use u32 instead of usize for memory offsets/sizes to avoid i32->usize casts (#16)

crates/it-memory-traits/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "it-memory-traits"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["Fluence Labs"]
 description = "Defines traits that IT uses for accessing memory"
 edition = "2018"

crates/it-memory-traits/src/errors.rs

@@ -20,8 +20,8 @@ use thiserror::Error as ThisError;
 pub enum MemoryAccessError {
     #[error("Out-of-bound Wasm memory access: offset {offset}, size {size}, while memory_size {memory_size}")]
     OutOfBounds {
-        offset: usize,
-        size: usize,
-        memory_size: usize,
+        offset: u32,
+        size: u32,
+        memory_size: u32,
     },
 }

crates/it-memory-traits/src/lib.rs

@@ -48,7 +48,7 @@ pub trait SequentialReader {
 }
 
 pub trait SequentialWriter {
-    fn start_offset(&self) -> usize;
+    fn start_offset(&self) -> u32;
 
     // specialization of write_array for u8
     fn write_u8(&self, value: u8);
@@ -65,17 +65,9 @@ pub trait SequentialMemoryView<'s> {
     type SR: SequentialReader + 's;
     type SW: SequentialWriter + 's;
 
-    fn sequential_writer(
-        &'s self,
-        offset: usize,
-        size: usize,
-    ) -> Result<Self::SW, MemoryAccessError>;
+    fn sequential_writer(&'s self, offset: u32, size: u32) -> Result<Self::SW, MemoryAccessError>;
 
-    fn sequential_reader(
-        &'s self,
-        offset: usize,
-        size: usize,
-    ) -> Result<Self::SR, MemoryAccessError>;
+    fn sequential_reader(&'s self, offset: u32, size: u32) -> Result<Self::SR, MemoryAccessError>;
 }
 
 pub trait Memory<View>