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Access数据库位图文件数据的读写(一)

news 2026/6/11 10:23:42

读取位图文件到VARIANT结构中

/*从位图文件中读取数据到VARIANT参数:pBitmapPath        位图文件路径varVal            VARIANT结构dwFileSize        文件大小*/
HRESULT QAdo::ReadBitmapFileToVariant(const char* pBitmapPath, VARIANT& varVal,DWORD* fileSize)
{HRESULT hr = S_OK;BYTE* pBuffer = nullptr;//DWORD fileSize = 0;SAFEARRAY* psa = nullptr;void* pData = nullptr;//1.读取图片文件hr=ReadBitmapFileToBuffer(pBitmapPath, pBuffer,fileSize);if (!pBuffer) {return E_FAIL;}//2.创建safeArry用于存储二进制数据
    SAFEARRAYBOUND rgsabound;rgsabound.lLbound = 0;rgsabound.cElements = *fileSize;psa = SafeArrayCreate(VT_UI1, 1, &rgsabound);if (!psa) {if (pBuffer) free(pBuffer);if (psa) SafeArrayDestroy(psa);return E_FAIL;}//3.拷贝数据到saveArryhr = SafeArrayAccessData(psa, &pData);//CHECK_HR(hr, "SafeArrayAccessData failed");assert(hr == S_OK);memcpy(pData, pBuffer, *fileSize);SafeArrayUnaccessData(psa);//VARIANT varData;VariantInit(&varVal);V_VT(&varVal) = VT_ARRAY | VT_UI1;V_ARRAY(&varVal) = psa;//memcpy(V_ARRAY(&varVal), psa,fileSize);if (pBuffer) free(pBuffer);//if (psa) SafeArrayDestroy(psa);return hr;
}

自定义函数 ReadBitmapFileToBuffer

/*从文件中读取位图到数组中参数:filename	位图文件路径名称pBuffer		保存数据的缓存fileSize	文件大小返回:成功返回s_ok,失败为s_flase*/
HRESULT QAdo::ReadBitmapFileToBuffer(const char* filename,BYTE*& pBuffer, DWORD* fileSize) {HANDLE hFile = CreateFileA(filename, GENERIC_READ, 0, nullptr,OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);if (hFile == INVALID_HANDLE_VALUE) {return S_FALSE;}*fileSize = GetFileSize(hFile, nullptr);pBuffer = (BYTE*)malloc(*fileSize);if (!pBuffer){CloseHandle(hFile);return S_FALSE;}DWORD bytesRead = 0;ReadFile(hFile, pBuffer, *fileSize, &bytesRead, nullptr);CloseHandle(hFile);return S_OK;}

把VARIANT结构数据写入Access数据库中

QAdo::InitConnString(0, TEXT(".\\test.accdb"));
QAdo ado;
VARIANT varVal;
DWORD lgSize = 0;
ado.ReadBitmapFileToVariant(".\\测试美女位图.bmp",varVal,&lgSize);TCHAR sql[256] = TEXT("INSERT INTO Images (ID,ImgData) VALUES (@id,@imgdata)");ado.SetParameter(TEXT("@id"), 13);
ado.SetParameter(TEXT("@imgdata"), varVal, lgSize);if (ado.Open()) {if (ado.CommandExecute(sql) > 0) {//保存成功}ado.Close();
}

VARIANT数据类型的参数设置

//VARIANT类型的参数设置,要多传个数组大小
void QAdo::SetParameter(LPCTSTR lpParamName, VARIANT& varVal,long lgSize)
{try {if (m_pCommand == 0) {m_pCommand.CreateInstance(__uuidof(Command));}m_pCommand->Parameters->Append(m_pCommand->CreateParameter((_bstr_t)lpParamName, adBinary, adParamInput, lgSize, varVal));}catch (_com_error& e) {ShowErrorMsg(TEXT("SetParam参数错误!!!"), e);}
}

数据库数据图片