r.columnNames = columns
		}
	}

	r.bufferPool.New = func() interface{} {
		return make([]byte, csvSplitSize+1024)
	}

	// Return first block
	next, nextErr := r.nextSplit(csvSplitSize, r.bufferPool.Get().([]byte))
	// Check if first block is valid.
	if !utf8.Valid(next) {
		return errInvalidTextEncodingError()
	}

	// Create queue
	r.queue = make(chan *queueItem, runtime.GOMAXPROCS(0))

	need := len(buf)         // number of bytes requested by caller
	hdr := r.opts.HeaderSize // remaining header bytes
	var tokens int           // number of tokens to request

	if hdr > 0 { // available tokens go towards header first
		if hdr < b { // all of header can be accommodated
			r.opts.HeaderSize = 0
			need = int(math.Min(float64(b-hdr), float64(need))) // use remaining tokens towards payload
			tokens = need + hdr