citra/src/core/hle/kernel/semaphore.cpp

// Copyright 2014 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include "common/archives.h"
#include "core/hle/kernel/errors.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/process.h"
#include "core/hle/kernel/resource_limit.h"
#include "core/hle/kernel/semaphore.h"
#include "core/hle/kernel/thread.h"

SERIALIZE_EXPORT_IMPL(Kernel::Semaphore)

namespace Kernel {

Semaphore::Semaphore(KernelSystem& kernel) : WaitObject(kernel) {}

Semaphore::~Semaphore() {
    if (resource_limit) {
        resource_limit->Release(ResourceLimitType::Semaphore, 1);
    }
}

ResultVal<std::shared_ptr<Semaphore>> KernelSystem::CreateSemaphore(s32 initial_count,
                                                                    s32 max_count,
                                                                    std::string name) {

    if (initial_count > max_count) {
        return ERR_INVALID_COMBINATION_KERNEL;
    }

    // When the semaphore is created, some slots are reserved for other threads,
    // and the rest is reserved for the caller thread
    auto semaphore = std::make_shared<Semaphore>(*this);
    semaphore->max_count = max_count;
    semaphore->available_count = initial_count;
    semaphore->name = std::move(name);
    return semaphore;
}

bool Semaphore::ShouldWait(const Thread* thread) const {
    return available_count <= 0;
}

void Semaphore::Acquire(Thread* thread) {
    if (available_count <= 0)
        return;
    --available_count;
}

ResultVal<s32> Semaphore::Release(s32 release_count) {
    if (max_count - available_count < release_count)
        return ERR_OUT_OF_RANGE_KERNEL;

    s32 previous_count = available_count;
    available_count += release_count;

    WakeupAllWaitingThreads();

    return previous_count;
}

} // namespace Kernel