Code:

volatile static uchar   myData[8];
uchar   usbFunctionWrite(uchar *data, uchar len)
{
    if(bytesRemaining == 0)
        return 1;               /* end of transfer */
    if(len > bytesRemaining)
        len = bytesRemaining;

   currentAddress += len;
    bytesRemaining -= len;

    // copy the whole content of "data"
    uchar i;
    for ( i=0 ; i<len ; i++ ){
       myData[i] = data[i];
    }

    return bytesRemaining == 0; /* return 1 if this was the last chunk */
}

Code:

uchar   usbFunctionRead(uchar *data, uchar len)
{
    if(len > bytesRemaining)
        len = bytesRemaining;

    uchar i;
    for ( i=0 ; i<len ; i++ ){
       data[i] = myData[i];
    }

    currentAddress += len;
    bytesRemaining -= len;
    return len;
}