePath();
        // open files, prime caches, etc.
    }
};

Available getters:

Getter	Description
modulePath()	Directory containing the module's plugin file. Useful for loading bundled resources (icons, QML files, schema docs).
instanceId()	Stable per-instance ID assigned by the host. Two side-by-side instances of the same module get distinct IDs.
instancePersistencePath()	Per-instance writable data directory the host owns the lifecycle of. The canonical place for module state (config, caches, small databases). Wiped on uninstall; survives upgrades.
modules()	The module's flat LogosModules aggregate — one accessor per metadata.json#dependencies entry (nothing else; apps that need to manage the core do so via liblogos' C API). LogosModules is forward-declared in the SDK header and made complete by the impl's #include "logos_sdk.h", so the call site just writes modules().some_dep.someMethod(...). Each accessor's wrapper class signatures use the type surface picked at THIS module's build time (see "API style" below).

API style: Qt vs std

Each module's build picks one API style for the generated <Module> client wrappers and the LogosModules umbrella — they're mutually exclusive, no composite output:

metadata.json#interface	LOGOS_API_STYLE	Wrapper signatures
"universal"	std	std::string, std::vector<std::string>, LogosMap, LogosList, int64_t, StdLogosResult
"legacy" / "provider" / absent	qt (default)	QString, QStringList, QVariantList, QVariantMap, int, LogosResult

mkLogosModule.nix reads interface and threads -DLOGOS_API_STYLE=std through to the codegen for universal modules; everyone else defaults to Qt and stays bit-for-bit backward compatible. Inside the universal module's .cpp, the call site is:

// Universal module (api-style=std):
std::string reply = modules().some_dep.echo("hi");

…and in a handcrafted Qt module the same call is:

// Legacy / provider module (api-style=qt):
QString reply = modules().some_dep.echo(QString("hi"));

The wire is identical (QVariant under the hood); for std mode the Qt↔std conversion is inlined in the generated wrapper's .cpp, so the calling translation unit needs zero Qt headers.

Migrating to std types: The choice is driven entirely by interface. A handcrafted module that wants std types should switch to interface: "universal" — there's no per-flag override on metadata.json.

All getters return empty / null values when the module is loaded outside a host that provisions a context (CLI tests, unit tests using the impl directly). The onContextReady() hook still fires once at framework load time; tests that bypass the framework can call _logosCoreSetContext_ / _logosCoreSetLogosModulesPtr_ directly to simulate.

Codegen does NOT require inheritance — modules that don't inherit LogosModuleContext compile unchanged. The generator emits a single onInit override per provider that delegates to SFINAE'd helpers (_logos_codegen_::maybeSet*), and the non-inheriting overloads collapse to no-ops.

Events: logos_events:

Universal modules declare events in a Qt-signals:-style logos_events: section. The codegen parses each prototype, emits the matching method bodies in a sidecar <name>_events.cpp (Qt-MOC style), and ships a <name>.lidl file describing them so consumer-side codegen can produce typed subscribers:

#include <logos_module_context.h>

class MyModuleImpl : public LogosModuleContext {
public:
    void doWork() {
        userLoggedIn("alice", 12345);              // typed emit — same name as the declaration
    }

logos_events:                                       // expands to `public:`; parsed by the codegen
    void userLoggedIn(const std::string& userId, int64_t timestamp);
    void messageReceived(const std::string& from, const std::string& body);
};

The author writes only the declarations; the codegen supplies the bodies (analogous to Qt MOC for signals:). Each call marshals typed args into a QVariantList and routes them through LogosModuleContext::emitEventImpl_ → LogosProviderBase::emitEvent → the existing QRO eventResponse channel. No wire-format change.

Consumer side — typed on<EventName>(...) accessors are generated on the dep's <Module> wrapper. The generic onEvent(name, cb) channel stays available as a forward-compat escape hatch:

// From any module that depends on the one declaring the events:
modules().my_module.onUserLoggedIn(
    [](const std::string& userId, int64_t timestamp) {
        // typed args, no manual QVariantList unpacking
    });

The accessor's parameter types follow the consumer's own --api-style (so a universal consumer sees const std::string& / int64_t, a handcrafted Qt consumer sees const QString& / int).

Legacy — modules that haven't migrated keep the old std::function<void(const std::string&, const std::string&)> emitEvent member working. The codegen still detects it and wires the lambda in the provider constructor. New code should prefer logos_events:.

API

LogosResult

LogosResult provides a structured way to return either a value or an error from synchronous method calls.

If the success attribute is true, you can retrieve the value using a cast. Otherwise, retrieve the error which should be a string (though not enforced).

The success attribute should ALWAYS be asserted. Accessing the value of an errored LogosResult or the error of a valid LogosResult will result in a LogosResultException being thrown.

Example

LogosResult result = m_logos->my_module.someMethod();
if (result.success) {
    // Use shorthand
    QString value = result.getString();
    // Or
    QString value = result.getValue<QString>();
} else {
    // Use shorthand
    QString error = result.getError();
    // Or
    QString error = result.getError<QString>();
}

Complex objects

Let's say you need to return a complex object. In the SDK, you have to build your type with primitive like QVariantMap:

// Received JSON: {"cid": "QmXyz...", "filename": "photo.jpg", "size": 2048576, "mimetype": "image/jpeg"}

QVariantMap manifest;
manifest["cid"] = "QmXyz...";
manifest["filename"] = "photo.jpg";
manifest["size"] = 2048576;
manifest["mimetype"] = "image/jpeg";
return {true, manifest};

And then to consume by using the shorthand function:

LogosResult result = m_logos->my_plugin.someMethod(cid);
if (result.success) {
  QString cid = result.getString("cid");
  // You can define a default value as well
  QString cid = result.getString("cid", "unknown");
}

Or you can use the value directly:

LogosResult result = m_logos->my_plugin.someMethod(cid);
if (result.success) {
    QVariantMap manifest = result.getMap();
    QString cid = manifest["cid"].toString();
}

Same thing for a list, you can use QVariantList:

QVariantList manifests;

QVariantMap m1;
m1["cid"] = "QmAbc...";
m1["filename"] = "document.pdf";
m1["size"] = 1024000;
manifests.append(m1);

QVariantMap m2;
m2["cid"] = "QmDef...";
m2["filename"] = "image.png";
m2["size"] = 512000;
manifests.append(m2);

return {true, manifests};

To consume it using the shorthand function:

LogosResult result = m_logos->my_plugin.someMethod();
if (result.success) {
    for (int i = 0; i < list.size(); ++i) {
        QString cid = result.getString(i, "cid");
        // You can define a default value as well
        QString cid = result.getString(0, "cid", "unknown");
    }
}

Or you can use the value directly:

LogosResult result = m_logos->my_plugin.someMethod();
if (result.success) {
    QVariantList list = result.getList();
    for (const QVariant& item : list) {
        QVariantMap manifest = item.toMap();
        QString cid = manifest["cid"].toString();
    }
}

Consuming the SDK

The SDK installs a CMake package. Consumers use find_package:

find_package(logos-cpp-sdk REQUIRED)
target_link_libraries(my_target PRIVATE logos-cpp-sdk::logos_sdk)

The package config re-resolves transitive dependencies (Qt6 Core/RemoteObjects, Boost system, OpenSSL, nlohmann_json), so consumers don't have to wire them up manually. The static archive references OpenSSL SSL_CTX_*/X509_* and Boost system::error_code; without find_package's imported target the link step fails.

Transports

The SDK supports multiple transports, selected via LogosTransportConfig:

Protocol	Backend	Use case
LocalSocket	Qt Remote Objects over QLocalSocket	In-host, module-to-module (default)
Tcp	Boost.Asio + JSON/CBOR framing	Cross-host or container-to-host
TcpSsl	Boost.Asio + OpenSSL + JSON/CBOR framing	Same as TCP, with TLS

A LogosTransportSet (= std::vector<LogosTransportConfig>) lets a single provider publish on multiple endpoints simultaneously (e.g. local socket for in-process clients + TCP+SSL for remote ones):

LogosTransportConfig local;  // protocol = LocalSocket (default)

LogosTransportConfig tls;
tls.protocol = LogosProtocol::TcpSsl;
tls.host     = "0.0.0.0";
tls.port     = 7443;
tls.caFile   = "/etc/logos/ca.pem";
tls.certFile = "/etc/logos/server.pem";
tls.keyFile  = "/etc/logos/server.key";

LogosAPI* api = new LogosAPI("core_service", LogosTransportSet{local, tls}, this);

For processes that want to override the SDK-wide default, use LogosTransportConfigGlobal::setDefault() once at startup before any LogosAPI is constructed.

Requirements

Build Tools

• CMake (3.x or later)
• Ninja build system
• pkg-config

Dependencies

• Qt6 (qtbase)
• Qt6 Remote Objects (qtremoteobjects)
• Boost (system)
• OpenSSL
• nlohmann_json

Supported Platforms

• macOS (aarch64-darwin, x86_64-darwin)
• Linux (aarch64-linux, x86_64-linux)