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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