nasm astrncat_s函数 x86

xxx.asm:

%define p1 ebp+8

%define p2 ebp+12

%define p3 ebp+16

%define p4 ebp+20

section .text

  global dllmain

  export astrncat_s

dllmain:

  mov eax,1

  ret 12

;------------------------------------------------;

;	将字符追加到字符串

;------------------------------------------------;

astrncat_s:

  push ebp

  mov ebp,esp

  sub esp,8

  mov [ebp-4],ebx

  mov ecx,[p1]	; char *strDest

  mov eax,[p2]	; size_t numberOfElements

  mov edx,[p3]	; const char *strSource

  mov ebx,[p4]	; size_t count

  ; get strDest end

  .for1:

  test eax,eax

  jz .return

  cmp byte [ecx],0

  je .eachCopy

  inc ecx

  dec eax

  jmp .for1

  .eachCopy:

  test ebx,ebx

  jz .return

  test eax,eax

  jz .return

  mov [ebp-8],ebx

  ; copy

  mov bl,byte [edx]

  test bl,bl

  je .return

  mov byte [ecx],bl

  ; next

  mov ebx,[ebp-8]

  inc ecx

  inc edx

  dec eax

  dec ebx

  jmp .eachCopy

  .return:

  xor eax,eax

  mov ebx,[ebp+4]

  add esp,8

  mov esp,ebp

  pop ebp

  ret 16

c++:

#include <iostream>

#include <Windows.h>

typedef int (CALLBACK* astrncat_s_t)(char* strDest, size_t numberOfElements, const char* strSource, size_t count); 

astrncat_s_t astrncat_s;

int main()

{

  HMODULE myDLL = LoadLibraryA("xxx.dll");

  astrncat_s = (astrncat_s_t)GetProcAddress(myDLL, "astrncat_s");

  char s1[10] = "ab";

  const char* s2 = "cde";

  strncat_s(s1, sizeof(s1), s2, 2);

  printf("%s\n", s1); // abcd

  //----------------------------------------------------------------------

  char s3[10] = "ab";

  const char* s4 = "cde";

  astrncat_s(s3, sizeof(s3), s4, 2);

  printf("%s\n", s3); // abcd

  return 0;

}

巴特西

nasm astrncat_s函数 x86

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