gtests/Initializer.h

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#ifndef GLSLANG_GTESTS_INITIALIZER_H
#define GLSLANG_GTESTS_INITIALIZER_H

#include <mutex>

#include "glslang/Public/ShaderLang.h"

namespace glslangtest {

// Initializes glslang on creation, and destroys it on completion.
// And provides .Acquire() as a way to reinitialize glslang if semantics change.
// This object is expected to be a singleton, so that internal glslang state
// can be correctly handled.
//
// TODO(antiagainst): It's a known bug that some of the internal states need to
// be reset if semantics change:
//   https://github.com/KhronosGroup/glslang/issues/166
// Therefore, the following mechanism is needed. Remove this once the above bug
// gets fixed.
class GlslangInitializer {
public:
    GlslangInitializer() : lastMessages(EShMsgDefault)
    {
        glslang::InitializeProcess();
    }

    ~GlslangInitializer() { glslang::FinalizeProcess(); }

    // A token indicates that the glslang is reinitialized (if necessary) to the
    // required semantics. And that won't change until the token is destroyed.
    class InitializationToken {
    public:
        InitializationToken() : initializer(nullptr) {}
        ~InitializationToken()
        {
            if (initializer) {
                initializer->release();
            }
        }

        InitializationToken(InitializationToken&& other)
            : initializer(other.initializer)
        {
            other.initializer = nullptr;
        }

        InitializationToken(const InitializationToken&) = delete;

    private:
        InitializationToken(GlslangInitializer* initializer)
            : initializer(initializer) {}

        friend class GlslangInitializer;
        GlslangInitializer* initializer;
    };

    // Obtains exclusive access to the glslang state. The state remains
    // exclusive until the Initialization Token has been destroyed.
    // Re-initializes glsl state iff the previous messages and the current
    // messages are incompatible.
    InitializationToken acquire(EShMessages new_messages)
    {
        stateLock.lock();

        if ((lastMessages ^ new_messages) &
            (EShMsgVulkanRules | EShMsgSpvRules)) {
            glslang::FinalizeProcess();
            glslang::InitializeProcess();
        }
        lastMessages = new_messages;
        return InitializationToken(this);
    }

private:
    void release() { stateLock.unlock(); }

    friend class InitializationToken;

    EShMessages lastMessages;
    std::mutex stateLock;
};

}  // namespace glslangtest

#endif  // GLSLANG_GTESTS_INITIALIZER_H