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Add FNV1a, manual documentation.

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Peter D. Barnes, Jr.
2012-11-13 16:30:38 -08:00
parent 0564f7e024
commit a2019b566f
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72
doc/manual/source/hash-functions.rst Normal file
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.. include:: replace.txt
Hash Functions
----------------
|ns3| provides a generic interface to general purpose hash functions.
In the simplest usage, the hash function returns the 32-bit or 64-bit
hash of a data buffer or string. The default underlying hash function
is murmur3_, chosen because it has good hash function properties and
offers a 64-bit version. The venerable FNV1a hash is also available.
There is a straight-forward mechanism to
add (or provide at run time) alternative hash function implementations.
.. _murmur3: http://code.google.com/p/smhasher/wiki/MurmurHash3
Basic Usage
***********
The simplest way to get a hash value of a data buffer or string is just::
#include "ns3/hash.h"
char * buffer = ...
size_t buffer_size = ...
Hash::Hash32_t buffer_hash = Hash32 ( (const char *) buffer, buffer_size);
std::string s;
Hash::Hash32_t s_hash = Hash32 (s);
The ``Hash::Hash32_t`` type is just an ``uint32_t``, as a reminder that hash
values are opaque.
Equivalent functions and ``Hash::Hash64_t`` type are defined for 64-bit hash
values.
Adding New Hash Function Implementations
****************************************
To add the hash function ``foo``, follow the ``hash-murmur3.h``/``.cc`` pattern:
* Create a class declaration (``.h``) and definition (``.cc``) inheriting
from ``HashImplementation``.
* ``include`` the declaration in ``hash.h`` (at the point where
``hash-murmur3.h`` is included.
* In your own code, instantiate a ``Hash`` object via the constructor
``Hash (Ptr<HashImplementation> (Foo))``
If your hash function is a single function, e.g. ``hashf``, you don't
even need to create a new class derived from HashImplementation::
Hash (Ptr<HashImplementation> (Hash32Implementation<&hashf>))
For this to compile, your ``hashf`` has to match one of the function pointer
signatures::
typedef Hash::Hash32_t (*Hash32Function_ptr) (const char *, const size_t);
typedef Hash::Hash64_t (*Hash64Function_ptr) (const char *, const size_t);
Sources for Hash Functions
**************************
Sources for other hash function implementations include:
* Peter Kankowski: http://www.strchr.com
* Arash Partow: http://www.partow.net/programming/hashfunctions/index.html
* SMHasher:
* Sanmayce: http://www.sanmayce.com/Fastest_Hash/index.html

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doc/manual/source/index.rst
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organization
random-variables
hash-functions
events
callbacks
object-model

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src/core/model/hash-fnv.cc Normal file
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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2012 Lawrence Livermore National Laboratory
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation;
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Author: Peter D. Barnes, Jr. <pdbarnes@llnl.gov>
*
* This copyright notice applies strictly to the wrapper material.
*
* The FNV source code itself is in the public domain. The FNV source
* code sections are marked by
* // Begin <fnv-file> ---->
* and
* // End <fnv-file> ---->
* comments.
*/
#include <sys/types.h>
#include <stdlib.h>
#include "ns3/hash.h"
#include "ns3/hash-fnv.h"
#include "ns3/log.h"
namespace ns3 {
NS_LOG_COMPONENT_DEFINE ("Hash-Fnv");
namespace HashImplNS {
namespace FnvNS {
/*************************************************
** class FnvHashImplementation
************************************************/
extern "C" {
// Changes from FNV distribution are marked with `//PDB'
//
// Begin fnv.h ----------------------------------->
/*
* fnv - Fowler/Noll/Vo- hash code
*
* @(#) $Revision: 5.4 $
* @(#) $Id: fnv.h,v 5.4 2009/07/30 22:49:13 chongo Exp $
* @(#) $Source: /usr/local/src/cmd/fnv/RCS/fnv.h,v $
*
***
*
* Fowler/Noll/Vo- hash
*
* The basis of this hash algorithm was taken from an idea sent
* as reviewer comments to the IEEE POSIX P1003.2 committee by:
*
* Phong Vo (http://www.research.att.com/info/kpv/)
* Glenn Fowler (http://www.research.att.com/~gsf/)
*
* In a subsequent ballot round:
*
* Landon Curt Noll (http://www.isthe.com/chongo/)
*
* improved on their algorithm. Some people tried this hash
* and found that it worked rather well. In an EMail message
* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
*
* FNV hashes are designed to be fast while maintaining a low
* collision rate. The FNV speed allows one to quickly hash lots
* of data while maintaining a reasonable collision rate. See:
*
* http://www.isthe.com/chongo/tech/comp/fnv/index.html
*
* for more details as well as other forms of the FNV hash.
*
***
*
* NOTE: The FNV-0 historic hash is not recommended. One should use
* the FNV-1 hash instead.
*
* To use the 32 bit FNV-0 historic hash, pass FNV0_32_INIT as the
* Fnv32_t hashval argument to fnv_32_buf() or fnv_32_str().
*
* To use the 64 bit FNV-0 historic hash, pass FNV0_64_INIT as the
* Fnv64_t hashval argument to fnv_64_buf() or fnv_64_str().
*
* To use the recommended 32 bit FNV-1 hash, pass FNV1_32_INIT as the
* Fnv32_t hashval argument to fnv_32_buf() or fnv_32_str().
*
* To use the recommended 64 bit FNV-1 hash, pass FNV1_64_INIT as the
* Fnv64_t hashval argument to fnv_64_buf() or fnv_64_str().
*
* To use the recommended 32 bit FNV-1a hash, pass FNV1_32A_INIT as the
* Fnv32_t hashval argument to fnv_32a_buf() or fnv_32a_str().
*
* To use the recommended 64 bit FNV-1a hash, pass FNV1A_64_INIT as the
* Fnv64_t hashval argument to fnv_64a_buf() or fnv_64a_str().
*
***
*
* Please do not copyright this code. This code is in the public domain.
*
* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*
* By:
* chongo <Landon Curt Noll> /\oo/\
* http://www.isthe.com/chongo/
*
* Share and Enjoy! :-)
*/
#if !defined(__FNV_H__)
#define __FNV_H__
//#include <sys/types.h> //PDB
#define FNV_VERSION "5.0.2" /* @(#) FNV Version */
/*
* 32 bit FNV-0 hash type
*/
typedef u_int32_t Fnv32_t;
/*
* 32 bit FNV-0 zero initial basis
*
* This historic hash is not recommended. One should use
* the FNV-1 hash and initial basis instead.
*/
#define FNV0_32_INIT ((Fnv32_t)0)
/*
* 32 bit FNV-1 and FNV-1a non-zero initial basis
*
* The FNV-1 initial basis is the FNV-0 hash of the following 32 octets:
*
* chongo <Landon Curt Noll> /\../\
*
* NOTE: The \'s above are not back-slashing escape characters.
* They are literal ASCII backslash 0x5c characters.
*
* NOTE: The FNV-1a initial basis is the same value as FNV-1 by definition.
*/
#define FNV1_32_INIT ((Fnv32_t)0x811c9dc5)
#define FNV1_32A_INIT FNV1_32_INIT
/*
* determine how 64 bit unsigned values are represented
*/
//#include "longlong.h" //PDB - assume `unsigned long long' is 64 bit
#define HAVE_64BIT_LONG_LONG
/*
* 64 bit FNV-0 hash
*/
#if defined(HAVE_64BIT_LONG_LONG)
typedef u_int64_t Fnv64_t;
#else /* HAVE_64BIT_LONG_LONG */
typedef struct {
u_int32_t w32[2]; /* w32[0] is low order, w32[1] is high order word */
} Fnv64_t;
#endif /* HAVE_64BIT_LONG_LONG */
/*
* 64 bit FNV-0 zero initial basis
*
* This historic hash is not recommended. One should use
* the FNV-1 hash and initial basis instead.
*/
#if defined(HAVE_64BIT_LONG_LONG)
#define FNV0_64_INIT ((Fnv64_t)0)
#else /* HAVE_64BIT_LONG_LONG */
extern const Fnv64_t fnv0_64_init;
#define FNV0_64_INIT (fnv0_64_init)
#endif /* HAVE_64BIT_LONG_LONG */
/*
* 64 bit FNV-1 non-zero initial basis
*
* The FNV-1 initial basis is the FNV-0 hash of the following 32 octets:
*
* chongo <Landon Curt Noll> /\../\
*
* NOTE: The \'s above are not back-slashing escape characters.
* They are literal ASCII backslash 0x5c characters.
*
* NOTE: The FNV-1a initial basis is the same value as FNV-1 by definition.
*/
#if defined(HAVE_64BIT_LONG_LONG)
#define FNV1_64_INIT ((Fnv64_t)0xcbf29ce484222325ULL)
#define FNV1A_64_INIT FNV1_64_INIT
#else /* HAVE_64BIT_LONG_LONG */
extern const fnv1_64_init;
extern const Fnv64_t fnv1a_64_init;
#define FNV1_64_INIT (fnv1_64_init)
#define FNV1A_64_INIT (fnv1a_64_init)
#endif /* HAVE_64BIT_LONG_LONG */
/*
* hash types
*/
enum fnv_type {
FNV_NONE = 0, /* invalid FNV hash type */
FNV0_32 = 1, /* FNV-0 32 bit hash */
FNV1_32 = 2, /* FNV-1 32 bit hash */
FNV1a_32 = 3, /* FNV-1a 32 bit hash */
FNV0_64 = 4, /* FNV-0 64 bit hash */
FNV1_64 = 5, /* FNV-1 64 bit hash */
FNV1a_64 = 6, /* FNV-1a 64 bit hash */
};
//PDB test vector declarations deleted
/*
* external functions //PDB converted to forward declarations
*/
/* hash_32.c */
/* extern */ Fnv32_t fnv_32_buf(void *buf, size_t len, Fnv32_t hashval);
/* extern */ Fnv32_t fnv_32_str(char *buf, Fnv32_t hashval);
/* hash_32a.c */
/* extern */ Fnv32_t fnv_32a_buf(void *buf, size_t len, Fnv32_t hashval);
/* extern */ Fnv32_t fnv_32a_str(char *buf, Fnv32_t hashval);
/* hash_64.c */
/* extern */ Fnv64_t fnv_64_buf(void *buf, size_t len, Fnv64_t hashval);
/* extern */ Fnv64_t fnv_64_str(char *buf, Fnv64_t hashval);
/* hash_64a.c */
/* extern */ Fnv64_t fnv_64a_buf(void *buf, size_t len, Fnv64_t hashval);
/* extern */ Fnv64_t fnv_64a_str(char *buf, Fnv64_t hashval);
//PDB test vector declarations deleted
#endif /* __FNV_H__ */
// End fnv.h ------------------------------->
// Begin hash_32a.c ------------------------------>
/*
* hash_32 - 32 bit Fowler/Noll/Vo FNV-1a hash code
*
* @(#) $Revision: 5.1 $
* @(#) $Id: hash_32a.c,v 5.1 2009/06/30 09:13:32 chongo Exp $
* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_32a.c,v $
*
***
*
* Fowler/Noll/Vo hash
*
* The basis of this hash algorithm was taken from an idea sent
* as reviewer comments to the IEEE POSIX P1003.2 committee by:
*
* Phong Vo (http://www.research.att.com/info/kpv/)
* Glenn Fowler (http://www.research.att.com/~gsf/)
*
* In a subsequent ballot round:
*
* Landon Curt Noll (http://www.isthe.com/chongo/)
*
* improved on their algorithm. Some people tried this hash
* and found that it worked rather well. In an EMail message
* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
*
* FNV hashes are designed to be fast while maintaining a low
* collision rate. The FNV speed allows one to quickly hash lots
* of data while maintaining a reasonable collision rate. See:
*
* http://www.isthe.com/chongo/tech/comp/fnv/index.html
*
* for more details as well as other forms of the FNV hash.
***
*
* To use the recommended 32 bit FNV-1a hash, pass FNV1_32A_INIT as the
* Fnv32_t hashval argument to fnv_32a_buf() or fnv_32a_str().
*
***
*
* Please do not copyright this code. This code is in the public domain.
*
* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*
* By:
* chongo <Landon Curt Noll> /\oo/\
* http://www.isthe.com/chongo/
*
* Share and Enjoy! :-)
*/
//#include <stdlib.h> //PDB
//#include "fnv.h" //PDB
/*
* 32 bit magic FNV-1a prime
*/
#define FNV_32_PRIME ((Fnv32_t)0x01000193)
/*
* fnv_32a_buf - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a buffer
*
* input:
* buf - start of buffer to hash
* len - length of buffer in octets
* hval - previous hash value or 0 if first call
*
* returns:
* 32 bit hash as a static hash type
*
* NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
* hval arg on the first call to either fnv_32a_buf() or fnv_32a_str().
*/
Fnv32_t
fnv_32a_buf(void *buf, size_t len, Fnv32_t hval)
{
unsigned char *bp = (unsigned char *)buf; /* start of buffer */
unsigned char *be = bp + len; /* beyond end of buffer */
/*
* FNV-1a hash each octet in the buffer
*/
while (bp < be) {
/* xor the bottom with the current octet */
hval ^= (Fnv32_t)*bp++;
/* multiply by the 32 bit FNV magic prime mod 2^32 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_32_PRIME;
#else
hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
#endif
}
/* return our new hash value */
return hval;
}
/*
* fnv_32a_str - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a string
*
* input:
* str - string to hash
* hval - previous hash value or 0 if first call
*
* returns:
* 32 bit hash as a static hash type
*
* NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
* hval arg on the first call to either fnv_32a_buf() or fnv_32a_str().
*/
Fnv32_t
fnv_32a_str(char *str, Fnv32_t hval)
{
unsigned char *s = (unsigned char *)str; /* unsigned string */
/*
* FNV-1a hash each octet in the buffer
*/
while (*s) {
/* xor the bottom with the current octet */
hval ^= (Fnv32_t)*s++;
/* multiply by the 32 bit FNV magic prime mod 2^32 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_32_PRIME;
#else
hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
#endif
}
/* return our new hash value */
return hval;
}
// End hash_32a.c -------------------------->
// Begin hash_64a.c------------------------------->
/*
* hash_64 - 64 bit Fowler/Noll/Vo-0 FNV-1a hash code
*
* @(#) $Revision: 5.1 $
* @(#) $Id: hash_64a.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64a.c,v $
*
***
*
* Fowler/Noll/Vo hash
*
* The basis of this hash algorithm was taken from an idea sent
* as reviewer comments to the IEEE POSIX P1003.2 committee by:
*
* Phong Vo (http://www.research.att.com/info/kpv/)
* Glenn Fowler (http://www.research.att.com/~gsf/)
*
* In a subsequent ballot round:
*
* Landon Curt Noll (http://www.isthe.com/chongo/)
*
* improved on their algorithm. Some people tried this hash
* and found that it worked rather well. In an EMail message
* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
*
* FNV hashes are designed to be fast while maintaining a low
* collision rate. The FNV speed allows one to quickly hash lots
* of data while maintaining a reasonable collision rate. See:
*
* http://www.isthe.com/chongo/tech/comp/fnv/index.html
*
* for more details as well as other forms of the FNV hash.
*
***
*
* To use the recommended 64 bit FNV-1a hash, pass FNV1A_64_INIT as the
* Fnv64_t hashval argument to fnv_64a_buf() or fnv_64a_str().
*
***
*
* Please do not copyright this code. This code is in the public domain.
*
* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*
* By:
* chongo <Landon Curt Noll> /\oo/\
* http://www.isthe.com/chongo/
*
* Share and Enjoy! :-)
*/
//#include <stdlib.h> //PDB
//#include "fnv.h" //PDB
/*
* FNV-1a defines the initial basis to be non-zero
*/
#if !defined(HAVE_64BIT_LONG_LONG)
const Fnv64_t fnv1a_64_init = { 0x84222325, 0xcbf29ce4 };
#endif /* ! HAVE_64BIT_LONG_LONG */
/*
* 64 bit magic FNV-1a prime
*/
#if defined(HAVE_64BIT_LONG_LONG)
#define FNV_64_PRIME ((Fnv64_t)0x100000001b3ULL)
#else /* HAVE_64BIT_LONG_LONG */
#define FNV_64_PRIME_LOW ((unsigned long)0x1b3) /* lower bits of FNV prime */
#define FNV_64_PRIME_SHIFT (8) /* top FNV prime shift above 2^32 */
#endif /* HAVE_64BIT_LONG_LONG */
/*
* fnv_64a_buf - perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
*
* input:
* buf - start of buffer to hash
* len - length of buffer in octets
* hval - previous hash value or 0 if first call
*
* returns:
* 64 bit hash as a static hash type
*
* NOTE: To use the recommended 64 bit FNV-1a hash, use FNV1A_64_INIT as the
* hval arg on the first call to either fnv_64a_buf() or fnv_64a_str().
*/
Fnv64_t
fnv_64a_buf(void *buf, size_t len, Fnv64_t hval)
{
unsigned char *bp = (unsigned char *)buf; /* start of buffer */
unsigned char *be = bp + len; /* beyond end of buffer */
#if defined(HAVE_64BIT_LONG_LONG)
/*
* FNV-1a hash each octet of the buffer
*/
while (bp < be) {
/* xor the bottom with the current octet */
hval ^= (Fnv64_t)*bp++;
/* multiply by the 64 bit FNV magic prime mod 2^64 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_64_PRIME;
#else /* NO_FNV_GCC_OPTIMIZATION */
hval += (hval << 1) + (hval << 4) + (hval << 5) +
(hval << 7) + (hval << 8) + (hval << 40);
#endif /* NO_FNV_GCC_OPTIMIZATION */
}
#else /* HAVE_64BIT_LONG_LONG */
unsigned long val[4]; /* hash value in base 2^16 */
unsigned long tmp[4]; /* tmp 64 bit value */
/*
* Convert Fnv64_t hval into a base 2^16 array
*/
val[0] = hval.w32[0];
val[1] = (val[0] >> 16);
val[0] &= 0xffff;
val[2] = hval.w32[1];
val[3] = (val[2] >> 16);
val[2] &= 0xffff;
/*
* FNV-1a hash each octet of the buffer
*/
while (bp < be) {
/* xor the bottom with the current octet */
val[0] ^= (unsigned long)*bp++;
/*
* multiply by the 64 bit FNV magic prime mod 2^64
*
* Using 0x100000001b3 we have the following digits base 2^16:
*
* 0x0 0x100 0x0 0x1b3
*
* which is the same as:
*
* 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
*/
/* multiply by the lowest order digit base 2^16 */
tmp[0] = val[0] * FNV_64_PRIME_LOW;
tmp[1] = val[1] * FNV_64_PRIME_LOW;
tmp[2] = val[2] * FNV_64_PRIME_LOW;
tmp[3] = val[3] * FNV_64_PRIME_LOW;
/* multiply by the other non-zero digit */
tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
/* propagate carries */
tmp[1] += (tmp[0] >> 16);
val[0] = tmp[0] & 0xffff;
tmp[2] += (tmp[1] >> 16);
val[1] = tmp[1] & 0xffff;
val[3] = tmp[3] + (tmp[2] >> 16);
val[2] = tmp[2] & 0xffff;
/*
* Doing a val[3] &= 0xffff; is not really needed since it simply
* removes multiples of 2^64. We can discard these excess bits
* outside of the loop when we convert to Fnv64_t.
*/
}
/*
* Convert base 2^16 array back into an Fnv64_t
*/
hval.w32[1] = ((val[3]<<16) | val[2]);
hval.w32[0] = ((val[1]<<16) | val[0]);
#endif /* HAVE_64BIT_LONG_LONG */
/* return our new hash value */
return hval;
}
/*
* fnv_64a_str - perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
*
* input:
* buf - start of buffer to hash
* hval - previous hash value or 0 if first call
*
* returns:
* 64 bit hash as a static hash type
*
* NOTE: To use the recommended 64 bit FNV-1a hash, use FNV1A_64_INIT as the
* hval arg on the first call to either fnv_64a_buf() or fnv_64a_str().
*/
Fnv64_t
fnv_64a_str(char *str, Fnv64_t hval)
{
unsigned char *s = (unsigned char *)str; /* unsigned string */
#if defined(HAVE_64BIT_LONG_LONG)
/*
* FNV-1a hash each octet of the string
*/
while (*s) {
/* xor the bottom with the current octet */
hval ^= (Fnv64_t)*s++;
/* multiply by the 64 bit FNV magic prime mod 2^64 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
hval *= FNV_64_PRIME;
#else /* NO_FNV_GCC_OPTIMIZATION */
hval += (hval << 1) + (hval << 4) + (hval << 5) +
(hval << 7) + (hval << 8) + (hval << 40);
#endif /* NO_FNV_GCC_OPTIMIZATION */
}
#else /* !HAVE_64BIT_LONG_LONG */
unsigned long val[4]; /* hash value in base 2^16 */
unsigned long tmp[4]; /* tmp 64 bit value */
/*
* Convert Fnv64_t hval into a base 2^16 array
*/
val[0] = hval.w32[0];
val[1] = (val[0] >> 16);
val[0] &= 0xffff;
val[2] = hval.w32[1];
val[3] = (val[2] >> 16);
val[2] &= 0xffff;
/*
* FNV-1a hash each octet of the string
*/
while (*s) {
/* xor the bottom with the current octet */
/*
* multiply by the 64 bit FNV magic prime mod 2^64
*
* Using 1099511628211, we have the following digits base 2^16:
*
* 0x0 0x100 0x0 0x1b3
*
* which is the same as:
*
* 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
*/
/* multiply by the lowest order digit base 2^16 */
tmp[0] = val[0] * FNV_64_PRIME_LOW;
tmp[1] = val[1] * FNV_64_PRIME_LOW;
tmp[2] = val[2] * FNV_64_PRIME_LOW;
tmp[3] = val[3] * FNV_64_PRIME_LOW;
/* multiply by the other non-zero digit */
tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
/* propagate carries */
tmp[1] += (tmp[0] >> 16);
val[0] = tmp[0] & 0xffff;
tmp[2] += (tmp[1] >> 16);
val[1] = tmp[1] & 0xffff;
val[3] = tmp[3] + (tmp[2] >> 16);
val[2] = tmp[2] & 0xffff;
/*
* Doing a val[3] &= 0xffff; is not really needed since it simply
* removes multiples of 2^64. We can discard these excess bits
* outside of the loop when we convert to Fnv64_t.
*/
val[0] ^= (unsigned long)(*s++);
}
/*
* Convert base 2^16 array back into an Fnv64_t
*/
hval.w32[1] = ((val[3]<<16) | val[2]);
hval.w32[0] = ((val[1]<<16) | val[0]);
#endif /* !HAVE_64BIT_LONG_LONG */
/* return our new hash value */
return hval;
}
// End hash_64a.c--------------------------->
} /* extern "C" */
//-----------------------------------------------------------------------------
} // namespace FnvNS
Hash::Hash32_t
Fnv::GetHash32 (const char * buffer, const size_t size)
{
uint32_t result = FnvNS::fnv_32a_buf ((void *)buffer, size, FNV1_32A_INIT);
return result;
}
Hash::Hash64_t
Fnv::GetHash64 (const char * buffer, const size_t size)
{
uint64_t result = FnvNS::fnv_64a_buf ((void *)buffer, size, FNV1A_64_INIT);
return result;
}
} // namespace HashImpl
} // namespace ns3

74
src/core/model/hash-fnv.h Normal file
View File

@@ -0,0 +1,74 @@
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
* Copyright (c) 2012 Lawrence Livermore National Laboratory
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation;
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Author: Peter D. Barnes, Jr. <pdbarnes@llnl.gov>
*/
#ifndef HASH_FNV_H
#define HASH_FNV_H
#include "ns3/hash.h"
namespace ns3 {
namespace HashImplNS {
/**
* \ingroup hash
*
* \brief Fnv hash function implementation
*
*/
class Fnv : public HashImplementation
{
public:
/**
* Compute 32-bit hash of a byte buffer
*
* \param [in] buffer pointer to the beginning of the buffer
* \param [in] size length of the buffer, in bytes
* \return 32-bit hash of the buffer
*/
Hash::Hash32_t GetHash32 (const char * buffer, const size_t size);
/**
* Compute 64-bit hash of a byte buffer.
*
* \param [in] buffer pointer to the beginning of the buffer
* \param [in] size length of the buffer, in bytes
* \return 64-bit hash of the buffer
*/
Hash::Hash64_t GetHash64 (const char * buffer, const size_t size);
private:
/**
* Seed value
*
* This has to be a constant for all MPI ranks to generate
* the same hash from the same string.
*/
enum seed
{
SEED = 0x8BADF00D // Ate bad food
};
}; // class Fnv
} // namespace HashImplNS
} // namespace ns3
#endif /* HASH_FNV_H */

3
src/core/model/hash.h
View File

@@ -40,7 +40,7 @@ class HashImplementation;
* The choice of hash function can be made at construction by
* passing a Ptr<> to the desired HashImplementation.
* The available implementations are documented in group hash.
* The default implementation is Murmur3.
* The default implementation is Murmur3. FNV is also available.
*
* In addition to this class interface, global functions are
* defined which use the default hash implementation.
@@ -246,6 +246,7 @@ class Hash64Implementation : public HashImplementation
************************************************/
#include "ns3/hash-murmur3.h"
#include "ns3/hash-fnv.h"
/*************************************************

2
src/core/wscript
View File

@@ -151,6 +151,7 @@ def build(bld):
'helper/event-garbage-collector.cc',
'model/hash.cc',
'model/hash-murmur3.cc',
'model/hash-fnv.cc',
]
core_test = bld.create_ns3_module_test_library('core')
@@ -256,6 +257,7 @@ def build(bld):
'helper/random-variable-stream-helper.h',
'model/hash.h',
'model/hash-murmur3.h',
'model/hash-fnv.h',
]
if sys.platform == 'win32':