# MTLIOCommandBuffer A command buffer that contains input/output commands that work with files in the file systems and Metal resources. ``` protocol MTLIOCommandBuffer : NSObjectProtocol ``` ## Overview Add commands an input/output command buffer to load assets from the file system directly into Metal resources. Your app can then use those resources with other commands it submits to [`MTLCommandQueue`](/documentation/Metal/MTLCommandQueue). ## Topics ### Loading assets [`load(_:offset:size:sourceHandle:sourceHandleOffset:)`](/documentation/Metal/MTLIOCommandBuffer/load(_:offset:size:sourceHandle:sourceHandleOffset:)) Encodes a command that loads data from a file handle into a GPU buffer. [`load(_:slice:level:size:sourceBytesPerRow:sourceBytesPerImage:destinationOrigin:sourceHandle:sourceHandleOffset:)`](/documentation/Metal/MTLIOCommandBuffer/load(_:slice:level:size:sourceBytesPerRow:sourceBytesPerImage:destinationOrigin:sourceHandle:sourceHandleOffset:)) Encodes a command that loads data from a file handle into a GPU texture. [`loadBytes(_:size:sourceHandle:sourceHandleOffset:)`](/documentation/Metal/MTLIOCommandBuffer/loadBytes(_:size:sourceHandle:sourceHandleOffset:)) Encodes a command that loads data from a file handle into CPU-accessible memory buffer. ### Adding a barrier [`addBarrier()`](/documentation/Metal/MTLIOCommandBuffer/addBarrier()) Encodes a barrier into the command buffer. ### Synchronizing a command buffer [`signalEvent(_:value:)`](/documentation/Metal/MTLIOCommandBuffer/signalEvent(_:value:)) Encodes a command that signals a shared event to other parts of your app. [`waitForEvent(_:value:)`](/documentation/Metal/MTLIOCommandBuffer/waitForEvent(_:value:)) Encodes a command that pauses the command buffer’s execution until another part of your app signals a shared event. ### Adding final commands [`copyStatus(buffer:offset:)`](/documentation/Metal/MTLIOCommandBuffer/copyStatus(buffer:offset:)) Encodes a command that writes the input/output command buffer’s status to a buffer. [`addCompletedHandler(_:)`](/documentation/Metal/MTLIOCommandBuffer/addCompletedHandler(_:)) Adds a closure that Metal calls immediately after the GPU finishes executing the commands in the input/output command buffer. ### Submitting a command buffer [`commit()`](/documentation/Metal/MTLIOCommandBuffer/commit()) Submits the command buffer to the queue for execution on the GPU. [`enqueue()`](/documentation/Metal/MTLIOCommandBuffer/enqueue()) Reserves a place for the input/output command buffer in the input/output command queue without committing the command buffer. ### Canceling a command buffer [`tryCancel()`](/documentation/Metal/MTLIOCommandBuffer/tryCancel()) Submits a request to abandon a command buffer the queue is currently running. ### Waiting for a command buffer [`waitUntilCompleted()`](/documentation/Metal/MTLIOCommandBuffer/waitUntilCompleted()) Blocks the current thread until the GPU finishes executing the input/output command buffer and all of its completion handlers. ### Checking the state of a command buffer [`status`](/documentation/Metal/MTLIOCommandBuffer/status) Represents the state of the input/output command buffer. [`error`](/documentation/Metal/MTLIOCommandBuffer/error) Stores the details of an error when the GPU experienced a problem with the input/output command buffer. ### Debugging a command buffer [`label`](/documentation/Metal/MTLIOCommandBuffer/label) An optional name for the input/output command buffer. [`pushDebugGroup(_:)`](/documentation/Metal/MTLIOCommandBuffer/pushDebugGroup(_:)) Sets the current name for this input/output command encoder by adding it to the top of the debug name stack. [`popDebugGroup()`](/documentation/Metal/MTLIOCommandBuffer/popDebugGroup()) Restores the previous name for this input/output command encoder by removing the top item of the debug name stack. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)