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

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

序列号存储是我们常用的文件存储方式，蚊子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.    }

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