ABAP语言实现左移 <<、无符号右移 >>> 位移操作

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ABAP语言实现左移 <<、无符号右移 >>> 位移操作

这几天要在ABAP中实现 3DES 标准对称加密算法，与其他外部系统进行加密/解密操作。由于ABAP语言中没有左移 <<、无符号右移 >>> 操作，只能自己实现

思路：

如果移动的位数bit是字节（8位）的整数倍，则直接使用 SHIFT BY p PLACES RIGHT IN BYTE MODE.这样的语句搞定（这样效率会更高），如果非字节整数倍，则需要借助于SET BIT来完成，实现时，要注意整型的字节序格式，本人开发环境是低字节序（低位在前，高位在后），与人的阅读习惯是反的（但要注意的字节里面还是高位在前，低位在后），左右位移规则如下（同一种颜色为移动后所在位置）：

DATA: BEGIN OF index_map OCCURS 0,
 index_inner TYPE i,
 index TYPE i,
 END OF index_map .

FORM init .
 CLEAR: index_map[].
 index_map-index_inner = 1.
 index_map-index = 8.
 APPEND index_map.
 index_map-index_inner = 2.
 index_map-index = 7.
 APPEND index_map.
 index_map-index_inner = 3.
 index_map-index = 6.
 APPEND index_map.
 index_map-index_inner = 4.
 index_map-index = 5.
 APPEND index_map.
 index_map-index_inner = 5.
 index_map-index = 4.
 APPEND index_map.
 index_map-index_inner = 6.
 index_map-index = 3.
 APPEND index_map.
 index_map-index_inner = 7.
 index_map-index = 2.
 APPEND index_map.
 index_map-index_inner = 8.
 index_map-index = 1.
 APPEND index_map.
 index_map-index_inner = 9.
 index_map-index = 16.
 APPEND index_map.
 index_map-index_inner = 10.
 index_map-index = 15.
 APPEND index_map.
 index_map-index_inner = 11.
 index_map-index = 14.
 APPEND index_map.
 index_map-index_inner = 12.
 index_map-index = 13.
 APPEND index_map.
 index_map-index_inner = 13.
 index_map-index = 12.
 APPEND index_map.
 index_map-index_inner = 14.
 index_map-index = 11.
 APPEND index_map.
 index_map-index_inner = 15.
 index_map-index = 10.
 APPEND index_map.
 index_map-index_inner = 16.
 index_map-index = 9.
 APPEND index_map.
 index_map-index_inner = 17.
 index_map-index = 24.
 APPEND index_map.
 index_map-index_inner = 18.
 index_map-index = 23.
 APPEND index_map.
 index_map-index_inner = 19.
 index_map-index = 22.
 APPEND index_map.
 index_map-index_inner = 20.
 index_map-index = 21.
 APPEND index_map.
 index_map-index_inner = 21.
 index_map-index = 20.
 APPEND index_map.
 index_map-index_inner = 22.
 index_map-index = 19.
 APPEND index_map.
 index_map-index_inner = 23.
 index_map-index = 18.
 APPEND index_map.
 index_map-index_inner = 24.
 index_map-index = 17.
 APPEND index_map.
 index_map-index_inner = 25.
 index_map-index = 32.
 APPEND index_map.
 index_map-index_inner = 26.
 index_map-index = 31.
 APPEND index_map.
 index_map-index_inner = 27.
 index_map-index = 30.
 APPEND index_map.
 index_map-index_inner = 28.
 index_map-index = 29.
 APPEND index_map.
 index_map-index_inner = 29.
 index_map-index = 28.
 APPEND index_map.
 index_map-index_inner = 30.
 index_map-index = 27.
 APPEND index_map.
 index_map-index_inner = 31.
 index_map-index = 26.
 APPEND index_map.
 index_map-index_inner = 32.
 index_map-index = 25.
 APPEND index_map.
ENDFORM.

*&---------------------------------------------------------------------*
*& Form lshfit_i
*&---------------------------------------------------------------------*
* 整型左移
*----------------------------------------------------------------------*
* -->I 待位移的数
* -->PLACES 移几位
* -->I2 位移后的数
*----------------------------------------------------------------------*
FORM lshfit_i USING i TYPE i places TYPE i i2 TYPE i.
 DATA: start1 TYPE i ,start2 TYPE i.
 DATA: b TYPE n.
 DATA: i3 TYPE i.
 FIELD-SYMBOLS: <i3> TYPE x.

 FIELD-SYMBOLS: TYPE x.
 FIELD-SYMBOLS: TYPE x.
 DATA: _31(4) TYPE x,p TYPE i.
 p = places.
 IF places < 0.
 _31 = '1F000000'.
 ASSIGN p TO CASTING.
 = BIT-AND _31.
 ENDIF.

 i2 = i.
 ASSIGN i2 TO CASTING.

 IF p = 24 OR p = 16 OR p = 8.
 p = p / 8.
 SHIFT BY p PLACES RIGHT IN BYTE MODE.
 ELSE.
 ASSIGN i3 TO <i3> CASTING.
 start1 = 32 - p.

 WHILE start1 >= 1.
 READ TABLE index_map INDEX start1.
 GET BIT index_map-index OF INTO b.
 IF b = 1.
 start2 = start1 + p.
 READ TABLE index_map INDEX start2.
 SET BIT index_map-index OF <i3> TO b.
 ENDIF.
 start1 = start1 - 1.
 ENDWHILE.
 = <i3>.
 ENDIF.
ENDFORM. "lshfit_i

*&---------------------------------------------------------------------*
*& Form rshfit_i
*&---------------------------------------------------------------------*
* 整型右移
*----------------------------------------------------------------------*
* -->I 待位移的数
* -->PLACES 移几位
* -->I2 位移后的数
*----------------------------------------------------------------------*
FORM rshfit_i USING i TYPE i places TYPE i i2 TYPE i.
 DATA: start1 TYPE i ,start2 TYPE i.
 DATA: b TYPE n.
 DATA: i3 TYPE i.
 FIELD-SYMBOLS: <i3> TYPE x.
 FIELD-SYMBOLS: TYPE x.
 FIELD-SYMBOLS: TYPE x.
 DATA: _31(4) TYPE x,p TYPE i.
 DATA multiplier TYPE i.

 p = places.
 IF p < 0.
 _31 = '1F000000'.
 ASSIGN p TO CASTING.
 = BIT-AND _31.
 ENDIF.

 i2 = i.

 ASSIGN i2 TO CASTING.

 IF p = 24 OR p = 16 OR p = 8.
 p = p / 8.
 SHIFT BY p PLACES LEFT IN BYTE MODE.
 ELSE.
 IF i >= 0 AND p < 31 .
 multiplier = 2 ** p.
 i2 = i DIV multiplier.
 ELSE.
 ASSIGN i3 TO <i3> CASTING.

 start1 = p + 1.

 WHILE start1 <= 32.
 READ TABLE index_map INDEX start1.
 GET BIT index_map-index OF INTO b.
 IF b = 1.
 start2 = start1 - p.
 READ TABLE index_map INDEX start2.
 SET BIT index_map-index OF <i3> TO b.
 ENDIF.
 start1 = start1 + 1.
 ENDWHILE.
 = <i3>.
 ENDIF.
 ENDIF.
ENDFORM. "rshfit_i

*&---------------------------------------------------------------------*
*& Form c2int
*&---------------------------------------------------------------------*
* 字符转整型
*----------------------------------------------------------------------*
* -->C1 text
* -->I text
*----------------------------------------------------------------------*
FORM c2int USING c1 TYPE c i TYPE i.
 FIELD-SYMBOLS <c1> TYPE x.
 FIELD-SYMBOLS: TYPE x.
 ASSIGN c1 TO <c1> CASTING.
 ASSIGN i TO CASTING.
 = <c1>.
ENDFORM.

*&---------------------------------------------------------------------*
*& Form lshfit_c
*&---------------------------------------------------------------------*
* 字符左移
*----------------------------------------------------------------------*
* -->C1 待位移的字符
* -->PLACES 移几位
* -->I 位移后的结果
*----------------------------------------------------------------------*
FORM lshfit_c USING c1 TYPE c places TYPE i i TYPE i.
 PERFORM c2int USING c1 i.
 PERFORM lshfit_i USING i places i.
ENDFORM. "lshfit

*&---------------------------------------------------------------------*
*& Form rshfit_c
*&---------------------------------------------------------------------*
* 字符右移
*----------------------------------------------------------------------*
* -->C1 待位移的字符
* -->PLACES 移几位
* -->I 位移后的结果
*----------------------------------------------------------------------*
FORM rshfit_c USING c1 TYPE c places TYPE i i TYPE i.
 PERFORM c2int USING c1 i.
 PERFORM rshfit_i USING i places i.
ENDFORM. "rshfit_c

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原文地址：https://www.cnblogs.com/jiangzhengjun/p/6434000.html

ABAP语言实现 左移 <<、无符号右移 >>> 位移操作

ABAP语言实现左移 <<、无符号右移 >>> 位移操作