while let Some((buf, a, size)) = channel.pending_data.pop_front() {
                let (buf, size_) = Self::data_noqueue(&mut self.write, channel, buf, size);
                pending_size += size_;
                if size_ < buf.len() {
                    channel.pending_data.push_front((buf, a, size_));

            while let Some((buf, a, from)) = channel.pending_data.pop_front() {
                let size = Self::data_noqueue(&mut self.write, channel, &buf, from);
                pending_size += size;
                if from + size < buf.len() {
                    channel.pending_data.push_front((buf, a, from + size));

    /// Push the largest amount of `&buf0[from..]` that can fit into
    /// the window, dividing it into packets if it is too large, and
    /// return the length that was written.

        buf0: CryptoVec,

        buf0: &[u8],

    ) -> (CryptoVec, usize) {

    ) -> usize {

        (buf0, from + buf_len)

        buf_len

            let (buf0, buf_len) = Self::data_noqueue(&mut self.write, channel, buf0, 0);

            let buf_len = Self::data_noqueue(&mut self.write, channel, &buf0, 0);