如何使用Move复制类型是否安全？ [英] How can I test if a type is safe to copy using Move
问题描述
我正在编写一个通用的矢量类型：
type
TBigVector< T：record> = class
private
FSize：Integer;
FEntries：TArray< T>;
函数GetEntry（Index：Integer）：T;
程序SetEntry（Index：Integer; const Value：T）;
过程SetSize（Value：Integer）;
public
构造函数Create（ASize：Integer）;
属性大小：整数读取FSize写SetSize;
属性Entry [Index：Integer]：T读取GetEntry写入SetEntry;默认;
程序零度;
函数ToArray：TArray< T>;
结束
然后我想推出这样的课程：
TDoubleBigVector = class（TBigVector< Double>）
....
end;
TComplexBigVector = class（TBigVector< Complex>）
....
end;
我必须派生类，因为我不能在泛型类型中实现算术运算。这是因为通用约束不足以使我限制 T 来支持所需的算术运算。 Grr！
无论如何，足够了。我的问题涉及到 Zeroise 和 ToArray 的实现。出于性能原因，我想使用原始内存操作。例如， Zeroise 可能是：
程序TBigVector&T。零零度
begin
ZeroMemory（指针（FEntries），Size * SizeOf（T））;
结束
现在，对于像 Double 和我的定制复杂类型。我知道他们没有管理，原始的内存副本没有创造出困难。我想做的是添加一个运行时检查，也许只有在我的调试版本中调用，强制执行 T 没有托管类型的约束。我该怎么做？
我会这样做：
程序SO21753006;
{$ APPTYPE CONSOLE}
使用
TypInfo，
Windows，
SysUtils;
类型
TProblemRecord1 =记录
I：整数;
S：String;
结束
TProblemRecord2 = record
Obj：TObject;
结束
TGoodRecord = record
I：整数;
K：双;
S：数组[0..10]的Char;
结束
TBigVector< T：record> = class
private
FSize：Integer;
FEntries：TArray< T>;
函数GetEntry（Index：Integer）：T;
程序SetEntry（Index：Integer; const Value：T）;
过程SetSize（Value：Integer）;
public
构造函数Create（ASize：Integer）;
属性大小：整数读取FSize写SetSize;
属性Entry [Index：Integer]：T读取GetEntry写入SetEntry;默认;
程序零度;
函数ToArray：TArray< T>;
结束
函数RecordHasNoManagedTypes（Typ：PTypeInfo）：Boolean;
var
TypeData：PTypeData;
begin
Assert（Assigned（Typ））;
结果：= True;
//只检查我们是否有记录，否则我们有一个值类型
如果Typ.Kind = tkRecord然后
begin
TypeData：= GetTypeData（Typ）;
结果：= TypeData.ManagedFldCount = 0;
结束
结束
{TBigVector< T> }
构造函数TBigVector< T> .Create（ASize：Integer）;
begin
大小：= ASize;
结束
函数TBigVector> .GetEntry（Index：Integer）：T;
begin
end;
程序TBigVector< T> .SetEntry（Index：Integer; const Value：T）;
begin
end;
程序TBigVector< T> .SetSize（Value：Integer）;
begin
SetLength（FEntries，Value）;
结束
函数TBigVector&T; .ToArray：TArray< T>;
begin
end;
程序TBigVector< T> .Zeroise;
begin
Assert（RecordHasNoManagedTypes（TypeInfo（T）），'T不能有托管类型！
ZeroMemory（指针（FEntries），Size * SizeOf（T））;
结束
var
Rec1：TBigVector< Double> ;;
Rec2：TBigVector< TGoodRecord> ;;
Rec3：TBigVector< TProblemRecord1> ;;
Rec4：TBigVector< TProblemRecord2> ;;
begin
try
Writeln（'Double type'）;
Rec1：= TBigVector< Double> .Create（1）;
Rec1.Zeroise;
Writeln（'GoodRecord type'）;
Rec2：= TBigVector< TGoodRecord>。创建（10）;
Rec2.Zeroise;
try
Writeln（'Problemrecord1 type'）;
Rec3：= TBigVector< TProblemRecord1>。创建（10）;
Rec3.Zeroise;
除了
在E：Exception do
Writeln（E.ClassName，'：'，E.Message）;
结束
try
Writeln（'Problemrecord2 type'）;
Rec4：= TBigVector< TProblemRecord2>。创建（10）;
Rec4.Zeroise;
除了
在E：Exception do
Writeln（E.ClassName，'：'，E.Message）;
结束
除了
在E：Exception do
Writeln（E.ClassName，'：'，E.Message）;
结束
Readln;
结束。对于非ARC平台，
TObject 管理这样使用 ManagedFldCount 在此处有效。
更新
$如David所指出，在更新的Delphi版本（Read：from D2010）中，您可以使用 Rtti.IsManaged 函数。代码如下所示：
程序TBigVector< T> .Zeroise;
begin
Assert（不是RTTI.IsManaged（TypeInfo（T）），'T不能有托管类型！
ZeroMemory（指针（FEntries），Size * SizeOf（T））;
结束
I'm writing a generic vector type:
type
TBigVector<T: record> = class
private
FSize: Integer;
FEntries: TArray<T>;
function GetEntry(Index: Integer): T;
procedure SetEntry(Index: Integer; const Value: T);
procedure SetSize(Value: Integer);
public
constructor Create(ASize: Integer);
property Size: Integer read FSize write SetSize;
property Entry[Index: Integer]: T read GetEntry write SetEntry; default;
procedure Zeroise;
function ToArray: TArray<T>;
end;
I then want to derive classes like this:
TDoubleBigVector = class(TBigVector<Double>)
....
end;
TComplexBigVector = class(TBigVector<Complex>)
....
end;
I'm having to derive classes because I cannot implement arithmetic operations in the generic type. That is because generic constraints are not rich enough for me to constrain T to support the required arithmetic operations. Grr!
Anyway, enough of that. My question concerns the implementation of Zeroise and ToArray. For performance reasons, I want to use raw memory operations. For instance, Zeroise might be:
procedure TBigVector<T>.Zeroise;
begin
ZeroMemory(Pointer(FEntries), Size*SizeOf(T));
end;
Now, I'm fine with doing that for types like Double and my bespoke Complex type. I know that they are not managed and a raw memory copy creates no difficulty. What I would like to do is add a runtime check, perhaps only called in my debug builds, that enforces the constraint that T has no managed types. How can I do that?
I would do it like this:
program SO21753006;
{$APPTYPE CONSOLE}
uses
TypInfo,
Windows,
SysUtils;
type
TProblemRecord1 = record
I : Integer;
S : String;
end;
TProblemRecord2 = record
Obj : TObject;
end;
TGoodRecord = record
I : Integer;
K : Double;
S : Array[0..10] of Char;
end;
TBigVector<T: record> = class
private
FSize: Integer;
FEntries: TArray<T>;
function GetEntry(Index: Integer): T;
procedure SetEntry(Index: Integer; const Value: T);
procedure SetSize(Value: Integer);
public
constructor Create(ASize: Integer);
property Size: Integer read FSize write SetSize;
property Entry[Index: Integer]: T read GetEntry write SetEntry; default;
procedure Zeroise;
function ToArray: TArray<T>;
end;
function RecordHasNoManagedTypes(Typ : PTypeInfo) : Boolean;
var
TypeData : PTypeData;
begin
Assert(Assigned(Typ));
Result := True;
// only check if we have a record, or else we have a value type
if Typ.Kind = tkRecord then
begin
TypeData := GetTypeData(Typ);
Result := TypeData.ManagedFldCount = 0;
end;
end;
{ TBigVector<T> }
constructor TBigVector<T>.Create(ASize: Integer);
begin
Size := ASize;
end;
function TBigVector<T>.GetEntry(Index: Integer): T;
begin
end;
procedure TBigVector<T>.SetEntry(Index: Integer; const Value: T);
begin
end;
procedure TBigVector<T>.SetSize(Value: Integer);
begin
SetLength(FEntries, Value);
end;
function TBigVector<T>.ToArray: TArray<T>;
begin
end;
procedure TBigVector<T>.Zeroise;
begin
Assert(RecordHasNoManagedTypes(TypeInfo(T)), 'T must not have managed types!');
ZeroMemory(Pointer(FEntries), Size*SizeOf(T));
end;
var
Rec1 : TBigVector<Double>;
Rec2 : TBigVector<TGoodRecord>;
Rec3 : TBigVector<TProblemRecord1>;
Rec4 : TBigVector<TProblemRecord2>;
begin
try
Writeln('Double type');
Rec1 := TBigVector<Double>.Create(1);
Rec1.Zeroise;
Writeln('GoodRecord type');
Rec2 := TBigVector<TGoodRecord>.Create(10);
Rec2.Zeroise;
try
Writeln('Problemrecord1 type');
Rec3 := TBigVector<TProblemRecord1>.Create(10);
Rec3.Zeroise;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
try
Writeln('Problemrecord2 type');
Rec4 := TBigVector<TProblemRecord2>.Create(10);
Rec4.Zeroise;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
Readln;
end.
TObject for non-ARC platforms is not managed so the use ManagedFldCount is valid here.
UPDATE
As David pointed out, in more recent Delphi versions (Read: from D2010) you can use the Rtti.IsManaged function.
the code would look like this:
procedure TBigVector<T>.Zeroise;
begin
Assert(not RTTI.IsManaged(TypeInfo(T)), 'T must not have managed types!');
ZeroMemory(Pointer(FEntries), Size*SizeOf(T));
end;
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