index.js

/*! fetch-blob. MIT License. Jimmy Wärting <https://jimmy.warting.se/opensource> */

if (!globalThis.ReadableStream) {
  try {
    const process = await import('node:process').then(m => m.default)
    const { emitWarning } = process
    try {
      process.emitWarning = () => {}
      const streams = await import('node:stream/web').then(m => m.default)
      Object.assign(globalThis, streams)
      process.emitWarning = emitWarning
    } catch (error) {
      process.emitWarning = emitWarning
      throw error
    }
  } catch (error) {}
}

// 64 KiB (same size chrome slice theirs blob into Uint8array's)
const POOL_SIZE = 65536

/**
 * @param {(Blob | Uint8Array)[]} parts
 * @param {boolean} clone
 * @returns {AsyncIterableIterator<Uint8Array>}
 */
async function * toIterator (parts, clone) {
  for (const part of parts) {
    if (ArrayBuffer.isView(part)) {
      if (clone) {
        let position = part.byteOffset
        const end = part.byteOffset + part.byteLength
        while (position !== end) {
          const size = Math.min(end - position, POOL_SIZE)
          const chunk = part.buffer.slice(position, position + size)
          position += chunk.byteLength
          yield new Uint8Array(chunk)
        }
      } else {
        yield part
      }
    } else {
      // @ts-ignore TS Think blob.stream() returns a node:stream
      yield * part.stream()
    }
  }
}

const _Blob = class Blob {
  /** @type {Array.<(Blob|Uint8Array)>} */
  #parts = []
  #type = ''
  #size = 0
  #endings = 'transparent'

  /**
   * The Blob() constructor returns a new Blob object. The content
   * of the blob consists of the concatenation of the values given
   * in the parameter array.
   *
   * @param {*} blobParts
   * @param {{ type?: string, endings?: string }} [options]
   */
  constructor (blobParts = [], options = {}) {
    if (typeof blobParts !== 'object' || blobParts === null) {
      throw new TypeError('Failed to construct \'Blob\': The provided value cannot be converted to a sequence.')
    }

    if (typeof blobParts[Symbol.iterator] !== 'function') {
      throw new TypeError('Failed to construct \'Blob\': The object must have a callable @@iterator property.')
    }

    if (typeof options !== 'object' && typeof options !== 'function') {
      throw new TypeError('Failed to construct \'Blob\': parameter 2 cannot convert to dictionary.')
    }

    if (options === null) options = {}

    const encoder = new TextEncoder()
    for (const element of blobParts) {
      let part
      if (ArrayBuffer.isView(element)) {
        part = new Uint8Array(element.buffer.slice(element.byteOffset, element.byteOffset + element.byteLength))
      } else if (element instanceof ArrayBuffer) {
        part = new Uint8Array(element.slice(0))
      } else if (element instanceof Blob) {
        part = element
      } else {
        part = encoder.encode(`${element}`)
      }

      const size = ArrayBuffer.isView(part) ? part.byteLength : part.size
      // Avoid pushing empty parts into the array to better GC them
      if (size) {
        this.#size += size
        this.#parts.push(part)
      }
    }

    this.#endings = `${options.endings === undefined ? 'transparent' : options.endings}`
    const type = options.type === undefined ? '' : String(options.type)
    this.#type = /^[\x20-\x7E]*$/.test(type) ? type : ''
  }

  /**
   * The Blob interface's size property returns the
   * size of the Blob in bytes.
   */
  get size () {
    return this.#size
  }

  /**
   * The type property of a Blob object returns the MIME type of the file.
   */
  get type () {
    return this.#type
  }

  /**
   * The text() method in the Blob interface returns a Promise
   * that resolves with a string containing the contents of
   * the blob, interpreted as UTF-8.
   *
   * @return {Promise<string>}
   */
  async text () {
    // More optimized than using this.arrayBuffer()
    // that requires twice as much ram
    const decoder = new TextDecoder()
    let str = ''
    for await (const part of toIterator(this.#parts, false)) {
      str += decoder.decode(part, { stream: true })
    }
    // Remaining
    str += decoder.decode()
    return str
  }

  /**
   * The arrayBuffer() method in the Blob interface returns a
   * Promise that resolves with the contents of the blob as
   * binary data contained in an ArrayBuffer.
   *
   * @return {Promise<ArrayBuffer>}
   */
  async arrayBuffer () {
    const data = new Uint8Array(this.size)
    let offset = 0
    for await (const chunk of toIterator(this.#parts, false)) {
      data.set(chunk, offset)
      offset += chunk.length
    }

    return data.buffer
  }

  stream () {
    const it = toIterator(this.#parts, true)

    return new globalThis.ReadableStream({
      // @ts-ignore
      type: 'bytes',
      async pull (ctrl) {
        const chunk = await it.next()
        chunk.done ? ctrl.close() : ctrl.enqueue(chunk.value)
      },

      async cancel () {
        await it.return()
      }
    })
  }

  /**
   * The Blob interface's slice() method creates and returns a
   * new Blob object which contains data from a subset of the
   * blob on which it's called.
   *
   * @param {number} [start]
   * @param {number} [end]
   * @param {string} [type]
   */
  slice (start = 0, end = this.size, type = '') {
    const { size } = this

    let relativeStart = start < 0 ? Math.max(size + start, 0) : Math.min(start, size)
    let relativeEnd = end < 0 ? Math.max(size + end, 0) : Math.min(end, size)

    const span = Math.max(relativeEnd - relativeStart, 0)
    const parts = this.#parts
    const blobParts = []
    let added = 0

    for (const part of parts) {
      // don't add the overflow to new blobParts
      if (added >= span) {
        break
      }

      const size = ArrayBuffer.isView(part) ? part.byteLength : part.size
      if (relativeStart && size <= relativeStart) {
        // Skip the beginning and change the relative
        // start & end position as we skip the unwanted parts
        relativeStart -= size
        relativeEnd -= size
      } else {
        let chunk
        if (ArrayBuffer.isView(part)) {
          chunk = part.subarray(relativeStart, Math.min(size, relativeEnd))
          added += chunk.byteLength
        } else {
          chunk = part.slice(relativeStart, Math.min(size, relativeEnd))
          added += chunk.size
        }
        relativeEnd -= size
        blobParts.push(chunk)
        relativeStart = 0 // All next sequential parts should start at 0
      }
    }

    const blob = new Blob([], { type: `${type}` })
    blob.#size = span
    blob.#parts = blobParts

    return blob
  }

  get [Symbol.toStringTag] () {
    return 'Blob'
  }

  static [Symbol.hasInstance] (object) {
    return (
      object &&
      typeof object === 'object' &&
      typeof object.constructor === 'function' &&
      (
        typeof object.stream === 'function' ||
        typeof object.arrayBuffer === 'function'
      ) &&
      /^(Blob|File)$/.test(object[Symbol.toStringTag])
    )
  }
}

Object.defineProperties(_Blob.prototype, {
  size: { enumerable: true },
  type: { enumerable: true },
  slice: { enumerable: true }
})

/** @type {typeof globalThis.Blob} */
export const Blob = _Blob