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Copyright (c) 2018 The Go Authors. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   * Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
   * Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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// +build darwin

// Package mtl provides access to Apple's Metal API (https://developer.apple.com/documentation/metal).
//
// This package is in very early stages of development.
// Less than 5% of the Metal API surface is implemented.
// Current functionality is sufficient to list Metal-capable devices
// on the system and query basic information about them.
package mtl

import (
	"errors"
	"unsafe"
)

/*
#cgo CFLAGS: -x objective-c
#cgo LDFLAGS: -framework Metal
#include <stdlib.h>
#include "mtl.h"
*/
import "C"

// Device is abstract representation of the GPU that
// serves as the primary interface for a Metal app.
//
// Reference: https://developer.apple.com/documentation/metal/mtldevice.
type Device struct {
	device unsafe.Pointer

	// Headless indicates whether a device is configured as headless.
	Headless bool

	// LowPower indicates whether a device is low-power.
	LowPower bool

	// Removable determines whether or not a GPU is removable.
	Removable bool

	// RegistryID is the registry ID value for the device.
	RegistryID uint64

	// Name is the name of the device.
	Name string
}

// CreateSystemDefaultDevice returns the preferred system default Metal device.
//
// Reference: https://developer.apple.com/documentation/metal/1433401-mtlcreatesystemdefaultdevice.
func CreateSystemDefaultDevice() (Device, error) {
	d := C.CreateSystemDefaultDevice()
	if d.device == nil {
		return Device{}, errors.New("Metal is not supported on this system")
	}

	return Device{
		device:     d.device,
		Headless:   d.headless != 0,
		LowPower:   d.lowPower != 0,
		Removable:  d.removable != 0,
		RegistryID: uint64(d.registryID),
		Name:       C.GoString(d.name),
	}, nil
}

// CopyAllDevices returns all Metal devices in the system.
//
// Reference: https://developer.apple.com/documentation/metal/1433367-mtlcopyalldevices.
func CopyAllDevices() []Device {
	d := C.CopyAllDevices()
	defer C.free(unsafe.Pointer(d.devices))

	ds := make([]Device, d.length)
	for i := 0; i < len(ds); i++ {
		d := (*C.struct_Device)(unsafe.Pointer(uintptr(unsafe.Pointer(d.devices)) + uintptr(i)*C.sizeof_struct_Device))

		ds[i].device = d.device
		ds[i].Headless = d.headless != 0
		ds[i].LowPower = d.lowPower != 0
		ds[i].Removable = d.removable != 0
		ds[i].RegistryID = uint64(d.registryID)
		ds[i].Name = C.GoString(d.name)
	}
	return ds
}

// SupportsFeatureSet reports whether device d supports feature set fs.
//
// Reference: https://developer.apple.com/documentation/metal/mtldevice/1433418-supportsfeatureset.
func (d Device) SupportsFeatureSet(fs FeatureSet) bool {
	return C.Device_SupportsFeatureSet(d.device, C.uint16_t(fs)) != 0
}

// NewCommandQueue creates a new command queue object.
//
// Reference: https://developer.apple.com/documentation/metal/mtldevice/1433388-newcommandqueue.
func (d Device) NewCommandQueue() CommandQueue {
	return CommandQueue{C.Device_NewCommandQueue(d.device)}
}

// FeatureSet defines a specific platform, hardware, and software configuration.
//
// Reference: https://developer.apple.com/documentation/metal/mtlfeatureset.
type FeatureSet uint16

const (
	MacOSGPUFamily1V1 FeatureSet = 10000 // The GPU family 1, version 1 feature set for macOS.
	MacOSGPUFamily1V2 FeatureSet = 10001 // The GPU family 1, version 2 feature set for macOS.
	MacOSGPUFamily1V3 FeatureSet = 10003 // The GPU family 1, version 3 feature set for macOS.
	MacOSGPUFamily1V4 FeatureSet = 10004 // The GPU family 1, version 4 feature set for macOS.
	MacOSGPUFamily2V1 FeatureSet = 10005 // The GPU family 2, version 1 feature set for macOS.
)

// CommandQueue is a queue that organizes the order
// in which command buffers are executed by the GPU.
//
// Reference: https://developer.apple.com/documentation/metal/mtlcommandqueue.
type CommandQueue struct {
	commandQueue unsafe.Pointer
}

// CommandBuffer creates a command buffer.
//
// Reference: https://developer.apple.com/documentation/metal/mtlcommandqueue/1508686-commandbuffer.
func (cq CommandQueue) CommandBuffer() CommandBuffer {
	return CommandBuffer{C.CommandQueue_CommandBuffer(cq.commandQueue)}
}

// CommandBuffer is a container that stores encoded commands
// that are committed to and executed by the GPU.
//
// Reference: https://developer.apple.com/documentation/metal/mtlcommandbuffer.
type CommandBuffer struct {
	commandBuffer unsafe.Pointer
}

@@ -0,0 +1,25 @@
// +build darwin

typedef signed char BOOL;
typedef unsigned short uint16_t;
typedef unsigned long long uint64_t;

struct Device {
	void *       device;
	BOOL         headless;
	BOOL         lowPower;
	BOOL         removable;
	uint64_t     registryID;
	const char * name;
};

struct Devices {
	struct Device * devices;
	int             length;
};

struct Device CreateSystemDefaultDevice();
struct Devices CopyAllDevices();
BOOL Device_SupportsFeatureSet(void * device, uint16_t featureSet);
void * Device_NewCommandQueue(void * device);
void * CommandQueue_CommandBuffer(void * commandQueue);

@@ -0,0 +1,53 @@
// +build darwin

#include <stdlib.h>
#import <Metal/Metal.h>
#include "mtl.h"

struct Device CreateSystemDefaultDevice() {
	id<MTLDevice> device = MTLCreateSystemDefaultDevice();
	if (!device) {
		struct Device d;
		d.device = NULL;
		return d;
	}

	struct Device d;
	d.device = device;
	d.headless = device.headless;
	d.lowPower = device.lowPower;
	d.removable = device.removable;
	d.registryID = device.registryID;
	d.name = device.name.UTF8String;
	return d;
}

// Caller must call free(d.devices).
struct Devices CopyAllDevices() {
	NSArray<id<MTLDevice>> * devices = MTLCopyAllDevices();

	struct Devices d;
	d.devices = malloc(devices.count * sizeof(struct Device));
	for (int i = 0; i < devices.count; i++) {
		d.devices[i].device = devices[i];
		d.devices[i].headless = devices[i].headless;
		d.devices[i].lowPower = devices[i].lowPower;
		d.devices[i].removable = devices[i].removable;
		d.devices[i].registryID = devices[i].registryID;
		d.devices[i].name = devices[i].name.UTF8String;
	}
	d.length = devices.count;
	return d;
}

BOOL Device_SupportsFeatureSet(void * device, uint16_t featureSet) {
	return [(id<MTLDevice>)device supportsFeatureSet:featureSet];
}

void * Device_NewCommandQueue(void * device) {
	return [(id<MTLDevice>)device newCommandQueue];
};

void * CommandQueue_CommandBuffer(void * commandQueue) {
	return [(id<MTLCommandQueue>)commandQueue commandBuffer];
};