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MurMurHash64B in Transact-SQL
create function [dbo].[MurmurHash64B]
(
@s varbinary(max),
@seed bigint = 0
)
returns bigint
as
begin
declare @len int = datalength(@s), @i int = 1
declare @m bigint = 0x5bd1e995
declare @h1 bigint = @len ^ (@seed & 0xffffffff)
declare @h2 bigint = 0
declare @k1 bigint, @k2 bigint
while @len >= 8
begin
set @k1 = cast(convert(binary(4), reverse(substring(@s, @i, 4))) as int)
set @k1 = (@k1 * @m) & 0xffffffff
set @k1 ^= @k1 / 0x1000000
set @k1 = (@k1 * @m) & 0xffffffff
set @h1 = (@h1 * @m) & 0xffffffff
set @h1 ^= @k1;
set @k2 = cast(convert(binary(4), reverse(substring(@s, @i+4, 4))) as int)
set @k2 = (@k2 * @m) & 0xffffffff
set @k2 ^= @k2 / 0x1000000
set @k2 = (@k2 * @m) & 0xffffffff
set @h2 = (@h2 * @m) & 0xffffffff
set @h2 ^= @k2
set @len -= 8
set @i += 8
end
if @len >= 4
begin
set @k1 = cast(convert(binary(4), reverse(substring(@s, @i, 4))) as int)
set @k1 = (@k1 * @m) & 0xffffffff
set @k1 ^= @k1 / 0x1000000
set @k1 = (@k1 * @m) & 0xffffffff
set @h1 = (@h1 * @m) & 0xffffffff
set @h1 ^= @k1
set @len -= 4
set @i += 4
end
if @len >= 1
begin
if @len >= 2
begin
if @len >= 3
set @h2 ^= ascii(substring(@s, @i+2, 1)) * 0x10000
set @h2 ^= ascii(substring(@s, @i+1, 1)) * 0x100
end
set @h2 ^= ascii(substring(@s, @i, 1))
set @h2 = (@h2 * @m) & 0xffffffff
end
set @h1 = ((@h1 ^ (@h2 / 0x40000)) * @m) & 0xffffffff
set @h2 = ((@h2 ^ (@h1 / 0x400000)) * @m) & 0xffffffff
set @h1 = ((@h1 ^ (@h2 / 0x20000)) * @m) & 0xffffffff
set @h2 = ((@h2 ^ (@h1 / 0x80000)) * @m) & 0xffffffff
declare @h bigint
if (@h1 & 0x80000000) <> 0
begin
set @h1 &= 0x7fffffff
set @h = (@h1 * 0x100000000) | 0x8000000000000000
end
else
set @h = @h1 * 0x100000000
set @h |= @h2
return @h
end
@sevaa
Owner
sevaa commented Nov 7, 2016

MSSQL is capable of storing 64-bit variables, but it doesn't support unsigned integer types, and treats arithmetic overflow as an exception. So the B flavor, which was originally geared towards 32-bit machines, is a better fit than A.

The official home of MurmurHash is at Github.

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