nasm astrspn函数 x86

xxx.asm

%define p1 ebp+8
%define p2 ebp+12
%define p3 ebp+16

section .text
  global dllmain
  export astrspn

dllmain:
  mov eax,1
  ret 12

;---------------------------------------------------;
; 返回不属于一组字符的字符串中第一个字符的索引
;---------------------------------------------------;
astrspn:
  push ebp
  mov ebp,esp
  sub esp,8

  mov edx,[p1]	; const char *str
  mov ecx,[p2]	; const char *strCharSet
  xor eax,eax

  ; 临时变量
  mov [ebp-4],ecx
  mov [ebp-8],ebx

  ;-------------------------------------;
  ; 遍历 str
  ;-------------------------------------;
  .forStr:
  mov bh,[edx]
  test bh,bh
  jz .return

  ;-------------------------------------;
  ; 遍历 strCharSet
  ;-------------------------------------;
  .forStrCharSet:
  mov bl,[ecx]
  test bl,bl
  jz .return	; 没找到退出函数

  cmp bh,bl
  je .forbreak	; 相等 next str

  inc ecx
  jmp .forStrCharSet	; 不相等 next strCharSet

  .forbreak:
  mov ecx,[ebp-4]
  inc edx
  inc eax
  jmp .forStr

  .return:
  mov ebx,[ebp-8]
  add esp,8
  mov esp,ebp
  pop ebp
  ret 8

c++:

#include <iostream>
#include <Windows.h>

typedef int (CALLBACK* astrspn_t)(const char* str, const char* strCharSet);
astrspn_t astrspn;

int main()
{
  HMODULE myDLL = LoadLibraryA("xxx.dll");
  astrspn = (astrspn_t)GetProcAddress(myDLL, "astrspn");

  printf("%d\n", strspn( "abbbc", "ab")); // 4
  printf("%d\n", astrspn("abbbc", "ab")); // 4
  return 0;
}