Rework memory access interface to support non-wasmer environments (#14)

crates/it-memory-traits/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "it-memory-traits"
+version = "0.1.0"
+authors = ["Fluence Labs"]
+description = "Defines traits that IT uses for accessing memory"
+edition = "2018"
+license = "Apache-2.0"
+
+[lib]
+name = "it_memory_traits"
+path = "src/lib.rs"
+
+[dependencies]
+thiserror = "1.0.24"

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

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2022 Fluence Labs Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use thiserror::Error as ThisError;
+
+#[derive(Debug, 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,
+    },
+}

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

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2022 Fluence Labs Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+mod errors;
+
+pub use errors::MemoryAccessError;
+
+macro_rules! read_ty {
+    ($func_name:ident, $ty:ty, $size:literal) => {
+        fn $func_name(&self) -> $ty {
+            <$ty>::from_le_bytes(self.read_bytes::<$size>())
+        }
+    };
+}
+
+pub trait SequentialReader {
+    fn read_byte(&self) -> u8;
+
+    fn read_bytes<const COUNT: usize>(&self) -> [u8; COUNT];
+
+    fn read_bool(&self) -> bool {
+        self.read_byte() != 0
+    }
+
+    read_ty!(read_u8, u8, 1);
+    read_ty!(read_i8, i8, 1);
+    read_ty!(read_u16, u16, 2);
+    read_ty!(read_i16, i16, 2);
+    read_ty!(read_u32, u32, 4);
+    read_ty!(read_i32, i32, 4);
+    read_ty!(read_f32, f32, 4);
+    read_ty!(read_u64, u64, 8);
+    read_ty!(read_i64, i64, 8);
+    read_ty!(read_f64, f64, 8);
+}
+
+pub trait SequentialWriter {
+    fn start_offset(&self) -> usize;
+
+    // specialization of write_array for u8
+    fn write_u8(&self, value: u8);
+
+    // specialization of write_array for u32
+    fn write_u32(&self, value: u32);
+
+    fn write_bytes(&self, bytes: &[u8]);
+}
+
+// the lifetime is needed because some implementations
+// need to bind SR and SW lifetimes to lifetime of &self in methods
+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_reader(
+        &'s self,
+        offset: usize,
+        size: usize,
+    ) -> Result<Self::SR, MemoryAccessError>;
+}
+
+pub trait Memory<View>
+where
+    View: for<'a> SequentialMemoryView<'a>,
+{
+    fn view(&self) -> View;
+}