extend index buffer

Sources/Alloy/Core/MTLIndexBuffer.swift

@@ -6,6 +6,25 @@ public class MTLIndexBuffer {
     public let count: Int
     public let type: MTLIndexType
 
+    public init(device: MTLDevice,
+                count: Int,
+                type: MTLIndexType,
+                options: MTLResourceOptions = .cpuCacheModeWriteCombined) throws {
+        let indexStride: Int
+        switch type {
+        case .uint16: indexStride = MemoryLayout<UInt16>.stride
+        case .uint32: indexStride = MemoryLayout<UInt32>.stride
+        @unknown default: throw MetalError.MTLBufferError.incompatibleData
+        }
+
+        guard let allocatedBuffer = device.makeBuffer(length: count * indexStride, options: options)
+        else { throw MetalError.MTLDeviceError.bufferCreationFailed }
+
+        self.buffer = allocatedBuffer
+        self.count = count
+        self.type = type
+    }
+
     public init(device: MTLDevice,
                 indexArray: [UInt16],
                 options: MTLResourceOptions = []) throws {
@@ -31,4 +50,74 @@ public class MTLIndexBuffer {
         self.count = indexArray.count
         self.type = .uint32
     }
+
+    func pointer<T>(of type: T.Type) -> UnsafeMutablePointer<T>? {
+        return self.buffer.pointer(of: T.self)
+    }
+
+    func bufferPointer<T>(of type: T.Type,
+                          count: Int) -> UnsafeBufferPointer<T>? {
+        return self.buffer.bufferPointer(of: T.self, count: count)
+    }
+
+    func array<T>(of type: T.Type,
+                  count: Int) -> [T]? {
+        return self.buffer.array(of: T.self, count: count)
+    }
+
+    /// Put a value in `MTLIndexBuffer` at desired offset.
+    /// - Parameters:
+    ///   - value: value to put in the buffer.
+    ///   - offset: offset in bytes.
+    func put(_ value: UInt16,
+             at offset: Int = 0) throws {
+        #if DEBUG
+        if self.type != .uint16 {
+            assertionFailure("WARNING: Trying to insert UInt16 index into different type index buffer")
+        }
+        #endif
+        try self.buffer.put(value, at: offset)
+    }
+
+    /// Put values in `MTLIndexBuffer` at desired offset.
+    /// - Parameters:
+    ///   - values: values to put in the buffer.
+    ///   - offset: offset in bytes.
+    func put(_ values: [UInt16],
+             at offset: Int = 0) throws {
+        #if DEBUG
+        if self.type != .uint16 {
+            assertionFailure("WARNING: Trying to insert UInt16 index into different type index buffer")
+        }
+        #endif
+        try self.buffer.put(values, at: offset)
+    }
+
+    /// Put a value in `MTLIndexBuffer` at desired offset.
+    /// - Parameters:
+    ///   - value: value to put in the buffer.
+    ///   - offset: offset in bytes.
+    func put(_ value: UInt32,
+             at offset: Int = 0) throws {
+        #if DEBUG
+        if self.type != .uint32 {
+            assertionFailure("WARNING: Trying to insert UInt16 index into different type index buffer")
+        }
+        #endif
+        try self.buffer.put(value, at: offset)
+    }
+
+    /// Put values in `MTLIndexBuffer` at desired offset.
+    /// - Parameters:
+    ///   - values: values to put in the buffer.
+    ///   - offset: offset in bytes.
+    func put(_ values: [UInt32],
+             at offset: Int = 0) throws {
+        #if DEBUG
+        if self.type != .uint32 {
+            assertionFailure("WARNING: Trying to insert UInt16 index into different type index buffer")
+        }
+        #endif
+        try self.buffer.put(values, at: offset)
+    }
 }