kissfft-wasm/src/rfftnd.ts

A WebAssembly version of KissFFT.

import { ComplexArray, KissFFTArray, RealArray, Int, KissFFTConfig, ConfigPointer, Float32 } from "./types.js"
import { checkRealFFT } from "./rfft.js"
import { wasm } from "./wasm.js"

abstract class AbstractRealFFTNDConfig<T extends KissFFTArray, K extends KissFFTArray> extends KissFFTConfig<
  T,
  K
> {
  protected ptr = 0 as ConfigPointer

  constructor(public readonly dims: readonly Int[], inverse: boolean) {
    super(
      dims.reduce((x, y) => (x * y) as Int),
      inverse
    )
    const ndims = dims.length
    checkRealFFT(dims[ndims - 1])
    const dimsPtr = wasm._malloc<Int>((Int32Array.BYTES_PER_ELEMENT * ndims) as Int)
    dims.forEach((x, i) => {
      wasm.HEAP32[dimsPtr / Int32Array.BYTES_PER_ELEMENT + i] = x
    })
    this.ptr = wasm._kiss_fftndr_alloc(dimsPtr, ndims as Int, inverse, 0 as Int, 0 as Int)
    wasm._free(dimsPtr)
  }

  public get pointer() {
    return this.ptr
  }

  public free(): void {
    wasm._free(this.ptr)
    this.ptr = 0 as ConfigPointer
  }
}

export class RealFFTNDConfig extends AbstractRealFFTNDConfig<RealArray, ComplexArray> {
  constructor(dims: Int[]) {
    super(dims, false)
  }

  public work(input: RealArray, output: ComplexArray): void {
    this.check(input, output)
    wasm._kiss_fftndr(this.ptr, input.pointer, output.pointer)
  }
}

export class InverseRealFFTNDConfig extends AbstractRealFFTNDConfig<ComplexArray, RealArray> {
  constructor(dims: Int[]) {
    super(dims, true)
  }

  public work(input: ComplexArray, output: RealArray): void {
    this.check(input, output)
    wasm._kiss_fftndri(this.ptr, input.pointer, output.pointer)
    wasm._scale(output.pointer, this.nfft, (1.0 / this.nfft) as Float32)
  }
}