summaryrefslogtreecommitdiff
path: root/delta.h
AgeCommit message (Collapse)AuthorFilesLines
2009-06-18Fix big left-shifts of unsigned charLibravatar Linus Torvalds1-3/+2
Shifting 'unsigned char' or 'unsigned short' left can result in sign extension errors, since the C integer promotion rules means that the unsigned char/short will get implicitly promoted to a signed 'int' due to the shift (or due to other operations). This normally doesn't matter, but if you shift things up sufficiently, it will now set the sign bit in 'int', and a subsequent cast to a bigger type (eg 'long' or 'unsigned long') will now sign-extend the value despite the original expression being unsigned. One example of this would be something like unsigned long size; unsigned char c; size += c << 24; where despite all the variables being unsigned, 'c << 24' ends up being a signed entity, and will get sign-extended when then doing the addition in an 'unsigned long' type. Since git uses 'unsigned char' pointers extensively, we actually have this bug in a couple of places. I may have missed some, but this is the result of looking at git grep '[^0-9 ][ ]*<<[ ][a-z]' -- '*.c' '*.h' git grep '<<[ ]*24' which catches at least the common byte cases (shifting variables by a variable amount, and shifting by 24 bits). I also grepped for just 'unsigned char' variables in general, and converted the ones that most obviously ended up getting implicitly cast immediately anyway (eg hash_name(), encode_85()). In addition to just avoiding 'unsigned char', this patch also tries to use a common idiom for the delta header size thing. We had three different variations on it: "& 0x7fUL" in one place (getting the sign extension right), and "& ~0x80" and "& 0x7f" in two other places (not getting it right). Apart from making them all just avoid using "unsigned char" at all, I also unified them to then use a simple "& 0x7f". I considered making a sparse extension which warns about doing implicit casts from unsigned types to signed types, but it gets rather complex very quickly, so this is just a hack. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2007-07-12Support fetching the memory usage of a delta indexLibravatar Brian Downing1-0/+7
Delta indices, at least on 64-bit platforms, tend to be larger than the actual uncompressed data. As such, keeping track of this storage is important if you want to successfully limit the memory size of your pack window. Squirrel away the total allocation size inside the delta_index struct, and add an accessor "sizeof_delta_index" to access it. Signed-off-by: Brian Downing <bdowning@lavos.net> Acked-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2006-05-15pack-object: slightly more efficientLibravatar Nicolas Pitre1-0/+2
Avoid creating a delta index for objects with maximum depth since they are not going to be used as delta base anyway. This also reduce peak memory usage slightly as the current object's delta index is not useful until the next object in the loop is considered for deltification. This saves a bit more than 1% on CPU usage. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-04-24split the diff-delta interfaceLibravatar Nicolas Pitre1-7/+68
This patch splits the diff-delta interface into index creation and delta generation. A wrapper is provided to preserve the diff-delta() call. This will allow for an optimization in pack-objects.c where the source object could be fixed and a full window of objects tentatively tried against that same source object without recomputing the source index each time. This patch only restructure things, plus a couple cleanups for good measure. There is no performance change yet. Signed-off-by: Nicolas Pitre <nico@cam.org>
2006-04-07check patch_delta bounds more carefullyLibravatar Nicolas Pitre1-2/+3
Let's avoid going south with invalid delta data. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-02-10delta micro optimizationLibravatar Nicolas Pitre1-5/+5
My kernel work habit made me look at the generated assembly for the delta code, and one obvious albeit small improvement is this patch. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2005-06-29[PATCH] assorted delta code cleanupLibravatar Nicolas Pitre1-0/+22
This is a wrap-up patch including all the cleanups I've done to the delta code and its usage. The most important change is the factorization of the delta header handling code. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-27[PATCH] Remove "delta" object representation.Libravatar Junio C Hamano1-9/+0
Packed delta files created by git-pack-objects seems to be the way to go, and existing "delta" object handling code has exposed the object representation details to too many places. Remove it while we refactor code to come up with a proper interface in sha1_file.c. Signed-off-by: Junio C Hamano <junkio@cox.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-25Add a "max_size" parameter to diff_delta()Libravatar Linus Torvalds1-1/+1
Anything that generates a delta to see if two objects are close usually isn't interested in the delta ends up being bigger than some specified size, and this allows us to stop delta generation early when that happens.
2005-06-08[PATCH] Anal retentive 'const unsigned char *sha1'Libravatar Jason McMullan1-1/+1
Make 'sha1' parameters const where possible Signed-off-by: Jason McMullan <jason.mcmullan@timesys.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-20[PATCH] delta checkLibravatar Nicolas Pitre1-0/+15
This adds knowledge of delta objects to fsck-cache and various object parsing code. A new switch to git-fsck-cache is provided to display the maximum delta depth found in a repository. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-19[PATCH] Deltification library work by Nicolas Pitre.Libravatar Nicolas Pitre1-0/+6
This patch adds the basic library functions to create and replay delta information. Also included is a test-delta utility to validate the code. diff-delta was based on LibXDiff written by Davide Libenzi Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>