Question

我正在做这个小任务。 C代码传入值基本上是函数，如果找不到该字符，将返回传入的字符串中第一个字符'c'的偏移量，返回-1

目前我在cld和POP ecx说must be the same size

时遇到错误

mov edi, BYTE PTR [esi + eax]说invalid instruction operands

时出错

在PROCS上遇到错误expression expected

我真的不知道该怎么办。

这是C

#include <stdint.h>
#include <stdio.h>

extern "C" {

    int32_t findFirstChar(char *, char);
}

static char *testStrings[] = {
    "",
    "#",
    "abc",
    "abcd",
    "abdefg",
    "ABCdefg",
    "bcdefgh",
    "abdefabcd",
    "abcdefgh",
    "abcabcabcda",
};
#define NUM_TEST_CASES  (sizeof (testStrings) / sizeof (*testStrings))
static char testChars[] = { 'c', 'd' };

int main()
{
    printf("CSIS ICE 11\n\n");

    //int f = findFirstChar(testStrings2[2], 'd');

    for (int i = 0; i < sizeof(testChars); i++) {
        char c = testChars[i];
        for (int j = 0; j < NUM_TEST_CASES; j++) {
            char *s = testStrings[j];
            printf("Char [%c] String [%s] offset [%d]\n", c, s, findFirstChar(s, c));
        }
        printf("\n");
    }


    return 0;
}

这是asm（x86）Masm

.386P           ; use 80386 instruction set
.MODEL flat,C     ; use flat memory model

printf PROTO C, :VARARG

.DATA           ; declare initialzed data here
target DWORD 100 DUP(?)     ;storage space

.STACK          ; use default 1k stack space

doPrologue MACRO nvars  
    PUSH    ebp             ; save caller base pointer
    MOV     ebp, esp        ; set our base pointer
    PUSH    edi
    PUSH    esi             ; end prologuee
ENDM

doEpilogue MACRO
    POP     esi         ; start epilogue
    POP     edi
    MOV     esp, ebp    ; deallocate locals
    POP     ebp         ; restore caller base pointer
ENDM

.CODE           ; contains our code


stringLength PROC PUBLIC
    doPrologue

    MOV     esi, [ebp + 8]
    MOV     eax, 0

    cld                                 ; clear destination
    mov     esi,    BYTE PTR [esi + eax]        ;start
    mov     edi,    OFFSET target       ;emd
    INC     ecx
    rep     movsd                       ;will inc ecx by 1 a as everything is getting coppied 
    PUSH    ecx                         ;saves the counter number

    doEpilogue
    RET
stringLength ENDP

;----------------------------------------------------------------------------
findFirstChar PROC PUBLIC
    doPrologue


    ;CALL stringLength
    POP     ecx
    mov     edi, BYTE PTR [esi + eax]   
    mov     al, [eax]               ; search for 'eax'
                                    ;ecx is already counting length
    cld
    repne   scasb                   ; repeat while not equal
    jnz negOne                      ; no value found so, -1
    MOV eax, edi                    ; get the number of which the char is at

    doEpilogue;
    RET

negONE:
    MOV     eax,-1

    doEpilogue
    RET
findFirstChar ENDP
END

x86 asm在字符串中查找char

0 个答案: