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2015-02-18Merge branch 'jk/pack-bitmap'Libravatar Junio C Hamano1-1/+2
The pack bitmap support did not build with older versions of GCC. * jk/pack-bitmap: ewah: fix building with gcc < 3.4.0
2015-02-04ewah: fix building with gcc < 3.4.0Libravatar Tom G. Christensen1-1/+2
The __builtin_ctzll function was added in gcc 3.4.0. This extends the check for gcc so that use of __builtin_ctzll is only enabled if gcc >= 3.4.0. Signed-off-by: Tom G. Christensen <tgc@statsbiblioteket.dk> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-29ewah: delete unused ewah_read_mmap_native declarationLibravatar Nguyễn Thái Ngọc Duy1-1/+0
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-29ewah: fix constness of ewah_read_mmapLibravatar Nguyễn Thái Ngọc Duy1-1/+1
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-30ewah: compressed bitmap implementationLibravatar Vicent Marti1-0/+233
EWAH is a word-aligned compressed variant of a bitset (i.e. a data structure that acts as a 0-indexed boolean array for many entries). It uses a 64-bit run-length encoding (RLE) compression scheme, trading some compression for better processing speed. The goal of this word-aligned implementation is not to achieve the best compression, but rather to improve query processing time. As it stands right now, this EWAH implementation will always be more efficient storage-wise than its uncompressed alternative. EWAH arrays will be used as the on-disk format to store reachability bitmaps for all objects in a repository while keeping reasonable sizes, in the same way that JGit does. This EWAH implementation is a mostly straightforward port of the original `javaewah` library that JGit currently uses. The library is self-contained and has been embedded whole (4 files) inside the `ewah` folder to ease redistribution. The library is re-licensed under the GPLv2 with the permission of Daniel Lemire, the original author. The source code for the C version can be found on GitHub: https://github.com/vmg/libewok The original Java implementation can also be found on GitHub: https://github.com/lemire/javaewah [jc: stripped debug-only code per Peff's $gmane/239768] Signed-off-by: Vicent Marti <tanoku@gmail.com> Signed-off-by: Jeff King <peff@peff.net> Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>