fill(buffers, totalLength) {
        this._size = Math.min(this.capacity, totalLength);
        let i = 0, j = 0, targetOffset = 0, sourceOffset = 0, totalCopiedNum = 0;
        while (totalCopiedNum < this._size) {
            const source = buffers[i];
            const target = this.buffers[j];
            const copiedNum = source.copy(target, targetOffset, sourceOffset);
            totalCopiedNum += copiedNum;
            sourceOffset += copiedNum;
            targetOffset += copiedNum;
            if (sourceOffset === source.length) {
                i++;
                sourceOffset = 0;
            }
            if (targetOffset === target.length) {
                j++;
                targetOffset = 0;
            }
        }
        // clear copied from source buffers
        buffers.splice(0, i);
        if (buffers.length > 0) {
            buffers[0] = buffers[0].slice(sourceOffset);
        }
    }
Fill the internal buffers with data in the input buffers serially
with respect to the total length and the total capacity of the internal buffers.
Data copied will be shift out of the input buffers.

@param buffers - Input buffers containing the data to be filled in the pooled buffer
@param totalLength - Total length of the data to be filled in.