bare-operating-system/packages/bare-os-coreutils/lib/agent-text-polyfill.js

/** TextEncoder/TextDecoder when missing on globalThis (Bare/Pear guest eval). */

/**
 * @param {Uint8Array} bytes
 */
function bareAgentUtf8Decode(bytes) {
  let out = ''
  let i = 0
  const len = bytes.length
  while (i < len) {
    const b0 = bytes[i++]
    if (b0 < 0x80) {
      out += String.fromCharCode(b0)
      continue
    }
    if ((b0 & 0xe0) === 0xc0) {
      if (i >= len || (bytes[i] & 0xc0) !== 0x80) {
        out += '\ufffd'
        continue
      }
      const b1 = bytes[i++]
      const cp = ((b0 & 0x1f) << 6) | (b1 & 0x3f)
      if (cp < 0x80) out += '\ufffd'
      else out += String.fromCharCode(cp)
      continue
    }
    if ((b0 & 0xf0) === 0xe0) {
      if (i + 1 >= len || (bytes[i] & 0xc0) !== 0x80 || (bytes[i + 1] & 0xc0) !== 0x80) {
        out += '\ufffd'
        continue
      }
      const b1 = bytes[i++]
      const b2 = bytes[i++]
      let cp = ((b0 & 0x0f) << 12) | ((b1 & 0x3f) << 6) | (b2 & 0x3f)
      if (cp < 0x800 || (cp >= 0xd800 && cp <= 0xdfff)) out += '\ufffd'
      else out += String.fromCharCode(cp)
      continue
    }
    if ((b0 & 0xf8) === 0xf0) {
      if (
        i + 2 >= len ||
        (bytes[i] & 0xc0) !== 0x80 ||
        (bytes[i + 1] & 0xc0) !== 0x80 ||
        (bytes[i + 2] & 0xc0) !== 0x80
      ) {
        out += '\ufffd'
        continue
      }
      const b1 = bytes[i++]
      const b2 = bytes[i++]
      const b3 = bytes[i++]
      let cp =
        ((b0 & 0x07) << 18) |
        ((b1 & 0x3f) << 12) |
        ((b2 & 0x3f) << 6) |
        (b3 & 0x3f)
      if (cp < 0x10000 || cp > 0x10ffff) out += '\ufffd'
      else {
        cp -= 0x10000
        out += String.fromCharCode(0xd800 + (cp >> 10), 0xdc00 + (cp & 0x3ff))
      }
      continue
    }
    out += '\ufffd'
  }
  return out
}

/**
 * @param {string} str
 */
function bareAgentUtf8Encode(str) {
  const out = []
  for (let i = 0; i < str.length; i++) {
    let c = str.charCodeAt(i)
    if (c < 0x80) {
      out.push(c)
    } else if (c < 0x800) {
      out.push(0xc0 | (c >> 6), 0x80 | (c & 0x3f))
    } else if (c >= 0xd800 && c <= 0xdbff && i + 1 < str.length) {
      const c2 = str.charCodeAt(i + 1)
      if ((c2 & 0xfc00) === 0xdc00) {
        i++
        const cp = 0x10000 + ((c & 0x3ff) << 10) + (c2 & 0x3ff)
        out.push(
          0xf0 | (cp >> 18),
          0x80 | ((cp >> 12) & 0x3f),
          0x80 | ((cp >> 6) & 0x3f),
          0x80 | (cp & 0x3f)
        )
      } else {
        out.push(0xe0 | (c >> 12), 0x80 | ((c >> 6) & 0x3f), 0x80 | (c & 0x3f))
      }
    } else if (c < 0xd800 || c >= 0xe000) {
      out.push(0xe0 | (c >> 12), 0x80 | ((c >> 6) & 0x3f), 0x80 | (c & 0x3f))
    }
  }
  return new Uint8Array(out)
}

function bareAgentEnsureTextCodecPolyfill() {
  const g =
    typeof globalThis !== 'undefined'
      ? globalThis
      : typeof global !== 'undefined'
        ? global
        : typeof self !== 'undefined'
          ? self
          : /** @type {Record<string, unknown>} */ ({})

  if (typeof g.TextDecoder !== 'function') {
    function BareTextDecoder() {
      /** @type {'utf-8'} */
      this.encoding = 'utf-8'
    }
    BareTextDecoder.prototype.decode = function (input, options) {
      let u8
      if (input instanceof Uint8Array) u8 = input
      else if (typeof ArrayBuffer !== 'undefined' && input instanceof ArrayBuffer)
        u8 = new Uint8Array(input)
      else if (input != null && typeof input === 'object' && 'length' in input) {
        u8 = new Uint8Array(/** @type {ArrayLike<number>} */ (input))
      } else if (input == null || input === undefined) {
        return ''
      } else {
        return ''
      }
      const stream = !!(options && options.stream)
      void stream
      return bareAgentUtf8Decode(u8)
    }
    if (typeof globalThis !== 'undefined') globalThis.TextDecoder = BareTextDecoder
    else g.TextDecoder = BareTextDecoder
  }

  if (typeof g.TextEncoder !== 'function') {
    function BareTextEncoder() {
      this.encoding = 'utf-8'
    }
    BareTextEncoder.prototype.encode = function (input) {
      return bareAgentUtf8Encode(String(input == null ? '' : input))
    }
    if (typeof globalThis !== 'undefined') globalThis.TextEncoder = BareTextEncoder
    else g.TextEncoder = BareTextEncoder
  }
}

bareAgentEnsureTextCodecPolyfill()