Tôi sẽ để nó ở đây vì tôi sẽ cần sử dụng nó sau. Đây là một nguồn cho một công cụ tương thích nhị phân nhỏ sẽ hoạt động tốt như nhau trong lắp ráp, C và C ++.
GetErrorMessageLib.c (được biên dịch thành GetErrorMessageLib.dll)
#include <Windows.h>
/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
__declspec(dllexport)
int GetErrorMessageA(DWORD dwErrorCode, LPSTR lpResult, DWORD dwBytes)
{
LPSTR tmp;
DWORD result_len;
result_len = FormatMessageA (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPSTR)&tmp,
0,
NULL
);
if (result_len == 0) {
return -1;
}
// FormatMessage's return is 1 character too short.
++result_len;
strncpy(lpResult, tmp, dwBytes);
lpResult[dwBytes - 1] = 0;
LocalFree((HLOCAL)tmp);
if (result_len <= dwBytes) {
return 0;
} else {
return result_len;
}
}
/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
__declspec(dllexport)
int GetErrorMessageW(DWORD dwErrorCode, LPWSTR lpResult, DWORD dwBytes)
{
LPWSTR tmp;
DWORD nchars;
DWORD result_bytes;
nchars = dwBytes >> 1;
result_bytes = 2 * FormatMessageW (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPWSTR)&tmp,
0,
NULL
);
if (result_bytes == 0) {
return -1;
}
// FormatMessage's return is 1 character too short.
result_bytes += 2;
wcsncpy(lpResult, tmp, nchars);
lpResult[nchars - 1] = 0;
LocalFree((HLOCAL)tmp);
if (result_bytes <= dwBytes) {
return 0;
} else {
return result_bytes * 2;
}
}
phiên bản nội tuyến (GetErrorMessage.h):
#ifndef GetErrorMessage_H
#define GetErrorMessage_H
#include <Windows.h>
/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
static inline int GetErrorMessageA(DWORD dwErrorCode, LPSTR lpResult, DWORD dwBytes)
{
LPSTR tmp;
DWORD result_len;
result_len = FormatMessageA (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPSTR)&tmp,
0,
NULL
);
if (result_len == 0) {
return -1;
}
// FormatMessage's return is 1 character too short.
++result_len;
strncpy(lpResult, tmp, dwBytes);
lpResult[dwBytes - 1] = 0;
LocalFree((HLOCAL)tmp);
if (result_len <= dwBytes) {
return 0;
} else {
return result_len;
}
}
/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
static inline int GetErrorMessageW(DWORD dwErrorCode, LPWSTR lpResult, DWORD dwBytes)
{
LPWSTR tmp;
DWORD nchars;
DWORD result_bytes;
nchars = dwBytes >> 1;
result_bytes = 2 * FormatMessageW (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPWSTR)&tmp,
0,
NULL
);
if (result_bytes == 0) {
return -1;
}
// FormatMessage's return is 1 character too short.
result_bytes += 2;
wcsncpy(lpResult, tmp, nchars);
lpResult[nchars - 1] = 0;
LocalFree((HLOCAL)tmp);
if (result_bytes <= dwBytes) {
return 0;
} else {
return result_bytes * 2;
}
}
#endif /* GetErrorMessage_H */
usecase động (giả sử rằng mã lỗi là hợp lệ, nếu không thì cần kiểm tra -1):
#include <Windows.h>
#include <Winbase.h>
#include <assert.h>
#include <stdio.h>
int main(int argc, char **argv)
{
int (*GetErrorMessageA)(DWORD, LPSTR, DWORD);
int (*GetErrorMessageW)(DWORD, LPWSTR, DWORD);
char result1[260];
wchar_t result2[260];
assert(LoadLibraryA("GetErrorMessageLib.dll"));
GetErrorMessageA = (int (*)(DWORD, LPSTR, DWORD))GetProcAddress (
GetModuleHandle("GetErrorMessageLib.dll"),
"GetErrorMessageA"
);
GetErrorMessageW = (int (*)(DWORD, LPWSTR, DWORD))GetProcAddress (
GetModuleHandle("GetErrorMessageLib.dll"),
"GetErrorMessageW"
);
GetErrorMessageA(33, result1, sizeof(result1));
GetErrorMessageW(33, result2, sizeof(result2));
puts(result1);
_putws(result2);
return 0;
}
trường hợp sử dụng thông thường (giả sử mã lỗi là hợp lệ, nếu không thì cần kiểm tra trả lại -1):
#include <stdio.h>
#include "GetErrorMessage.h"
#include <stdio.h>
int main(int argc, char **argv)
{
char result1[260];
wchar_t result2[260];
GetErrorMessageA(33, result1, sizeof(result1));
puts(result1);
GetErrorMessageW(33, result2, sizeof(result2));
_putws(result2);
return 0;
}
ví dụ sử dụng với gnu lắp ráp như trong MinGW32 (một lần nữa, giả sử rằng mã lỗi là hợp lệ, nếu không thì cần kiểm tra -1).
.global _WinMain@16
.section .text
_WinMain@16:
// eax = LoadLibraryA("GetErrorMessageLib.dll")
push $sz0
call _LoadLibraryA@4 // stdcall, no cleanup needed
// eax = GetProcAddress(eax, "GetErrorMessageW")
push $sz1
push %eax
call _GetProcAddress@8 // stdcall, no cleanup needed
// (*eax)(errorCode, szErrorMessage)
push $200
push $szErrorMessage
push errorCode
call *%eax // cdecl, cleanup needed
add $12, %esp
push $szErrorMessage
call __putws // cdecl, cleanup needed
add $4, %esp
ret $16
.section .rodata
sz0: .asciz "GetErrorMessageLib.dll"
sz1: .asciz "GetErrorMessageW"
errorCode: .long 33
.section .data
szErrorMessage: .space 200
kết quả: The process cannot access the file because another process has locked a portion of the file.