iterators

iterFlatVec3Buf.js

/*
const pnts = [-2,0,-2,-2,0,2,2,0,2,2,0,-2];
for( let v of iterFlatVec3Buf( pnts ) ) console.log( v );

instead of

const v = [0,0,0];
for( let i=0; i < pnts.length; i+=3 ){
    v[0] = pnts[i+0];
    v[1] = pnts[i+1];
    v[2] = pnts[i+2];
    console.log( v );
}
*/

function iterFlatVec3Buf( buf ){
    let i        = 0;
    const len    = buf.length;
    const result = { value:[0,0,0], done:false };
    const next   = ()=>{
        if( i >= len ) result.done = true;
        else{
            result.value[ 0 ] = buf[ i++ ];
            result.value[ 1 ] = buf[ i++ ];
            result.value[ 2 ] = buf[ i++ ];
        }
        return result;
    };
    return { [Symbol.iterator](){ return { next }; } };
}

iterFlatVec3Line.js

export default function iterFlatVec3Line( buf, isClosedLoop=false ){
    let i        = 0;
    let j        = 0;
    let jj       = 0;
    const a      = [0,0,0];
    const b      = [0,0,0];
    const cnt    = buf.length / 3;
    const iEnd   = ( !isClosedLoop )? cnt-1 : cnt;
    const result = { value:{ a, b }, done:false };

    const next   = ()=>{
        if( i >= iEnd ) result.done = true;
        else{
            j  = i * 3;
            jj = ( ( i + 1 ) % cnt ) * 3;

            a[ 0 ] = buf[ j+0 ];
            a[ 1 ] = buf[ j+1 ];
            a[ 2 ] = buf[ j+2 ];

            b[ 0 ] = buf[ jj+0 ];
            b[ 1 ] = buf[ jj+1 ];
            b[ 2 ] = buf[ jj+2 ];
            
            i++;
        }
        return result;
    };
    return { [Symbol.iterator](){ return { next }; } };
}