蚊子132 如何结合 CMenFile 与 CArchive 进行高效的序列 ...

柔光的暖阳◎ 2022-08-27 10:45 117阅读 0赞

来源：[蚊子132 如何结合 CMenFile 与 CArchive 进行高效的序列 ...][132 _ CMenFile _ CArchive _ ...]

序列号存储是我们常用的文件存储方式，[蚊子132][132] 这篇文章介绍如何结合 CMenFile 与 CArchive 进行高效的序列号存储。  
BYTE \* ppBuf;  
long pcBufLen;  
CMemFile file(ppBuf,pcBufLen);  
CArchive ar(&file,CArchive::load);  
将CArchive 与COleVariant相互转换就可以在内存文件存入到数据库大字段中  
下面是COleVariant与BYTE 转换：

1.  //Extensive error checking is left out to make the code more readable  
    
2.    
    
3.     BOOL GetBinaryFromVariant(COleVariant & ovData, BYTE \*\* ppBuf,  
    
4.                                  unsigned long \* pcBufLen)  
    
5.     \{  
    
6.       BOOL fRetVal = FALSE;  
    
7.    
    
8.     //Binary data is stored in the variant as an array of unsigned char  
    
9.       if(ovData.vt == (VT\_ARRAY|VT\_UI1))  // (OLE SAFEARRAY)  
    
10.      \{  
    
11.        //Retrieve size of array  
    
12.        \*pcBufLen = ovData.parray->rgsabound\[0\].cElements;  
    
13.   
    
14.        \*ppBuf = new BYTE\[\*pcBufLen\]; //Allocate a buffer to store the data  
    
15.        if(\*ppBuf != NULL)  
    
16.        \{  
    
17.          void \* pArrayData;  
    
18.   
    
19.          //Obtain safe pointer to the array  
    
20.          SafeArrayAccessData(ovData.parray,&pArrayData);  
    
21.   
    
22.          //Copy the bitmap into our buffer  
    
23.          memcpy(\*ppBuf, pArrayData, \*pcBufLen);  
    
24.   
    
25.          //Unlock the variant data  
    
26.          SafeArrayUnaccessData(ovData.parray);  
    
27.          fRetVal = TRUE;  
    
28.        \}  
    
29.      \}  
    
30.      return fRetVal;  
    
31.    \}  
    
32.   
    
33.    BOOL PutBinaryIntoVariant(COleVariant \* ovData, BYTE \* pBuf,  
    
34.                                 unsigned long cBufLen)  
    
35.    \{  
    
36.      BOOL fRetVal = FALSE;  
    
37.   
    
38.      VARIANT var;  
    
39.      VariantInit(&var);  //Initialize our variant  
    
40.   
    
41.      //Set the type to an array of unsigned chars (OLE SAFEARRAY)  
    
42.      var.vt = VT\_ARRAY | VT\_UI1;  
    
43.   
    
44.      //Set up the bounds structure  
    
45.      SAFEARRAYBOUND  rgsabound\[1\];  
    
46.   
    
47.      rgsabound\[0\].cElements = cBufLen;  
    
48.      rgsabound\[0\].lLbound = 0;  
    
49.   
    
50.      //Create an OLE SAFEARRAY  
    
51.      var.parray = SafeArrayCreate(VT\_UI1,1,rgsabound);  
    
52.   
    
53.      if(var.parray != NULL)  
    
54.      \{  
    
55.        void \* pArrayData = NULL;  
    
56.   
    
57.        //Get a safe pointer to the array  
    
58.        SafeArrayAccessData(var.parray,&pArrayData);  
    
59.   
    
60.        //Copy bitmap to it  
    
61.        memcpy(pArrayData, pBuf, cBufLen);  
    
62.   
    
63.        //Unlock the variant data  
    
64.        SafeArrayUnaccessData(var.parray);  
    
65.   
    
66.        \*ovData = var;  // Create a COleVariant based on our variant  
    
67.        VariantClear(&var);  
    
68.        fRetVal = TRUE;  
    
69.      \}  
    
70.   
    
71.      return fRetVal;  
    
72.    \}  
    
73.   
    
74.   
    
75.    //How you might call these functions  
    
76.   
    
77.    CdbRecordset rs;  
    
78.   
    
79.    //Code for initializing DAO and opening the recordset left out...  
    
80.   
    
81.    COleVariant ovData = rs.GetField(\_T("MyBinaryField"));  
    
82.   
    
83.    BYTE \* pBuf = NULL;  
    
84.    unsigned long cBufLen;  
    
85.   
    
86.    if(GetBinaryFromVariant(ovData,&pBuf,&cBufLen))  
    
87.    \{  
    
88.      //Do something with binary data in pBuf...  
    
89.   
    
90.      //Write back a new record containing the binary data  
    
91.   
    
92.      COleVariant ovData2;  
    
93.      if(PutBinaryIntoVariant(&ovData2,pBuf,cBufLen))  
    
94.      \{  
    
95.        rs.AddNew();  
    
96.        rs.SetField(\_T("MyBinaryField"), ovData2); //Write our COleVariant  
    
97.    to the table  
    
98.        rs.Update();  
    
99.      \}  
    
100.      //Clean up memory allocated by GetBinaryFromVariant  
    
101.      if(pBuf)  
    
102.        delete pBuf;  
    
103.    \}

*复制代码*

[132 _ CMenFile _ CArchive _ ...]: http://www.wz132.com/thread-33985-1-1.html
[132]: http://www.wz132.com/