src/string/strdict/StrDict.js

// jshint undef:true
// jshint unused:true
/*
Copyright (c) 2020, Nurul Choudhury
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

/**
 * [EMPTY_STR description]
 * @type {String}
 */
const EMPTY_STR = '';

/**
 * String Dictionary implememtation that minimizes the garbage created
 * 
 */
export class StrDict {
	/**
	 * [constructor description]
	 * @param  {int32} maxLen [description]
	 */
	constructor(maxLen) {
		let len = (maxLen || 1997)|0;
		this.dictI = new Array(len);  
		this.dictV = new Array(len);
		this.length = 0;
		for(let i=0; i<len; i++) {
			this.dictI[i] = 0;
			this.dictV[i] = EMPTY_STR;
		}
		
	}
/**
 * [get description]
 * @param  {String} str    [description]
 * @param  {int32} start  [description]
 * @param  {int32} end    [description]
 * @param  {string/opt} valStr If this is set the value is used to populate the hsh table
 * @return {[type]}        [description]
 */
	get(str, start, end, valStr) { // always return a string, if it is not in the dictionary then add it, valStr is only used during expand
		//throw new Error("not implementes");
		
		start = (start || 0) | 0;
		end = (end || str.length) | 0;
		if( start === end) return EMPTY_STR;
		let hx = strHash(str, start,end);
		let dictI = this.dictI, dictV = this.dictV;
		let len = dictI.length;
		let ix = hx % len;
		// while( dictI[ix] ) {
		//   if( dictI[ix] === hx && strEq(str,start,end, dictV[ix]) ) return dictV[ix];
		//   ix = (ix + 1) % len;
		// }
		let s,vx;
		let slen = end-start;
		while( vx = dictI[ix] ) {
			check: {
				if( vx === hx ) {
					let otherStr = dictV[ix];
					let ol = otherStr.length | 0;
					if( slen !== ol) { ix = (ix + 1) % len; continue }
					
					for(let i=start; i<end; i++) {
						if( str[i] !== otherStr[i-start]) break check;
					}
					//if( i === end ) 
					return dictV[ix];
				}
			}
			ix = (ix + 1) % len;
		}
		if( !vx ) {
			dictI[ix] = hx;
			dictV[ix] = valStr !== undefined ? valStr : str.substring(start,end);
			this.length++;
			let rStr = dictV[ix];
			if( this.length > len * 0.8 ) this.expand();
			return rStr;
		} 
		throw new Error("str: "+str.substring(start,end) + " not found");
	}

	getV(str) {
		if(!str) return str;
		let hx = strHash(str, 0,str.length);
		let dictI = this.dictI, dictV = this.dictV;
		let len = dictI.length;
		let ix = hx % len;
		let end = str.length;
		let s,vx;
		while( vx = dictI[ix] ) {
			if( vx === hx && str === dictV[ix] ) return dictV[ix];
			ix = (ix + 1) % len;
		}
		if( !vx ) {
			dictI[ix] = hx;
			dictV[ix] = str;
			this.length++;
			let rStr = dictV[ix];
			if( this.length > len * 0.8 ) this.expand();
			return rStr;
		} 
		throw new Error("str: "+str + " not found");
	}

/**
 * [expand description]
 * @return {[type]} [description]
 */
	expand() {
		let len = this.dictI.length;
		let dictV = this.dictV;
		let newDict = new StrDict(this.dictI.length*2+1);
		for(let i=0; i < len; i++) {
			let str = dictV[i];
			if(str) newDict.getV(str);
		} 
		this.dictI = newDict.dictI;
		this.dictV = newDict.dictV;
		this.length = newDict.length;
	}
/**
 * [values description]
 * @return {[type]} [description]
 */
	values() {
		return this.dictV.filter(x => x);
	}
}