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February 1, 2019 15:18
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class properties as per-type cache
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program MetaClassCache; | |
{$APPTYPE CONSOLE} | |
{$R *.res} | |
uses | |
System.TypInfo, | |
System.SysUtils; | |
type | |
TypeInfoCache<T> = class | |
class var | |
FMinIntVal: Integer; | |
FMaxIntVal: Integer; | |
public | |
class constructor Create; | |
class property MaxIntVal: Integer read FMaxIntVal; | |
class property MinIntVal: Integer read FMinIntVal; | |
end; | |
Range<T> = record | |
private | |
class function MaxIntVal: Integer; static; inline; | |
class function MinIntVal: Integer; static; inline; | |
public | |
class function Check(const value: Integer): T; static; | |
end; | |
{ Range<T> } | |
class function Range<T>.Check(const value: Integer): T; | |
begin | |
if (value < MinIntVal) or (value > MaxIntVal) then | |
raise Exception.CreateFmt('Value %d lies outside allowed range for %s (%d .. %d)', | |
[value, PTypeInfo(TypeInfo(T)).Name, MinIntVal, MaxIntVal]); | |
Move(value, Result, SizeOf(Result)); | |
end; | |
class function Range<T>.MaxIntVal: Integer; | |
begin | |
Result := TypeInfoCache<T>.MaxIntVal; | |
end; | |
class function Range<T>.MinIntVal: Integer; | |
begin | |
Result := TypeInfoCache<T>.MinIntVal; | |
end; | |
{ TypeInfoCache<T> } | |
class constructor TypeInfoCache<T>.Create; | |
var | |
ti: PTypeInfo; | |
typeData: PTypeData; | |
isSet: Boolean; | |
i: Integer; | |
begin | |
ti := TypeInfo(T); | |
isSet := ti.Kind = tkSet; | |
if isSet then | |
ti := GetTypeData(ti).CompType^; | |
typeData := GetTypeData(ti); | |
FMinIntVal := typeData.MinValue; | |
if isSet then | |
begin | |
FMaxIntVal := 0; | |
for i := typeData.MinValue to typeData.MaxValue do | |
FMaxIntVal := FMaxIntVal or (1 shl i); | |
end | |
else | |
FMaxIntVal := typeData.MaxValue; | |
end; | |
type | |
TEnum = (en1, en2, en3); | |
TEnumSet = set of TEnum; | |
var | |
en: TEnum; | |
ens: TEnumSet; | |
begin | |
try | |
en := Range<TEnum>.Check(0); | |
en := Range<TEnum>.Check(2); | |
try | |
en := Range<TEnum>.Check(3); | |
except | |
on E: Exception do | |
Writeln('Expected exception: ', E.ClassName, ' ', E.Message); | |
end; | |
ens := Range<TEnumSet>.Check(0); | |
ens := Range<TEnumSet>.Check(7); | |
try | |
ens := Range<TEnumSet>.Check(8); | |
except | |
on E: Exception do | |
Writeln('Expected exception: ', E.ClassName, ' ', E.Message); | |
end; | |
except | |
on E: Exception do | |
Writeln(E.ClassName, ': ', E.Message); | |
end; | |
if DebugHook <> 0 then | |
Readln; | |
end. |
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