Semaphore.kt

src/jvmMain/kotlin/afield/graphics/vulkan/device/Semaphore.kt · 69 lines

package afield.graphics.vulkan.device

import org.lwjgl.system.MemoryStack
import org.lwjgl.vulkan.VK10
import org.lwjgl.vulkan.VK12
import org.lwjgl.vulkan.VkSemaphoreCreateInfo
import org.lwjgl.vulkan.VkSemaphoreTypeCreateInfo
import afield.graphics.vulkan.util.vkCheck

A Vulkan semaphore for GPU-to-GPU ordering between queue submissions, timeline by default.

A timeline Semaphore keeps its own counter: nextSignalValue advances it for the submission that will signal, currentValue is the value to wait on, and markExternallySignaled advances it when something outside Field's submissions (such as image acquisition) signals it. Constructed with timeline = false it is a binary semaphore, and both values are always 0.

class Semaphore(private val device: Device, private val timeline: Boolean = true)

Semaphore wrapper that can be either binary or timeline.

var vkSemaphore: Long = 0

    private var value: Long = 0

init

    init {
        MemoryStack.stackPush().use { stack ->
            val semaphoreCreateInfo = VkSemaphoreCreateInfo.calloc(stack)
                .sType(VK10.VK_STRUCTURE_TYPE_SEMAPHORE_CREATE_INFO)

            if (timeline) {
                val typeInfo = VkSemaphoreTypeCreateInfo.calloc(stack)
                    .sType(VK12.VK_STRUCTURE_TYPE_SEMAPHORE_TYPE_CREATE_INFO)
                    .semaphoreType(VK12.VK_SEMAPHORE_TYPE_TIMELINE)
                    .initialValue(value)
                semaphoreCreateInfo.pNext(typeInfo.address())
            }

            val lp = stack.mallocLong(1)
            vkCheck(
                VK10.vkCreateSemaphore(device.vkDevice, semaphoreCreateInfo, null, lp),
                "Failed to create semaphore"
            )
            vkSemaphore = lp[0]
        }
    }

fun currentValue(): Long = if (timeline) value else 0

Value to wait on (current signaled value). For binary this is always 0.

fun nextSignalValue(): Long

Value to signal next; increments internal counter for timelines, returns 0 for binary.

    fun nextSignalValue(): Long {
        if (timeline) {
            value += 1
            return value
        }
        return 0
    }

fun markExternallySignaled()

Mark externally signaled (e.g., vkAcquireNextImageKHR).

    fun markExternallySignaled() {
        if (timeline) value += 1
    }

fun cleanup()

    fun cleanup() {
        VK10.vkDestroySemaphore(device.vkDevice, vkSemaphore, null)
    }
}