ewah: compressed bitmap implementation
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>
diff --git a/Makefile b/Makefile
index 48ff0bd..64a1ed7 100644
--- a/Makefile
+++ b/Makefile
@@ -667,6 +667,8 @@
LIB_H += diffcore.h
LIB_H += dir.h
LIB_H += exec_cmd.h
+LIB_H += ewah/ewok.h
+LIB_H += ewah/ewok_rlw.h
LIB_H += fetch-pack.h
LIB_H += fmt-merge-msg.h
LIB_H += fsck.h
@@ -800,6 +802,10 @@
LIB_OBJS += editor.o
LIB_OBJS += entry.o
LIB_OBJS += environment.o
+LIB_OBJS += ewah/bitmap.o
+LIB_OBJS += ewah/ewah_bitmap.o
+LIB_OBJS += ewah/ewah_io.o
+LIB_OBJS += ewah/ewah_rlw.o
LIB_OBJS += exec_cmd.o
LIB_OBJS += fetch-pack.o
LIB_OBJS += fsck.o
@@ -2474,8 +2480,9 @@
$(RM) $(addsuffix *.gcno,$(addprefix $(PROFILE_DIR)/, $(object_dirs)))
clean: profile-clean coverage-clean
- $(RM) *.o *.res block-sha1/*.o ppc/*.o compat/*.o compat/*/*.o xdiff/*.o vcs-svn/*.o \
- builtin/*.o $(LIB_FILE) $(XDIFF_LIB) $(VCSSVN_LIB)
+ $(RM) *.o *.res block-sha1/*.o ppc/*.o compat/*.o compat/*/*.o
+ $(RM) xdiff/*.o vcs-svn/*.o ewah/*.o builtin/*.o
+ $(RM) $(LIB_FILE) $(XDIFF_LIB) $(VCSSVN_LIB)
$(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) git$X
$(RM) $(TEST_PROGRAMS) $(NO_INSTALL)
$(RM) -r bin-wrappers $(dep_dirs)
