Delphi XE3探索：Winapi.Functiondiscovery （二）

　　这是Delphi XE3探索：Winapi.Functiondiscovery系列到第二篇文章了。

思路分析

　　Discovery API　的重要功能之一是对设备枚举结果的筛选。为此需要用到CreateInstanceCollectionQuery 方法，然后使用AddPropertyConstraint 方法添加条件。
　　下面的代码尝试枚举了Intel的所有处理器。

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.Win.ComObj,
  Winapi.Windows,
  Winapi.Activex,
  Winapi.PropSys,
  Winapi.Functiondiscovery,
  System.SysUtils;

procedure Enumerate;
var
    LFunctionDiscovery : IFunctionDiscovery;
    LFunctionInstance  : IFunctionInstance;
    ppIFunctionInstanceCollection: IFunctionInstanceCollection;
    ppIFunctionInstanceCollectionQuery: IFunctionInstanceCollectionQuery;
    ppIPropertyStore  : IPropertyStore;
    pv : TPropVariant;
    pdwCount : DWORD;
    pszCategory: PWCHAR;
    hr : HResult;
    i : integer;
begin
  //create an instance to the  IFunctionDiscovery interface
  LFunctionDiscovery := CreateComObject(CLSID_FunctionDiscovery) as IFunctionDiscovery;
  try
    //set the provider to search
    pszCategory:=FCTN_CATEGORY_PNP;
    //get the devices collection
    hr := LFunctionDiscovery.CreateInstanceCollectionQuery(pszCategory, nil, false, nil, nil, ppIFunctionInstanceCollectionQuery);
      if Succeeded(hr)  then
      begin
       PropVariantClear(pv);
       pv.vt:=VT_LPWSTR;
       pv.pwszVal:='Intel';
       hr := ppIFunctionInstanceCollectionQuery.AddPropertyConstraint(PKEY_Device_Manufacturer, pv, QC_EQUALS);
       if not Succeeded(hr) then RaiseLastOSError;

       PropVariantClear(pv);
       pv.vt:=VT_LPWSTR;
       pv.pwszVal:='Processor';
       hr := ppIFunctionInstanceCollectionQuery.AddPropertyConstraint(PKEY_Device_Class, pv, QC_EQUALS);
       if not Succeeded(hr) then RaiseLastOSError;

        hr := ppIFunctionInstanceCollectionQuery.Execute(ppIFunctionInstanceCollection);
        if Succeeded(hr)  then
        begin
          //get the collection count
          ppIFunctionInstanceCollection.GetCount(pdwCount);
          if pdwCount=0 then
            Writeln(Format('No items was found for the %s category',[pszCategory]))
          else
          for i := 0 to pdwCount - 1 do begin
            //get the n Item of the collection
            if Succeeded(ppIFunctionInstanceCollection.Item(i, LFunctionInstance)) then
            begin
              //init the propertiess store
              LFunctionInstance.OpenPropertyStore(STGM_READ, ppIPropertyStore);
              //read the properties values
              if Succeeded(ppIPropertyStore.GetValue(PKEY_NAME, pv)) then
               Writeln(Format('Name          %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_InstanceId, pv)) then
               Writeln(Format('Instance Id   %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Driver, pv)) then
               Writeln(Format('Device Driver %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Model, pv)) then
               Writeln(Format('Model         %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Manufacturer, pv)) then
               Writeln(Format('Manufacturer  %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_LocationInfo, pv)) then
               Writeln(Format('Location      %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_Class, pv)) then
               Writeln(Format('Class        %s',[pv.pwszVal]));
              if Succeeded(ppIPropertyStore.GetValue(PKEY_Device_ClassGuid, pv)) then
               Writeln(Format('Class Guid   %s',[pv.puuid^.ToString]));
              Writeln;
            end
            else
             RaiseLastOSError;
           end;
        end;
      end
      else
       RaiseLastOSError;
  finally
    LFunctionDiscovery:=nil;
  end;
end;

begin
 try
   ReportMemoryLeaksOnShutdown:=True;
   if (Win32MajorVersion >= 6) then  // available on Vista (or later)
   begin
    if Succeeded(CoInitializeEx(nil, COINIT_MULTITHREADED)) then
    try
     Enumerate;
    finally
      CoUninitialize;
    end;
   end
   else
   Writeln('Windows version not compatible');
 except
    on E:Exception do
        Writeln(E.Classname, ':', E.Message);
 end;
 Writeln('Press Enter to exit');
 Readln;
end.

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