static_collections/

vec.rs

// The static-vector module

use core::{mem::MaybeUninit, ops::{Deref, DerefMut}, ptr, slice};

#[derive(Debug)]
pub struct StaticVec<const N:usize,T>
{
	length:usize,
	buff:MaybeUninit<[T;N]>
}

impl<const N:usize,T:Copy> Clone for StaticVec<N,T>
{
	fn clone(&self) -> Self
	{
		Self
		{
			length:self.length,
			buff:self.buff
		}
	}
}

impl<const N:usize,T> Default for StaticVec<N,T>
{
	fn default() -> Self
	{
		Self::new()
	}
}

impl<const N:usize,T> StaticVec<N,T>
{
	/// Constructs a new, empty StaticVec<N,T>.
	/// 
	/// The `new` method will not zero the buffer, so the initial operation is very inexpensive.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// ```
	pub const fn new()->Self
	{
		Self
		{
			length:0,
			buff:MaybeUninit::uninit()
		}
	}

	pub const fn as_slice(&self)->&[T]
	{
		unsafe
		{
			slice::from_raw_parts(self.as_ptr(),self.length)
		}
	}

	pub const fn as_mut_slice(&mut self)->&mut [T]
	{
		unsafe
		{
			slice::from_raw_parts_mut(self.as_mut_ptr(),self.length)
		}
	}

	pub const fn as_ptr(&self)->*const T
	{
		unsafe
		{
			self.buff.assume_init_ref().as_ptr()
		}
	}

	pub const fn as_mut_ptr(&mut self)->*mut T
	{
		unsafe
		{
			self.buff.assume_init_mut().as_mut_ptr()
		}
	}

	/// Put value `v` to the end of static vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(1234);
	/// assert_eq!(v.as_slice(),&[1234]);
	/// v.push(4567);
	/// assert_eq!(v.as_slice(),&[1234,4567]);
	/// ```
	pub fn push(&mut self,v:T)
	{
		if self.length<N
		{
			unsafe
			{
				let vector=self.buff.assume_init_mut();
				// Use ptr::write to avoid `Drop` trait requirement.
				ptr::write(&raw mut vector[self.length],v);
			}
			self.length+=1;
		}
	}

	/// Read and remove the value at the end of the static vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(1234);
	/// assert_eq!(v.pop(),1234);
	/// ```
	pub fn pop(&mut self)->T
	{
		if self.length>0
		{
			self.length-=1;
			// Use unsafe codes to avoid `Copy` trait.
			unsafe
			{
				ptr::read(self.as_ptr().add(self.length))
			}
		}
		else
		{
			panic!("popping a value from an empty static vector!");
		}
	}

	/// Insert value `v` to a specific location of static vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(1234);
	/// v.push(4567);
	/// v.insert(1,2333);
	/// assert_eq!(v.as_slice(),&[1234,2333,4567]);
	/// ```
	pub fn insert(&mut self,index:usize,v:T)
	{
		if self.length<N && index<=self.length
		{
			// Use unsafe codes to avoid `Copy` trait.
			unsafe
			{
				let p=self.as_mut_ptr().add(index);
				ptr::copy(p,p.add(1),self.length-index);
				ptr::write(p,v);
			}
			self.length+=1;
		}
	}

	/// Read and remove the value at location `index` of the static vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(1234);
	/// v.push(4567);
	/// v.push(7890);
	/// assert_eq!(v.remove(1),4567);
	/// assert_eq!(v.as_slice(),&[1234,7890]);
	/// ```
	pub fn remove(&mut self,index:usize)->T
	{
		if self.length>index
		{
			// Use unsafe codes to avoid `Copy` trait.
			unsafe
			{
				let p=self.as_mut_ptr().add(index);
				let v=ptr::read(self.as_ptr().add(index));
				ptr::copy(p.add(1),p,self.length-index-1);
				self.length-=1;
				v
			}
		}
		else
		{
			panic!("removal index ({index}) is out of bound ({})!",self.length);
		}
	}

	/// Shortens this static-vector to the specified `new_len`.
	/// 
	/// # Examples
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(0);
	/// v.push(1);
	/// v.push(2);
	/// v.push(3);
	/// v.push(4);
	/// v.push(5);
	/// v.truncate(2);
	/// assert_eq!(v.as_slice(),&[0,1]);
	/// ```
	pub fn truncate(&mut self,new_len:usize)
	{
		if new_len<self.length
		{
			self.length=new_len;
		}
	}

	/// Removes all values from the static-vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(12345);
	/// v.push(67890);
	/// v.clear();
	/// assert_eq!(v.as_slice(),&[]);
	/// ```
	pub fn clear(&mut self)
	{
		for item in self.as_mut_slice()
		{
			// Force drop every item.
			drop(unsafe{ptr::read(item)});
		}
		self.length=0;
	}

	/// Checks if the static-vector is empty.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// v.push(12);
	/// v.push(34);
	/// assert!(!v.is_empty());
	/// v.clear();
	/// assert!(v.is_empty());
	/// ```
	pub fn is_empty(&self)->bool
	{
		self.len()==0
	}

	/// Returns the number of values in the static-vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let mut v:StaticVec<8,u64>=StaticVec::new();
	/// assert_eq!(v.len(),0);
	/// v.push(1);
	/// assert_eq!(v.len(),1);
	/// ```
	pub const fn len(&self)->usize
	{
		self.length
	}

	/// Returns the capacity of the static-vector.
	/// 
	/// # Example
	/// ```
	/// use static_collections::vec::StaticVec;
	/// let v:StaticVec<12,u64>=StaticVec::new();
	/// assert_eq!(v.capacity(),12);
	/// ```
	pub const fn capacity(&self)->usize
	{
		N
	}

	/// This routine is a helper routine that constructs a static-vector for the `vec_static!` macro. \
	/// This routine assigns the `value` specified at location `index` in the static-vector.
	/// 
	/// # Safety
	/// Do not use this routine on your own. This routine is only supposed to be called by `vec_static!` macro, \
	/// and the `index` is allowed to go beyond the `self.len()` limit. That's why this routine is unsafe.
	/// 
	/// # Panic
	/// If `index>=N`, internal assertion would fail.
	pub const unsafe fn force_assign(&mut self,index:usize,value:T)
	{
		assert!(index<N);
		unsafe
		{
			ptr::write(self.buff.assume_init_mut().as_mut_ptr().add(index),value);
		}
	}

	/// This routine is a helper routine that constructs a static-vector for the `vec_static!` macro. \
	/// This routine resizes the static vector with specified length. \
	/// Should you wish to use `force_resize` method, read the `# Safety` and `# Panic` chapters.
	/// 
	/// # Safety
	/// If `index>self.length`, the static-vector may end with undefined contents. \
	/// You should get rid of these undefined contents after you force resized this vector.
	/// 
	/// # Panic
	/// If `length>N`, internal assertion would fail.
	pub const unsafe fn force_resize(&mut self,length:usize)
	{
		assert!(length<=N,"The new length exceeds capacity!");
		self.length=length;
	}
}

impl<const N:usize,T> Drop for StaticVec<N,T>
{
	fn drop(&mut self)
	{
		self.clear();
	}
}

impl<const N:usize,T> Deref for StaticVec<N,T>
{
	type Target = [T];

	fn deref(&self) -> &Self::Target
	{
		self.as_slice()
	}
}

impl<const N:usize,T> DerefMut for StaticVec<N,T>
{
	fn deref_mut(&mut self) -> &mut Self::Target
	{
		self.as_mut_slice()
	}
}

/// The `vec_static!` macro helps building a static-vector easily,
/// similar to the `vec!` macro in `std`/`alloc` crate.
/// 
/// # Example
/// ```
/// use static_collections::{vec_static,vec::StaticVec};
/// let a:StaticVec<12,u64>=vec_static![4;7];
/// assert_eq!(a.as_slice(),&[4;7]);
/// let b:StaticVec<16,u32>=vec_static![1,2,3,4,5,6,7,8];
/// assert_eq!(b.as_slice(),&[1,2,3,4,5,6,7,8]);
/// ```
#[macro_export] macro_rules! vec_static
{
	()=>
	(
		$crate::vec::StaticVec::new()
	);
	($elem:expr;$len:expr)=>
	(
		{
			let mut v=StaticVec::new();
			unsafe
			{
				let mut i:usize=0;
				while i<$len
				{
					v.force_assign(i,$elem);
					i+=1;
				}
				v.force_resize($len);
			}
			v
		}
	);
	($($x:expr),+$(,)?)=>
	(
		{
			let mut v=StaticVec::new();
			let mut index:usize=0;
			unsafe
			{
				$(
					{
						v.force_assign(index,$x);
						index+=1;
					}
				)*
				v.force_resize(index);
			}
			v
		}
	);
}

#[cfg(test)] mod test
{
	extern crate std;

	use std::println;
	use crate::vec::StaticVec;

	#[should_panic]
	#[test] fn vec_macro_overflow()
	{
		let x:StaticVec<12,u64>=vec_static![1234;16];
		println!("{x:?}")
	}

	#[test] fn clone()
	{
		let x:StaticVec<16,u64>=vec_static![1,2,3,4,5,6,7,8,9,10];
		assert_eq!(x.len(),10);
		let y=x.clone();
		assert_eq!(*y,[1,2,3,4,5,6,7,8,9,10]);
	}

	#[test] fn drop()
	{
		use core::sync::atomic::{AtomicUsize,Ordering};

		struct DropCounter<'a>
		{
			counter:&'a AtomicUsize
		}

		impl<'a> Drop for DropCounter<'a>
		{
			fn drop(&mut self)
			{
				self.counter.fetch_add(1,Ordering::SeqCst);
			}
		}

		let drop_count:AtomicUsize=AtomicUsize::new(0);
		{
			let mut v:StaticVec<8,DropCounter>=StaticVec::new();
			v.push(DropCounter{counter:&drop_count});
			v.push(DropCounter{counter:&drop_count});
			assert_eq!(drop_count.load(Ordering::SeqCst),0);
			v.pop();
			assert_eq!(drop_count.load(Ordering::SeqCst),1);
			v.clear();
			assert_eq!(drop_count.load(Ordering::SeqCst),2);
			v.push(DropCounter{counter:&drop_count});
			v.push(DropCounter{counter:&drop_count});
			assert_eq!(drop_count.load(Ordering::SeqCst),2);
		}
		assert_eq!(drop_count.load(Ordering::SeqCst),4);
	}
}