On 09/27/2012 08:55 PM, Jim Meyering wrote: >> And having said that, here is that function. > ... >> Subject: [PATCH] Added hash-pjw-s. > ... > Hi Nikos, > Thanks for working on this.
Updated. regards, Nikos
>From 14a0d1ac40de4fcd16dff605a0fdf86a8227520f Mon Sep 17 00:00:00 2001 From: Nikos Mavrogiannopoulos <n...@gnutls.org> Date: Thu, 27 Sep 2012 08:42:07 +0200 Subject: [PATCH] Added hash-pjw-s. --- lib/hash-pjw-s.c | 42 ++++++++++++++++++++++++++++++++++++++++++ lib/hash-pjw-s.h | 24 ++++++++++++++++++++++++ modules/hash-pjw-s | 22 ++++++++++++++++++++++ 3 files changed, 88 insertions(+) create mode 100644 lib/hash-pjw-s.c create mode 100644 lib/hash-pjw-s.h create mode 100644 modules/hash-pjw-s diff --git a/lib/hash-pjw-s.c b/lib/hash-pjw-s.c new file mode 100644 index 0000000..3765e35 --- /dev/null +++ b/lib/hash-pjw-s.c @@ -0,0 +1,42 @@ +/* hash-pjw-s.c -- compute a hash value from a provided buffer. + + Copyright (C) 2012 Free Software Foundation, Inc. + + This program 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 3 of the License, or + (at your option) any later version. + + This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */ + +#include <config.h> + +#include "hash-pjw-s.h" + +#include <limits.h> + +#define SIZE_BITS (sizeof (size_t) * CHAR_BIT) + +/* Return a hash of the N bytes of X using the method described by + Bruno Haible in http://www.haible.de/bruno/hashfunc.html. + Note that while many hash functions reduce their result via modulo + to a 0..table_size-1 range, this function does not do that. */ + +size_t +hash_pjw_s (const void *x, size_t n) +{ + const unsigned char *s = x; + size_t h = 0; + unsigned i; + + for (i = 0; i < n; i++) + h = s[i] + ((h << 9) | (h >> (SIZE_BITS - 9))); + + return h; +} diff --git a/lib/hash-pjw-s.h b/lib/hash-pjw-s.h new file mode 100644 index 0000000..cf61f8d --- /dev/null +++ b/lib/hash-pjw-s.h @@ -0,0 +1,24 @@ +/* hash-pjw-s.h -- declaration for a simple hash function + Copyright (C) 2012 Free Software Foundation, Inc. + + This program 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 3 of the License, or + (at your option) any later version. + + This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */ + +#include <stddef.h> + +/* Compute a hash code for a buffer starting at X and of size N, + and return the hash code. Note that unlike hash_pjw(), it does not + return it modulo a table size. + The result is platform dependent: it depends on the size of the 'size_t' + type and on the signedness of the 'char' type. */ +extern size_t hash_pjw_s (const void *x, size_t n) _GL_ATTRIBUTE_PURE; diff --git a/modules/hash-pjw-s b/modules/hash-pjw-s new file mode 100644 index 0000000..d8735ca --- /dev/null +++ b/modules/hash-pjw-s @@ -0,0 +1,22 @@ +Description: +Compute a hash value for a buffer of known size. + +Files: +lib/hash-pjw-s.h +lib/hash-pjw-s.c + +Depends-on: + +configure.ac: + +Makefile.am: +lib_SOURCES += hash-pjw-s.h hash-pjw-s.c + +Include: +"hash-pjw-s.h" + +License: +LGPLv2+ + +Maintainer: +Jim Meyering -- 1.7.10.4
