X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/mLib/blobdiff_plain/8fe3c82b561e58c894d9b8392ef4003158f44dd8..bb1cbbe82a40a9cffb8d143bed2e3aa245595450:/unihash.h

diff --git a/unihash.h b/unihash.h
index 5fb5741..22cecf9 100644
--- a/unihash.h
+++ b/unihash.h
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: unihash.h,v 1.1 2003/10/12 14:43:24 mdw Exp $
+ * $Id: unihash.h,v 1.4 2004/04/08 01:36:13 mdw Exp $
  *
  * Simple and efficient universal hashing for hashtables
  *
  * (c) 2003 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of the mLib utilities library.
  *
@@ -15,26 +15,18 @@
  * it under the terms of the GNU Library General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
- * 
+ *
  * mLib 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 Library General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Library General Public
  * License along with mLib; if not, write to the Free
  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: unihash.h,v $
- * Revision 1.1  2003/10/12 14:43:24  mdw
- * Universal hashing.
- *
- */
-
 #ifndef MLIB_UNIHASH_H
 #define MLIB_UNIHASH_H
 
@@ -50,7 +42,7 @@
  * $m_{n-1}, m_{n-2}, \ldots, m_2, m_1, m_0$% in %$\gf{q}%.
  * Then we compute
  *
- *   %$H_k(M) = k^{n+1} \sum_{0\le i<n} m_i k^{i+1}.$%
+ *   %$H_k(M) = k^{n+1} + \sum_{0\le i<n} m_i k^{i+1}.$%
  *
  * Note that %$H_0(M) = 0$% for all messages %$M$%.
  *
@@ -82,15 +74,15 @@
  * computationally unbounded adversaries.  Simply XOR the hash with a random
  * string indexed from a large random pad by some nonce sent with the
  * message.  The probability of a forgery attempt being successful is then
- * %$(\ell + 1)/2^t$%, where %$t$% is the tag length and %$n$% is the longest
- * message permitted.
+ * %$(\ell + 1)/2^t$%, where %$t$% is the tag length and %$\ell$% is the
+ * longest message permitted.
  */
 
 /*----- Practicalities ----------------------------------------------------*
  *
  * We work in %$\gf{2^32}$%, represented as a field of polynomials modulo
- * %$\{104c11db7}_x$% (this is the standard CRC-32 polynomial).  Our blocks
- * are bytes.  We append a big-endian byte length.
+ * %$\texttt{104c11db7}_x$% (this is the standard CRC-32 polynomial).  Our
+ * blocks are bytes.
  *
  * The choice of a 32-bit hash is made for pragmatic reasons: we're never
  * likely to actually want all 32 bits for a real hashtable anyway.  The
@@ -135,6 +127,10 @@ typedef struct unihash_info {
   uint32 s[UNIHASH_NBATCH][4][256];	/* S-tables as described */
 } unihash_info;
 
+/*----- A global hash-info table ------------------------------------------*/
+
+extern unihash_info unihash_global;	/* Key this if you like */
+
 /*----- Functions provided ------------------------------------------------*/
 
 /* --- @unihash_setkey@ --- *
@@ -156,9 +152,9 @@ extern void unihash_setkey(unihash_info */*i*/, uint32 /*k*/);
  *		@const void *p@ = pointer to data to hash
  *		@size_t sz@ = size of the data
  *
- * Returns:	---
+ * Returns:	Hash of data so far.
  *
- * Use:		Hashes data.  Call this as many times as needed.  
+ * Use:		Hashes data.  Call this as many times as needed.
  */
 
 #define UNIHASH_INIT(i) ((i)->s[0][0][1]) /* %$k$% */
@@ -175,7 +171,7 @@ extern uint32 unihash_hash(const unihash_info */*i*/, uint32 /*a*/,
  * Returns:	The hash value computed.
  *
  * Use:		All-in-one hashing function.  No faster than using the
- * 		separate calls, but more convenient.
+ *		separate calls, but more convenient.
  */
 
 #define UNIHASH(i, p, sz) (unihash_hash((i), UNIHASH_INIT((i)), (p), (sz)))