将这段代码用oracle function实现

可以使用 PL/SQL 编写一个 Oracle Function 来实现该算法，具体实现如下：

CREATE OR REPLACE FUNCTION Murmurhash3(input_data VARCHAR2, seed NUMBER) RETURN NUMBER IS
  h NUMBER := seed;
  c1 NUMBER := 3.432918353;
  c2 NUMBER := 0.461845907;
  r1 NUMBER := 15;
  r2 NUMBER := 13;
  m NUMBER := 5;
  n NUMBER := 3.864292196;
  blkNums NUMBER := TRUNC(DBMS_LOB.GETLENGTH(input_data)/4);
  remaining_bytes VARCHAR2(4);
  k NUMBER := 0;
  i NUMBER := 0;
BEGIN
  FOR i IN 0..blkNums-1 LOOP
    k := ASCII(SUBSTR(input_data, i*4+1, 1)) + 
         ASCII(SUBSTR(input_data, i*4+2, 1))*256 +
         ASCII(SUBSTR(input_data, i*4+3, 1))*65536 +
         ASCII(SUBSTR(input_data, i*4+4, 1))*16777216;
    k := k * c1;
    k := BITAND(BITOR(BITAND(BITOR(BITAND(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(k BITAND 16711935, 65280), 16711935), 255), 4278190080), 16711680), 65280), 16711935), 16711935), 65280), 4278190080), 16711680), 65280), 16711935), 16711935), 65280), r1);
    k := k * c2;
    h := MOD(h*m + n, POWER(2,32));
    h := MOD(h+k, POWER(2,32));
  END LOOP;

  remaining_bytes := SUBSTR(input_data, blkNums*4+1);
  IF LENGTH(remaining_bytes) > 0 THEN
    k := ASCII(SUBSTR(remaining_bytes, 1, 1));
    IF LENGTH(remaining_bytes) > 1 THEN
      k := BITAND(k + ASCII(SUBSTR(remaining_bytes, 2, 1))*256, POWER(2,16)-1);
    END IF;
    IF LENGTH(remaining_bytes) > 2 THEN
      k := BITAND(k + ASCII(SUBSTR(remaining_bytes, 3, 1))*65536, POWER(2,24)-1);
    END IF;
    k := k * c1;
    k := BITAND(BITOR(BITAND(BITOR(BITAND(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(BITOR(k BITAND 16711935, 65280), 16711935), 255), 4278190080), 16711680), 65280), 16711935), 16711935), 65280), 4278190080), 16711680), 65280), 16711935), 16711935), 65280), r1);
    k := k * c2;
    h := MOD(h XOR k, POWER(2,32));
  END IF;

  h := MOD(h XOR LENGTH(input_data), POWER(2,32));
  h := MOD(h XOR (h SHR 16), POWER(2,32));
  h := MOD(h * 0x85ebca6b, POWER(2,32));
  h := MOD(h XOR (h SHR 13), POWER(2,32));
  h := MOD(h * 0xc2b2ae35, POWER(2,32));
  h := MOD(h XOR (h SHR 16), POWER(2,32));

  RETURN h;
END;
/

这个函数接受一个字符串和一个随机数种子作为输入，返回一个 32 位的哈希值。其中，`DBMS_LOB.GETLENGTH` 函数用于获取输入字符串的长度，`ASCII` 函数用于获取字符串中指定位置的字符的 ASCII 码值，`SUBSTR` 函数用于截取字符串的子串，`BITAND` 和 `BITOR` 函数用于位运算，`MOD` 函数用于计算模数，`POWER` 函数用于计算幂次。