Tests and better documentation for memory.stateSize

This commit is contained in:
Eugen Wissner 2017-10-06 07:45:46 +02:00
parent 2f4dd34582
commit 211f590caa

View File

@ -141,21 +141,54 @@ body
* Returns the size in bytes of the state that needs to be allocated to hold an
* object of type $(D_PARAM T).
*
* There is a difference between the `.sizeof`-property and
* $(D_PSYMBOL stateSize) if $(D_PARAM T) is a class or an interface.
* `T.sizeof` is constant on the given architecture then and is the same as
* `size_t.sizeof` and `ptrdiff_t.sizeof`. This is because classes and
* interfaces are reference types and `.sizeof` returns the size of the
* reference which is the same as the size of a pointer. $(D_PSYMBOL stateSize)
* returns the size of the instance itself.
*
* The size of a dynamic array is `size_t.sizeof * 2` since a dynamic array
* stores its length and a data pointer. The size of the static arrays is
* calculated differently since they are value types. It is the array length
* multiplied by the element size.
*
* `stateSize!void` is `1` since $(D_KEYWORD void) is mostly used as a synonym
* for $(D_KEYWORD byte)/$(D_KEYWORD ubyte) in `void*`.
*
* Params:
* T = Object type.
*
* Returns: Size of an instance of type $(D_PARAM T).
*/
template stateSize(T)
{
static if (is(T == class) || is(T == interface))
static if (isPolymorphic!T)
{
enum stateSize = __traits(classInstanceSize, T);
enum size_t stateSize = __traits(classInstanceSize, T);
}
else
{
enum stateSize = T.sizeof;
enum size_t stateSize = T.sizeof;
}
}
///
@nogc nothrow pure @safe unittest
{
static assert(stateSize!int == 4);
static assert(stateSize!bool == 1);
static assert(stateSize!(int[]) == (size_t.sizeof * 2));
static assert(stateSize!(short[3]) == 6);
static struct Empty
{
}
static assert(stateSize!Empty == 1);
static assert(stateSize!void == 1);
}
/**
* Params:
* size = Raw size.