ATL Internals 2ed复习.chapter 3.SAFEARRAY

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A Review of the COM SAFEARRAY Data Type

为了在COM函数间传递Array参数，IDL定义了SAFEARRAY类型：

interface IMyInterface : IUnknown {           HRESULT GetArray([out,retval]                 SAFEARRAY(VARIANT_BOOL)* myArray);};

typedef struct tagSAFEARRAY {         USHORT cDims;                     USHORT fFeatures;                 ULONG cbElements;                 ULONG cLocks;                     PVOID pvData;                     SAFEARRAYBOUND rgsabound[ 1 ];} SAFEARRAY;

其中

cDims数组的维数

cbElements每一个元素的size

pvData指向真实数据

SAFEARRAYBOUND用于规定上下限：rgsabound[0]用于规定最左维，rgsabound[cDims-1]规定最右维

typedef struct tagSAFEARRAYBOUND {    ULONG cElements;                  LONG lLbound;                 } SAFEARRAYBOUND;

创建Array例子：

SAFEARRAYBOUND rgsabound[2];rgsabound[0].cElements = 3;rgsabound[0].lLbound = 0;rgsabound[1].cElements = 4;rgsabound[1].lLbound = 0;

SAFEARRAY* psa = ::SafeArrayCreate(VT_R8, 2, rgsabound);

读取Array中数据例子：

long rgIndices[] = { 2, 1 };double lElem;::SafeArrayGetElement(psa, rgIndices, (void*)&lElem);

注意上面例子取得[1][2]的数据，

销毁Array应该使用：

::SafeArrayDestroy(psa);