Syntax

mapAsync(mode)
mapAsync(mode, offset, size)

Parameters

mode

A bitwise flag that specifies whether the GPUBuffer is mapped for reading or writing. Possible values are:

GPUMapMode.READ

The GPUBuffer is mapped for reading. Values can be read, but any changes made to the ArrayBuffer returned by GPUBuffer.getMappedRange() will be discarded once GPUBuffer.unmap() is called.

Read-mode mapping can only be used on GPUBuffers that have a usage of GPUBufferUsage.MAP_READ set on them (i.e., when created with GPUDevice.createBuffer()).

GPUMapMode.WRITE

The GPUBuffer is mapped for writing. Values can be read and updated — any changes made to the ArrayBuffer returned by GPUBuffer.getMappedRange() will be saved to the GPUBuffer once GPUBuffer.unmap() is called.

Write-mode mapping can only be used on GPUBuffers that have a usage of GPUBufferUsage.MAP_WRITE set on them (i.e., when created with GPUDevice.createBuffer()).

offset Optional

A number representing the offset, in bytes, from the start of the buffer to the start of the range to be mapped. If offset is omitted, it defaults to 0.

size Optional

A number representing the size, in bytes, of the range to be mapped. If size is omitted, the range mapped extends to the end of the GPUBuffer.

Return value

A Promise that resolves to Undefined when the GPUBuffer's content is ready to be accessed.

Validation

The following criteria must be met when calling mapAsync(), otherwise an OperationError DOMException is thrown, the promise is rejected, and a GPUValidationError is generated:

• offset is a multiple of 8.
• The total range to be mapped (size if specified, or GPUBuffer.size - offset if not) is a multiple of 4.
• The total range to be mapped is inside the bounds of the GPUBuffer.
• If mode is GPUMapMode.READ, the GPUBuffer has a usage of GPUBufferUsage.MAP_READ.
• If mode is GPUMapMode.WRITE, the GPUBuffer has a usage of GPUBufferUsage.MAP_WRITE.

Examples

See the main GPUBuffer page for an example.

Specifications

Browser compatibility

See also

• The WebGPU API