lz77 compression

function lz77_compress(str, dictlen, bufflen){
    let dl=dictlen, drl=0, bl=bufflen;
    let maxlen, maxa, maxk, output=[];
    while( str.length>drl ){
        maxlen=0;
        maxk=0;
        for(let i=Math.max(drl-dl,0); i<drl; i++){
            let l=i, k=0;
            while( drl+k<str.length-1 && k+1<bl && str[l]==str[drl+k] ){
                l++;
                k++;
            }
            if( l-i>maxlen ){
                maxlen=l-i;
                maxa=i;
                maxk=k;
            }
        }
        if( maxlen!=0 ){
            let ind = maxa-(drl-dl);
            output.push( {
                index: ind, length: maxlen, char: str[drl+maxk]
            } );
        }else{
            output.push( {
                index: 0, length: 0, char: str[drl+maxk]
            } );
        }
        drl += maxlen+1;
    }
    return output;
}