Decompressing bzip2

[stunaep via Digitalmars-d-learn]

On Monday, 4 April 2016 at 08:26:07 UTC, Thomas Brix Larsen wrote:
> On Sunday, 3 April 2016 at 02:03:29 UTC, stunaep wrote:
>> I am trying to use the bzip2 bindings that are available on 
>> code.dlang.org/packages, but I am having a really hard time 
>> using it due to the pointers. It needs to be an array once 
>> it's decompressed.
>>
>> Here is what I have:
>>>>import std.stdio;
>>>>import bzlib;
>>>>
>>>>void main(string[] args)
>>>>{
>>>>
>>>>    File f = File("./test.bz2");
>>>>    ubyte[] data = new ubyte[f.size];
>>>>   f.rawRead(data);
>>>>    writeln(data);
>>>>
>>>>    ubyte* output;
>>>>    uint avail_out;
>>>>    bz_stream* stream = new bz_stream();
>>>>    stream.avail_out = avail_out;
>>>>    stream.next_out = output;
>>>>
>>>>    int init_error = BZ2_bzDecompressInit(stream, 0, 0);
>>>>    int bzipresult = BZ2_bzDecompress(stream);
>>>>
>>>>    stream.avail_in = cast(uint) data.length;
>>>>    stream.next_in = cast(ubyte*) data;
>>>>
>>>>    bzipresult = BZ2_bzDecompress(stream);
>>>>    int read = stream.total_out_lo32;
>>>>    BZ2_bzDecompressEnd(stream);
>>>>    delete stream;
>>>>    writeln(output);
>>>>}
>>
>> It's not working at all so any help would be very much 
>> appreciated.
>
> You need to allocate the output array:
>
> import std.stdio;
> import bzlib;
>
> void main(string[] args)
> {
>     File f = File("./test.bz2");
>     auto data = new ubyte[](f.size);
>     f.rawRead(data);
>     writeln(data);
>
>     auto output = new ubyte[](4096);
>     scope stream = new bz_stream();
>     stream.avail_out = cast(uint)output.length;
>     stream.next_out = output.ptr;
>
>     int init_error = BZ2_bzDecompressInit(stream, 0, 0);
>     int bzipresult = BZ2_bzDecompress(stream);
>
>     stream.avail_in = cast(uint)data.length;
>     stream.next_in = data.ptr;
>
>     bzipresult = BZ2_bzDecompress(stream);
>     int read = stream.total_out_lo32;
>     BZ2_bzDecompressEnd(stream);
>     writeln(output);
> }

Can you please explain what the scope keyword does and if there 
is any benefit to using
"new byte[](size)" over "new byte[size]" with a 1D array?