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stdlib_32_bit_fnv_hashes.fypp
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!!------------------------------------------------------------------------------
!! `FNV_1_HASH` and `FNV_1A_Hash` are translations to Fortran 2008 of the
!! `FNV-1` and `FNV-1a` hash functions of Glenn Fowler, Landon Curt Noll,
!! and Phong Vo, that has been released into the public domain. Permission
!! has been granted, by Landon Curt Noll, for the use of these algorithms
!! in the Fortran Standard Library. A description of these functions is
!! available at https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function.
!!------------------------------------------------------------------------------
!#! Integer kinds to be considered during templating
#:set INT_KINDS = ["int16", "int32", "int64"]
submodule(stdlib_32_bit_hash_functions) stdlib_32_bit_fnv_hashes
!! An implementation of the FNV hashes 1 and 1a of Glenn Fowler, Landon Curt
!! Noll, and Kiem-Phong-Vo,
!! https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function
implicit none
integer(int_hash), parameter :: &
offset_basis = int( z'811C9DC5', int_hash ), &
prime = int( z'01000193', int_hash )
contains
pure module function int8_fnv_1( key ) result(hash_code)
!! The original FNV-1 8-bit key algorithm.
integer(int8), intent(in) :: key(:)
integer(int_hash) :: hash_code
integer(int64) :: i
hash_code = offset_basis
do i=1_int64, size(key, kind=int64)
hash_code = hash_code * prime
if ( little_endian ) then
hash_code = ieor( hash_code, &
transfer( [key(i), 0_int8, 0_int8, 0_int8], &
0_int_hash ) )
else
hash_code = ieor( hash_code, &
transfer( [0_int8, 0_int8, 0_int8, key(i)], &
0_int_hash ) )
end if
end do
end function int8_fnv_1
#:for k1 in INT_KINDS
pure module function ${k1}$_fnv_1( key ) result(hash_code)
! A ${k1}$ array key wrapper for the FNV-1 algorithm.
integer(${k1}$), intent(in) :: key(:)
integer(int_hash) :: hash_code
hash_code = int8_fnv_1( transfer( key, 0_int8, &
bytes_${k1}$* &
size( key, kind=int64 ) ) )
end function ${k1}$_fnv_1
#:endfor
pure module function character_fnv_1( key ) result(hash_code)
! A default character key wrapper for the FNV-1 algorithm.
character(*), intent(in) :: key
integer(int_hash) :: hash_code
hash_code = int8_fnv_1( transfer( key, &
0_int8, &
bytes_char* &
len(key, kind=int64) ) )
end function character_fnv_1
pure module function int8_fnv_1a( key ) result(hash_code)
!! The original FNV-1a 8-bit key algorithm.
integer(int8), intent(in) :: key(:)
integer(int_hash) :: hash_code
integer(int64) :: i
hash_code = offset_basis
do i=1_int64, size(key, kind=int64)
if ( little_endian ) then
hash_code = ieor( hash_code, &
transfer( [key(i), 0_int8, 0_int8, 0_int8], &
0_int_hash ) )
else
hash_code = ieor( hash_code, &
transfer( [0_int8, 0_int8, 0_int8, key(i)], &
0_int_hash ) )
end if
hash_code = hash_code * prime
end do
end function int8_fnv_1a
#:for k1 in INT_KINDS
pure module function ${k1}$_fnv_1a( key ) result(hash_code)
! A ${k1}$ array key wrapper for the FNV-1a algorithm.
integer(${k1}$), intent(in) :: key(:)
integer(int_hash) :: hash_code
hash_code = int8_fnv_1a( transfer( key, 0_int8, &
bytes_${k1}$* &
size(key, kind=int64)) )
end function ${k1}$_fnv_1a
#:endfor
pure module function character_fnv_1a( key ) result(hash_code)
! A default character key wrapper for the FNV-1 algorithm.
character(*), intent(in) :: key
integer(int_hash) :: hash_code
hash_code = int8_fnv_1a( transfer( key, 0_int8, &
(bits_char/bits_int8)* &
len(key, kind=int64) ) )
end function character_fnv_1a
end submodule stdlib_32_bit_fnv_hashes