cafebabe - Developer IT

Why is the first four bytes of Java class file format is CAFEBABE?

- by zengr

Why is the first four bytes of Java class file format is CAFEBABE? Who named it? Your views/guesses? Source: IBM Java Programing Dynamics

Missing files on branch after cvs2svn import

A colleague has imported a CVS repository into a pre-existing SVN repository using a cvs2svn dumpfile (like "svnadmin load --parent-dir /path < dumpfile") , which I originally created from the CVS repo. Now that I'm trying to checkout and build from SVN, I've noticed that some files seem to be missing in the SVN checkout that were present when I checked out the same branch from CVS, although the majority are present. They are mostly but not exclusively binary files (jars and gifs etc.) and I think (though I haven't checked exhaustively) that they are also files that have not been modified on the branch that I'm trying to check out. I should also point out that they don't show up using cvsweb (I would provide a link to the cvsweb documentation but I have no way of knowing its version etc), although they do appear doing a standard checkout of the branch. If anyone has any idea what's wrong here, or where to start looking to address this, I'd be very grateful! New to SVN so not sure if this is normal! Also, I know I could fairly easily "fix" it by copying over the files but I'd ideally like to keep their revision history so a more complete solution would be preferable. Thanks!

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Java obfuscators

- by jbu

I'm looking for a good Java obfuscator. I've done initial research into the following Java obfuscators: proguard, yguard, retroguard, dasho, allatori, jshrink, smokescreen, jobfuscate, marvin, jbco, jode, javaguard, jarg, joga, cafebabe, donquixote, mwobfu, bbmug, zelix klassmaster, sandmark, jcloak, thicket, blufuscator, and java code protector. I tried proguard and it has a really nice GUI, seems really stable, and seems to be the most popular, but it seemed to not like some enumeration on a referenced jar file (not within the code I was trying to obfuscate) which was weird. Yguard seems to require some interaction with ant, which I didn't know too much about. What is a good java obfuscator? It doesn't need to be free, it just needs to work well and be easy to use.

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Why does mmap() fail with ENOMEM on a 1TB sparse file?

- by metadaddy

I've been working with large sparse files on openSUSE 11.2 x86_64. When I try to mmap() a 1TB sparse file, it fails with ENOMEM. I would have thought that the 64 bit address space would be adequate to map in a terabyte, but it seems not. Experimenting further, a 1GB file works fine, but a 2GB file (and anything bigger) fails. I'm guessing there might be a setting somewhere to tweak, but an extensive search turns up nothing. Here's some sample code that shows the problem - any clues? #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char *argv[]) { char * filename = argv[1]; int fd; off_t size = 1UL << 40; // 30 == 1GB, 40 == 1TB fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666); ftruncate(fd, size); printf("Created %ld byte sparse file\n", size); char * buffer = (char *)mmap(NULL, (size_t)size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if ( buffer == MAP_FAILED ) { perror("mmap"); exit(1); } printf("Done mmap - returned 0x0%lx\n", (unsigned long)buffer); strcpy( buffer, "cafebabe" ); printf("Wrote to start\n"); strcpy( buffer + (size - 9), "deadbeef" ); printf("Wrote to end\n"); if ( munmap(buffer, (size_t)size) < 0 ) { perror("munmap"); exit(1); } close(fd); return 0; }

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