microstack/

stack.rs

// Copyright (c) 2023 Yegor Bugayenko
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

use crate::Stack;

impl<V: Copy, const N: usize> Stack<V, N> {
    /// Make it from vector.
    #[inline]
    #[must_use]
    pub fn from_vec(v: Vec<V>) -> Self {
        let mut p = Self::new();
        for i in v {
            unsafe { p.push_unchecked(i) };
        }
        p
    }

    /// Get the capacity.
    #[inline]
    #[must_use]
    pub fn capacity(&mut self) -> usize {
        N
    }

    /// Push new element into it.
    ///
    /// # Safety
    ///
    /// It may lead to undefined behavior, if you go over the boundary.
    #[inline]
    pub unsafe fn push_unchecked(&mut self, v: V) {
        self.items.as_mut_ptr().add(self.next).write(v);
        self.next += 1;
    }

    /// Push new element into it.
    ///
    /// # Panics
    ///
    /// If there is no more space in the stack, it will panic.
    #[inline]
    pub fn push(&mut self, v: V) {
        assert!(self.next < N, "No more space left in the stack");
        unsafe {
            self.push_unchecked(v);
        }
    }

    /// Makes an attempt to push a new element into the stack.
    ///
    /// If there was enough space in the stack, `Ok(v)` is returned, while
    /// `Err` is returned otherwise.
    ///
    /// # Errors
    ///
    /// If there is not enough space in the stack, `Err` is returned.
    #[inline]
    pub fn try_push(&mut self, v: V) -> Result<(), String> {
        if self.next < N {
            self.push(v);
            Ok(())
        } else {
            Err(format!(
                "There are no space left in the stack of {}",
                self.capacity()
            ))
        }
    }

    /// Pop a element from it.
    ///
    /// # Safety
    ///
    /// If there are no items in the array, the result is undefined.
    #[inline]
    pub unsafe fn pop_unchecked(&mut self) -> V {
        self.next -= 1;
        self.items.as_ptr().add(self.next).read()
    }

    /// Pop a element from it.
    ///
    /// # Panics
    ///
    /// If there are no items in the array, it will panic.
    #[inline]
    pub fn pop(&mut self) -> V {
        assert!(self.next > 0, "No more items left in the stack");
        unsafe { self.pop_unchecked() }
    }

    /// Pop a element from it.
    ///
    /// # Errors
    ///
    /// If there is no more elements left, it will return `None`.
    #[inline]
    pub fn try_pop(&mut self) -> Result<V, String> {
        if self.next == 0 {
            Err(format!(
                "There are no items left in the stack of {}",
                self.capacity()
            ))
        } else {
            Ok(self.pop())
        }
    }

    /// Clear.
    #[inline]
    pub fn clear(&mut self) {
        self.next = 0;
    }

    /// Is it empty.
    #[inline]
    #[must_use]
    pub const fn is_empty(&self) -> bool {
        self.len() == 0
    }

    /// Length of it.
    #[inline]
    #[must_use]
    pub const fn len(&self) -> usize {
        self.next
    }
}

#[test]
fn push_one() {
    let mut s: Stack<u64, 1> = Stack::new();
    unsafe { s.push_unchecked(42) };
    assert_eq!(42, s.pop());
}

#[test]
fn push_safely() {
    let mut s: Stack<u64, 1> = Stack::new();
    s.push(42);
    assert_eq!(42, s.pop());
}

#[test]
fn try_to_push() {
    let mut s: Stack<u64, 1> = Stack::new();
    assert!(s.try_push(42).is_ok());
    assert!(s.try_push(16).is_err());
    assert_eq!(42, s.pop());
}

#[test]
fn push_after_clear() {
    let mut s: Stack<u64, 1> = Stack::new();
    unsafe { s.push_unchecked(42) };
    s.clear();
    s.push(16);
    assert_eq!(16, s.pop());
}

#[test]
fn build_from_vec() {
    let mut s: Stack<u64, 1> = Stack::from_vec(vec![42]);
    assert_eq!(42, s.pop());
}

#[test]
fn pop_none() {
    let mut s: Stack<u64, 1> = Stack::new();
    assert_eq!(0, s.len());
    assert!(s.is_empty());
    assert!(s.try_pop().is_err());
}

#[test]
fn read_capacity() {
    let mut s: Stack<u64, 1> = Stack::new();
    assert_eq!(1, s.capacity());
}

#[test]
fn safely_pop() {
    let mut s: Stack<u64, 1> = Stack::new();
    s.push(42);
    assert_eq!(42, s.try_pop().unwrap());
}

#[test]
fn with_str() {
    let mut s: Stack<&str, 1> = Stack::new();
    s.push("Hello!");
    assert_eq!("Hello!", s.pop());
}

#[test]
#[should_panic]
fn panic_on_empty_stack_push() {
    let mut s: Stack<u64, 0> = Stack::new();
    assert_eq!(0, s.len());
    s.push(11);
}

#[test]
#[should_panic]
fn panic_on_empty_stack_pop() {
    let mut s: Stack<u64, 0> = Stack::new();
    assert_eq!(0, s.len());
    s.pop();
}

#[test]
fn push_and_pop() {
    let mut s: Stack<u64, 16> = Stack::new();
    s.push(42);
    assert_eq!(42, s.pop());
}