Difference between revisions of "Cardinal"
(Created page with "Cardinal is an integer type defined as an alias for DWord under a 32bit plateform. Like the DWord (double word) it's a 32 bit data interpreted as an unsigned integer. As it's ...") |
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| − | Cardinal is an integer type defined as an alias for DWord under a 32bit plateform. Like the DWord (double word) it's a 32 bit data interpreted as an unsigned integer. As it's only used on 32 bit systems, its minimal value is 0x0000000 and its maximal value 0xFFFFFFFF. | + | Cardinal is an integer type defined as an alias for DWord under a 32bit plateform. Like the DWord (double word) type it's a 32 bit data interpreted as an unsigned integer. As it's only used on 32 bit systems, its minimal value is 0x0000000 and its maximal value 0xFFFFFFFF. |
| − | On the x86 systems Cardinal type is often used to hold a memory | + | On the x86 systems Cardinal type is often used to hold a memory address, like a pointer: |
<code> | <code> | ||
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begin | begin | ||
AnAddress := Cardinal(Self); | AnAddress := Cardinal(Self); | ||
| − | + | with TObject(AnAddress) do | |
begin | begin | ||
// AnAddress is casted as a TObject. | // AnAddress is casted as a TObject. | ||
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</code> | </code> | ||
| − | However, because of the 32 and 64 bits little endian systems, using | + | However, because of the 32 and 64 bits little endian systems, using the Cardinal type is not recommended anymore for memory/pointer operations/arithmetic. |
| − | Actually it's recommended to use '''NativeInt''' or '''NativeUInt''' types. These types will match to a CPU register wide data which can be used to encode | + | Actually it's rather recommended to use '''NativeInt''' or '''NativeUInt''' types. These types will match to a CPU register wide data which can be used to encode a memory address and so will be always valid. For example under a 64bit OS, a NativeUInt will be like a UInt64 or a QuadWord and under a 32 bit OS, a NativeUInt will be like a DWord or a Cardinal. |
Revision as of 00:00, 10 February 2013
Cardinal is an integer type defined as an alias for DWord under a 32bit plateform. Like the DWord (double word) type it's a 32 bit data interpreted as an unsigned integer. As it's only used on 32 bit systems, its minimal value is 0x0000000 and its maximal value 0xFFFFFFFF.
On the x86 systems Cardinal type is often used to hold a memory address, like a pointer:
var
AnAddress: Cardinal;
AnObject: TObject;
begin
AnAddress := Cardinal(Self);
with TObject(AnAddress) do
begin
// AnAddress is casted as a TObject.
end;
end;
However, because of the 32 and 64 bits little endian systems, using the Cardinal type is not recommended anymore for memory/pointer operations/arithmetic. Actually it's rather recommended to use NativeInt or NativeUInt types. These types will match to a CPU register wide data which can be used to encode a memory address and so will be always valid. For example under a 64bit OS, a NativeUInt will be like a UInt64 or a QuadWord and under a 32 bit OS, a NativeUInt will be like a DWord or a Cardinal.
