BaseValue.js

  1. const bitmask = bitsNumber => -1 >>> (32 - bitsNumber);
  3. const check = (byteSize, value, isSigned) => {
  4. 	let lowerBound;
  5. 	let upperBound;
  6. 	if (8 === byteSize) {
  7. 		if ('bigint' !== typeof value)
  8. 			throw new TypeError(`"value" (${value}) has invalid type, expected BigInt`);
  10. 		lowerBound = isSigned ? -0x80000000_00000000n : 0n;
  11. 		upperBound = isSigned ? 0x7FFFFFFF_FFFFFFFFn : 0xFFFFFFFF_FFFFFFFFn;
  12. 	} else {
  13. 		if (!Number.isInteger(value))
  14. 			throw new RangeError(`"value" (${value}) is not an integer`);
  16. 		// note: all expressions are tricky, they're used due to JS dumbness re 1<<32 == 0 and 1<<31 = min signed int
  17. 		lowerBound = isSigned ? -bitmask((8 * byteSize) - 1) - 1 : 0;
  18. 		upperBound = isSigned ? bitmask((8 * byteSize) - 1) : bitmask(8 * byteSize);
  19. 	}
  21. 	if (value < lowerBound || value > upperBound)
  22. 		throw RangeError(`"value" (${value}) is outside of valid ${8 * byteSize}-bit range`);
  24. 	return value;
  25. };
  27. const isNonNegative = value => {
  28. 	if ('bigint' === typeof value)
  29. 		return 0n <= value;
  31. 	return 0 <= value;
  32. };
  34. /**
  35.  * Represents a base integer.
  36.  */
  37. export default class BaseValue {
  38. 	/**
  39. 	 * Creates a base value.
  40. 	 * @param {number} size Size of the integer.
  41. 	 * @param {number|bigint} value Value.
  42. 	 * @param {boolean} isSigned \c true if the value should be treated as signed.
  43. 	 */
  44. 	constructor(size, value, isSigned = false) {
  45. 		/**
  46. 		 * Size of the integer.
  47. 		 * @type number
  48. 		 */
  49. 		this.size = size;
  51. 		/**
  52. 		 * \c true if the value should be treated as signed.
  53. 		 * @type boolean
  54. 		 */
  55. 		this.isSigned = isSigned;
  57. 		/**
  58. 		 * Value.
  59. 		 * @type number|bigint
  60. 		 */
  61. 		this.value = check(size, value, isSigned);
  62. 	}
  64. 	/**
  65. 	 * Converts base value to string.
  66. 	 * @returns {string} String representation.
  67. 	 */
  68. 	toString() {
  69. 		let unsignedValue;
  70. 		if (!this.isSigned || isNonNegative(this.value)) {
  71. 			unsignedValue = this.value;
  72. 		} else {
  73. 			const upperBoundPlusOne = (8 === this.size ? 0x1_00000000_00000000n : BigInt(bitmask(this.size * 8) + 1));
  74. 			unsignedValue = BigInt(this.value) + upperBoundPlusOne;
  75. 		}
  77. 		return `0x${unsignedValue.toString(16).toUpperCase().padStart(this.size * 2, '0')}`;
  78. 	}
  79. }