Refactor.

src/memory/mod.rs

@@ -12,9 +12,6 @@ use parity_wasm::elements::ResizableLimits;
 use value::LittleEndianConvert;
 use Error;
 
-use std::alloc::{System, Layout, GlobalAlloc};
-use std::{slice, ptr};
-
 /// Size of a page of [linear memory][`MemoryInstance`] - 64KiB.
 ///
 /// The size of a memory is always a integer multiple of a page size.
@@ -72,100 +69,8 @@ impl fmt::Debug for MemoryInstance {
     }
 }
 
-struct ByteBuf {
-    ptr: *mut u8,
-    len: usize,
-}
-
-impl ByteBuf {
-    fn layout(len: usize) -> Layout {
-        Layout::from_size_align(len, 1).expect("")
-    }
-
-    pub fn new(len: usize) -> Self {
-        let ptr = if len == 0 {
-            ptr::null_mut()
-        } else {
-            // Alignment of byte is 1.
-            // TODO: proof
-
-            let ptr = unsafe {
-                // TODO: proof
-                System.alloc_zeroed(Self::layout(len))
-            };
-
-            // TODO: proof
-            assert!(!ptr.is_null());
-
-            ptr
-        };
-
-        Self {
-            ptr,
-            len,
-        }
-    }
-
-    pub fn realloc(&mut self, new_len: usize) {
-        let new_ptr = if self.len == 0 {
-            // special case, when the memory wasn't allocated before.
-            // Alignment of byte is 1.
-            // TODO: proof
-            let ptr = unsafe {
-                // TODO: proof
-                System.alloc_zeroed(Self::layout(new_len))
-            };
-
-            // TODO: proof
-            assert!(!ptr.is_null());
-
-            ptr
-        } else {
-            // TODO: proof
-            let cur_layout = Self::layout(self.len);
-            let new_ptr = unsafe {
-                System.realloc(self.ptr, cur_layout, new_len)
-            };
-            assert!(!new_ptr.is_null());
-
-            unsafe {
-                let new_area = new_ptr.offset(self.len as isize);
-                ptr::write_bytes(new_area, 0, new_len - self.len);
-            }
-
-            new_ptr
-        };
-
-        self.ptr = new_ptr;
-        self.len = new_len;
-    }
-
-    pub fn len(&self) -> usize {
-        self.len
-    }
-
-    pub fn as_slice(&self) -> &[u8] {
-        unsafe {
-            slice::from_raw_parts(self.ptr, self.len)
-        }
-    }
-
-    pub fn as_slice_mut(&mut self) -> &mut [u8] {
-        unsafe {
-            slice::from_raw_parts_mut(self.ptr, self.len)
-        }
-    }
-}
-
-impl Drop for ByteBuf {
-    fn drop(&mut self) {
-        if self.len != 0 {
-            unsafe {
-                System.dealloc(self.ptr, Self::layout(self.len))
-            }
-        }
-    }
-}
+mod rust_alloc;
+use self::rust_alloc::ByteBuf;
 
 struct CheckedRegion {
     offset: usize,
@@ -579,6 +484,9 @@ impl MemoryInstance {
         self.clear(offset, 0, len)
     }
 
+    /// Set every byte in the entire linear memory to 0.
+    ///
+    /// Might be useful for some optimization shenanigans.
     pub fn erase(&self) {
         let cur_size = self.buffer.borrow().len();
         *self.buffer.borrow_mut() = ByteBuf::new(cur_size);

src/memory/rust_alloc.rs

@@ -0,0 +1,104 @@
+//! An implementation of a `ByteBuf` based on Rust's `GlobalAlloc`.
+//!
+//! The performance of this is really depends on the underlying allocator implementation,
+//! specifically on `alloc_zeroed`. On macOS, for example, it calls to `bzero` which
+//! can ruin the performance for some workloads.
+
+use std::alloc::{System, Layout, GlobalAlloc};
+use std::{slice, ptr};
+
+pub struct ByteBuf {
+    // If the `len` is 0, this would store a dangling pointer but not `null`.
+    ptr: *mut u8,
+    len: usize,
+}
+
+impl ByteBuf {
+    pub fn new(len: usize) -> Self {
+        let ptr = if len == 0 {
+            // Craft a pointer which is not null, but
+            ptr::NonNull::dangling().as_ptr()
+        } else {
+            let ptr = unsafe {
+                // TODO: proof
+                System.alloc_zeroed(Self::layout(len))
+            };
+
+            // TODO: proof
+            assert!(!ptr.is_null());
+
+            ptr
+        };
+
+        Self {
+            ptr,
+            len,
+        }
+    }
+
+    pub fn realloc(&mut self, new_len: usize) {
+        let new_ptr = if self.len == 0 {
+            // special case, when the memory wasn't allocated before.
+            // Alignment of byte is 1.
+            // TODO: proof
+            let ptr = unsafe {
+                // TODO: proof
+                System.alloc_zeroed(Self::layout(new_len))
+            };
+
+            // TODO: proof
+            assert!(!ptr.is_null());
+
+            ptr
+        } else {
+            // TODO: proof
+            let cur_layout = Self::layout(self.len);
+            let new_ptr = unsafe {
+                System.realloc(self.ptr, cur_layout, new_len)
+            };
+            assert!(!new_ptr.is_null());
+
+            unsafe {
+                let new_area = new_ptr.offset(self.len as isize);
+                ptr::write_bytes(new_area, 0, new_len - self.len);
+            }
+
+            new_ptr
+        };
+
+        self.ptr = new_ptr;
+        self.len = new_len;
+    }
+
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        unsafe {
+            //
+            slice::from_raw_parts(self.ptr, self.len)
+        }
+    }
+
+    pub fn as_slice_mut(&mut self) -> &mut [u8] {
+        unsafe {
+            // TODO: zero sized.
+            slice::from_raw_parts_mut(self.ptr, self.len)
+        }
+    }
+
+    fn layout(len: usize) -> Layout {
+        Layout::from_size_align(len, 1).expect("")
+    }
+}
+
+impl Drop for ByteBuf {
+    fn drop(&mut self) {
+        if self.len != 0 {
+            unsafe {
+                System.dealloc(self.ptr, Self::layout(self.len))
+            }
+        }
+    }
+}