Add helper types and half-ish of the wasi signatures

lib/wasi/src/ptr.rs

@@ -0,0 +1,89 @@
+use std::{cell::Cell, fmt, marker::PhantomData, mem};
+use wasmer_runtime_core::{
+    memory::Memory,
+    types::{Type, ValueType, WasmExternType},
+};
+
+pub struct Array;
+pub struct Item;
+
+#[repr(transparent)]
+pub struct WasmPtr<T: Copy, Ty = Item> {
+    offset: u32,
+    _phantom: PhantomData<(T, Ty)>,
+}
+
+impl<T: Copy, Ty> WasmPtr<T, Ty> {
+    pub fn new(offset: u32) -> Self {
+        Self {
+            offset,
+            _phantom: PhantomData,
+        }
+    }
+
+    pub fn offset(self) -> u32 {
+        self.offset
+    }
+}
+
+impl<T: Copy + ValueType> WasmPtr<T, Item> {
+    pub fn deref<'a>(self, memory: &'a Memory) -> Option<&'a Cell<T>> {
+        if (self.offset as usize) + mem::size_of::<T>() >= memory.size().bytes().0 {
+            return None;
+        }
+        unsafe {
+            let cell_ptr = memory
+                .view::<T>()
+                .get_unchecked((self.offset() as usize) / mem::size_of::<T>())
+                as *const _;
+            Some(&*cell_ptr)
+        }
+    }
+}
+
+impl<T: Copy + ValueType> WasmPtr<T, Array> {
+    pub fn deref<'a>(self, memory: &'a Memory, length: u32) -> Option<&'a [Cell<T>]> {
+        if (self.offset as usize) + (mem::size_of::<T>() * (length as usize))
+            >= memory.size().bytes().0
+        {
+            return None;
+        }
+
+        unsafe {
+            let cell_ptrs = memory.view::<T>().get_unchecked(
+                ((self.offset() as usize) / mem::size_of::<T>())
+                    ..((self.offset() as usize) / mem::size_of::<T>()) + (length as usize),
+            ) as *const _;
+            Some(&*cell_ptrs)
+        }
+    }
+}
+
+unsafe impl<T: Copy, Ty> WasmExternType for WasmPtr<T, Ty> {
+    const TYPE: Type = Type::I32;
+}
+
+impl<T: Copy, Ty> Clone for WasmPtr<T, Ty> {
+    fn clone(&self) -> Self {
+        Self {
+            offset: self.offset,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<T: Copy, Ty> Copy for WasmPtr<T, Ty> {}
+
+impl<T: Copy, Ty> PartialEq for WasmPtr<T, Ty> {
+    fn eq(&self, other: &Self) -> bool {
+        self.offset == other.offset
+    }
+}
+
+impl<T: Copy, Ty> Eq for WasmPtr<T, Ty> {}
+
+impl<T: Copy, Ty> fmt::Debug for WasmPtr<T, Ty> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "WasmPtr({:#x})", self.offset)
+    }
+}