102 lines
3.0 KiB
JavaScript
102 lines
3.0 KiB
JavaScript
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/*
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* Qap is a quick parser/matcher for string or buffer patterns.
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* It is optimized for using with pattern strings/buffers <= 255 bytes.
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* Better results are achieved with sparse and long patterns in the data to be parsed.
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* It is an implementation of QuickSearch algorithm :
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* http://www-igm.univ-mlv.fr/~lecroq/string/node19.html#SECTION00190.
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*
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* Copyright(c) 2015 Guglielmo Ferri <44gatti@gmail.com>
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* MIT Licensed
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*/
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exports.version = require( '../package' ).version;
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exports.Qap = ( function () {
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var isArray = Array.isArray
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, isBuffer = Buffer.isBuffer
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// shifting table
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, lookupTable = function ( p ) {
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var m = p.length
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, t = m > 255 ? [] : new Buffer( 256 )
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, i = 255
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, j = 0
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;
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for ( ; i >= 0 ; t[ i ] = 0, i-- );
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for ( ; m > 0; t[ p[ j++ ] ] = m-- );
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return t;
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}
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, convert = function ( data ) {
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if ( ! isBuffer( data ) ) {
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// obviously, string conversion is slow
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if ( typeof data === 'string' ) return new Buffer( data );
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else throw new TypeError( 'the argument type should be Buffer or String' );
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}
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return data;
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}
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, set = function ( pattern ) {
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var me = this
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;
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me.p = convert( pattern );
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me.plkb = lookupTable( me.p );
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return me.p;
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}
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// Quick Parser
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, Qap = function ( pattern ) {
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var me = this
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, is = me instanceof Qap
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;
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if ( ! is ) return new Qap( pattern );
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set.call( me, pattern );
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}
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, qproto = Qap.prototype
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;
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qproto.set = set;
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qproto.parse = function ( data, start, rlimit, array ) {
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var me = this
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, d = convert( data )
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, plkb = me.plkb
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, p = me.p
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, m = p.length
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, n = d.length
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, ixs = isArray( array ) ? array : []
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, j = start || 0
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, ok = 1
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, z = 0
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, x = p[ 0 ]
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, pos = 0 + j
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, y = d[ pos ]
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, i = m + j
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, c = d[ i ]
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, offset = n - m
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, l = rlimit || Infinity
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;
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for ( ; j <= offset;
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i = j + m,
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c = d[ i ],
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z = 0,
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ok = 1,
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pos = j,
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x = p[ 0 ],
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y = d[ pos ] ) {
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for ( ; z < m ;
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z++,
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pos++,
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x = p[ z ],
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y = d[ pos ] ) {
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if ( x === y ) continue;
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else {
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ok = 0;
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break;
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}
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}
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// if ( ok && ( ixs.push( j, pos ) >= l ) ) {
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if ( ok && ( ixs.push( j ) >= l ) ) break;
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j += plkb[ c ] || m + 1;
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}
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return ixs;
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};
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return Qap;
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} )();
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