utils/base32.js

  1. import charMapping from './charMapping.js';
  3. const ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567';
  4. const DECODED_BLOCK_SIZE = 5;
  5. const ENCODED_BLOCK_SIZE = 8;
  7. // region encode
  9. const encodeBlock = (input, inputOffset, output, outputOffset) => {
  10. 	output[outputOffset + 0] = ALPHABET[input[inputOffset + 0] >> 3];
  11. 	output[outputOffset + 1] = ALPHABET[((input[inputOffset + 0] & 0x07) << 2) | (input[inputOffset + 1] >> 6)];
  12. 	output[outputOffset + 2] = ALPHABET[(input[inputOffset + 1] & 0x3E) >> 1];
  13. 	output[outputOffset + 3] = ALPHABET[((input[inputOffset + 1] & 0x01) << 4) | (input[inputOffset + 2] >> 4)];
  14. 	output[outputOffset + 4] = ALPHABET[((input[inputOffset + 2] & 0x0F) << 1) | (input[inputOffset + 3] >> 7)];
  15. 	output[outputOffset + 5] = ALPHABET[(input[inputOffset + 3] & 0x7F) >> 2];
  16. 	output[outputOffset + 6] = ALPHABET[((input[inputOffset + 3] & 0x03) << 3) | (input[inputOffset + 4] >> 5)];
  17. 	output[outputOffset + 7] = ALPHABET[input[inputOffset + 4] & 0x1F];
  18. };
  20. // endregion
  22. // region decode
  24. const Char_To_Decoded_Char_Map = (() => {
  25. 	const builder = charMapping.createBuilder();
  26. 	builder.addRange('A', 'Z', 0);
  27. 	builder.addRange('2', '7', 26);
  28. 	return builder.map;
  29. })();
  31. const decodeChar = c => {
  32. 	const decodedChar = Char_To_Decoded_Char_Map[c];
  33. 	if (undefined !== decodedChar)
  34. 		return decodedChar;
  36. 	throw Error(`illegal base32 character ${c}`);
  37. };
  39. const decodeBlock = (input, inputOffset, output, outputOffset) => {
  40. 	const bytes = new Uint8Array(ENCODED_BLOCK_SIZE);
  41. 	for (let i = 0; i < ENCODED_BLOCK_SIZE; ++i)
  42. 		bytes[i] = decodeChar(input[inputOffset + i]);
  44. 	output[outputOffset + 0] = (bytes[0] << 3) | (bytes[1] >> 2);
  45. 	output[outputOffset + 1] = ((bytes[1] & 0x03) << 6) | (bytes[2] << 1) | (bytes[3] >> 4);
  46. 	output[outputOffset + 2] = ((bytes[3] & 0x0F) << 4) | (bytes[4] >> 1);
  47. 	output[outputOffset + 3] = ((bytes[4] & 0x01) << 7) | (bytes[5] << 2) | (bytes[6] >> 3);
  48. 	output[outputOffset + 4] = ((bytes[6] & 0x07) << 5) | bytes[7];
  49. };
  51. // endregion
  53. /**
  54.  * Base32 encodes a binary buffer.
  55.  * @param {Uint8Array} data Binary data to encode.
  56.  * @returns {string} Base32 encoded string corresponding to the input data.
  57.  */
  58. const encode = data => {
  59. 	if (0 !== data.length % DECODED_BLOCK_SIZE)
  60. 		throw Error(`decoded size must be multiple of ${DECODED_BLOCK_SIZE}`);
  62. 	const output = new Array(data.length / DECODED_BLOCK_SIZE * ENCODED_BLOCK_SIZE);
  63. 	for (let i = 0; i < data.length / DECODED_BLOCK_SIZE; ++i)
  64. 		encodeBlock(data, i * DECODED_BLOCK_SIZE, output, i * ENCODED_BLOCK_SIZE);
  66. 	return output.join('');
  67. };
  69. /**
  70.  * Base32 decodes a base32 encoded string.
  71.  * @param {string} encoded Base32 encoded string to decode.
  72.  * @returns {Uint8Array} Binary data corresponding to the input string.
  73.  */
  74. const decode = encoded => {
  75. 	if (0 !== encoded.length % ENCODED_BLOCK_SIZE)
  76. 		throw Error(`encoded size must be multiple of ${ENCODED_BLOCK_SIZE}`);
  78. 	const output = new Uint8Array(encoded.length / ENCODED_BLOCK_SIZE * DECODED_BLOCK_SIZE);
  79. 	for (let i = 0; i < encoded.length / ENCODED_BLOCK_SIZE; ++i)
  80. 		decodeBlock(encoded, i * ENCODED_BLOCK_SIZE, output, i * DECODED_BLOCK_SIZE);
  82. 	return output;
  83. };
  85. export default { encode, decode };