fnv

Fowler/Noll/Vo hash

• The fnv1a32, fnv1a64 implement the recommended FNV-1a hash.

• The fnv132, fnv164 implement the common FNV-1 hash.

• The fnv032, fnv064 implement the historic FNV-0 hash (used to generate FNV-1a and FNV-1 offset basis only).

To install

make clobber all test
sudo make install clobber

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 Glenn Fowler

In a subsequent ballot round Landon Curt Noll 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:

fnv1a64 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
fnv1a32 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]

fnv164 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
fnv132 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]

fnv064 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]
fnv032 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [-v] [arg ...]

-h         print help and exit
-v         verbose mode, print arg after hash (implies -m)
-V         print version and exit

-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

arg       string (if -s was given) or filename (default stdin)

• The fnv1a32, fnv1a64 implement the recommended FNV-1a hash.

• The fnv132, fnv164 implement the common FNV-1 hash.

• The fnv032, fnv064 implement the historic FNV-0 hash (used to generate FNV-1a and FNV-1 offset basis only).

To test FNV hashes, try:

/usr/local/bin/fnv1a64 -t 1 -v
/usr/local/bin/fnv1a32 -t 1 -v

/usr/local/bin/fnv164 -t 1 -v
/usr/local/bin/fnv132 -t 1 -v

/usr/local/bin/fnv032 -t 1 -v
/usr/local/bin/fnv064 -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-1a:

FNV1A_32_INIT               /* 32 bit FNV-1a initial basis */
FNV1A_64_INIT               /* 64 bit FNV-1a initial basis */

FNV-1:

FNV1_32_INIT                /* 32 bit FNV-1 initial basis */
FNV1_64_INIT                /* 64 bit FNV-1 initial basis */

FNV-0:

FNV0_32_INIT                /* 32 bit FNV-0 initial basis */
FNV0_64_INIT                /* 64 bit FNV-0 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 of the recommended FNV-1a 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);

To use

FNV-1a 64-bit

Recommended FNV-1a 64-bit hash:

/usr/local/bin/fnv1a64 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [arg ...]

    -h         print help and exit
    -v         verbose mode, print arg after hash (implies -m)
    -V         print version and exit

    -b bcnt    mask off all but the lower bcnt bits (default 64)
    -m         multiple hashes, one per line for each arg
    -s arg     hash arg as a string (ignoring terminating NUL bytes)
    -t code    test hash code: (0 ==> generate test vectors
                                1 ==> validate against FNV test vectors)

    arg        string (if -s was given) or filename (default stdin)

Exit codes:
    0         all OK
    2         -h and help string printed or -V and version string printed
    3         command line error
    4         error on opening or reading file
 >= 10        test suite error
 >= 20        internal error

fnv1a64 version: 5.0.5 2025-04-13

FNV-1a 32-bit

Recommended FNV-1a 32-bit hash:

/usr/local/bin/fnv1a32 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [arg ...]

    -h         print help and exit
    -v         verbose mode, print arg after hash (implies -m)
    -V         print version and exit

    -b bcnt    mask off all but the lower bcnt bits (default 32)
    -m         multiple hashes, one per line for each arg
    -s arg     hash arg as a string (ignoring terminating NUL bytes)
    -t code    test hash code: (0 ==> generate test vectors
                                1 ==> validate against FNV test vectors)

    arg        string (if -s was given) or filename (default stdin)

Exit codes:
    0         all OK
    2         -h and help string printed or -V and version string printed
    3         command line error
    4         error on opening or reading file
 >= 10        test suite error
 >= 20        internal error

fnv1a32 version: 5.0.5 2025-04-13

FNV-1 64-bit

Common FNV-1 64-bit hash:

/usr/local/bin/fnv164 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [arg ...]

    -h         print help and exit
    -v         verbose mode, print arg after hash (implies -m)
    -V         print version and exit

    -b bcnt    mask off all but the lower bcnt bits (default 64)
    -m         multiple hashes, one per line for each arg
    -s arg     hash arg as a string (ignoring terminating NUL bytes)
    -t code    test hash code: (0 ==> generate test vectors
                                1 ==> validate against FNV test vectors)

    arg        string (if -s was given) or filename (default stdin)

Exit codes:
    0         all OK
    2         -h and help string printed or -V and version string printed
    3         command line error
    4         error on opening or reading file
 >= 10        test suite error
 >= 20        internal error

fnv164 version: 5.0.5 2025-04-13

FNV-1 32-bit

Common FNV-1 32-bit hash:

/usr/local/bin/fnv132 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [arg ...]

    -h         print help and exit
    -v         verbose mode, print arg after hash (implies -m)
    -V         print version and exit

    -b bcnt    mask off all but the lower bcnt bits (default 32)
    -m         multiple hashes, one per line for each arg
    -s arg     hash arg as a string (ignoring terminating NUL bytes)
    -t code    test hash code: (0 ==> generate test vectors
                                1 ==> validate against FNV test vectors)

    arg        string (if -s was given) or filename (default stdin)

Exit codes:
    0         all OK
    2         -h and help string printed or -V and version string printed
    3         command line error
    4         error on opening or reading file
 >= 10        test suite error
 >= 20        internal error

fnv132 version: 5.0.5 2025-04-13

FNV-0 64-bit

Historic FNV-0 64-bit hash (used to generate FNV-1a and FNV-1 offset basis only):

/usr/local/bin/fnv064 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [arg ...]

    -h         print help and exit
    -v         verbose mode, print arg after hash (implies -m)
    -V         print version and exit

    -b bcnt    mask off all but the lower bcnt bits (default 64)
    -m         multiple hashes, one per line for each arg
    -s arg     hash arg as a string (ignoring terminating NUL bytes)
    -t code    test hash code: (0 ==> generate test vectors
                                1 ==> validate against FNV test vectors)

    arg        string (if -s was given) or filename (default stdin)

Exit codes:
    0         all OK
    2         -h and help string printed or -V and version string printed
    3         command line error
    4         error on opening or reading file
 >= 10        test suite error
 >= 20        internal error

NOTE: Programs that begin with fnv0 implement the FNV-0 hash.
      The FNV-0 hash is historic FNV algorithm that is now deprecated.

fnv064 version: 5.0.5 2025-04-13

FNV-0 32-bit

Historic FNV-0 32-bit hash (used to generate FNV-1a and FNV-1 offset basis only):

/usr/local/bin/fnv032 [-h] [-v] [-V] [-b bcnt] [-m] [-s arg] [-t code] [arg ...]

    -h         print help and exit
    -v         verbose mode, print arg after hash (implies -m)
    -V         print version and exit

    -b bcnt    mask off all but the lower bcnt bits (default 32)
    -m         multiple hashes, one per line for each arg
    -s arg     hash arg as a string (ignoring terminating NUL bytes)
    -t code    test hash code: (0 ==> generate test vectors
                                1 ==> validate against FNV test vectors)

    arg        string (if -s was given) or filename (default stdin)

Exit codes:
    0         all OK
    2         -h and help string printed or -V and version string printed
    3         command line error
    4         error on opening or reading file
 >= 10        test suite error
 >= 20        internal error

NOTE: Programs that begin with fnv0 implement the FNV-0 hash.
      The FNV-0 hash is historic FNV algorithm that is now deprecated.

fnv032 version: 5.0.5 2025-04-13

Reporting Security Issues

To report a security issue, please visit "Reporting Security Issues".