122 lines
3.1 KiB
TypeScript
122 lines
3.1 KiB
TypeScript
/*************************************************************
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*
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* Copyright (c) 2018-2022 The MathJax Consortium
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* @fileoverview Implements bit-fields with extendable field names
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*
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* @author dpvc@mathjax.org (Davide Cervone)
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*/
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export class BitField {
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/**
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* The largest bit available
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*/
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protected static MAXBIT = 1 << 31;
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/**
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* The next bit to be allocated
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*/
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protected static next: number = 1;
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/**
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* The map of names to bit positions
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*/
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protected static names: Map<string, number> = new Map();
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/**
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* The bits that are set
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*/
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protected bits: number = 0;
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/**
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* @param {string} names The names of the bit positions to reserve
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*/
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public static allocate(...names: string[]) {
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for (const name of names) {
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if (this.has(name)) {
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throw new Error('Bit already allocated for ' + name);
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}
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if (this.next === BitField.MAXBIT) {
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throw new Error('Maximum number of bits already allocated');
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}
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this.names.set(name, this.next);
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this.next <<= 1;
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}
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}
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/**
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* @param {string} name The name of the bit to check for being defined
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* @return {boolean} True if the named bit is already allocated
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*/
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public static has(name: string): boolean {
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return this.names.has(name);
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}
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/**
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* @param {string} name The name of the bit position to set
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*/
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public set(name: string) {
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this.bits |= this.getBit(name);
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}
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/**
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* @param {string} name The name of the bit position to clear
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*/
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public clear(name: string) {
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this.bits &= ~this.getBit(name);
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}
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/**
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* @param {string} name The name of the bit to check if set
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* @return {boolean} True if the named bit is set
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*/
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public isSet(name: string): boolean {
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return !!(this.bits & this.getBit(name));
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}
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/**
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* Clear all bits
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*/
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public reset() {
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this.bits = 0;
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}
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/**
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* @param {string} name The name whose bit position is needed (error if not defined)
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* @return {number} The position of the named bit
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*/
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protected getBit(name: string): number {
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const bit = (this.constructor as typeof BitField).names.get(name);
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if (!bit) {
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throw new Error('Unknown bit-field name: ' + name);
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}
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return bit;
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}
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}
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/**
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* @param {string[]} names The name of the positions to allocate initially
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* @return {typeof AbstractBitField} The bit-field class with names allocated
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*/
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export function BitFieldClass(...names: string[]): typeof BitField {
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const Bits = class extends BitField {};
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Bits.allocate(...names);
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return Bits;
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}
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