Written in CPP DLL in CPP call no problem, but the call in vb times wrong: VB6. 0 in EXE x66c36314 (Cipher. DLL) with untreated exception: 0 xc0000005: access conflict while reading position 0 x00000000
The younger brother pretty good, really don't understand, please help to see and appreciate

Cipher. CPP

 
# include "stdafx. H" 
# include "Cipher. H" 


BOOL APIENTRY DllMain (HMODULE HMODULE, 
DWORD ul_reason_for_call, 
LPVOID lpReserved 
) 
{
The switch (ul_reason_for_call) 
{
Case DLL_PROCESS_ATTACH: 
Case DLL_THREAD_ATTACH: 
Case DLL_THREAD_DETACH: 
Case DLL_PROCESS_DETACH: 
break; 
} 
Return TRUE; 
} 
__declspec (dllexport) string __stdcall compress_wireless (string STR) 
{int j, k, g, resend_buf [MAX_PACK_SIZE], wireless_buf [MAX_PACK_SIZE]; 
The static string array [MAX_PACK_SIZE], compress_data1, compress_data2; 
Unsigned int compress_data; 

For (unsigned int I=0; i<=STR. Length (); I +=3) {
G=I/3; 
Array [g]=STR. Substr (I, 2); } 
For (int h=0; H<=14; H++) {
Stringstream ss_1; 
Ss_1 & lt; Ss_1 & gt;> Wireless_buf [h]; 
Ss_1. STR (" "); 
} 
for(j=0; J<15. J++) 
Resend_buf [1 + j]=wireless_buf [j]; 
for(j=0; J<14. J++) {
compress_data=https://bbs.csdn.net/topics/wireless_buf [j] * 0 x100 + wireless_buf [j + 1); 
If ((compress_data & amp; 0 x8000)!=0) 
compress_data=https://bbs.csdn.net/topics/((compress_data/0 x100) ^ 0 x89) * 0 x100 + compress_data % 0 x100; 
For (k=0; k<8; K++) {
Compress_data & lt; <=1; 
If ((compress_data & amp; 0 x8000)!=0) 
compress_data=https://bbs.csdn.net/topics/((compress_data/0 x100) ^ 0 x89) * 0 x100 + compress_data % 0 x100; 
} 
Wireless_buf [j + 1)=compress_data/0 x100; 
} 
For (k=0; k<7. K++) {
Compress_data & lt; <=1; 
If ((compress_data & amp; 0 x8000)!=0) 
compress_data=https://bbs.csdn.net/topics/((compress_data/0 x100) ^ 0 x89) * 0 x100 + compress_data % 0 x100; 
} 
Compress_data & lt; <=1; 
Stringstream ss_2; 
Ss_2 & lt; Ss_2 & gt;> Compress_data1; 
Compress_data2=compress_data1. Substr (0, 2); 
The transform (compress_data2. The begin (), compress_data2 end (), compress_data2. The begin (), towupper); 
Return compress_data2; 
} 

Cipher. H

 # pragma once 
# include "targetver. H" 
# include "stdafx. H" 
#include  
#include  
#include  
#include  
#include  
#include 
using namespace std; 
# define WIN32_LEAN_AND_MEAN 
# define MAX_PACK_SIZE 20 

# ifdef CIPHER_EXPORTS 
# define CIPHER_API __declspec (dllexport) 
# the else 
# define CIPHER_API __declspec (dllimport) 
# endif 

//this is from the Cipher. DLL export 

__declspec (dllexport) string __stdcall compress_wireless (string STR); 

Cipher. Def

 LIBRARY Cipher 
EXPORTS compress_wireless 

VB calls

 Option Explicit 
Private Declare Function compress_wireless Lib "C: \ Users/Administrator/Desktop/Cipher \ Debug \ Cipher DLL" (ByVal p As String) As String 

Private Sub Command1_Click () 
Dim STR As String 
STR=compress_wireless (80, 66 a, 99 b "28 a 0 0 0 0 0 0 0 d d d d d d d 00 0") 
Text1.. Text=STR 
End Sub 

Private Sub Text1_Change () 

End Sub 

CodePudding user response:

Feel you in VB API function type declaration is not correct,
From Cipher. CPP code line 22, I think the API returns a value of "first address pointer string",
So in VB6 should put the function return value statement for Long,

Then, according to return a pointer to the value directly, direct Copy "MAX_PACK_SIZE" bytes of data to a Byte array,

//definition of data types: 
The static string array [MAX_PACK_SIZE], compress_data1, compress_data2; 

//API return: 
Return compress_data2; 

If this "return data" are valid ASCII characters,
Can use Strconv () function converts it from a Byte array into a string, and then assigned to the TextBox control,

CodePudding user response:

Collapsed in the pop-up dialog box, press the corresponding button to enter debugging press Alt + 7 key to view the Call Stack, namely "the Call Stack" from the inside to the following out of from the inner to outer function Call history, double-click a row to the cursor to the Call of the source code or assembly instruction, don't understand when double click on the next line, until we can read ,

CodePudding user response:

The vc interface function of all string into a char * try