mirror of
https://github.com/firewalkwithm3/qmk_firmware.git
synced 2024-11-22 03:21:48 +08:00
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>
159 lines
4.4 KiB
Plaintext
159 lines
4.4 KiB
Plaintext
#=====================#
|
|
# 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.
|
|
Comments, questions, bug fixes and suggestions welcome at
|
|
the address given in the above URL.
|
|
|
|
|
|
#==================#
|
|
# FNV hash utility #
|
|
#==================#
|
|
|
|
Two hash utilities (32 bit and 64 bit) are provided:
|
|
|
|
fnv032 [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
|
|
fnv132 [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
|
|
fnv1a32 [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
|
|
|
|
fnv064 [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
|
|
fnv164 [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
|
|
fnv1a64 [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
|
|
|
|
-b bcnt mask off all but the lower bcnt bits (default: 32)
|
|
-m multiple hashes, one per line for each arg
|
|
-s hash arg as a string (ignoring terminating NUL bytes)
|
|
-t code 0 ==> generate test vectors, 1 ==> test FNV hash
|
|
-v verbose mode, print arg after hash (implies -m)
|
|
arg string (if -s was given) or filename (default stdin)
|
|
|
|
The fnv032, fnv064 implement the historic FNV-0 hash.
|
|
The fnv132, fnv164 implement the recommended FNV-1 hash.
|
|
The fnv1a32, fnv1a64 implement the recommended FNV-1a hash.
|
|
|
|
This is the original historic FNV algorithm with a 0 offset basis.
|
|
It is recommended that FNV-1, with a non-0 offset basis be used instead.
|
|
|
|
To test FNV hashes, try:
|
|
|
|
fnv032 -t 1 -v
|
|
fnv132 -t 1 -v
|
|
fnv1a32 -t 1 -v
|
|
|
|
fnv064 -t 1 -v
|
|
fnv164 -t 1 -v
|
|
fnv1a64 -t 1 -v
|
|
|
|
If you are compiling, try:
|
|
|
|
make check
|
|
|
|
|
|
#==================#
|
|
# FNV hash library #
|
|
#==================#
|
|
|
|
The libfnv.a library implements both a 32 bit and a 64 bit FNV hash
|
|
on collections of bytes, a NUL terminated strings or on an open file
|
|
descriptor.
|
|
|
|
Here is the 32 bit FNV 1 hash:
|
|
|
|
Fnv32_t fnv_32_buf(void *buf, int len, Fnv32_t hval); /* byte buf */
|
|
Fnv32_t fnv_32_str(char *string, Fnv32_t hval); /* string */
|
|
|
|
Here is the 32 bit FNV 1a hash:
|
|
|
|
Fnv32_t fnv_32a_buf(void *buf, int len, Fnv32_t hval); /* byte buf */
|
|
Fnv32_t fnv_32a_str(char *string, Fnv32_t hval); /* string */
|
|
|
|
Here is the 64 bit FNV 1 hash:
|
|
|
|
Fnv64_t fnv_64_buf(void *buf, int len, Fnv64_t hval); /* byte buf */
|
|
Fnv64_t fnv_64_str(char *string, Fnv64_t hval); /* string */
|
|
|
|
Here is the 64 bit FNV 1a hash:
|
|
|
|
Fnv64_t fnv_64a_buf(void *buf, int len, Fnv64_t hval); /* byte buf */
|
|
Fnv64_t fnv_64a_str(char *string, Fnv64_t hval); /* string */
|
|
|
|
On the first call to a hash function, one must supply the initial basis
|
|
that is appropriate for the hash in question:
|
|
|
|
FNV-0: (not recommended)
|
|
|
|
FNV0_32_INIT /* 32 bit FNV-0 initial basis */
|
|
FNV0_64_INIT /* 64 bit FNV-0 initial basis */
|
|
|
|
FNV-1:
|
|
|
|
FNV1_32_INIT /* 32 bit FNV-1 initial basis */
|
|
FNV1_64_INIT /* 64 bit FNV-1 initial basis */
|
|
|
|
FNV-1a:
|
|
|
|
FNV1A_32_INIT /* 32 bit FNV-1a initial basis */
|
|
FNV1A_64_INIT /* 64 bit FNV-1a initial basis */
|
|
|
|
For example to perform a 64 bit FNV-1 hash:
|
|
|
|
#include "fnv.h"
|
|
|
|
Fnv64_t hash_val;
|
|
|
|
hash_val = fnv_64_str("a string", FNV1_64_INIT);
|
|
hash_val = fnv_64_str("more string", hash_val);
|
|
|
|
produces the same final hash value as:
|
|
|
|
hash_val = fnv_64_str("a stringmore string", FNV1_64_INIT);
|
|
|
|
NOTE: If one used 'FNV0_64_INIT' instead of 'FNV1_64_INIT' one would get the
|
|
historic FNV-0 hash instead recommended FNV-1 hash.
|
|
|
|
To perform a 32 bit FNV-1 hash:
|
|
|
|
#include "fnv.h"
|
|
|
|
Fnv32_t hash_val;
|
|
|
|
hash_val = fnv_32_buf(buf, length_of_buf, FNV1_32_INIT);
|
|
hash_val = fnv_32_str("more data", hash_val);
|
|
|
|
To perform a 64 bit FNV-1a hash:
|
|
|
|
#include "fnv.h"
|
|
|
|
Fnv64_t hash_val;
|
|
|
|
hash_val = fnv_64a_buf(buf, length_of_buf, FNV1_64_INIT);
|
|
hash_val = fnv_64a_str("more data", hash_val);
|
|
|
|
=-=
|
|
|
|
chongo <Landon Curt Noll> /\oo/\
|
|
http://www.isthe.com/chongo
|
|
|
|
Share and Enjoy!
|