tagVARIANT、VARIANT、_variant_t和COleVariant

最新推荐文章于 2023-03-20 14:27:27 发布

转载最新推荐文章于 2023-03-20 14:27:27 发布 · 235 阅读

文章标签：

#c/c++

本文详细解析了VARIANT数据结构，包括其内部组成、VARTYPE枚举类型的意义及使用场景，并介绍了_variant_t和COleVariant两个封装类的功能与用法。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

　　tagVARIANT是一个结构体struct：

 C++ Code： tagVARIANT

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63

struct  tagVARIANT
    {
    union
        {
        struct  __tagVARIANT
            {
            VARTYPE vt;
            WORD wReserved1;
            WORD wReserved2;
            WORD wReserved3;
            union
                {
                LONG lVal;
                BYTE bVal;
                SHORT iVal;
                FLOAT fltVal;
                DOUBLE dblVal;
                VARIANT_BOOL boolVal;
                _VARIANT_BOOL bool;
                SCODE scode;
                CY cyVal;
                DATE date;
                BSTR bstrVal;
                IUnknown __RPC_FAR *punkVal;
                IDispatch __RPC_FAR *pdispVal;
                SAFEARRAY __RPC_FAR *parray;
                BYTE __RPC_FAR *pbVal;
                SHORT __RPC_FAR *piVal;
                LONG __RPC_FAR *plVal;
                FLOAT __RPC_FAR *pfltVal;
                DOUBLE __RPC_FAR *pdblVal;
                VARIANT_BOOL __RPC_FAR *pboolVal;
                _VARIANT_BOOL __RPC_FAR *pbool;
                SCODE __RPC_FAR *pscode;
                CY __RPC_FAR *pcyVal;
                DATE __RPC_FAR *pdate;
                BSTR __RPC_FAR *pbstrVal;
                IUnknown __RPC_FAR *__RPC_FAR *ppunkVal;
                IDispatch __RPC_FAR *__RPC_FAR *ppdispVal;
                SAFEARRAY __RPC_FAR *__RPC_FAR *pparray;
                VARIANT __RPC_FAR *pvarVal;
                PVOID byref;
                CHAR cVal;
                USHORT uiVal;
                ULONG ulVal;
                INT intVal;
                UINT uintVal;
                DECIMAL __RPC_FAR *pdecVal;
                CHAR __RPC_FAR *pcVal;
                USHORT __RPC_FAR *puiVal;
                ULONG __RPC_FAR *pulVal;
                INT __RPC_FAR *pintVal;
                UINT __RPC_FAR *puintVal;
                struct  __tagBRECORD
                    {
                    PVOID pvRecord;
                    IRecordInfo __RPC_FAR *pRecInfo;
                    }   __VARIANT_NAME_4;
                }   __VARIANT_NAME_3;
            }   __VARIANT_NAME_2;
        DECIMAL decVal;
        }   __VARIANT_NAME_1;
    };

　　VARIANT是tagVARIANT的别名：

 C++ Code：VARIANT

typedef /* [wire_marshal] */ struct tagVARIANT VARIANT;

　　_variant_t 是VARIANT的包装管理类：

　　A _variant_t object encapsulates the VARIANT data type.

　　The class manages resource allocation and deallocation and makes function calls to VariantInit and VariantClear as appropriate.

 C++ Code： _variant_t类

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

//////////////////////////////////////////////////////////////////////////////
//
// Wrapper class for VARIANT
//
//////////////////////////////////////////////////////////////////////////////

/*
* VARENUM usage key,
*
* * [V] - may appear in a VARIANT
* * [T] - may appear in a TYPEDESC
* * [P] - may appear in an OLE property set
* * [S] - may appear in a Safe Array
* * [C] - supported by class _variant_t
*
*
*  VT_EMPTY            [V]   [P]        nothing
*  VT_NULL             [V]   [P]        SQL style Null
*  VT_I2               [V][T][P][S][C]  2 byte signed int
*  VT_I4               [V][T][P][S][C]  4 byte signed int
*  VT_R4               [V][T][P][S][C]  4 byte real
*  VT_R8               [V][T][P][S][C]  8 byte real
*  VT_CY               [V][T][P][S][C]  currency
*  VT_DATE             [V][T][P][S][C]  date
*  VT_BSTR             [V][T][P][S][C]  OLE Automation string
*  VT_DISPATCH         [V][T][P][S][C]  IDispatch *
*  VT_ERROR            [V][T]   [S][C]  SCODE
*  VT_BOOL             [V][T][P][S][C]  True=-1, False=0
*  VT_VARIANT          [V][T][P][S]     VARIANT *
*  VT_UNKNOWN          [V][T]   [S][C]  IUnknown *
*  VT_DECIMAL          [V][T]   [S][C]  16 byte fixed point
*  VT_I1                  [T]           signed char
*  VT_UI1              [V][T][P][S][C]  unsigned char
*  VT_UI2                 [T][P]        unsigned short
*  VT_UI4                 [T][P]        unsigned short
*  VT_I8                  [T][P]        signed 64-bit int
*  VT_UI8                 [T][P]        unsigned 64-bit int
*  VT_INT                 [T]           signed machine int
*  VT_UINT                [T]           unsigned machine int
*  VT_VOID                [T]           C style void
*  VT_HRESULT             [T]           Standard return type
*  VT_PTR                 [T]           pointer type
*  VT_SAFEARRAY           [T]          (use VT_ARRAY in VARIANT)
*  VT_CARRAY              [T]           C style array
*  VT_USERDEFINED         [T]           user defined type
*  VT_LPSTR               [T][P]        null terminated string
*  VT_LPWSTR              [T][P]        wide null terminated string
*  VT_FILETIME               [P]        FILETIME
*  VT_BLOB                   [P]        Length prefixed bytes
*  VT_STREAM                 [P]        Name of the stream follows
*  VT_STORAGE                [P]        Name of the storage follows
*  VT_STREAMED_OBJECT        [P]        Stream contains an object
*  VT_STORED_OBJECT          [P]        Storage contains an object
*  VT_BLOB_OBJECT            [P]        Blob contains an object
*  VT_CF                     [P]        Clipboard format
*  VT_CLSID                  [P]        A Class ID
*  VT_VECTOR                 [P]        simple counted array
*  VT_ARRAY            [V]              SAFEARRAY*
*  VT_BYREF            [V]              void* for local use
*/

class _variant_t : public ::tagVARIANT {
public:
    // Constructors
    //
    _variant_t() throw();

    _variant_t(const VARIANT& varSrc) throw(_com_error);
    _variant_t(const VARIANT* pSrc) throw(_com_error);
    _variant_t(const _variant_t& varSrc) throw(_com_error);

    _variant_t(VARIANT& varSrc, bool fCopy) throw(_com_error);          // Attach VARIANT if !fCopy

    _variant_t(short sSrc, VARTYPE vtSrc = VT_I2) throw(_com_error);    // Creates a VT_I2, or a VT_BOOL
    _variant_t(long lSrc, VARTYPE vtSrc = VT_I4) throw(_com_error);     // Creates a VT_I4, a VT_ERROR, or a VT_BOOL
    _variant_t(float fltSrc) throw();                                   // Creates a VT_R4
    _variant_t(double dblSrc, VARTYPE vtSrc = VT_R8) throw(_com_error); // Creates a VT_R8, or a VT_DATE
    _variant_t(const CY& cySrc) throw();                                // Creates a VT_CY
    _variant_t(const _bstr_t& bstrSrc) throw(_com_error);               // Creates a VT_BSTR
    _variant_t(const wchar_t *pSrc) throw(_com_error);                  // Creates a VT_BSTR
    _variant_t(const char* pSrc) throw(_com_error);                     // Creates a VT_BSTR
    _variant_t(IDispatch* pSrc, bool fAddRef = true) throw();           // Creates a VT_DISPATCH
    _variant_t(bool bSrc) throw();                                      // Creates a VT_BOOL
    _variant_t(IUnknown* pSrc, bool fAddRef = true) throw();            // Creates a VT_UNKNOWN
    _variant_t(const DECIMAL& decSrc) throw();                          // Creates a VT_DECIMAL
    _variant_t(BYTE bSrc) throw();                                      // Creates a VT_UI1

    // Destructor
    //
    ~_variant_t() throw(_com_error);

    // Extractors
    //
    operator short() const throw(_com_error);           // Extracts a short from a VT_I2
    operator long() const throw(_com_error);            // Extracts a long from a VT_I4
    operator float() const throw(_com_error);           // Extracts a float from a VT_R4
    operator double() const throw(_com_error);          // Extracts a double from a VT_R8
    operator CY() const throw(_com_error);              // Extracts a CY from a VT_CY
    operator _bstr_t() const throw(_com_error);         // Extracts a _bstr_t from a VT_BSTR
    operator IDispatch*() const throw(_com_error);      // Extracts a IDispatch* from a VT_DISPATCH
    operator bool() const throw(_com_error);            // Extracts a bool from a VT_BOOL
    operator IUnknown*() const throw(_com_error);       // Extracts a IUnknown* from a VT_UNKNOWN
    operator DECIMAL() const throw(_com_error);         // Extracts a DECIMAL from a VT_DECIMAL
    operator BYTE() const throw(_com_error);            // Extracts a BTYE (unsigned char) from a VT_UI1

    // Assignment operations
    //
    _variant_t& operator=(const VARIANT& varSrc) throw(_com_error);
    _variant_t& operator=(const VARIANT* pSrc) throw(_com_error);
    _variant_t& operator=(const _variant_t& varSrc) throw(_com_error);

    _variant_t& operator=(short sSrc) throw(_com_error);                // Assign a VT_I2, or a VT_BOOL
    _variant_t& operator=(long lSrc) throw(_com_error);                 // Assign a VT_I4, a VT_ERROR or a VT_BOOL
    _variant_t& operator=(float fltSrc) throw(_com_error);              // Assign a VT_R4
    _variant_t& operator=(double dblSrc) throw(_com_error);             // Assign a VT_R8, or a VT_DATE
    _variant_t& operator=(const CY& cySrc) throw(_com_error);           // Assign a VT_CY
    _variant_t& operator=(const _bstr_t& bstrSrc) throw(_com_error);    // Assign a VT_BSTR
    _variant_t& operator=(const wchar_t* pSrc) throw(_com_error);       // Assign a VT_BSTR
    _variant_t& operator=(const char* pSrc) throw(_com_error);          // Assign a VT_BSTR
    _variant_t& operator=(IDispatch* pSrc) throw(_com_error);           // Assign a VT_DISPATCH
    _variant_t& operator=(bool bSrc) throw(_com_error);                 // Assign a VT_BOOL
    _variant_t& operator=(IUnknown* pSrc) throw(_com_error);            // Assign a VT_UNKNOWN
    _variant_t& operator=(const DECIMAL& decSrc) throw(_com_error);     // Assign a VT_DECIMAL
    _variant_t& operator=(BYTE bSrc) throw(_com_error);                 // Assign a VT_UI1

    // Comparison operations
    //
    bool operator==(const VARIANT& varSrc) const throw(_com_error);
    bool operator==(const VARIANT* pSrc) const throw(_com_error);

    bool operator!=(const VARIANT& varSrc) const throw(_com_error);
    bool operator!=(const VARIANT* pSrc) const throw(_com_error);

    // Low-level operations
    //
    void Clear() throw(_com_error);

    void Attach(VARIANT& varSrc) throw(_com_error);
    VARIANT Detach() throw(_com_error);

    void ChangeType(VARTYPE vartype, const _variant_t* pSrc = NULL) throw(_com_error);

    void SetString(const char* pSrc) throw(_com_error); // used to set ANSI string
};

　　COleVariant 也是对VARIANT的封装类：

 C++ Code：COleVariant类

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67

class COleVariant : public tagVARIANT
{
// Constructors
public:
    COleVariant();

    COleVariant(const VARIANT& varSrc);
    COleVariant(LPCVARIANT pSrc);
    COleVariant(const COleVariant& varSrc);

    COleVariant(LPCTSTR lpszSrc);
    COleVariant(LPCTSTR lpszSrc, VARTYPE vtSrc); // used to set to ANSI string
    COleVariant(CString& strSrc);

    COleVariant(BYTE nSrc);
    COleVariant(short nSrc, VARTYPE vtSrc = VT_I2);
    COleVariant(long lSrc, VARTYPE vtSrc = VT_I4);
    COleVariant(const COleCurrency& curSrc);

    COleVariant(float fltSrc);
    COleVariant(double dblSrc);
    COleVariant(const COleDateTime& timeSrc);

    COleVariant(const CByteArray& arrSrc);
    COleVariant(const CLongBinary& lbSrc);

    COleVariant(LPCITEMIDLIST pidl);

// Operations
public:
    void Clear();
    void ChangeType(VARTYPE vartype, LPVARIANT pSrc = NULL);
    void Attach(VARIANT& varSrc);
    VARIANT Detach();

    BOOL operator==(const VARIANT& varSrc) const;
    BOOL operator==(LPCVARIANT pSrc) const;

    const COleVariant& operator=(const VARIANT& varSrc);
    const COleVariant& operator=(LPCVARIANT pSrc);
    const COleVariant& operator=(const COleVariant& varSrc);

    const COleVariant& operator=(const LPCTSTR lpszSrc);
    const COleVariant& operator=(const CString& strSrc);

    const COleVariant& operator=(BYTE nSrc);
    const COleVariant& operator=(short nSrc);
    const COleVariant& operator=(long lSrc);
    const COleVariant& operator=(const COleCurrency& curSrc);

    const COleVariant& operator=(float fltSrc);
    const COleVariant& operator=(double dblSrc);
    const COleVariant& operator=(const COleDateTime& dateSrc);

    const COleVariant& operator=(const CByteArray& arrSrc);
    const COleVariant& operator=(const CLongBinary& lbSrc);

    void SetString(LPCTSTR lpszSrc, VARTYPE vtSrc); // used to set ANSI string

    operator LPVARIANT();
    operator LPCVARIANT() const;

// Implementation
public:
    ~COleVariant();
    void _ClearCompat();
};