int read_packet(void *opaque, uint8_t *buf, int buf_size) {

    BufferContext *pBufferCtx = (BufferContext*) opaque;

    void* inputBufferAddress = pBufferCtx->pBufferAddress;
    int inputBufferSize = pBufferCtx->iBufferSize;
    int inputBytesRead = pBufferCtx->iBytesRead;    //bytes already read

    int outputBytesRead = 0;                        //bytes read this f'n call

    //bufferPointer pBufferCtx = (bufferPointer)h->priv_data; //pretending priv_data is a buffer

    REFERENCE_VAR(buf); //what does this do? Left over from original read_buffer f'n

    //the rest of this is a mess. Sorry :(
    if (buf_size >= inputBufferSize) {
        if (inputBytesRead > 0) {
            memcpy(buf, inputBufferAddress + inputBytesRead,inputBufferSize - inputBytesRead);
            outputBytesRead = inputBufferSize - inputBytesRead;
        } else { // inputBytesRead == 0
            memcpy(buf, inputBufferAddress, inputBufferSize);
            outputBytesRead = inputBufferSize;
        }

    } else { // buf_min_size < inputBufferSize
        if (inputBytesRead > 0) {
            if (buf_size >= inputBufferSize - inputBytesRead) {
                memcpy(buf, inputBufferAddress + inputBytesRead, inputBufferSize - inputBytesRead);
                outputBytesRead = inputBufferSize - inputBytesRead;//
            }

            else { // buf_min_size < inputBufferSize - inputBytesRead
                memcpy(buf, inputBufferAddress + inputBytesRead, buf_size );
                outputBytesRead = buf_size;
            }
        } else {

            memcpy(buf, inputBufferAddress, inputBufferSize);
            outputBytesRead = buf_size;

        }

    }
    pBufferCtx->iBytesRead += outputBytesRead;
    if(pBufferCtx->iBytesRead > pBufferCtx->iBufferSize)
        exit(-1);
    return outputBytesRead;
}