rlp-decode.js 3.1 KB

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  1. //See: https://github.com/ethereum/wiki/wiki/RLP
  2. import { hexlify } from "./data.js";
  3. import { assert, assertArgument } from "./errors.js";
  4. import { getBytes } from "./data.js";
  5. function hexlifyByte(value) {
  6. let result = value.toString(16);
  7. while (result.length < 2) {
  8. result = "0" + result;
  9. }
  10. return "0x" + result;
  11. }
  12. function unarrayifyInteger(data, offset, length) {
  13. let result = 0;
  14. for (let i = 0; i < length; i++) {
  15. result = (result * 256) + data[offset + i];
  16. }
  17. return result;
  18. }
  19. function _decodeChildren(data, offset, childOffset, length) {
  20. const result = [];
  21. while (childOffset < offset + 1 + length) {
  22. const decoded = _decode(data, childOffset);
  23. result.push(decoded.result);
  24. childOffset += decoded.consumed;
  25. assert(childOffset <= offset + 1 + length, "child data too short", "BUFFER_OVERRUN", {
  26. buffer: data, length, offset
  27. });
  28. }
  29. return { consumed: (1 + length), result: result };
  30. }
  31. // returns { consumed: number, result: Object }
  32. function _decode(data, offset) {
  33. assert(data.length !== 0, "data too short", "BUFFER_OVERRUN", {
  34. buffer: data, length: 0, offset: 1
  35. });
  36. const checkOffset = (offset) => {
  37. assert(offset <= data.length, "data short segment too short", "BUFFER_OVERRUN", {
  38. buffer: data, length: data.length, offset
  39. });
  40. };
  41. // Array with extra length prefix
  42. if (data[offset] >= 0xf8) {
  43. const lengthLength = data[offset] - 0xf7;
  44. checkOffset(offset + 1 + lengthLength);
  45. const length = unarrayifyInteger(data, offset + 1, lengthLength);
  46. checkOffset(offset + 1 + lengthLength + length);
  47. return _decodeChildren(data, offset, offset + 1 + lengthLength, lengthLength + length);
  48. }
  49. else if (data[offset] >= 0xc0) {
  50. const length = data[offset] - 0xc0;
  51. checkOffset(offset + 1 + length);
  52. return _decodeChildren(data, offset, offset + 1, length);
  53. }
  54. else if (data[offset] >= 0xb8) {
  55. const lengthLength = data[offset] - 0xb7;
  56. checkOffset(offset + 1 + lengthLength);
  57. const length = unarrayifyInteger(data, offset + 1, lengthLength);
  58. checkOffset(offset + 1 + lengthLength + length);
  59. const result = hexlify(data.slice(offset + 1 + lengthLength, offset + 1 + lengthLength + length));
  60. return { consumed: (1 + lengthLength + length), result: result };
  61. }
  62. else if (data[offset] >= 0x80) {
  63. const length = data[offset] - 0x80;
  64. checkOffset(offset + 1 + length);
  65. const result = hexlify(data.slice(offset + 1, offset + 1 + length));
  66. return { consumed: (1 + length), result: result };
  67. }
  68. return { consumed: 1, result: hexlifyByte(data[offset]) };
  69. }
  70. /**
  71. * Decodes %%data%% into the structured data it represents.
  72. */
  73. export function decodeRlp(_data) {
  74. const data = getBytes(_data, "data");
  75. const decoded = _decode(data, 0);
  76. assertArgument(decoded.consumed === data.length, "unexpected junk after rlp payload", "data", _data);
  77. return decoded.result;
  78. }
  79. //# sourceMappingURL=rlp-decode.js.map