Effect schema Uint8ArrayList

Uint8ArrayList.ts

import { Schema } from '@effect/schema'

/**
 * The encoded structure is alternating 4 bytes to represent the length of the following Uint8Array,
 * followed by the Uint8Array itself, repeated.
 */
export const Uint8ArrayList = Schema.transform(Schema.Uint8ArrayFromSelf, Schema.Array(Schema.Uint8ArrayFromSelf), {
  decode: (encodedArrayList) => {
    const arrayList: Uint8Array[] = []

    const dataView = new DataView(encodedArrayList.buffer)

    let offset = 0

    while (offset < dataView.byteLength) {
      const length = dataView.getUint32(offset)
      const array = new Uint8Array(dataView.buffer, offset + 4, length)
      arrayList.push(array)
      offset += 4 + length
    }

    return arrayList
  },
  encode: (arrayList) => {
    const numberOfTotalBytes = arrayList.reduce((acc, array) => acc + array.byteLength, 0)
    const encodedArrayList = new Uint8Array(numberOfTotalBytes)

    let offset = 0

    for (const array of arrayList) {
      encodedArrayList.set(array, offset)
      offset += array.byteLength
    }

    return encodedArrayList
  },
  strict: true,
})