XM code questions

Code (Text):

1. &nbsp;&nbsp;&nbsp;&nbsp;for (I = 0; I < ninst; I++) {
2. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int nsamps;
3. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;QStringList sn;
4.  
5. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (readlelong(f) != 0x107)
6. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return QString("instrument header length for instrument %1 not 0x107 - probably nonstandard XM file").arg(I, 0, 16);
7. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;instrNames.append(readFLString(f, 22));
8. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (readbyte(f) != 0)
9. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return QString("instrument type for instrument %1 not 0 - probably nonstandard XM file").arg(I, 0, 16);
10. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;nsamps = readleword(f);
11. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sn.clear();
12. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (readlelong(f) != 0x28)
13. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return QString("sample header size for instrument %1 not 0x28 - probably nonstandard XM file").arg(I, 0, 16);
14. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;skipnbytes(f, 96+48+48+1+1+1+1+1+1+1+1+1+1+1+1+1+1+2+2); // skip instrument settings
15. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (int j = 0; j < nsamps; j++) {
16. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;quint32 samplen;
17.  
18. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;samplen = readlelong(f);
19. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;skipnbytes(f, 4+4+1+1+1+1+1+1); // skip other sample settings
20. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sn.append(readFLString(f, 22));
21. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;skipnbytes(f, samplen);
22. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}
23. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sampleNames.push_back(sn);
24. &nbsp;&nbsp;&nbsp;&nbsp;}

If f is pointed to where the XM instruments start, the code doesn't get the instrument information correctly; right at the samplen=readlelong(f) it appears to be 20 (decimal) bytes before where it should be. What am I doing wrong? Thanks.

 

Ok, I found two things I was doing wrong and I changed some lines to

Code (Text):

1. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (nsamps > 0) {
2. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (readlelong(f) != 0x28)
3. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return QString("sample header size for instrument %1 not 0x28 - probably nonstandard XM file").arg(I, 0, 16);
4. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;skipnbytes(f, 96+48+48+1+1+1+1+1+1+1+1+1+1+1+1+1+1+2+22); // skip instrument settings
5. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}

However, now I'm winding up with the last instrument before an empty one leaving the file pointer 145 bytes before where it should be; namely, this file on the first instrument without any samples. What am I doing wrong now?

 

Bah, figured it out: MilkyTracker is dumb and writes a header size of 0x1D instead of 0x107 for instruments that have no samples. Thanks anyway.

 

Yes this is for importing; in fact I can release a build with importing in it as soon as I squash one last bug.