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Buffers

In this example, we will show you how to use the CreativeEditor SDK’s CreativeEngine to create buffers through the editor API. Buffers can hold arbitrary data.

public func createBuffer() -> URL

Create a resizable buffer that can hold arbitrary data.

  • Returns: A URL to identify the buffer.
public func destroyBuffer(url: URL) throws

Destroy a buffer and free its resources.

  • url: The URL of the buffer to destroy.
public func setBufferData(url: URL, offset: UInt, data: Data) throws

Set the data of a buffer.

  • url: The URL of the buffer.
  • offset: The offset in bytes at which to start writing.
  • data: The data to write.
public func getBufferData(url: URL, offset: UInt, length: UInt) throws -> Data

Get the data of a buffer.

  • url: The URL of the buffer.
  • offset: The offset in bytes at which to start reading.
  • length: The number of bytes to read.
  • Returns: The data read from the buffer or an error.
public func setBufferLength(url: URL, length: UInt) throws

Set the length of a buffer.

  • url: The URL of the buffer.
  • length: The new length of the buffer in bytes.
public func getBufferLength(url: URL) throws -> NSNumber

Get the length of a buffer.

  • url: The URL of the buffer.
  • Returns: The length of the buffer in bytes.

Full Code

Here’s the full code:

// Create an audio block and append it to the page
let audioBlock = try engine.block.create(.audio)
try engine.block.appendChild(to: page, child: audioBlock)


// Create a buffer
let audioBuffer = engine.editor.createBuffer()


// Reference the audio buffer resource from the audio block
try engine.block.setURL(audioBlock, property: "audio/fileURI", value: audioBuffer)


// Generate 10 seconds of stereo 48 kHz audio data
let samples = ContiguousArray<Float>(unsafeUninitializedCapacity: 10 * 2 * 48000) { buffer, initializedCount in
  for i in stride(from: 0, to: buffer.count, by: 2) {
    let sample = sin((440.0 * Float(i) * Float.pi) / 48000.0)
    buffer[i + 0] = sample
    buffer[i + 1] = sample
  }
  initializedCount = buffer.count
}


// Assign the audio data to the buffer
try samples.withUnsafeBufferPointer { buffer in
try engine.editor.setBufferData(url: audioBuffer, offset: 0, data: Data(buffer: buffer))
}


// We can get subranges of the buffer data
let chunk = try engine.editor.getBufferData(url: audioBuffer, offset: 0, length: 4096)


// Get current length of the buffer in bytes
let length = try engine.editor.getBufferLength(url: audioBuffer)


// Reduce the buffer to half its length, leading to 5 seconds worth of audio
try engine.editor.setBufferLength(url: audioBuffer,length: UInt(truncating: length) / 2)


// Free data
try engine.editor.destroyBuffer(url: audioBuffer)