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//!Memory utilities //! use core::mem; #[inline] ///Returns size of the value at compile time. /// ///Doesn't work with unsized types as they can be only evaluated at runtime. pub const fn size_of<T: Sized>(_: &T) -> usize { mem::size_of::<T>() } #[inline] ///Returns minimum alignment of the value at compile time.. /// ///Doesn't work with unsized types as they can be only evaluated at runtime.. pub const fn align_of<T>(_: &T) -> usize { mem::align_of::<T>() } #[inline] ///Returns whether value requires a drop. /// ///Doesn't work with unsized types as they can be only evaluated at runtime.. pub const fn needs_drop<T>(_: &T) -> bool { mem::needs_drop::<T>() } #[macro_export] ///Returns size of supplied expression at compile time. /// ///Accepts both type and value. /// ///Doesn't work with unsized values /// ///## Usage /// ///``` ///use type_traits::size_of; ///let array = [0u8; 4]; /// ///assert_eq!(size_of!(array[0]), size_of!(u8)); ///assert_eq!(size_of!(array.len()), size_of!(usize)); ///``` /// ///This will fail to compile because Rust macro system is actually just syntax replacement ///It is not aware about actual properties of passed arguments /// ///Anything that resembles type, will be tired as such ///As Rust lacks any utility to get type out of expression, you have to work it around by tricking ///macro into making something expression. /// ///```compile_fail ///use type_traits::size_of; ///let array = [0u8; 4]; ///assert_eq!(size_of!(array), size_of!(u32)); ///``` /// ///Instead you can append colon to tell macro to treat it as value /// ///``` ///use type_traits::size_of; ///let array = [0u8; 4]; ///assert_eq!(size_of!(array,), size_of!(u32)); /// /////When dealing with references, one should remember that Rust doesn't collapse references ///fn test<T>(val: &T) -> usize { /// size_of!(val,) ///} ///assert_eq!(test(&255u8), size_of!(usize)); // this will cause to return ptr size /// ///fn test2<T>(val: &T) -> usize { /// //We use special syntax * to tell macro to not create extra reference /// size_of!(*val) ///} ///assert_eq!(test2(&255u8), size_of!(u8)); ///``` macro_rules! size_of { (*$val:expr) => { $crate::mem::size_of($val) }; ($type:ty) => { core::mem::size_of::<$type>() }; ($val:expr$(,)?) => { $crate::mem::size_of(&$val) }; } #[macro_export] ///Returns minimum alignment of the value at compile time.. /// ///Accepts both type and value. /// ///Doesn't work with unsized values /// ///## Usage /// ///``` ///use type_traits::align_of; ///let array = [0u8; 4]; ///let array_ref = &array; /// ///assert_eq!(align_of!(array[0]), align_of!(u8)); ///assert_eq!(align_of!(array.len()), align_of!(usize)); ///assert_eq!(align_of!(array,), align_of!(u8)); ///assert_eq!(align_of!(*array_ref), align_of!(u8)); /// ///``` macro_rules! align_of { (*$val:expr) => { $crate::mem::align_of($val) }; ($type:ty) => { core::mem::align_of::<$type>() }; ($val:expr$(,)?) => { $crate::mem::align_of(&$val) } } #[macro_export] ///Returns minimum alignment of the value at compile time.. /// ///Accepts both type and value. /// ///Doesn't work with unsized values /// ///## Usage /// ///``` ///use type_traits::needs_drop; ///let array = [0u8; 4]; ///let string = "lolka".to_owned(); ///let string_ref = &string; /// ///assert!(!needs_drop!(array,)); ///assert!(needs_drop!(string,)); ///assert!(needs_drop!(*string_ref)); ///assert!(!needs_drop!(string.as_bytes()[0])); ///``` macro_rules! needs_drop { (*$val:expr) => { $crate::mem::needs_drop($val) }; ($type:ty) => { core::mem::needs_drop::<$type>() }; ($val:expr$(,)?) => { $crate::mem::needs_drop(&$val) } }