GPUCommandEncoder: copyBufferToBuffer() method

{{APIRef("WebGPU API")}}{{SecureContext_Header}}

The copyBufferToBuffer() method of the {{domxref("GPUCommandEncoder")}} interface encodes a command that copies data from one {{domxref("GPUBuffer")}} to another.

Syntax

copyBufferToBuffer(source, destination)
copyBufferToBuffer(source, destination, size)
copyBufferToBuffer(source, sourceOffset, destination, destinationOffset, size)

Parameters

• source
  • : The {{domxref("GPUBuffer")}} to copy from.
• sourceOffset {{optional_inline}}
  • : The offset, in bytes, into the source to begin copying from.
• destination
  • : The {{domxref("GPUBuffer")}} to copy to.
• destinationOffset {{optional_inline}}
  • : The offset, in bytes, into the destination to begin copying to.
• size {{optional_inline}}
  • : The number of bytes to copy.

[!NOTE] The sourceOffset and destinationOffset can be omitted if you are copying part of the source buffer at a 0 offset in both the source and destination buffers. The sourceOffset, destinationOffset, and size can be omitted if you are copying the entire source buffer to the destination buffer.

Return value

None ({{jsxref("Undefined")}}).

Validation

The following criteria must be met when calling copyBufferToBuffer(), otherwise a {{domxref("GPUValidationError")}} is generated and the {{domxref("GPUCommandEncoder")}} becomes invalid:

• The source's {{domxref("GPUBuffer.usage")}} includes the GPUBufferUsage.COPY_SRC flag.
• The destination's {{domxref("GPUBuffer.usage")}} includes the GPUBufferUsage.COPY_DST flag.
• size, sourceOffset, and destinationOffset are all multiples of 4.
• The source's {{domxref("GPUBuffer.size")}} is greater than or equal to sourceOffset + size.
• The destination's {{domxref("GPUBuffer.size")}} is greater than or equal to destinationOffset + size.
• source and destination are different {{domxref("GPUBuffer")}}s (you can't copy from and to the same buffer).

Examples

In our basic compute demo, we use copyBufferToBuffer() to copy the contents of our outputBuffer to the stagingBuffer.

// …

// Create an output buffer to read GPU calculations to, and a staging buffer to be mapped for JavaScript access

const outputBuffer = device.createBuffer({
  size: BUFFER_SIZE,
  usage: GPUBufferUsage.STORAGE | GPUBufferUsage.COPY_SRC,
});

const stagingBuffer = device.createBuffer({
  size: BUFFER_SIZE,
  usage: GPUBufferUsage.MAP_READ | GPUBufferUsage.COPY_DST,
});

// …

// Create GPUCommandEncoder to encode commands to issue to the GPU
const commandEncoder = device.createCommandEncoder();

// …

// Copy output buffer to staging buffer
commandEncoder.copyBufferToBuffer(
  outputBuffer,
  0, // Source offset
  stagingBuffer,
  0, // Destination offset
  BUFFER_SIZE,
);

// Since we are copying the entire buffer, this can be shortened to
// commandEncoder.copyBufferToBuffer(outputBuffer, stagingBuffer);

// …

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• The WebGPU API