【发布时间】：2012-04-03 04:28:46
【问题描述】：
我正在尝试将以下两个接口从 C 头文件转换为 Delphi PAS 单元，但在使用我自己做的那些时遇到了奇怪的问题。我需要帮助了解如何在 Delphi 中实现这些。
来自c头文件的源接口：
interface IParamConfig: IUnknown
{
HRESULT SetValue([in] const VARIANT* pValue, [in] BOOL bSetAndCommit);
HRESULT GetValue([out] VARIANT* pValue, [in] BOOL bGetCommitted);
HRESULT SetVisible(BOOL bVisible);
HRESULT GetVisible(BOOL* bVisible);
HRESULT GetParamID(GUID* pParamID);
HRESULT GetName([out] BSTR* pName);
HRESULT GetReadOnly(BOOL* bReadOnly);
HRESULT GetFullInfo([out] VARIANT* pValue, [out] BSTR* pMeaning, [out] BSTR* pName, [out] BOOL* bReadOnly, [out] BOOL* pVisible);
HRESULT GetDefValue([out] VARIANT* pValue);
HRESULT GetValidRange([out] VARIANT* pMinValue, [out] VARIANT* pMaxValue, [out] VARIANT* pDelta);
HRESULT EnumValidValues([in][out] long* pNumValidValues, [in][out] VARIANT* pValidValues,[in][out] BSTR* pValueNames);
HRESULT ValueToMeaning([in] const VARIANT* pValue, [out] BSTR* pMeaning);
HRESULT MeaningToValue([in] const BSTR pMeaning, [out] VARIANT* pValue);
}
interface IModuleConfig: IPersistStream
{
HRESULT SetValue([in] const GUID* pParamID, [in] const VARIANT* pValue);
HRESULT GetValue([in] const GUID* pParamID, [out] VARIANT* pValue);
HRESULT GetParamConfig([in] const GUID* pParamID, [out] IParamConfig** pValue);
HRESULT IsSupported([in] const GUID* pParamID);
HRESULT SetDefState();
HRESULT EnumParams([in][out] long* pNumParams, [in][out] GUID* pParamIDs);
HRESULT CommitChanges([out] VARIANT* pReason);
HRESULT DeclineChanges();
HRESULT SaveToRegistry([in] HKEY hKeyRoot, [in] const BSTR pszKeyName, [in] const BOOL bPreferReadable);
HRESULT LoadFromRegistry([in] HKEY hKeyRoot, [in] const BSTR pszKeyName, [in] const BOOL bPreferReadable);
HRESULT RegisterForNotifies([in] IModuleCallback* pModuleCallback);
HRESULT UnregisterFromNotifies([in] IModuleCallback* pModuleCallback);
}
这是我迄今为止的“最大努力”：
type
TWideStringArray = array[0..1024] of WideString;
TOleVariantArray = array[0..1024] of OleVariant;
TGUIDArray = array[0..1024] of TGUID;
IParamConfig = interface(IUnknown)
['{486F726E-5043-49B9-8A0C-C22A2B0524E8}']
function SetValue(const pValue: OleVariant; bSetAndCommit: BOOL): HRESULT; stdcall;
function GetValue(out pValue: OleVariant; bGetCommitted: BOOL): HRESULT; stdcall;
function SetVisible(bVisible: BOOL): HRESULT; stdcall;
function GetVisible(bVisible: BOOL): HRESULT; stdcall;
function GetParamID(pParamID: PGUID): HRESULT; stdcall;
function GetName(out pName: WideString): HRESULT; stdcall;
function GetReadOnly(bReadOnly: BOOL): HRESULT; stdcall;
function GetFullInfo(out pValue: OleVariant; out pMeaning: WideString; out pName: WideString; out pReadOnly: BOOL; out pVisible: BOOL): HRESULT; stdcall;
function GetDefValue(out pValue: OleVariant): HRESULT; stdcall;
function GetValidRange(out pMinValue: OleVariant; out pMaxValue: OleVariant; out pDelta: OleVariant): HRESULT; stdcall;
function EnumValidValues(var pNumValidValues: Integer; var pValidValues: TOleVariantArray; var pValueNames: TWideStringArray): HRESULT; stdcall;
function ValueToMeading(const pValue: OleVariant; out pMeaning: WideString): HRESULT; stdcall;
function MeaningToValue(const pMeaning: WideString; out pValue: OleVariant): HRESULT; stdcall;
end;
IModuleConfig = interface(IPersistStream)
['{486F726E-4D43-49B9-8A0C-C22A2B0524E8}']
function SetValue(const pParamID: TGUID; const pValue: OleVariant): HRESULT; stdcall;
function GetValue(const pParamID: TGUID; out pValue: OleVariant): HRESULT; stdcall;
function GetParamConfig(const ParamID: TGUID; out pValue: IParamConfig): HRESULT; stdcall;
function IsSupported(const pParamID: TGUID): HRESULT; stdcall;
function SetDefState: HRESULT; stdcall;
function EnumParams(var pNumParams: Integer; var pParamIDs: TGUIDArray): HRESULT; stdcall;
function CommitChanges(out pReason: OleVariant): HRESULT; stdcall;
function DeclineChanges: HRESULT; stdcall;
function SaveToRegistry(hKeyRoot: HKEY; const pszKeyName: WideString; const bPreferReadable: BOOL): HRESULT; stdcall;
function LoadFromRegistry(hKeyRoot: HKEY; const pszKeyName: WideString; const bPreferReadable: BOOL): HRESULT; stdcall;
function RegisterForNotifies(pModuleCallback: IModuleCallback): HRESULT; stdcall;
function UnregisterFromNotifies(pModuleCallback: IModuleCallback): HRESULT; stdcall;
end;
这是一些使用 DirectShow 过滤器并尝试在该对象上同时使用 IModuleConfig 和 IParamConfig 接口的示例代码：
procedure TForm10.Button1Click(Sender: TObject);
const
CLSID_VideoDecoder: TGUID = '{C274FA78-1F05-4EBB-85A7-F89363B9B3EA}';
var
HR: HRESULT;
Intf: IUnknown;
NumParams: Long;
I: Integer;
ParamConfig: IParamConfig;
ParamName: WideString;
Value: OleVariant;
ValAsString: String;
Params: TGUIDArray;
begin
CoInitializeEx(nil, COINIT_MULTITHREADED);
try
HR := CoCreateInstance(CLSID_VideoDecoder, nil, CLSCTX_INPROC_SERVER or CLSCTX_LOCAL_SERVER, IUnknown, Intf);
if Succeeded(HR) then
begin
FVideoDecoder := Intf as IBaseFilter;
if Supports(FVideoDecoder, IID_IModuleConfig) then
begin
HR := (FVideoDecoder as IModuleConfig).EnumParams(NumParams, Params);
if HR = S_OK then
begin
for I := 0 to NumParams - 1 do
begin
HR := (FVideoDecoder as IModuleConfig).GetParamConfig(Params[I], ParamConfig);
if HR = S_OK then
begin
try
ParamConfig.GetName(ParamName);
ParamConfig.GetValue(Value, True);
try
ValAsString := VarToStrDef(Value, 'Error');
SL.Add(String(ParamName) + '=' + String(ValAsString)); // <-- ADDING THIS LINE WILL ALWAYS MAKE EnumParams call return S_FALSE = 1
except
end;
finally
ParamConfig := nil;
end;
end;
end;
end;
end;
end;
finally
CoUninitialize;
end;
end;
使用调试器，我可以看到示例代码将数据检索到 ParamName 和 Value 变量，但是，当我尝试包含代码以将它们存储到字符串列表 (SL) 时，对 EnumParams 的调用将始终返回 S_FALSE (1)而不是 S_OK (0)。如果我注释掉 SL.Add(...) 和 RECOMPILE 行，它将再次起作用。如果我再次包含它并重新编译它不会。这让我相信，由于我对这些接口的错误实现，在某些时候某些东西会弄乱内存，并且包含额外的代码会导致这种情况发生。
我很确定我分配给变量的类型在某种程度上是造成这种情况的罪魁祸首，尤其是 EnumParams 的第二个参数，它应该返回一个 GUID* 数组。我也很不确定 IParamConfig.EnumValidValues 调用也会返回值数组。
我正在使用 Delphi XE2。
非常感谢您对此问题的任何帮助。
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标签： delphi com header translation variant