forked from forks/qmk_firmware
01ecf332ff
* Initial import of wear-leveling algorithm. * Alignment. * Docs tweaks. * Lock/unlock. * Update quantum/wear_leveling/wear_leveling_internal.h Co-authored-by: Stefan Kerkmann <karlk90@pm.me> * More tests, fix issue with consolidation when unlocked. * More tests. * Review comments. * Add plumbing for FNV1a. * Another test checking that checksum mismatch clears the cache. * Check that the write log still gets played back. Co-authored-by: Stefan Kerkmann <karlk90@pm.me>
145 lines
3.9 KiB
C
145 lines
3.9 KiB
C
/*
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* hash_32 - 32 bit Fowler/Noll/Vo FNV-1a hash code
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*
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* @(#) $Revision: 5.1 $
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* @(#) $Id: hash_32a.c,v 5.1 2009/06/30 09:13:32 chongo Exp $
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* @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_32a.c,v $
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*
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***
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*
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* Fowler/Noll/Vo hash
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*
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* The basis of this hash algorithm was taken from an idea sent
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* as reviewer comments to the IEEE POSIX P1003.2 committee by:
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*
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* Phong Vo (http://www.research.att.com/info/kpv/)
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* Glenn Fowler (http://www.research.att.com/~gsf/)
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*
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* In a subsequent ballot round:
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*
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* Landon Curt Noll (http://www.isthe.com/chongo/)
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*
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* improved on their algorithm. Some people tried this hash
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* and found that it worked rather well. In an EMail message
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* to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
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*
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* FNV hashes are designed to be fast while maintaining a low
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* collision rate. The FNV speed allows one to quickly hash lots
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* of data while maintaining a reasonable collision rate. See:
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*
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* http://www.isthe.com/chongo/tech/comp/fnv/index.html
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*
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* for more details as well as other forms of the FNV hash.
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***
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*
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* To use the recommended 32 bit FNV-1a hash, pass FNV1_32A_INIT as the
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* Fnv32_t hashval argument to fnv_32a_buf() or fnv_32a_str().
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*
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***
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*
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* Please do not copyright this code. This code is in the public domain.
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*
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* LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
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* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
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* EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
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* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
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* USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
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* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*
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* By:
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* chongo <Landon Curt Noll> /\oo/\
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* http://www.isthe.com/chongo/
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*
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* Share and Enjoy! :-)
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*/
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#include <stdlib.h>
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#include "fnv.h"
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/*
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* 32 bit magic FNV-1a prime
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*/
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#define FNV_32_PRIME ((Fnv32_t)0x01000193)
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/*
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* fnv_32a_buf - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a buffer
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*
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* input:
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* buf - start of buffer to hash
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* len - length of buffer in octets
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* hval - previous hash value or 0 if first call
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*
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* returns:
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* 32 bit hash as a static hash type
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*
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* NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
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* hval arg on the first call to either fnv_32a_buf() or fnv_32a_str().
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*/
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Fnv32_t
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fnv_32a_buf(void *buf, size_t len, Fnv32_t hval)
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{
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unsigned char *bp = (unsigned char *)buf; /* start of buffer */
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unsigned char *be = bp + len; /* beyond end of buffer */
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/*
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* FNV-1a hash each octet in the buffer
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*/
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while (bp < be) {
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/* xor the bottom with the current octet */
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hval ^= (Fnv32_t)*bp++;
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/* multiply by the 32 bit FNV magic prime mod 2^32 */
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#if defined(NO_FNV_GCC_OPTIMIZATION)
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hval *= FNV_32_PRIME;
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#else
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hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
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#endif
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}
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/* return our new hash value */
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return hval;
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}
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/*
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* fnv_32a_str - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a string
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*
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* input:
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* str - string to hash
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* hval - previous hash value or 0 if first call
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*
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* returns:
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* 32 bit hash as a static hash type
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*
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* NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
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* hval arg on the first call to either fnv_32a_buf() or fnv_32a_str().
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*/
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Fnv32_t
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fnv_32a_str(char *str, Fnv32_t hval)
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{
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unsigned char *s = (unsigned char *)str; /* unsigned string */
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/*
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* FNV-1a hash each octet in the buffer
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*/
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while (*s) {
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/* xor the bottom with the current octet */
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hval ^= (Fnv32_t)*s++;
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/* multiply by the 32 bit FNV magic prime mod 2^32 */
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#if defined(NO_FNV_GCC_OPTIMIZATION)
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hval *= FNV_32_PRIME;
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#else
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hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
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#endif
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}
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/* return our new hash value */
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return hval;
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}
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