From 3349bf265247e53728a683007291d452be9fbc02 Mon Sep 17 00:00:00 2001
From: Leonora Tindall <nora@nora.codes>
Date: Sun, 7 Nov 2021 12:53:43 -0600
Subject: [PATCH] feat: add conversion methods

---
 src/lib.rs | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 91 insertions(+), 5 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index ebde3ce..2587af5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -19,6 +19,16 @@ use std::slice;
 /// `MinSlice` is merely a way of reinterpreting an existing slice
 /// (`&[T]` or `&mut [T]`), and it is exactly the same size as a slice:
 /// one pointer and one `usize`.
+/// 
+/// # Example
+/// 
+/// ```
+/// # use nslice::MinSlice;
+/// let slice: &[u8] = b"Hello, world";
+/// let minslice = MinSlice::<u8, 12>::from_slice(slice).unwrap();
+/// let value: u8 = minslice.head[6];
+/// assert_eq!(value, b' ')
+/// ```
 pub struct MinSlice<T, const N: usize> {
     /// The bounded region of memory. Exactly `N` `T`s.
     pub head: [T; N],
@@ -47,7 +57,7 @@ impl<T, const N: usize> MinSlice<T, N> {
             None
         }
     }
-
+    
     /// Produce a `&mut MinSlice` from a mutable slice of `T`s.
     /// Returns `None` if there are not enough elements in `slice`.
     pub fn from_mut(slice: &mut [T]) -> Option<&mut MinSlice<T, N>> {
@@ -57,6 +67,70 @@ impl<T, const N: usize> MinSlice<T, N> {
             None
         }
     }
+}
+
+impl<T, const N: usize> MinSlice<T, N> {
+    /// Returns a slice over the memory referred to by the `MinSlice`.
+    /// Its length is guaranteed to be no less than `N`.
+    pub fn as_slice(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.head.as_ptr(), N + self.tail.len()) }
+    }
+
+    /// Returns a mutable slice over the memory referred to by the `MinSlice`.
+    /// Its length is guaranteed to be no less than `N`.
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        unsafe { slice::from_raw_parts_mut(self.head.as_mut_ptr(), N + self.tail.len()) }
+    }
+
+    /// Resize the `MinSlice`, returning a new `Some(&MinSlice<T, M>)`
+    /// if there are at least `M` `T`s in `self`. 
+    pub fn resize<const M: usize>(&self) -> Option<&MinSlice<T, M>> {
+        MinSlice::<T, M>::from_slice(self.as_slice())
+    }
+
+    /// Resize the `MinSlice`, returning a new `Some(&mut MinSlice<T, M>)`
+    /// if there are at least `M` `T`s in `self`. 
+    pub fn resize_mut<const M: usize>(&mut self) -> Option<&mut MinSlice<T, M>> {
+        MinSlice::<T, M>::from_mut(self.as_mut_slice())
+    }
+
+    /// Extend the `MinSlice`, returning a new `Some(&MinSlice<T, N + I>)`
+    /// if there are at least `I` `T`s in `tail`.
+    #[cfg(feature = "nightly")]
+    pub fn extend_by<const I: usize>(&self) -> Option<&MinSlice<T, {N + I}>> {
+        MinSlice::<T, {N + I}>::from_slice(self.as_slice())
+    }
+
+    /// Extend the `MinSlice`, returning a new `Some(&mut MinSlice<T, N + I>)`
+    /// if there are at least `I` `T`s in `tail`.
+    #[cfg(feature = "nightly")]
+    pub fn extend_by_mut<const I: usize>(&mut self) -> Option<&mut MinSlice<T, {N + I}>> {
+        MinSlice::<T, {N + I}>::from_mut(self.as_mut_slice())
+    } 
+
+    /// Get a reference to a value from the `MinSlice` by index.
+    /// 
+    /// Return `Some(&T)` for the `T` at index `i` if `i < (N + self.tail.len)`,
+    /// or `None` otherwise.
+    pub fn get(&self, i: usize) -> Option<&T> {
+        if i < N {
+            Some(&self.head[i])
+        } else {
+            self.tail.get(i)
+        }
+    }
+
+    /// Get a mutable reference to a value from the `MinSlice` by index.
+    /// 
+    /// Return `Some(&mut T)` for the `T` at index `i` if `i < (N + self.tail.len)`,
+    /// or `None` otherwise.
+    pub fn get_mut(&mut self, i: usize) -> Option<&mut T> {
+        if i < N {
+            Some(&mut self.head[i])
+        } else {
+            self.tail.get_mut(i)
+        }
+    } 
 
     /// Produce a `&MinSlice` from a slice of `T`s without checking its length.
     ///
@@ -112,14 +186,26 @@ impl<T, const N: usize> ExactSlice<T, N> {
         }
     }
 
+    /// Returns a slice over the memory referred to by the `ExactSlice`.
+    /// Its length is guaranteed to be exactly `N`.
+    pub fn as_slice(&self) -> &[T] {
+        unsafe { slice::from_raw_parts(self.head.as_ptr(), N) }
+    }
+
+    /// Returns a mutable slice over the memory referred to by the `ExactSlice`.
+    /// Its length is guaranteed to be exactly `N`.
+    pub fn as_mut_slice(&mut self) -> &mut [T] {
+        unsafe { slice::from_raw_parts_mut(self.head.as_mut_ptr(), N) }
+    }
+
     /// Produce a `&MinSlice` from this `&ExactSlice`. Its `tail` will be empty.
-    pub fn as_min_slice(&self) -> Option<&MinSlice<T, N>> {
-        MinSlice::from_slice(&self.head[..])
+    pub fn as_min_slice(&self) -> &MinSlice<T, N> {
+        unsafe { MinSlice::from_slice_unchecked(&self.head[..]) }
     }
 
     /// Produce a `&mut MinSlice` from this `&min ExactSlice`. Its `tail` will be empty.
-    pub fn as_mut_min_slice(&mut self) -> Option<&mut MinSlice<T, N>> {
-        MinSlice::from_mut(&mut self.head[..])
+    pub fn as_mut_min_slice(&mut self) -> &mut MinSlice<T, N> {
+        unsafe { MinSlice::from_mut_unchecked(&mut self.head[..]) }
     }
 
     /// Produce an `&ExactSlice` from a slice of `T`s without checking its length.