Add a wasmtime-specific wasmtime_wat2wasm C API (#1206)

* Add a wasmtime-specific `wasmtime_wat2wasm` C API

This commit implements a wasmtime-specific C API for converting the text
format to the binary format. An upstream spec issue exists for adding
this to the C API, but in the meantime we can experiment with our own
version of this API and use it in the C# extension, for example!

Closes #1000

* Reorder arguments

* Use wasm_byte_vec_t for input `*.wat`

* Mark wat input as const

* Return an error message and use `fixed`

* Actually include the error message

* Use `fixed` in `Module.cs` as well

Author: alexcrichton

Cargo.lock

@@ -20,3 +20,4 @@ doctest = false
 wasmtime = { path = "../api" }
 wasi-common = { path = "../wasi-common" }
 wasmtime-wasi = { path = "../wasi" }
+wat = "1.0"

crates/c-api/Cargo.toml

@@ -38,6 +38,26 @@ WASMTIME_CONFIG_PROP(cranelift_opt_level, wasmtime_opt_level_t)
 
 ///////////////////////////////////////////////////////////////////////////////
 
+// Converts from the text format of WebAssembly to to the binary format.
+//
+// * `engine` - a previously created engine which will drive allocations and
+//   such
+// * `wat` - this it the input buffer with the WebAssembly Text Format inside of
+//   it. This will be parsed and converted to the binary format.
+// * `ret` - if the conversion is successful, this byte vector is filled in with
+//   the WebAssembly binary format.
+// * `error_message` - if the conversion fails, this is filled in with a
+//   descriptive error message of why parsing failed. This parameter is
+//   optional.
+//
+// Returns `true` if conversion succeeded, or `false` if it failed.
+bool wasmtime_wat2wasm(
+    wasm_engine_t *engine,
+    const wasm_byte_vec_t *wat,
+    own wasm_byte_vec_t *ret,
+    own wasm_byte_vec_t *error_message,
+);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif

crates/c-api/include/wasmtime.h

@@ -1,7 +1,8 @@
 //! This file defines the extern "C" API extension, which are specific
 //! to the wasmtime implementation.
 
-use crate::wasm_config_t;
+use crate::{wasm_byte_vec_t, wasm_config_t, wasm_engine_t};
+use std::str;
 use wasmtime::{OptLevel, Strategy};
 
 #[repr(u8)]
@@ -86,3 +87,33 @@ pub unsafe extern "C" fn wasmtime_config_cranelift_opt_level_set(
         WASMTIME_OPT_LEVEL_SPEED_AND_SIZE => OptLevel::SpeedAndSize,
     });
 }
+
+#[no_mangle]
+pub unsafe extern "C" fn wasmtime_wat2wasm(
+    _engine: *mut wasm_engine_t,
+    wat: *const wasm_byte_vec_t,
+    ret: *mut wasm_byte_vec_t,
+    error: *mut wasm_byte_vec_t,
+) -> bool {
+    let wat = match str::from_utf8((*wat).as_slice()) {
+        Ok(s) => s,
+        Err(_) => {
+            if !error.is_null() {
+                (*error).set_from_slice(b"input was not valid utf-8");
+            }
+            return false;
+        }
+    };
+    match wat::parse_str(wat) {
+        Ok(bytes) => {
+            (*ret).set_from_slice(&bytes);
+            true
+        }
+        Err(e) => {
+            if !error.is_null() {
+                (*error).set_from_slice(e.to_string().as_bytes());
+            }
+            false
+        }
+    }
+}

crates/c-api/src/ext.rs

@@ -1,4 +1,6 @@
 using System;
+using System.Text;
+using System.Runtime.InteropServices;
 
 namespace Wasmtime
 {
@@ -40,6 +42,34 @@ public Store CreateStore()
             return new Store(this);
         }
 
+        /// <summary>
+        /// Converts the WebAssembly text format to the binary format
+        /// </summary>
+        /// <returns>Returns the binary-encoded wasm module.</returns>
+        public byte[] WatToWasm(string wat)
+        {
+            var watBytes = Encoding.UTF8.GetBytes(wat);
+            unsafe
+            {
+                fixed (byte *ptr = watBytes)
+                {
+                    Interop.wasm_byte_vec_t watByteVec;
+                    watByteVec.size = (UIntPtr)watBytes.Length;
+                    watByteVec.data = ptr;
+                    if (!Interop.wasmtime_wat2wasm(Handle, ref watByteVec, out var bytes, out var error)) {
+                        var errorSpan = new ReadOnlySpan<byte>(error.data, checked((int)error.size));
+                        var message = Encoding.UTF8.GetString(errorSpan);
+                        Interop.wasm_byte_vec_delete(ref error);
+                        throw new WasmtimeException("failed to parse input wat: " + message);
+                    }
+                    var byteSpan = new ReadOnlySpan<byte>(bytes.data, checked((int)bytes.size));
+                    var ret = byteSpan.ToArray();
+                    Interop.wasm_byte_vec_delete(ref bytes);
+                    return ret;
+                }
+            }
+        }
+
         /// <inheritdoc/>
         public void Dispose()
         {

crates/misc/dotnet/src/Engine.cs

@@ -899,7 +899,7 @@ public static extern unsafe void wasi_config_set_env(
         public static extern bool wasi_config_set_stdin_file(
             WasiConfigHandle config,
             [MarshalAs(UnmanagedType.LPUTF8Str)] string path
-        ); 
+        );
 
         [DllImport(LibraryName)]
         public static extern void wasi_config_inherit_stdin(WasiConfigHandle config);
@@ -909,7 +909,7 @@ public static extern bool wasi_config_set_stdin_file(
         public static extern bool wasi_config_set_stdout_file(
             WasiConfigHandle config,
             [MarshalAs(UnmanagedType.LPUTF8Str)] string path
-        ); 
+        );
 
         [DllImport(LibraryName)]
         public static extern void wasi_config_inherit_stdout(WasiConfigHandle config);
@@ -919,7 +919,7 @@ public static extern bool wasi_config_set_stdout_file(
         public static extern bool wasi_config_set_stderr_file(
             WasiConfigHandle config,
             [MarshalAs(UnmanagedType.LPUTF8Str)] string path
-        ); 
+        );
 
         [DllImport(LibraryName)]
         public static extern void wasi_config_inherit_stderr(WasiConfigHandle config);
@@ -974,5 +974,14 @@ out IntPtr trap
 
         [DllImport(LibraryName)]
         public static extern void wasmtime_config_cranelift_opt_level_set(WasmConfigHandle config, wasmtime_opt_level_t level);
+
+        [DllImport(LibraryName, CharSet=CharSet.Ansi)]
+        [return: MarshalAs(UnmanagedType.I1)]
+        public static extern bool wasmtime_wat2wasm(
+            EngineHandle engine,
+            ref wasm_byte_vec_t wat,
+            out wasm_byte_vec_t vec,
+            out wasm_byte_vec_t error_message
+        );
    }
 }

crates/misc/dotnet/src/Interop.cs

@@ -15,15 +15,13 @@ internal Module(Store store, string name, byte[] bytes)
                 throw new ArgumentNullException(nameof(store));
             }
 
-            var bytesHandle = GCHandle.Alloc(bytes, GCHandleType.Pinned);
-
-            try
+            unsafe
             {
-                unsafe
+                fixed (byte *ptr = bytes)
                 {
                     Interop.wasm_byte_vec_t vec;
                     vec.size = (UIntPtr)bytes.Length;
-                    vec.data = (byte*)bytesHandle.AddrOfPinnedObject();
+                    vec.data = ptr;
 
                     Handle = Interop.wasm_module_new(store.Handle, ref vec);
                 }
@@ -33,10 +31,6 @@ internal Module(Store store, string name, byte[] bytes)
                     throw new WasmtimeException($"WebAssembly module '{name}' is not valid.");
                 }
             }
-            finally
-            {
-                bytesHandle.Free();
-            }
 
             Store = store;
             Name = name;

crates/misc/dotnet/src/Module.cs

@@ -13,7 +13,9 @@ public ModuleFixture()
                 .WithReferenceTypes(true)
                 .Build();
             Store = Engine.CreateStore();
-            Module = Store.CreateModule(Path.Combine("Modules", ModuleFileName));
+            var wat = Path.Combine("Modules", ModuleFileName);
+            var wasm = Engine.WatToWasm(File.ReadAllText(wat));
+            Module = Store.CreateModule(wat, wasm);
         }
 
         public void Dispose()

crates/misc/dotnet/tests/Fixtures/ModuleFixture.cs

@@ -8,7 +8,7 @@ namespace Wasmtime.Tests
 {
     public class FunctionExportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "FunctionExports.wasm";
+        protected override string ModuleFileName => "FunctionExports.wat";
     }
 
     public class FunctionExportsTests : IClassFixture<FunctionExportsFixture>

crates/misc/dotnet/tests/FunctionExportsTests.cs

@@ -8,7 +8,7 @@ namespace Wasmtime.Tests
 {
     public class FunctionImportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "FunctionImports.wasm";
+        protected override string ModuleFileName => "FunctionImports.wat";
     }
 
     public class FunctionImportsTests : IClassFixture<FunctionImportsFixture>

crates/misc/dotnet/tests/FunctionImportsTests.cs

@@ -7,7 +7,7 @@ namespace Wasmtime.Tests
 {
     public class FunctionThunkingFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "FunctionThunking.wasm";
+        protected override string ModuleFileName => "FunctionThunking.wat";
     }
 
     public class FunctionThunkingTests : IClassFixture<FunctionThunkingFixture>

crates/misc/dotnet/tests/FunctionThunkingTests.cs

@@ -10,7 +10,7 @@ namespace Wasmtime.Tests
 {
     public class GlobalExportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "GlobalExports.wasm";
+        protected override string ModuleFileName => "GlobalExports.wat";
     }
 
     public class GlobalExportsTests : IClassFixture<GlobalExportsFixture>

crates/misc/dotnet/tests/GlobalExportsTests.cs

@@ -6,7 +6,7 @@ namespace Wasmtime.Tests
 {
     public class GlobalImportBindingFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "GlobalImportBindings.wasm";
+        protected override string ModuleFileName => "GlobalImportBindings.wat";
     }
 
     public class GlobalImportBindingTests : IClassFixture<GlobalImportBindingFixture>

crates/misc/dotnet/tests/GlobalImportBindingTests.cs

@@ -8,7 +8,7 @@ namespace Wasmtime.Tests
 {
     public class GlobalImportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "GlobalImports.wasm";
+        protected override string ModuleFileName => "GlobalImports.wat";
     }
 
     public class GlobalImportsTests : IClassFixture<GlobalImportsFixture>

crates/misc/dotnet/tests/GlobalImportsTests.cs

@@ -8,7 +8,7 @@ namespace Wasmtime.Tests
 {
     public class MemoryExportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "MemoryExports.wasm";
+        protected override string ModuleFileName => "MemoryExports.wat";
     }
 
     public class MemoryExportsTests : IClassFixture<MemoryExportsFixture>

crates/misc/dotnet/tests/MemoryExportsTests.cs

@@ -6,7 +6,7 @@ namespace Wasmtime.Tests
 {
     public class MemoryImportBindingFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "MemoryImportBinding.wasm";
+        protected override string ModuleFileName => "MemoryImportBinding.wat";
     }
 
     public class MemoryImportBindingTests : IClassFixture<MemoryImportBindingFixture>

crates/misc/dotnet/tests/MemoryImportBindingTests.cs

@@ -6,7 +6,7 @@ namespace Wasmtime.Tests
 {
     public class MemoryImportFromModuleFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "MemoryImportFromModule.wasm";
+        protected override string ModuleFileName => "MemoryImportFromModule.wat";
     }
 
     public class MemoryImportFromModuleTests : IClassFixture<MemoryImportFromModuleFixture>

crates/misc/dotnet/tests/MemoryImportFromModuleTests.cs

@@ -6,7 +6,7 @@ namespace Wasmtime.Tests
 {
     public class MemoryImportNoUpperBoundFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "MemoryImportNoUpperBound.wasm";
+        protected override string ModuleFileName => "MemoryImportNoUpperBound.wat";
     }
 
     public class MemoryImportNoUpperBoundTests : IClassFixture<MemoryImportNoUpperBoundFixture>

crates/misc/dotnet/tests/MemoryImportNoUpperBoundTests.cs

@@ -6,7 +6,7 @@ namespace Wasmtime.Tests
 {
     public class MemoryImportWithUpperBoundFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "MemoryImportWithUpperBound.wasm";
+        protected override string ModuleFileName => "MemoryImportWithUpperBound.wat";
     }
 
     public class MemoryImportWithUpperBoundTests : IClassFixture<MemoryImportWithUpperBoundFixture>

crates/misc/dotnet/tests/MemoryImportWithUpperBoundTests.cs

@@ -8,7 +8,7 @@ namespace Wasmtime.Tests
 {
     public class TableExportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "TableExports.wasm";
+        protected override string ModuleFileName => "TableExports.wat";
     }
 
     public class TableExportsTests : IClassFixture<TableExportsFixture>

crates/misc/dotnet/tests/Modules/FunctionExports.wasm

@@ -8,7 +8,7 @@ namespace Wasmtime.Tests
 {
     public class TableImportsFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "TableImports.wasm";
+        protected override string ModuleFileName => "TableImports.wat";
     }
 
     public class TableImportsTests : IClassFixture<TableImportsFixture>

crates/misc/dotnet/tests/Modules/FunctionImports.wasm

@@ -21,4 +21,4 @@ public void Dispose()
 
         public string Path { get; private set; }
     }
-}
+}

crates/misc/dotnet/tests/Modules/FunctionThunking.wasm

@@ -9,7 +9,7 @@ namespace Wasmtime.Tests
 {
     public class WasiFixture : ModuleFixture
     {
-        protected override string ModuleFileName => "Wasi.wasm";
+        protected override string ModuleFileName => "Wasi.wat";
     }
 
     public class WasiTests : IClassFixture<WasiFixture>

crates/misc/dotnet/tests/Modules/GlobalExports.wasm

@@ -27,7 +27,7 @@
   </Target>
 
   <ItemGroup>
-    <None Update="Modules/*.wasm" CopyToOutputDirectory="PreserveNewest" />
+    <None Update="Modules/*.wat" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
 </Project>