From 061cda36deff0d396735d57f4f883bcf14e12b1f Mon Sep 17 00:00:00 2001
From: Xu Shaohua <shaohua@biofan.org>
Date: Mon, 5 Aug 2024 17:11:01 +0800
Subject: [PATCH] queue: Add array queue v2

---
 queue/src/array_queue.rs  |   3 +-
 queue/src/array_queue2.rs | 256 ++++++++++++++++++++++++++++++++++++++
 queue/src/lib.rs          |   1 +
 3 files changed, 258 insertions(+), 2 deletions(-)
 create mode 100644 queue/src/array_queue2.rs

diff --git a/queue/src/array_queue.rs b/queue/src/array_queue.rs
index be2e4a22..c92bf5d8 100644
--- a/queue/src/array_queue.rs
+++ b/queue/src/array_queue.rs
@@ -4,7 +4,6 @@
 
 use std::cmp::Ordering;
 use std::fmt;
-use std::fmt::Formatter;
 use std::hash::{Hash, Hasher};
 
 pub struct ArrayQueue<T> {
@@ -145,7 +144,7 @@ impl<T> FromIterator<T> for ArrayQueue<T> {
 }
 
 impl<T: fmt::Debug> fmt::Debug for ArrayQueue<T> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(&self.buf, f)
     }
 }
diff --git a/queue/src/array_queue2.rs b/queue/src/array_queue2.rs
new file mode 100644
index 00000000..58d1fadc
--- /dev/null
+++ b/queue/src/array_queue2.rs
@@ -0,0 +1,256 @@
+// Copyright (c) 2024 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by General Public License that can be found
+// in the LICENSE file.
+
+use std::{fmt, ptr};
+use std::alloc::{alloc, Layout};
+use std::cmp::Ordering;
+use std::hash::{Hash, Hasher};
+use std::mem::ManuallyDrop;
+use std::ptr::NonNull;
+
+pub struct ArrayQueue2<T> {
+    len: usize,
+    buf: Box<[T]>,
+}
+
+struct RawVec<T> {
+    ptr: NonNull<T>,
+    cap: usize,
+}
+
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+enum AllocError {
+    CapacityOverflow,
+    AllocateError,
+}
+
+impl<T> ArrayQueue2<T> {
+    pub fn new(capacity: usize) -> Self {
+        assert!(capacity > 0);
+        let raw_vec = RawVec::<T>::try_allocate(capacity).expect("Failed to allocate buffer");
+        let buf: Box<[T]> = unsafe { raw_vec.into_box() };
+        Self {
+            len: 0,
+            buf,
+        }
+    }
+
+    /// # Errors
+    ///
+    /// 当栈已满时再将元素入队, 就会返回错误, 以及原有的元素 `value`.
+    pub fn push(&mut self, value: T) -> Result<(), T> {
+        if self.len == self.buf.len() {
+            return Err(value);
+        }
+
+        self.buf[self.len] = value;
+        self.len += 1;
+
+        Ok(())
+    }
+
+    pub fn pop(&mut self) -> Option<T> {
+        if self.len > 0 {
+            // Take the first value, without calling drop method.
+            let front = unsafe {
+                Some(ptr::read(self.buf.as_ptr()))
+            };
+            // Move memory.
+            unsafe {
+                ptr::copy(self.buf.as_ptr().wrapping_add(1), self.buf.as_mut_ptr(), self.len - 1);
+            }
+            self.len -= 1;
+            front
+        } else {
+            None
+        }
+    }
+
+    #[must_use]
+    #[inline]
+    pub const fn len(&self) -> usize {
+        self.len
+    }
+
+    #[must_use]
+    #[inline]
+    pub const fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+    #[must_use]
+    #[inline]
+    pub const fn capacity(&self) -> usize {
+        self.buf.len()
+    }
+
+    #[must_use]
+    #[inline]
+    pub const fn front(&self) -> Option<&T> {
+        if self.len > 0 {
+            Some(&self.buf[0])
+        } else {
+            None
+        }
+    }
+
+    #[must_use]
+    #[inline]
+    pub fn front_mut(&mut self) -> Option<&mut T> {
+        if self.len > 0 {
+            Some(&mut self.buf[0])
+        } else {
+            None
+        }
+    }
+
+    #[must_use]
+    #[inline]
+    pub const fn back(&self) -> Option<&T> {
+        if self.len > 0 {
+            Some(&self.buf[self.len - 1])
+        } else {
+            None
+        }
+    }
+
+    #[must_use]
+    #[inline]
+    pub fn back_mut(&mut self) -> Option<&mut T> {
+        if self.len > 0 {
+            Some(&mut self.buf[self.len - 1])
+        } else {
+            None
+        }
+    }
+}
+
+impl<T: PartialEq> PartialEq for ArrayQueue2<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.len == other.len && PartialEq::eq(&self.buf, &other.buf)
+    }
+}
+
+impl<T: Eq> Eq for ArrayQueue2<T> {}
+
+impl<T: PartialOrd> PartialOrd for ArrayQueue2<T> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        PartialOrd::partial_cmp(&self.buf, &other.buf)
+    }
+}
+
+impl<T: Ord> Ord for ArrayQueue2<T> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        Ord::cmp(&self.buf, &other.buf)
+    }
+}
+
+impl<T: Hash> Hash for ArrayQueue2<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        Hash::hash(&self.buf, state);
+    }
+}
+
+impl<T> FromIterator<T> for ArrayQueue2<T> {
+    fn from_iter<U: IntoIterator<Item=T>>(iter: U) -> Self {
+        let vec: Vec<T> = iter.into_iter().collect();
+        Self {
+            len: vec.len(),
+            buf: vec.into_boxed_slice(),
+        }
+    }
+}
+
+impl<T: fmt::Debug> fmt::Debug for ArrayQueue2<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.buf, f)
+    }
+}
+
+impl<T> RawVec<T> {
+    fn try_allocate(
+        capacity: usize,
+    ) -> Result<Self, AllocError> {
+        debug_assert!(capacity > 0);
+        let Ok(layout) = Layout::array::<T>(capacity) else {
+            return Err(AllocError::CapacityOverflow);
+        };
+
+        let ptr = unsafe { alloc(layout) };
+        if ptr.is_null() {
+            return Err(AllocError::AllocateError);
+        }
+        let ptr = unsafe {
+            NonNull::new_unchecked(ptr.cast::<T>())
+        };
+
+        Ok(Self { ptr, cap: capacity })
+    }
+
+    unsafe fn into_box(self) -> Box<[T]> {
+        let me = ManuallyDrop::new(self);
+        unsafe {
+            let slice = ptr::slice_from_raw_parts_mut(me.ptr.as_ptr(), me.cap);
+            Box::from_raw(slice)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ArrayQueue2;
+
+    #[test]
+    fn test_size() {
+        assert_eq!(size_of::<ArrayQueue2::<i32>>(), 24);
+    }
+
+    #[test]
+    fn test_new() {
+        let queue = ArrayQueue2::<i32>::new(5);
+        assert!(queue.is_empty());
+    }
+
+    #[test]
+    fn test_push() {
+        let mut queue = ArrayQueue2::new(3);
+        let ret = queue.push(0);
+        assert!(ret.is_ok());
+        assert_eq!(queue.front().copied(), Some(0));
+        assert_eq!(queue.len(), 1);
+
+        let ret = queue.push(1);
+        assert!(ret.is_ok());
+        assert_eq!(queue.front().copied(), Some(0));
+        assert_eq!(queue.len(), 2);
+
+        let ret = queue.push(2);
+        assert!(ret.is_ok());
+        let ret = queue.push(3);
+        assert_eq!(ret, Err(3));
+    }
+
+    #[test]
+    fn test_pop() {
+        let mut queue = ArrayQueue2::new(3);
+        assert!(queue.push(0).is_ok());
+        assert!(queue.push(1).is_ok());
+        assert!(queue.push(2).is_ok());
+        assert_eq!(queue.len(), 3);
+
+        let ret = queue.pop();
+        assert_eq!(ret, Some(0));
+        assert_eq!(queue.len(), 2);
+        assert_eq!(queue.front().copied(), Some(1));
+
+        let ret = queue.push(3);
+        assert!(ret.is_ok());
+        assert_eq!(queue.len(), 3);
+
+        assert_eq!(queue.pop(), Some(1));
+        assert_eq!(queue.pop(), Some(2));
+        assert_eq!(queue.pop(), Some(3));
+        assert!(queue.is_empty());
+    }
+}
\ No newline at end of file
diff --git a/queue/src/lib.rs b/queue/src/lib.rs
index 7807877f..faf3499b 100644
--- a/queue/src/lib.rs
+++ b/queue/src/lib.rs
@@ -12,3 +12,4 @@
 
 pub mod circular_buffer;
 mod array_queue;
+mod array_queue2;