C语言与汇编的嵌入式编程：统计字符串中各字符出现的次数

原始C语言：

#include<stdio.h>
void main(){

    char str[];
    char pipei[] = "abcdefghijklmnopqrstuvwxyz";
    int  count[]={};
    int i=,j=;

    scanf("%s",str);
    printf("%s\n",str);

    for(i=;i<;i++)
    {
        for(j=;j<;j++)
        {
            if(str[i]==pipei[j])
                count[j]+=;
        }
    }

    for(j=;j<;j++)
    {
        if(count[j]>)
            printf("%c=%d\n",pipei[j],count[j]);
    }
}

加入汇编后代码：

#include<stdio.h>
void main(){

    char str[];
    char pipei[] = "abcdefghijklmnopqrstuvwxyz";
    int  count[]={};
    int i=,j=;

    scanf("%s",str);
    printf("%s\n",str);

    //外层循环start
    _asm{
        mov eax,    //i=0
        mov ecx,    //i<1024
        loop1:
        mov i,eax
        push eax
        push ecx
    };
    //printf("%c\t",str[i]);

    //内层循环start
    _asm{
        mov eax,
        mov ecx,
        loop2:
        mov j,eax
        push eax
        push ecx
    };

    if(str[i]==pipei[j])
    {
        count[j]+=;
    }

    //内循环end
    __asm{
        pop ecx
        pop eax
        add eax,
        loop loop2
    };

    //外循环end
    _asm{
        pop ecx
        pop eax
        add eax,
        loop loop1
    };

    //输出统计个数
    //外层循环start
    _asm{
        mov eax,    //i=0
        mov ecx,    //i<26
        loop3:
        mov j,eax
        push eax
        push ecx
    };

    if(count[j]>)
        printf("%c=%d\n",pipei[j],count[j]);

    //外循环end
    _asm{
        pop ecx
        pop eax
        add eax,
        loop loop3
    };

}

后面有时间再优化了。。。。

优化如下：

需要掌握的知识  if语句的汇编表示

构造单循环：

#include<stdio.h>
void main(){

    char str[];
    char pipei[] = "abcdefghijklmnopqrstuvwxyz";
    int  count[]={};
    int i=,j=;

    char *str1 = "i=%d\n";
    char *str2 = "%d=%c\t";

    scanf("%s",str);
    printf("%s\n",str);

    printf(str2,i,str[i]);
    //mov         edx,dword ptr [ebp-48Ch]
    //movsx       eax,byte ptr [ebp+edx-400h]
    //push        eax
    //mov         ecx,dword ptr [ebp-48Ch]
    //push        ecx
    //mov         edx,dword ptr [ebp-498h]
    //push        edx
    //call        printf (0040d6c0)
    //add         esp,0Ch
    // ==
    //mov     edx, i
    //movsx    eax,str[edx]
    //push    eax
    //mov        ecx,i
    //push    ecx
    //mov        edx,str2
    //push    edx
    //call    printf
    //add        esp,12            //12=3个变量*4

    _asm{
            mov        i,            //i=0
start_1024:    nop
            mov        eax,i
            add        eax,
            mov        i,eax        //i++

            cmp        i,        //    if i<10
            jge        end_1024        

            //逐个输出    printf(str2,str[i]);
            mov     edx, i
            movsx    eax,str[edx]
            push    eax
            mov        ecx,i
            push    ecx
            mov        edx,str2
            push    edx
            call    printf
            add        esp,            //12=3个变量*4

            jmp        start_1024        //for 1024

end_1024:    nop
    }
}

进一步构造嵌套循环：

#include<stdio.h>
void main(){

    char str[];
    char pipei[] = "abcdefghijklmnopqrstuvwxyz";
    int  count[]={};
    int i=,j=;

    char *str1 = "i=%d\n";
    char *str2 = "\n第一层循环%d=%c\n";
    char *str3 = "%d=%c\t";

    scanf("%s",str);
    printf("%s\n",str);

    printf(str2,i,str[i]);

    _asm{
            //第一个外循环
            mov        i,            //i=0
start_1024:    nop
            mov        eax,i
            add        eax,
            mov        i,eax        //i++
            cmp        i,        //    if i<10
            jge        end_1024        

            //第二个内循环
            mov        j,            //j=0
start_26:    nop
            mov        eax,j
            add        eax,
            mov        j,eax        //j++
            cmp        j,
            jge        end_26

            //逐个输出pipei
            mov     edx, j
            movsx    eax,pipei[edx]
            push    eax
            mov        ecx,j
            push    ecx
            mov        edx,str3
            push    edx
            call    printf
            add        esp,            //12=3个变量*4

            jmp        start_26        //for 1024
end_26:        nop

            //逐个输出    printf(str2,str[i]);
            mov     edx, i
            movsx    eax,str[edx]
            push    eax
            mov        ecx,i
            push    ecx
            mov        edx,str2
            push    edx
            call    printf
            add        esp,            //12=3个变量*4

            jmp        start_1024        //for 1024

end_1024:    nop

    }

}

加入判断与统计输出代码：

#include<stdio.h>
void main(){
    char str[];
    char pipei[] = "abcdefghijklmnopqrstuvwxyz";
    int  count[]={};
    int i=,j=;

    char *str1 = "i=%d\n";
    char *str2 = "\n第一层循环%d=%c\n";
    char *str3 = "i=%d,j=%d,c=%c\t";
    char *str4 = "%c=%d\t";

    scanf("%s",str);
    printf("%s\n",str);

    _asm{
            //第一个外循环
            mov        i,-            //i=0
start_1024:    nop
            mov        eax,i
            add        eax,
            mov        i,eax        //i++
            cmp        i,        //    if i<1024
            jge        end_1024    

            //判断第i个字符串是否为结束符，如果是则退出总循环
            movsx    eax,str[eax]
            cmp        eax,0h
            je        end_1024

            //  \n第一层循环%d=%c\n  printf(str2,i,str[i]);
            mov     edx, i
            movsx    eax,str[edx]
            push    eax
            mov        ecx,i
            push    ecx
            mov        edx,str2
            push    edx
            call    printf
            add        esp,            //12=3个变量*4

                //第二个内循环
                mov        j,-            //j=-1
    start_26:    nop
                mov        eax,j
                add        eax,
                mov        j,eax        //j++
                cmp        j,
                jge        end_26

                //逐个输出 "i=%d,j=%d,c=%c\t";  pipei
                mov     edx, j
                movsx    eax,pipei[edx]
                push    eax
                mov        ecx,j
                push    ecx
                mov        ecx,i
                push    ecx
                mov        edx,str3
                push    edx
                call    printf
                add        esp,            //12=4个变量*4

                //判断str[i]是否与pipei[j]相等，相等加一并退出第二循环
                //if(str[i]==pipei[j])
                mov        edx,i
                movsx    eax,str[edx]
                mov        ecx,j
                movsx    edx,pipei[ecx]
                cmp        eax,edx
                jne        end_count//不相等
                //{count[j]+=1   //相等
                mov        eax,j
                mov        ecx,count[eax*]
                add        ecx,
                mov        edx,j
                mov        count[edx*],ecx
                //break;
                jmp start_1024                //如果找到一个匹配的，则退出第二循环

    end_count:    nop
                jmp        start_26        //for 26
    end_26:        nop

            jmp        start_1024        //for 1024
end_1024:    nop
        //到这里统计算法已经结束

            //输出统计个数
            mov        j,-            //j=-1
start_all:    nop
            mov        eax,j
            add        eax,
            mov        j,eax        //j++
            cmp        j,
            jge        end_all

            //逐个输出printf(str4,pipei[j],count[j]);
            mov     edx,j
            mov        ecx,count[edx*]
            push    ecx
            movsx    eax,pipei[edx]
            push    eax
            mov        edx,str4
            push    edx
            call    printf
            add        esp,            //12=3个变量*4

            jmp        start_all        //for 26
end_all:    nop

    }
}