包含返回代码部分,用C要想高效还是传递指针最好,可以通过指针直接修改原始数据,节省了大量的数据传递时间,那样应该和汇编效率不相上下.
原代码
unsigned long SwapINT32(unsigned long dData)
{
// dData = ((dData&0xff)<<24) |((dData&0xff00)<<8) |
// ((dData&0xff000000)>>24) | ((dData&0xff0000)>>8);
union{
U8 b[4];
U32 x;
}temp;
temp.b[3] = ((U8*)&dData)[0];
temp.b[2] = ((U8*)&dData)[1];
temp.b[1] = ((U8*)&dData)[2];
temp.b[0] = ((U8*)&dData)[3];
return temp.x;
}
编译效果
; #define U8 unsigned char
; #define U16 unsigned int
; #define U32 unsigned long
;
;
; unsigned long SwapINT32(unsigned long dData)
RSEG ?PR?_SwapINT32?MAIN
_SwapINT32:
USING 0
; SOURCE LINE # 130
MOV dData?141+03H,R7
MOV dData?141+02H,R6
MOV dData?141+01H,R5
MOV dData?141,R4
; {
; SOURCE LINE # 131
; // dData = ((dData&0xff)<<24) |((dData&0xff00)<<8) |
; // ((dData&0xff000000)>>24) | ((dData&0xff0000)>>8);
;
; union{
; U8 b[4];
; U32 x;
; }temp;
;
; temp.b[3] = ((U8*)&dData)[0];
; SOURCE LINE # 140
MOV temp?142+03H,dData?141
; temp.b[2] = ((U8*)&dData)[1];
; SOURCE LINE # 141
MOV temp?142+02H,dData?141+01H
; temp.b[1] = ((U8*)&dData)[2];
; SOURCE LINE # 142
MOV temp?142+01H,dData?141+02H
; temp.b[0] = ((U8*)&dData)[3];
; SOURCE LINE # 143
MOV temp?142,dData?141+03H
;
; return temp.x;
; SOURCE LINE # 145
MOV R7,temp?142+03H
MOV R6,temp?142+02H
MOV R5,temp?142+01H
MOV R4,temp?142
; }
; SOURCE LINE # 146
?C0020:
RET
; END OF _SwapINT32
END |
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