oracle16进制转10进制，双字节算法实现，优化后

CREATE OR REPLACE PROCEDURE CONVERT_16_10
/*16进制转10进制，双字节算法实现*/
(
  I_DATA          VARCHAR2, 
  O_DATA      OUT VARCHAR2
) 
AS
  V_TMP_BEGIN     INT;
  V_TMP_LEN       INT;
  V_TMP_VAL       INT := 0;
  V_TMP_TEXT      VARCHAR2(1);
  V_TMP_DATA      VARCHAR2(100);
BEGIN

  IF I_DATA IS NULL THEN
    RETURN;
  ELSE
    V_TMP_BEGIN := 1;
    V_TMP_LEN   := LENGTH(I_DATA);
  
    IF V_TMP_LEN > 8 THEN
      RETURN;
    END IF;
  
    IF V_TMP_LEN = 1 AND I_DATA = '0' THEN
      O_DATA := '0';
      RETURN;
    END IF;
  
  END IF;

  WHILE V_TMP_BEGIN <= V_TMP_LEN LOOP
  
    V_TMP_TEXT := SUBSTR(I_DATA, V_TMP_BEGIN, 1);
  
    IF V_TMP_TEXT NOT IN
       ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F') THEN
      RETURN;
    END IF;
  
    IF V_TMP_TEXT = '1' THEN
      V_TMP_DATA := V_TMP_DATA || '0001 ';
    
    ELSIF V_TMP_TEXT = '2' THEN
      V_TMP_DATA := V_TMP_DATA || '0010 ';
    
    ELSIF V_TMP_TEXT = '3' THEN
      V_TMP_DATA := V_TMP_DATA || '0011 ';
    
    ELSIF V_TMP_TEXT = '4' THEN
      V_TMP_DATA := V_TMP_DATA || '0100 ';
    
    ELSIF V_TMP_TEXT = '5' THEN
      V_TMP_DATA := V_TMP_DATA || '0101 ';
    
    ELSIF V_TMP_TEXT = '6' THEN
      V_TMP_DATA := V_TMP_DATA || '0110 ';
    
    ELSIF V_TMP_TEXT = '7' THEN
      V_TMP_DATA := V_TMP_DATA || '0111 ';
    
    ELSIF V_TMP_TEXT = '8' THEN
      V_TMP_DATA := V_TMP_DATA || '1000 ';
    
    ELSIF V_TMP_TEXT = '9' THEN
      V_TMP_DATA := V_TMP_DATA || '1001 ';
    
    ELSIF V_TMP_TEXT = 'A' THEN
      V_TMP_DATA := V_TMP_DATA || '1010 ';
    
    ELSIF V_TMP_TEXT = 'B' THEN
      V_TMP_DATA := V_TMP_DATA || '1011 ';
    
    ELSIF V_TMP_TEXT = 'C' THEN
      V_TMP_DATA := V_TMP_DATA || '1100 ';
    
    ELSIF V_TMP_TEXT = 'D' THEN
      V_TMP_DATA := V_TMP_DATA || '1101 ';
    
    ELSIF V_TMP_TEXT = 'E' THEN
      V_TMP_DATA := V_TMP_DATA || '1110 ';
    
    ELSIF V_TMP_TEXT = 'F' THEN
      V_TMP_DATA := V_TMP_DATA || '1111 ';
    
    ELSE
      V_TMP_DATA := V_TMP_DATA || '0000 ';
    
    END IF;
  
    V_TMP_BEGIN := V_TMP_BEGIN + 1;
  
  END LOOP;

  O_DATA := REPLACE(V_TMP_DATA, ' ', '');

  IF LENGTH(O_DATA) = 32 THEN
    -- 初始值要么为0，要么为最小值
    V_TMP_VAL := TO_NUMBER(SUBSTR(O_DATA, 1, 1)) * POWER(2, 31) * -1;
    -- 重新初始化字符串对象
    O_DATA := SUBSTR(O_DATA, 2);
  
  END IF;

  V_TMP_BEGIN := 1;
  V_TMP_LEN   := LENGTH(O_DATA);

  WHILE V_TMP_BEGIN <= V_TMP_LEN LOOP

    IF SUBSTR(O_DATA, V_TMP_BEGIN, 1) = '1' THEN
    
      V_TMP_VAL := V_TMP_VAL + POWER(2, V_TMP_LEN - V_TMP_BEGIN);
    
    END IF;
  
    V_TMP_BEGIN := V_TMP_BEGIN + 1;
  
  END LOOP;

  O_DATA := TO_CHAR(V_TMP_VAL);

END;