MurMurHash64B in MySQL dialect of SQL

MurMur.sql

drop function if exists MurmurHash64B;
delimiter $$
create function MurmurHash64B(s longblob, seed int unsigned)
returns bigint unsigned
deterministic no sql
begin
    declare m int unsigned default 0x5bd1e995;
    declare r int default 24;
    
    declare len int default length(s);
    declare i int default 1;
    declare h1 int unsigned default len ^ seed;
    declare h2 int unsigned default 0;
    declare k1, k2 int unsigned;
    declare h bigint unsigned;
    
    while len >= 8 do
        set k1 = cast(conv(hex(reverse(mid(s, i, 4))), 16, 10) as unsigned integer);
        set k1 = (k1 * m) & 0xffffffff;
        set k1 = k1 ^ (k1 >> r);
        set k1 = (k1 * m) & 0xffffffff;
        set h1 = (h1 * m) & 0xffffffff;
        set h1 = h1 ^ k1;

        set k2 = cast(conv(hex(reverse(mid(s, i + 4, 4))), 16, 10) as unsigned integer);
        set k2 = (k2 * m) & 0xffffffff;
        set k2 = k2 ^ (k2 >> r);
        set k2 = (k2 * m) & 0xffffffff;
        set h2 = (h2 * m) & 0xffffffff;
        set h2 = h2 ^ k2;
        set len = len - 8;
        set i = i + 8;
    end while;  
    
    if len >= 4 then
        set k1 = cast(conv(hex(reverse(mid(s, i, 4))), 16, 10) as unsigned integer);
        set k1 = (k1 * m) & 0xffffffff;
        set k1 = k1 ^ (k1 >> r);
        set k1 = (k1 * m) & 0xffffffff;
        set h1 = (h1 * m) & 0xffffffff;
        set h1 = h1 ^ k1;
        set len = len - 4;
        set i = i + 4; 
    end if;
    
    if len >= 1 then
        if len >= 2 then
            if len >= 3 then
                set h2 = h2 ^ (ord(mid(s, i + 2, 1)) << 16);
            end if;
            set h2 = h2 ^ (ord(mid(s, i + 1)) << 8);
        end if;
        set h2 = h2 ^ ord(mid(s, i, 1));
        set h2 = (h2 * m) & 0xffffffff;
    end if;
    
    set h1 = ((h1 ^ (h2 >> 18)) * m) & 0xffffffff;
    set h2 = ((h2 ^ (h1 >> 22)) * m) & 0xffffffff;
    set h1 = ((h1 ^ (h2 >> 17)) * m) & 0xffffffff;
    set h2 = ((h2 ^ (h1 >> 19)) * m) & 0xffffffff;
    
    set h = h1;
    set h = (h << 32) | h2;

    return h;
end$$
delimiter ;

An implementation of MurMurHash64B in MySQL's dialect of SQL. Similar, but not identical to Transact-SQL.