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Diffstat (limited to 'nis/nis_hash.c')
| -rw-r--r-- | nis/nis_hash.c | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/nis/nis_hash.c b/nis/nis_hash.c new file mode 100644 index 0000000000..ddd91515b0 --- /dev/null +++ b/nis/nis_hash.c @@ -0,0 +1,76 @@ +/* Copyright (c) 1997, 1998, 1999, 2004 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Thorsten Kukuk <kukuk@suse.de>, 1997. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <rpcsvc/nis.h> + +/* This is from libc/db/hash/hash_func.c, hash3 is static there */ +/* + * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte + * units. On the first time through the loop we get the "leftover bytes" + * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle + * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If + * this routine is heavily used enough, it's worth the ugly coding. + * + * OZ's original sdbm hash + */ +uint32_t +__nis_hash (const void *keyarg, register size_t len) +{ + register const u_char *key; + register size_t loop; + register uint32_t h; + +#define HASHC h = *key++ + 65599 * h + + h = 0; + key = keyarg; + if (len > 0) + { + loop = (len + 8 - 1) >> 3; + switch (len & (8 - 1)) + { + case 0: + do { + HASHC; + /* FALLTHROUGH */ + case 7: + HASHC; + /* FALLTHROUGH */ + case 6: + HASHC; + /* FALLTHROUGH */ + case 5: + HASHC; + /* FALLTHROUGH */ + case 4: + HASHC; + /* FALLTHROUGH */ + case 3: + HASHC; + /* FALLTHROUGH */ + case 2: + HASHC; + /* FALLTHROUGH */ + case 1: + HASHC; + } while (--loop); + } + } + return h; +} |