ensure len and capacity methods reflect their intentions

Author: neevek

src/lib.rs

@@ -9,6 +9,7 @@
 //!
 //! // Allocate a buffer with capacity 1024.
 //! let mut buf = pool.alloc(1024);
+//! buf.resize(1024, 0);
 //!
 //! // write some data into it
 //! for i in 0..100 {

src/pool.rs

@@ -90,7 +90,8 @@ impl<T: Poolable> BytePool<T> {
 
 impl<'a, T: Poolable> Drop for Block<'a, T> {
     fn drop(&mut self) {
-        let data = mem::ManuallyDrop::into_inner(unsafe { ptr::read(&self.data) });
+        let mut data = mem::ManuallyDrop::into_inner(unsafe { ptr::read(&self.data) });
+        data.reset();
         self.pool.push_raw_block(data);
     }
 }
@@ -138,6 +139,20 @@ unsafe impl<'a, T: StableDeref + Poolable> StableDeref for Block<'a, T> {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[test]
+    fn append() {
+        let pool = BytePool::<Vec<u8>>::new();
+        let mut buf = pool.alloc(4);
+        assert_eq!(0, buf.len());
+        assert_eq!(4, buf.capacity());
+        buf.push(12u8);
+        assert_eq!(1, buf.len());
+        buf.extend_from_slice("hello".as_bytes());
+        assert_eq!(6, buf.len());
+        buf.clear();
+        assert_eq!(0, buf.len());
+        assert!(buf.capacity() > 0);
+    }
 
     #[test]
     fn basics_vec_u8() {
@@ -174,6 +189,7 @@ mod tests {
         let _slice: &[u8] = &buf;
 
         assert_eq!(buf.capacity(), 10);
+        buf.resize(10, 0);
         for i in 0..10 {
             buf[i] = 1;
         }
@@ -199,15 +215,15 @@ mod tests {
         let h1 = std::thread::spawn(move || {
             for _ in 0..100 {
                 let mut buf = pool1.alloc(64);
-                buf[10] = 10;
+                buf.push(10);
             }
         });
 
         let pool2 = pool.clone();
         let h2 = std::thread::spawn(move || {
             for _ in 0..100 {
                 let mut buf = pool2.alloc(64);
-                buf[10] = 10;
+                buf.push(10);
             }
         });
 

src/poolable.rs

@@ -3,17 +3,32 @@ use std::hash::{BuildHasher, Hash};
 
 /// The trait required to be able to use a type in `BytePool`.
 pub trait Poolable {
+    fn empty(&self) -> bool;
+    fn len(&self) -> usize;
     fn capacity(&self) -> usize;
     fn alloc(size: usize) -> Self;
+    fn reset(&mut self);
 }
 
 impl<T: Default + Clone> Poolable for Vec<T> {
-    fn capacity(&self) -> usize {
+    fn empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    fn len(&self) -> usize {
         self.len()
     }
 
+    fn capacity(&self) -> usize {
+        self.capacity()
+    }
+
     fn alloc(size: usize) -> Self {
-        vec![T::default(); size]
+        Vec::<T>::with_capacity(size)
+    }
+
+    fn reset(&mut self) {
+        self.clear();
     }
 }
 
@@ -22,13 +37,25 @@ where
     K: Eq + Hash,
     S: BuildHasher + Default,
 {
-    fn capacity(&self) -> usize {
+    fn empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    fn len(&self) -> usize {
         self.len()
     }
 
+    fn capacity(&self) -> usize {
+        self.capacity()
+    }
+
     fn alloc(size: usize) -> Self {
         HashMap::with_capacity_and_hasher(size, Default::default())
     }
+
+    fn reset(&mut self) {
+        self.clear();
+    }
 }
 
 /// A trait allowing for efficient reallocation.
@@ -42,7 +69,7 @@ impl<T: Default + Clone> Realloc for Vec<T> {
 
         assert!(new_size > 0);
         match new_size.cmp(&self.capacity()) {
-            Greater => self.resize(new_size, T::default()),
+            Greater => self.reserve(new_size - self.capacity()),
             Less => {
                 self.truncate(new_size);
                 self.shrink_to_fit();