Merge pull request #1 from MarkMcCaskey/master

Add Rust-focused updates and clean up

.gitignore

@@ -7,6 +7,7 @@
 # Generated by Cargo
 # will have compiled files and executables
 **/target/
+**/**/target/
 
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html

passing-data/example-rust-wasm-crate/strings-wasm-is-cool/src/lib.rs

@@ -1,4 +1,3 @@
-
 // Import the standard string library
 use std::str;
 
@@ -13,7 +12,8 @@ static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
 
 // Create a static mutable byte buffer.
 // We will use for passing memory between our host and wasm.
-// NOTE: global `static mut` means we will have "unsafe" code
+// NOTE: global `static mut` means we have to access it with unsafe
+// and manually ensure that only one mutable reference exists to it at a time
 // but for passing memory between a host and wasm should be fine.
 const WASM_MEMORY_BUFFER_SIZE: usize = 1024;
 static mut WASM_MEMORY_BUFFER: [u8; WASM_MEMORY_BUFFER_SIZE] = [0; WASM_MEMORY_BUFFER_SIZE];
@@ -22,35 +22,24 @@ static mut WASM_MEMORY_BUFFER: [u8; WASM_MEMORY_BUFFER_SIZE] = [0; WASM_MEMORY_B
 // in wasm memory
 #[wasm_bindgen]
 pub fn get_wasm_memory_buffer_pointer() -> *const u8 {
-  let pointer: *const u8;
-  unsafe {
-    pointer = WASM_MEMORY_BUFFER.as_ptr();
-  }
-
-  return pointer;
+    unsafe { WASM_MEMORY_BUFFER.as_ptr() }
 }
 
 // Function to get the string from the buffer and add the text to it
 #[wasm_bindgen]
 pub fn add_wasm_is_cool(passed_string_length: usize) -> usize {
-
     // Let's get the passed string from our passed bytes
-    let mut passed_string = "";
-    unsafe {
-        passed_string = str::from_utf8(&WASM_MEMORY_BUFFER[0..passed_string_length]).unwrap();
-    }
+    let passed_string =
+        unsafe { str::from_utf8(&WASM_MEMORY_BUFFER[..passed_string_length]).unwrap() };
 
     // Let's add our phrase to the passed string
     let new_string = format!("{} Wasm is cool!", passed_string);
 
     // Let's write the new string back to our buffer
-    let new_string_bytes = new_string.as_bytes();
-    for i in 0..new_string_bytes.len() {
-        unsafe {
-            WASM_MEMORY_BUFFER[i] = new_string_bytes[i];
-        }
+    unsafe {
+        WASM_MEMORY_BUFFER[..new_string.len()].copy_from_slice(new_string.as_bytes());
     }
 
-    // Return the length of the new string for  the host to fetch it out of memory
-    return new_string.len();
+    // Return the length of the new string for the host to fetch it out of memory
+    new_string.len()
 }

passing-data/src/main.rs

@@ -1,39 +1,40 @@
 // Import the Filesystem so we can read our .wasm file
-use std::io::prelude::*;
 use std::fs::File;
+use std::io::prelude::*;
 
 // Import the wasmer runtime so we can use it
-use wasmer_runtime::{
-    instantiate,
-    imports,
-    error,
-    Func
-};
+use wasmer_runtime::{error, imports, instantiate, Func};
 
 // Import some helpers for handling Pointers into Wasm Memory
-use wasmer_runtime_core::memory::ptr::{WasmPtr, Array};
+use wasmer_runtime_core::memory::ptr::{Array, WasmPtr};
+
+// Create an absolute path to the Wasm file
+const WASM_FILE_LOCATION: &str = concat!(
+    env!("CARGO_MANIFEST_DIR"),
+    "/example-rust-wasm-crate/strings-wasm-is-cool/pkg/strings_wasm_is_cool_bg.wasm"
+);
 
 // Our entry point to our application
 fn main() -> error::Result<()> {
-
     // Let's read in our .wasm file as bytes
 
     // Let's open the file.
     // The file path may be different depending where you run `cargo run`, and where you place the file.
-    let mut file = File::open("./example-rust-wasm-crate/strings-wasm-is-cool/pkg/strings_wasm_is_cool_bg.wasm").expect("Incorrect file path to wasm module.");
+    let mut file = File::open(WASM_FILE_LOCATION).expect("Incorrect file path to wasm module.");
 
     // Let's read the file into a Vec
     let mut wasm_vec = Vec::new();
-    file.read_to_end(&mut wasm_vec).expect("Error reading the wasm file");
+    file.read_to_end(&mut wasm_vec)
+        .expect("Error reading the wasm file");
 
-    // Let's get our byte slice ( [u8] ) from our wasm_vec.
+    // Let's get our byte slice ( &[u8] ) from our wasm_vec.
     let wasm_bytes = wasm_vec.as_slice();
 
     // Now that we have the wasm file as bytes, let's run it with the wasmer runtime
 
     // Our import object, that allows exposing functions to our wasm module.
     // We're not importing anything, so make an empty import object.
-    let import_object = imports!{};
+    let import_object = imports! {};
 
     // Let's create an instance of wasm module running in the wasmer-runtime
     let instance = instantiate(wasm_bytes, &import_object)?;
@@ -42,34 +43,43 @@ fn main() -> error::Result<()> {
     let wasm_instance_context = instance.context();
     let wasm_instance_memory = wasm_instance_context.memory(0);
 
-    // Let's get the pointer to the buffer defined by the wasm module in the wasm memory
-    let get_wasm_memory_buffer_pointer: Func<(), i32> = 
-        instance
+    // Let's get the pointer to the buffer defined by the wasm module in the wasm memory.
+    // We use the type system and the power of generics to get a function we can call
+    // directly with a type signature of no arguments and returning 1 u32
+    let get_wasm_memory_buffer_pointer: Func<(), u32> = instance
         .func("get_wasm_memory_buffer_pointer")
         .expect("get_wasm_memory_buffer_pointer");
-    let response = get_wasm_memory_buffer_pointer.call().unwrap() as u32;
+    let response = get_wasm_memory_buffer_pointer.call().unwrap();
+    // Let's create a WasmPtr which is a thin wrapper around u32 to ergonomically access memory
     let wasm_buffer_pointer: WasmPtr<u8, Array> = WasmPtr::new(response);
 
     // Let's write a string to the wasm memory
     let original_string = "Did you know";
     println!("The original string is: {}", original_string);
-    let memory_writer = wasm_buffer_pointer.deref(wasm_instance_memory, 0, original_string.len() as u32).unwrap();
+    // We deref our WasmPtr to get a &[Cell<u8>]
+    let memory_writer = wasm_buffer_pointer
+        .deref(wasm_instance_memory, 0, original_string.len() as u32)
+        .unwrap();
     for (i, b) in original_string.bytes().enumerate() {
         memory_writer[i].set(b);
     }
 
     // Let's call the exported function that concatenates a phrase to our string.
-    let add_wasm_is_cool: Func<u32, i32> = instance.func("add_wasm_is_cool").expect("Wasm is cool export");
+    let add_wasm_is_cool: Func<u32, u32> = instance
+        .func("add_wasm_is_cool")
+        .expect("Wasm is cool export");
     let new_string_length = add_wasm_is_cool.call(original_string.len() as u32).unwrap();
 
-     // Get our pointer again, since memory may have shifted around
-    let new_pointer_response = get_wasm_memory_buffer_pointer.call().unwrap() as u32;
+    // Get our pointer again, since memory may have shifted around
+    let new_pointer_response = get_wasm_memory_buffer_pointer.call().unwrap();
     let new_wasm_buffer_pointer: WasmPtr<u8, Array> = WasmPtr::new(new_pointer_response);
 
     // Read the string from that new pointer.
-    let new_string = new_wasm_buffer_pointer.get_utf8_string(wasm_instance_memory, new_string_length as u32).unwrap();
+    let new_string = new_wasm_buffer_pointer
+        .get_utf8_string(wasm_instance_memory, new_string_length)
+        .unwrap();
     println!("The new string is: {}", new_string);
-    
+
     // Asserting that the returned value from the function is our expected value.
     assert_eq!(new_string, "Did you know Wasm is cool!");