search for: get_32

...yslinux.git/blob/0d82b71304d596d80f3c4520f9dcf90048ca50b7:/lzo/prepcore.c it seems that this change in line 374 could yield correct checksums: unsigned int ptr; - for (ptr = 64; ptr < offset; ptr += 4) + for (ptr = start+64; ptr < offset; ptr += 4) csum += get_32((uint32_t *)(infile+ptr)); A test whether it works would be to produce isolinux.bin, read the 4 checksum bytes from it at offset 20, put isolinux.bin into an ISO with mkisofs option -boot-info-table, and check whether the 4 bytes at offset 20 are still the same. (If you use mkisofs or genisoimage...

...6d80f3c4520f9dcf90048ca50b7:/lzo/prepcore.c > it seems that this change in line 374 could yield correct checksums: > > unsigned int ptr; > - for (ptr = 64; ptr < offset; ptr += 4) > + for (ptr = start+64; ptr < offset; ptr += 4) > csum += get_32((uint32_t *)(infile+ptr)); > > > A test whether it works would be to produce isolinux.bin, read the 4 checksum > bytes from it at offset 20, put isolinux.bin into an ISO with mkisofs option > -boot-info-table, and check whether the 4 bytes at offset 20 are still the > same. >...

...+331,7 @@ int main(int argc, char *argv[]) unsigned int ptr; outfile_len = ((offset - start + out_len + 2047) & ~2047) - (offset - start); - for (ptr = 64; ptr < offset; ptr += 4) + for (ptr = start + 64; ptr < offset; ptr += 4) csum += get_32((uint32_t *) (infile + ptr)); for (ptr = 0; ptr < outfile_len; ptr += 4) csum += get_32((uint32_t *) (out + ptr)); --

> Hi, > > Ady wrote: > > During May 2009, a commit by Peter deleted the checksumiso.pl file. The > > commit is: > > core: LZO compress the PM part of the core > > repo.or.cz/syslinux.git/commit/0d82b71304d596d80f3c4520f9dcf90048ca50b7 > > And so, since version 4.00, the 'code/checksumiso.pl' file is no longer > > included. > > How is

...ore.c +++ b/lzo/prepcore.c @@ -331,7 +331,7 @@ int main(int argc, char *argv[]) unsigned int ptr; outfile_len = ((offset - start + out_len + 2047) & ~2047) - (offset - start); - for (ptr = 64; ptr < offset; ptr += 4) + for (ptr = start + 64; ptr < offset; ptr += 4) csum += get_32((uint32_t *) (infile + ptr)); for (ptr = 0; ptr < outfile_len; ptr += 4) csum += get_32((uint32_t *) (out + ptr)); --

H, Ady wrote: > A_ The default checksum included in the tested isolinux.bin (offset 20, > 4-bytes-long) is the "correct" one (as oppose to the current situation, > since version 4.00). That's good news. > F_ In the tested isolinux.bin file, there are two additional bytes that > I found to be changed/affected by some ISO-building tools (e.g. > mkisofs), at

...in. But those bytes would also be part of prepcore's checksum computation. So the checksum should match the one from libisofs. I further tried to provoke the initial checksum of isolinux.bin by spoiling the byte order of the 4-byte unsigned integers which get added. But prepcode's function get_32() in both variants yields on amd64 the same integer values as libisofs sees. Willfully reverting byte order of the integers does not yield the initial checksum 0x09e675b8. Another suspect would be a difference between checksum computation and effective file writing. But the code looks good in that...