docs: string example

Signed-off-by: Henry Gressmann <mail@henrygressmann.de>

README.md

@@ -25,6 +25,7 @@ There are a couple of low-hanging fruits on the performance side, but they are n
 - [**Mutable Globals**](https://github.com/WebAssembly/mutable-global/blob/master/proposals/mutable-global/Overview.md) - **Fully implemented**
 - [**Multi-value**](https://github.com/WebAssembly/spec/blob/master/proposals/multi-value/Overview.md) - **Fully implemented**
 - [**Sign-extension operators**](https://github.com/WebAssembly/spec/blob/master/proposals/sign-extension-ops/Overview.md) - **Fully implemented**
+- [**Bulk Memory Operations**](https://github.com/WebAssembly/spec/blob/master/proposals/bulk-memory-operations/Overview.md) - **_Partially implemented_**
 - [**Reference Types**](https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md) - **_Partially implemented_**
 - [**Multiple Memories**](https://github.com/WebAssembly/multi-memory/blob/master/proposals/multi-memory/Overview.md) - **_Partially implemented_** (not tested yet)
 - [**Memory64**](https://github.com/WebAssembly/memory64/blob/master/proposals/memory64/Overview.md) - **_Partially implemented_** (only 32-bit addressing is supported at the moment, but larger memories can be created)

crates/tinywasm/src/instance.rs

@@ -199,14 +199,14 @@ impl ModuleInstance {
     pub fn memory(&self, store: &Store, addr: MemAddr) -> Result<MemoryRef> {
         let addr = self.resolve_mem_addr(addr);
         let mem = store.get_mem(addr as usize)?;
-        Ok(MemoryRef { _instance: mem.clone() })
+        Ok(MemoryRef { instance: mem.clone() })
     }
 
     /// Get the start function of the module
     ///
     /// Returns None if the module has no start function
     /// If no start function is specified, also checks for a _start function in the exports
-    /// (which is not part of the spec, but used by llvm)
+    /// (which is not part of the spec, but used by some compilers)
     ///
     /// See <https://webassembly.github.io/spec/core/syntax/modules.html#start-function>
     pub fn start_func(&self, store: &Store) -> Result<Option<FuncHandle>> {

crates/tinywasm/src/reference.rs

@@ -1,17 +1,135 @@
-use core::cell::RefCell;
+use core::{
+    cell::{Ref, RefCell},
+    ffi::CStr,
+};
+
+use crate::{GlobalInstance, MemoryInstance, Result};
+use alloc::{
+    ffi::CString,
+    rc::Rc,
+    string::{String, ToString},
+    vec::Vec,
+};
+use tinywasm_types::WasmValue;
 
-use crate::{GlobalInstance, MemoryInstance};
-use alloc::rc::Rc;
 // This module essentially contains the public APIs to interact with the data stored in the store
 
 /// A reference to a memory instance
 #[derive(Debug, Clone)]
 pub struct MemoryRef {
-    pub(crate) _instance: Rc<RefCell<MemoryInstance>>,
+    pub(crate) instance: Rc<RefCell<MemoryInstance>>,
+}
+
+/// A borrowed reference to a memory instance
+#[derive(Debug)]
+pub struct BorrowedMemory<'a> {
+    pub(crate) instance: Ref<'a, MemoryInstance>,
+}
+
+impl<'a> BorrowedMemory<'a> {
+    /// Load a slice of memory
+    pub fn load(&self, offset: usize, len: usize) -> Result<&[u8]> {
+        self.instance.load(offset, 0, len)
+    }
+
+    /// Load a C-style string from memory
+    pub fn load_cstr(&self, offset: usize, len: usize) -> Result<&CStr> {
+        let bytes = self.load(offset, len)?;
+        CStr::from_bytes_with_nul(bytes).map_err(|_| crate::Error::Other("Invalid C-style string".to_string()))
+    }
+
+    /// Load a C-style string from memory, stopping at the first nul byte
+    pub fn load_cstr_until_nul(&self, offset: usize, max_len: usize) -> Result<&CStr> {
+        let bytes = self.load(offset, max_len)?;
+        CStr::from_bytes_until_nul(bytes).map_err(|_| crate::Error::Other("Invalid C-style string".to_string()))
+    }
+}
+
+impl MemoryRef {
+    /// Borrow the memory instance
+    ///
+    /// This is useful for when you want to load only a reference to a slice of memory
+    /// without copying the data. The borrow should be dropped before any other memory
+    /// operations are performed.
+    pub fn borrow(&self) -> BorrowedMemory<'_> {
+        BorrowedMemory { instance: self.instance.borrow() }
+    }
+
+    /// Load a slice of memory
+    pub fn load_vec(&self, offset: usize, len: usize) -> Result<Vec<u8>> {
+        self.instance.borrow().load(offset, 0, len).map(|x| x.to_vec())
+    }
+
+    /// Grow the memory by the given number of pages
+    pub fn grow(&self, delta_pages: i32) -> Option<i32> {
+        self.instance.borrow_mut().grow(delta_pages)
+    }
+
+    /// Get the current size of the memory in pages
+    pub fn page_count(&self) -> usize {
+        self.instance.borrow().page_count()
+    }
+
+    /// Copy a slice of memory to another place in memory
+    pub fn copy_within(&self, src: usize, dst: usize, len: usize) -> Result<()> {
+        self.instance.borrow_mut().copy_within(src, dst, len)
+    }
+
+    /// Fill a slice of memory with a value
+    pub fn fill(&self, offset: usize, len: usize, val: u8) -> Result<()> {
+        self.instance.borrow_mut().fill(offset, len, val)
+    }
+
+    /// Load a UTF-8 string from memory
+    pub fn load_string(&self, offset: usize, len: usize) -> Result<String> {
+        let bytes = self.load_vec(offset, len)?;
+        Ok(String::from_utf8(bytes).map_err(|_| crate::Error::Other("Invalid UTF-8 string".to_string()))?)
+    }
+
+    /// Load a C-style string from memory
+    pub fn load_cstring(&self, offset: usize, len: usize) -> Result<CString> {
+        Ok(CString::from(self.borrow().load_cstr(offset, len)?))
+    }
+
+    /// Load a C-style string from memory, stopping at the first nul byte
+    pub fn load_cstring_until_nul(&self, offset: usize, max_len: usize) -> Result<CString> {
+        Ok(CString::from(self.borrow().load_cstr_until_nul(offset, max_len)?))
+    }
+
+    /// Load a JavaScript-style utf-16 string from memory
+    pub fn load_js_string(&self, offset: usize, len: usize) -> Result<String> {
+        let memref = self.borrow();
+        let bytes = memref.load(offset, len)?;
+        let mut string = String::new();
+        for i in 0..(len / 2) {
+            let c = u16::from_le_bytes([bytes[i * 2], bytes[i * 2 + 1]]);
+            string.push(
+                char::from_u32(c as u32).ok_or_else(|| crate::Error::Other("Invalid UTF-16 string".to_string()))?,
+            );
+        }
+        Ok(string)
+    }
+
+    /// Store a slice of memory
+    pub fn store(&self, offset: usize, len: usize, data: &[u8]) -> Result<()> {
+        self.instance.borrow_mut().store(offset, 0, data, len)
+    }
 }
 
 /// A reference to a global instance
 #[derive(Debug, Clone)]
 pub struct GlobalRef {
-    pub(crate) _instance: Rc<RefCell<GlobalInstance>>,
+    pub(crate) instance: Rc<RefCell<GlobalInstance>>,
+}
+
+impl GlobalRef {
+    /// Get the value of the global
+    pub fn get(&self) -> WasmValue {
+        self.instance.borrow().get()
+    }
+
+    /// Set the value of the global
+    pub fn set(&self, val: WasmValue) -> Result<()> {
+        self.instance.borrow_mut().set(val)
+    }
 }

crates/tinywasm/src/runtime/interpreter/macros.rs

@@ -63,7 +63,7 @@ macro_rules! mem_store {
         let val = val as $store_type;
         let val = val.to_le_bytes();
 
-        mem.borrow_mut().store(($arg.offset + addr) as usize, $arg.align as usize, &val)?;
+        mem.borrow_mut().store(($arg.offset + addr) as usize, $arg.align as usize, &val, val.len())?;
     }};
 }
 

crates/tinywasm/src/store.rs

@@ -306,7 +306,9 @@ impl Store {
                         })?;
 
                     // See comment for active element sections in the function above why we need to do this here
-                    if let Err(Error::Trap(trap)) = mem.borrow_mut().store(offset as usize, 0, &data.data) {
+                    if let Err(Error::Trap(trap)) =
+                        mem.borrow_mut().store(offset as usize, 0, &data.data, data.data.len())
+                    {
                         return Ok((data_addrs.into_boxed_slice(), Some(trap)));
                     }
 
@@ -607,8 +609,8 @@ impl MemoryInstance {
         }
     }
 
-    pub(crate) fn store(&mut self, addr: usize, _align: usize, data: &[u8]) -> Result<()> {
-        let end = addr.checked_add(data.len()).ok_or_else(|| {
+    pub(crate) fn store(&mut self, addr: usize, _align: usize, data: &[u8], len: usize) -> Result<()> {
+        let end = addr.checked_add(len).ok_or_else(|| {
             Error::Trap(crate::Trap::MemoryOutOfBounds { offset: addr, len: data.len(), max: self.data.len() })
         })?;
 
@@ -646,9 +648,37 @@ impl MemoryInstance {
         self.page_count
     }
 
-    pub(crate) fn grow(&mut self, delta: i32) -> Option<i32> {
+    pub(crate) fn fill(&mut self, addr: usize, len: usize, val: u8) -> Result<()> {
+        let end = addr
+            .checked_add(len)
+            .ok_or_else(|| Error::Trap(crate::Trap::MemoryOutOfBounds { offset: addr, len, max: self.data.len() }))?;
+        if end > self.data.len() {
+            return Err(Error::Trap(crate::Trap::MemoryOutOfBounds { offset: addr, len, max: self.data.len() }));
+        }
+        self.data[addr..end].fill(val);
+        Ok(())
+    }
+
+    pub(crate) fn copy_within(&mut self, dst: usize, src: usize, len: usize) -> Result<()> {
+        let end = src
+            .checked_add(len)
+            .ok_or_else(|| Error::Trap(crate::Trap::MemoryOutOfBounds { offset: src, len, max: self.data.len() }))?;
+        if end > self.data.len() || end < src {
+            return Err(Error::Trap(crate::Trap::MemoryOutOfBounds { offset: src, len, max: self.data.len() }));
+        }
+        let end = dst
+            .checked_add(len)
+            .ok_or_else(|| Error::Trap(crate::Trap::MemoryOutOfBounds { offset: dst, len, max: self.data.len() }))?;
+        if end > self.data.len() || end < dst {
+            return Err(Error::Trap(crate::Trap::MemoryOutOfBounds { offset: dst, len, max: self.data.len() }));
+        }
+        self.data[dst..end].copy_within(src..end, len);
+        Ok(())
+    }
+
+    pub(crate) fn grow(&mut self, pages_delta: i32) -> Option<i32> {
         let current_pages = self.page_count();
-        let new_pages = current_pages as i64 + delta as i64;
+        let new_pages = current_pages as i64 + pages_delta as i64;
 
         if new_pages < 0 || new_pages > MAX_PAGES as i64 {
             return None;
@@ -669,7 +699,7 @@ impl MemoryInstance {
         self.page_count = new_pages as usize;
 
         log::debug!("memory was {} pages", current_pages);
-        log::debug!("memory grown by {} pages", delta);
+        log::debug!("memory grown by {} pages", pages_delta);
         log::debug!("memory grown to {} pages", self.page_count);
 
         Some(current_pages.try_into().expect("memory size out of bounds, this should have been caught earlier"))
@@ -690,6 +720,25 @@ impl GlobalInstance {
     pub(crate) fn new(ty: GlobalType, value: RawWasmValue, owner: ModuleInstanceAddr) -> Self {
         Self { ty, value, _owner: owner }
     }
+
+    pub(crate) fn get(&self) -> WasmValue {
+        self.value.attach_type(self.ty.ty)
+    }
+
+    pub(crate) fn set(&mut self, val: WasmValue) -> Result<()> {
+        if val.val_type() != self.ty.ty {
+            return Err(Error::Other(format!(
+                "global type mismatch: expected {:?}, got {:?}",
+                self.ty.ty,
+                val.val_type()
+            )));
+        }
+        if !self.ty.mutable {
+            return Err(Error::Other("global is immutable".to_string()));
+        }
+        self.value = val.into();
+        Ok(())
+    }
 }
 
 /// A WebAssembly Element Instance

examples/rust/Cargo.toml

@@ -16,6 +16,10 @@ tinywasm={path="../../crates/tinywasm", features=["parser", "std"]}
 name="hello"
 path="src/hello.rs"
 
+[[bin]]
+name="print"
+path="src/print.rs"
+
 [[bin]]
 name="tinywasm"
 path="src/tinywasm.rs"

examples/rust/build.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 cd "$(dirname "$0")"
 
-bins=("hello" "tinywasm" "fibonacci")
+bins=("hello" "fibonacci" "print" "tinywasm")
 exclude_wat=("tinywasm")
 out_dir="./target/wasm32-unknown-unknown/wasm"
 dest_dir="out"
@@ -10,7 +10,7 @@ dest_dir="out"
 mkdir -p "$dest_dir"
 
 for bin in "${bins[@]}"; do
-    cargo build --target wasm32-unknown-unknown --package rust-wasm-examples --profile=wasm --bin "$bin"
+    RUSTFLAGS="-C target-feature=+reference-types -C panic=abort" cargo build --target wasm32-unknown-unknown --package rust-wasm-examples --profile=wasm --bin "$bin"
 
     cp "$out_dir/$bin.wasm" "$dest_dir/"
     wasm-opt "$dest_dir/$bin.wasm" -o "$dest_dir/$bin.wasm" -O --intrinsic-lowering -O

examples/rust/src/hello.rs

@@ -1,18 +1,28 @@
-#![no_std]
 #![no_main]
 
-#[cfg(not(test))]
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    core::arch::wasm32::unreachable()
-}
-
 #[link(wasm_import_module = "env")]
 extern "C" {
-    fn printi32(x: i32);
+    fn print_utf8(location: i32, len: i32);
+}
+
+const ARG: &[u8] = &[0u8; 100];
+
+#[no_mangle]
+pub unsafe extern "C" fn arg_ptr() -> i32 {
+    ARG.as_ptr() as i32
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn add_and_print(lh: i32, rh: i32) {
-    printi32(lh + rh);
+pub unsafe extern "C" fn arg_size() -> i32 {
+    ARG.len() as i32
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn hello(len: i32) {
+    let arg = core::str::from_utf8(&ARG[0..len as usize]).unwrap();
+    let res = format!("Hello, {}!", arg).as_bytes().to_vec();
+
+    let len = res.len() as i32;
+    let ptr = res.leak().as_ptr() as i32;
+    print_utf8(ptr, len);
 }

examples/rust/src/print.rs

@@ -0,0 +1,18 @@
+#![no_std]
+#![no_main]
+
+#[cfg(not(test))]
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    core::arch::wasm32::unreachable()
+}
+
+#[link(wasm_import_module = "env")]
+extern "C" {
+    fn printi32(x: i32);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn add_and_print(lh: i32, rh: i32) {
+    printi32(lh + rh);
+}

examples/rust/src/tinywasm.rs

@@ -12,7 +12,7 @@ pub extern "C" fn hello() {
 }
 
 fn run() -> tinywasm::Result<()> {
-    let module = tinywasm::Module::parse_bytes(include_bytes!("../out/hello.wasm"))?;
+    let module = tinywasm::Module::parse_bytes(include_bytes!("../out/print.wasm"))?;
     let mut store = tinywasm::Store::default();
     let mut imports = tinywasm::Imports::new();