GetViewByteLength.js 1.5 KB

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  1. 'use strict';
  2. var $TypeError = require('es-errors/type');
  3. var IsFixedLengthArrayBuffer = require('./IsFixedLengthArrayBuffer');
  4. var IsViewOutOfBounds = require('./IsViewOutOfBounds');
  5. var isDataViewWithBufferWitnessRecord = require('../helpers/records/data-view-with-buffer-witness-record');
  6. var dataViewBuffer = require('data-view-buffer');
  7. var dataViewByteLength = require('data-view-byte-length');
  8. var dataViewByteOffset = require('data-view-byte-offset');
  9. // https://262.ecma-international.org/15.0/#sec-getviewbytelength
  10. module.exports = function GetViewByteLength(viewRecord) {
  11. if (!isDataViewWithBufferWitnessRecord(viewRecord)) {
  12. throw new $TypeError('Assertion failed: `viewRecord` must be a DataView with Buffer Witness Record');
  13. }
  14. if (IsViewOutOfBounds(viewRecord)) {
  15. throw new $TypeError('Assertion failed: `viewRecord` is out of bounds'); // step 1
  16. }
  17. var view = viewRecord['[[Object]]']; // step 2
  18. var isFixed = IsFixedLengthArrayBuffer(dataViewBuffer(view));
  19. var viewByteLength = isFixed ? dataViewByteLength(view) : 'AUTO'; // view.[[ByteLength]]
  20. if (viewByteLength !== 'AUTO') {
  21. return viewByteLength; // step 3
  22. }
  23. if (isFixed) {
  24. throw new $TypeError('Assertion failed: DataView’s ArrayBuffer is not fixed length'); // step 4
  25. }
  26. var byteOffset = dataViewByteOffset(view); // step 5
  27. var byteLength = viewRecord['[[CachedBufferByteLength]]']; // step 6
  28. if (byteLength === 'DETACHED') {
  29. throw new $TypeError('Assertion failed: DataView’s ArrayBuffer is detached'); // step 7
  30. }
  31. return byteLength - byteOffset; // step 8
  32. };