Success! I finally managed to get a copy of the buffer as I wanted by using
a custom filter.
I created a custom filter called DataFilter, that would simply copy the
information of the buffer into a file (like a FileSink) as follows:
//This is just the "UselessFilter" from the wiki, slightly modified to act
as some kind of "manual" FileSink
class DataFilter : public Filter
{
public:
DataFilter(BufferedTransformation* attachment = NULL) : Filter(
attachment) {};
size_t Put2(const byte* inString, size_t length, int messageEnd, bool
blocking)
{
of.write((char*)inString, length); //<- inString is the buffer I
needed
return AttachedTransformation()->Put2(inString, length, messageEnd,
blocking );
}
bool IsolatedFlush(bool hardFlush, bool blocking)
{
return false;
}
};
Just to check if I could get a copy of the file I was decompressing, in
which case it would be a success. In my decompressing function, I created
an instance of this DataFilter, and attached it to my chain of filters.
DataFilter dat;
//...
source.Attach(new Redirector(filter));
filter.Attach(new Redirector(meter));
meter.Attach(new Redirector(dat));
dat.Attach(new Redirector(sink)); //<- Also I dont need this sink anymore,
but I will do it only as a test
I opened the file stream beforehand, of course, with a file called
"copy.mp4" in output, binary mode, and then closed it after the pump loop.
After running the program, I successfully got a file named copy.mp4 that I
can play using VLC, as well as the result.mp4 file resultant from the pump.
Thank you for your time and help. Very much appreciated.
El martes, 2 de mayo de 2017, 18:30:33 (UTC+2), Aarón CdC escribió:
>
> I found examples on the wiki about how to use crypto++ to compress and
> decompress files using Crypto++'s Gzip algorithm. But all examples I found
> process the whole file at once. Imagine I need to compress a 1GB+ file.
> Maybe now we have computers with large amounts of memory, but this is
> completely out of the question.
>
> What I'm trying to do is to process a file using buffers to load small
> chunks of data trough a File Source. This is what I got so far:
>
> ofstream output;
>
> //Compression
> output.open("TEST/out.a", fstream::binary);
> int got,ncomp,diff = 0;
> char* ib = new char [BUFSIZE];
> char* ob = new char [BUFSIZE];
>
> for(int x = 0; x < BUFSIZE; x++)
> {
> ib[x] |= 0x0;
> ob[x] |= 0x0;
> }
>
>
>
> FileSource fsr("TEST/a.jpg", false, new Gzip(new ArraySink((byte*)
> ob, BUFSIZE)));
> while(!fsr.SourceExhausted())
> {
> got = fsr.Pump(BUFSIZE);
> fsr.Flush(false);
> cout << "Pumped " << got << " bytes" << endl;
> if(got == 0)
> break;
> output.write(ob, got);
> }
>
> output.close();
>
> //Decompression
>
> for(int x = 0; x < BUFSIZE; x++)
> {
> ib[x] |= 0x0;
> ob[x] |= 0x0;
> }
>
> cout << "Decript" << endl;
> output.open("TEST/test.jpg", fstream::binary);
>
> FileSource fir("TEST/out.a", false, new Gunzip(new ArraySink((byte
> *)ib, BUFSIZE)));
> while(!fir.SourceExhausted())
> {
> got = fir.Pump(BUFSIZE);
> fir.Flush(false);
> cout << "Pumped " << got << " bytes" << endl;
> if(got == 0)
> break;
> output.write(ib, got);
> }
>
> output.close();
> delete[] ib, ob;
> cout << "Done" << endl;
>
> I have several problems with this code. First of all, the file is not
> processed entirely. Instead, one portion is processed, and then it repeats
> trough the whole file. This is obviously not what I want to do, I need to
> process the whole file, but in small chunks. Also, SourceExhausted() doesnt
> return true once it reaches the end of the file (thus why there is a break
> in this code when there shouldn't be needed).
>
> I know there are ways to do this directly without the need of a buffer,
> but I need to pass it trough memory because I need to implement this
> somewhere else, and I need all this data to be processed first in memory,
> so I cant use a FileSink.
>
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