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| author | Jabier Arraiza Cenoz <jabier.arraiza@marker.es> | 2015-04-09 18:54:52 +0000 |
|---|---|---|
| committer | Jabiertxof <jtx@jtx.marker.es> | 2015-04-09 18:54:52 +0000 |
| commit | 42569eeea6a78406c723a0c2139a6adbb5f9c9cc (patch) | |
| tree | 480aff49241ce0c5b30837bf8bd6137e0a9f2789 /src/trace/potrace/decompose.cpp | |
| parent | update to trunk (diff) | |
| parent | Cleaned up cmake files to build successfully on Linux. (diff) | |
| download | inkscape-42569eeea6a78406c723a0c2139a6adbb5f9c9cc.tar.gz inkscape-42569eeea6a78406c723a0c2139a6adbb5f9c9cc.zip | |
update to trunk
(bzr r12588.1.40)
Diffstat (limited to 'src/trace/potrace/decompose.cpp')
| -rw-r--r-- | src/trace/potrace/decompose.cpp | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/src/trace/potrace/decompose.cpp b/src/trace/potrace/decompose.cpp index 6c27a7ebf..7628b202d 100644 --- a/src/trace/potrace/decompose.cpp +++ b/src/trace/potrace/decompose.cpp @@ -1,4 +1,4 @@ -/* Copyright (C) 2001-2011 Peter Selinger. +/* Copyright (C) 2001-2015 Peter Selinger. This file is part of Potrace. It is free software and it is covered by the GNU General Public License. See the file COPYING for details. */ @@ -15,6 +15,33 @@ #include "decompose.h" #include "progress.h" +/* ---------------------------------------------------------------------- */ +/* deterministically and efficiently hash (x,y) into a pseudo-random bit */ + +static inline int detrand(int x, int y) { + unsigned int z; + static const unsigned char t[256] = { + /* non-linear sequence: constant term of inverse in GF(8), + mod x^8+x^4+x^3+x+1 */ + 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, + 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, + 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, + 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 1, + 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, + 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, + 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, + 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, + 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, + 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 1, + 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, + }; + + /* 0x04b3e375 and 0x05a8ef93 are chosen to contain every possible + 5-bit sequence */ + z = ((0x04b3e375 * x) ^ y) * 0x05a8ef93; + z = t[z & 0xff] ^ t[(z>>8) & 0xff] ^ t[(z>>16) & 0xff] ^ t[(z>>24) & 0xff]; + return z; +} /* ---------------------------------------------------------------------- */ /* auxiliary bitmap manipulations */ |