问题描述
为什么System.Boolean占用4个字节?它只存储一个状态,即 true 或 false ,可以将其存储在小于4个字节的空间中。
Why does a System.Boolean take 4 bytes? It just stores one state, either true or false, which could be stored in less space than 4 bytes.
推荐答案
bool
实际上只有1个字节,但是对齐可能导致4个字节在32位平台上使用,甚至在64位平台上为8个字节。例如, Nullable< bool>
(又名 bool?
)类型使用完整的32位或64位,具体取决于平台-即使仅由两个 bool
组成。 编辑:正如乔恩·斯凯特(Jon Skeet)指出的那样,总是不存在用于对齐的填充。例如, Nullable< bool>
s的数组每个对象仅占用2个字节,而不是4或8个字节。
A bool
is actually only 1 byte, but alignment may cause 4 bytes to be used on a 32-bit platform, or even 8 bytes on a 64-bit platform. For example, the Nullable<bool>
(aka bool?
) type uses a full 32 or 64 bits—depending on platform—even though it's comprised of just two bool
s. EDIT: As pointed out by Jon Skeet, padding for alignment isn't always present. As an example, an array of Nullable<bool>
s takes only 2 bytes per object instead of 4 or 8.
但是如果要存储很多甚至8位也被认为是浪费。因此,如果创建的类型具有很多 bool
作为成员,(或使用很多 Nullable<>
类型),类的和用户可能会创建它的许多实例,您可以考虑使用 BitVector32
来代替。框架本身使用这种技术来减少许多Windows窗体控件的内存占用。
But even 8 bits to represent a bool
can be considered wasteful if you have many of them to store. For this reason, if you create a type that has many bool
s as members, (or uses many Nullable<>
types), and users of your class might create many instances of it, you might consider using a BitVector32
instead. The framework itself uses this technique to reduce the memory footprint of many of the Windows Forms controls, for instance.
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