readMappings.js 3.0 KB

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  1. /*
  2. MIT License http://www.opensource.org/licenses/mit-license.php
  3. Author Tobias Koppers @sokra
  4. */
  5. "use strict";
  6. const ALPHABET =
  7. "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  8. const CONTINUATION_BIT = 0x20;
  9. const END_SEGMENT_BIT = 0x40;
  10. const NEXT_LINE = END_SEGMENT_BIT | 0x01;
  11. const INVALID = END_SEGMENT_BIT | 0x02;
  12. const DATA_MASK = 0x1f;
  13. const ccToValue = new Uint8Array("z".charCodeAt(0) + 1);
  14. ccToValue.fill(INVALID);
  15. for (let i = 0; i < ALPHABET.length; i++) {
  16. ccToValue[ALPHABET.charCodeAt(i)] = i;
  17. }
  18. ccToValue[",".charCodeAt(0)] = END_SEGMENT_BIT;
  19. ccToValue[";".charCodeAt(0)] = NEXT_LINE;
  20. const ccMax = ccToValue.length - 1;
  21. /** @typedef {(generatedLine: number, generatedColumn: number, sourceIndex: number, originalLine: number, originalColumn: number, nameIndex: number) => void} OnMapping */
  22. /**
  23. * @param {string} mappings the mappings string
  24. * @param {OnMapping} onMapping called for each mapping
  25. * @returns {void}
  26. */
  27. const readMappings = (mappings, onMapping) => {
  28. // generatedColumn, [sourceIndex, originalLine, orignalColumn, [nameIndex]]
  29. const currentData = new Uint32Array([0, 0, 1, 0, 0]);
  30. let currentDataPos = 0;
  31. // currentValue will include a sign bit at bit 0
  32. let currentValue = 0;
  33. let currentValuePos = 0;
  34. let generatedLine = 1;
  35. let generatedColumn = -1;
  36. for (let i = 0; i < mappings.length; i++) {
  37. const cc = mappings.charCodeAt(i);
  38. if (cc > ccMax) continue;
  39. const value = ccToValue[cc];
  40. if ((value & END_SEGMENT_BIT) !== 0) {
  41. // End current segment
  42. if (currentData[0] > generatedColumn) {
  43. if (currentDataPos === 1) {
  44. onMapping(generatedLine, currentData[0], -1, -1, -1, -1);
  45. } else if (currentDataPos === 4) {
  46. onMapping(
  47. generatedLine,
  48. currentData[0],
  49. currentData[1],
  50. currentData[2],
  51. currentData[3],
  52. -1,
  53. );
  54. } else if (currentDataPos === 5) {
  55. onMapping(
  56. generatedLine,
  57. currentData[0],
  58. currentData[1],
  59. currentData[2],
  60. currentData[3],
  61. currentData[4],
  62. );
  63. }
  64. [generatedColumn] = currentData;
  65. }
  66. currentDataPos = 0;
  67. if (value === NEXT_LINE) {
  68. // Start new line
  69. generatedLine++;
  70. currentData[0] = 0;
  71. generatedColumn = -1;
  72. }
  73. } else if ((value & CONTINUATION_BIT) === 0) {
  74. // last sextet
  75. currentValue |= value << currentValuePos;
  76. const finalValue =
  77. currentValue & 1 ? -(currentValue >> 1) : currentValue >> 1;
  78. currentData[currentDataPos++] += finalValue;
  79. currentValuePos = 0;
  80. currentValue = 0;
  81. } else {
  82. currentValue |= (value & DATA_MASK) << currentValuePos;
  83. currentValuePos += 5;
  84. }
  85. }
  86. // End current segment
  87. if (currentDataPos === 1) {
  88. onMapping(generatedLine, currentData[0], -1, -1, -1, -1);
  89. } else if (currentDataPos === 4) {
  90. onMapping(
  91. generatedLine,
  92. currentData[0],
  93. currentData[1],
  94. currentData[2],
  95. currentData[3],
  96. -1,
  97. );
  98. } else if (currentDataPos === 5) {
  99. onMapping(
  100. generatedLine,
  101. currentData[0],
  102. currentData[1],
  103. currentData[2],
  104. currentData[3],
  105. currentData[4],
  106. );
  107. }
  108. };
  109. module.exports = readMappings;