D memory consumption/runtime speed problem

[Daniel Keep]

sybrandy wrote:
> Hello,
> 
> I've been writing a bit of compression code and I noticed some strange
> behavior that's driving me a bit batty.  I don't know if it's a bug with
> D or something I did.  All I know is I can't figure it out.
> 
> ...
> 
> Am I doing something wrong?  I've tried every trick that I could find by
> reading the documentation.  Btw: The last time I tried this was with the
> latest version of D released at the beginning of the month.

I haven't verified this, but I'd be *deeply* suspicious of encodeNumber.
 I don't usually use array literals but, if I remember correctly, every
time it is called you're performing a heap allocation.  Even worse,
those concatentations might be performing separate allocations, too.

You could eliminate the overhead by using a passed-in buffer design like so:

ubyte[] encodeNumber(in uint count, ref ubyte[4] buffer)
{
    if (count <= ONE_BYTE_VAL)
    {
        buffer[0] = cast(ubyte)(ONE_BYTE_MASK | count);
        return buffer[0..1];
    }
    // ...
}

Then, in the calling function:

{
    ubyte[4] temp;
    foreach( ... )
    {
        appOutput.put(encodeNumber(count, temp));
    }
}

See if that helps.