@gmod/jbrowse/src/JBrowse/Util/TextIterator.js

JBrowse - client-side genome browser

/**
 * Classes to iterate over records in an array-like structure of bytes (FromBytes).
 */

define([
       ],
       function(
       ) {

var FromBytes = function(args) {
    this.bytes = args.bytes;
    this.offset = args.offset || 0;
    this.length = args.length || this.bytes.length;
    this._recordSeparator = (args.inputRecordSeparator || "\n").charCodeAt(0);
    this.returnPartialRecord = args.returnPartialRecord;
};

FromBytes.prototype.getOffset = function() {
    return this.offset;
};

// get a line of text, properly decoding UTF-8
FromBytes.prototype.getline = function() {
        var bytes = this.bytes;
        var i = this.offset;

        var line = [];
        while( i < this.length ) {
            var c1 = bytes[i], c2, c3;
            if (c1 < 128) {
                line.push( String.fromCharCode(c1) );
                i++;
                if( c1 == this._recordSeparator ) {
                    this.offset = i;
                    return line.join('');
                }
            } else if (c1 > 191 && c1 < 224) {
                c2 = bytes[i + 1];
                line.push( String.fromCharCode(((c1 & 31) << 6) | (c2 & 63)) );
                i += 2;
            } else {
                c2 = bytes[i + 1];
                c3 = bytes[i + 2];
                line.push( String.fromCharCode(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)) );
                i += 3;
            }
        }

        // did not get a full line
        this.offset = i;
        // return our partial line if we are set to return partial records
        return this.returnPartialRecord ? line.join('') : null;
};

return {
    FromBytes: FromBytes
};

});