Wasm: initial WASI support

classlib/src/main/java/org/teavm/classlib/impl/console/Console.java

@@ -16,7 +16,9 @@
 package org.teavm.classlib.impl.console;
 
 import org.teavm.backend.c.intrinsic.RuntimeInclude;
+import org.teavm.backend.wasm.runtime.WasmSupport;
 import org.teavm.classlib.PlatformDetector;
+import org.teavm.interop.Address;
 import org.teavm.interop.Import;
 import org.teavm.interop.Unmanaged;
 import org.teavm.jso.JSBody;
@@ -25,29 +27,35 @@ public final class Console {
     private Console() {
     }
 
-    public static void writeStderr(int b) {
+    public static void writeStderr(byte[] data, int off, int len) {
         if (PlatformDetector.isC()) {
-            writeC(b);
+            for (int i = 0; i < len; ++i) {
+                byte b = data[i + off];
+                writeC(b & 0xFF);
+            }
         } else if (PlatformDetector.isWebAssembly()) {
-            writeWasm(b);
+            WasmSupport.putCharsStderr(Address.ofData(data).add(off), len);
         } else {
-            writeJs(b);
+            for (int i = 0; i < len; ++i) {
+                byte b = data[i + off];
+                writeJs(b & 0xFF);
+            }
         }
     }
 
-    public static void writeStdout(int b) {
+    public static void writeStdout(byte[] data, int off, int len) {
         if (PlatformDetector.isC()) {
-            writeC(b);
+            for (int i = 0; i < len; ++i) {
+                byte b = data[i + off];
+                writeC(b & 0xFF);
+            }
         } else if (PlatformDetector.isWebAssembly()) {
-            writeWasm(b);
+            WasmSupport.putCharsStdout(Address.ofData(data).add(off), len);
         } else {
-            writeJsStdout(b);
+            for (int i = 0; i < len; ++i) {
-        }
+                byte b = data[i + off];
-    }
+                writeJs(b & 0xFF);
-
+            }
-    public static void writeStdout(String s) {
-        for (int i = 0; i < s.length(); ++i) {
-            writeStderr(s.charAt(i));
         }
     }
 
@@ -57,9 +65,6 @@ public final class Console {
     @JSBody(params = "b", script = "$rt_putStdout(b);")
     private static native void writeJsStdout(int b);
 
-    @Import(name = "putwchar", module = "teavm")
-    private static native void writeWasm(int b);
-
     @Unmanaged
     @Import(name = "teavm_logchar")
     @RuntimeInclude("log.h")

classlib/src/main/java/org/teavm/classlib/impl/console/ConsoleOutputStream.java

@@ -0,0 +1,32 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.classlib.impl.console;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+public abstract class ConsoleOutputStream extends OutputStream {
+    private byte[] buffer = new byte[1];
+
+    @Override
+    public void write(int b) throws IOException {
+        buffer[0] = (byte) b;
+        write(buffer);
+    }
+
+    @Override
+    public abstract void write(byte[] b, int off, int len) throws IOException;
+}

classlib/src/main/java/org/teavm/classlib/impl/console/StderrOutputStream.java

@@ -16,16 +16,15 @@
 package org.teavm.classlib.impl.console;
 
 import java.io.IOException;
-import java.io.OutputStream;
 
-public class StderrOutputStream extends OutputStream {
+public class StderrOutputStream extends ConsoleOutputStream {
     public static final StderrOutputStream INSTANCE = new StderrOutputStream();
 
     private StderrOutputStream() {
     }
 
     @Override
-    public void write(int b) throws IOException {
+    public void write(byte[] b, int off, int len) throws IOException {
-        Console.writeStderr(b);
+        Console.writeStderr(b, off, len);
     }
 }

classlib/src/main/java/org/teavm/classlib/impl/console/StdoutOutputStream.java

@@ -16,16 +16,15 @@
 package org.teavm.classlib.impl.console;
 
 import java.io.IOException;
-import java.io.OutputStream;
 
-public class StdoutOutputStream extends OutputStream {
+public class StdoutOutputStream extends ConsoleOutputStream {
     public static final StdoutOutputStream INSTANCE = new StdoutOutputStream();
 
     private StdoutOutputStream() {
     }
 
     @Override
-    public void write(int b) throws IOException {
+    public void write(byte[] b, int off, int len) throws IOException {
-        Console.writeStdout(b);
+        Console.writeStdout(b, off, len);
     }
 }

classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java

@@ -19,6 +19,7 @@ import java.util.Enumeration;
 import java.util.Properties;
 import org.teavm.backend.c.intrinsic.RuntimeInclude;
 import org.teavm.backend.javascript.spi.GeneratedBy;
+import org.teavm.backend.wasm.runtime.WasmSupport;
 import org.teavm.classlib.PlatformDetector;
 import org.teavm.classlib.fs.VirtualFileSystemProvider;
 import org.teavm.classlib.fs.c.CFileSystem;
@@ -144,15 +145,12 @@ public final class TSystem extends TObject {
 
     private static long currentTimeMillisLowLevel() {
         if (PlatformDetector.isWebAssembly()) {
-            return (long) currentTimeMillisWasm();
+            return WasmSupport.currentTimeMillis();
         } else {
-            return (long) currentTimeMillisC();
+            return currentTimeMillisC();
         }
     }
 
-    @Import(name = "currentTimeMillis", module = "teavm")
-    private static native double currentTimeMillisWasm();
-
     @Import(name = "teavm_currentTimeMillis")
     @RuntimeInclude("time.h")
     private static native long currentTimeMillisC();

core/src/main/java/org/teavm/backend/wasm/TeaVMWasmHost.java

@@ -20,4 +20,6 @@ import org.teavm.vm.spi.TeaVMHostExtension;
 
 public interface TeaVMWasmHost extends TeaVMHostExtension {
     void add(WasmIntrinsicFactory intrinsicFactory);
+
+    WasmRuntimeType getRuntimeType();
 }

core/src/main/java/org/teavm/backend/wasm/WasmHeap.java

@@ -15,8 +15,8 @@
  */
 package org.teavm.backend.wasm;
 
+import org.teavm.backend.wasm.runtime.WasmSupport;
 import org.teavm.interop.Address;
-import org.teavm.interop.Import;
 import org.teavm.interop.StaticInit;
 import org.teavm.interop.Unmanaged;
 
@@ -60,8 +60,9 @@ public final class WasmHeap {
 
     public static native void growMemory(int amount);
 
-    @Import(name = "init", module = "teavmHeapTrace")
+    private static void initHeapTrace(int maxHeap) {
-    private static native void initHeapTrace(int maxHeap);
+        WasmSupport.initHeapTrace(maxHeap);
+    }
 
     public static void initHeap(Address start, int minHeap, int maxHeap, int stackSize) {
         initHeapTrace(maxHeap);

core/src/main/java/org/teavm/backend/wasm/WasmRuntime.java

@@ -15,8 +15,8 @@
  */
 package org.teavm.backend.wasm;
 
+import org.teavm.backend.wasm.runtime.WasmSupport;
 import org.teavm.interop.Address;
-import org.teavm.interop.Import;
 import org.teavm.interop.StaticInit;
 import org.teavm.interop.Unmanaged;
 import org.teavm.runtime.RuntimeObject;
@@ -84,17 +84,21 @@ public final class WasmRuntime {
         return value;
     }
 
-    @Import(name = "print", module = "spectest")
+    public static void print(int a) {
-    public static native void print(int a);
+        WasmSupport.print(a);
+    }
 
-    @Import(name = "logString", module = "teavm")
+    public static void printString(String s) {
-    public static native void printString(String s);
+        WasmSupport.printString(s);
+    }
 
-    @Import(name = "logInt", module = "teavm")
+    public static void printInt(int i) {
-    public static native void printInt(int i);
+        WasmSupport.printInt(i);
+    }
 
-    @Import(name = "logOutOfMemory", module = "teavm")
+    public static void printOutOfMemory() {
-    public static native void printOutOfMemory();
+        WasmSupport.printOutOfMemory();
+    }
 
     public static void fillZero(Address address, int count) {
         fill(address, (byte) 0, count);

core/src/main/java/org/teavm/backend/wasm/WasmRuntimeType.java

@@ -0,0 +1,21 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm;
+
+public enum WasmRuntimeType {
+    TEAVM,
+    WASI
+}

core/src/main/java/org/teavm/backend/wasm/WasmTarget.java

@@ -106,6 +106,7 @@ import org.teavm.backend.wasm.render.WasmCRenderer;
 import org.teavm.backend.wasm.render.WasmRenderer;
 import org.teavm.backend.wasm.transformation.IndirectCallTraceTransformation;
 import org.teavm.backend.wasm.transformation.MemoryAccessTraceTransformation;
+import org.teavm.backend.wasm.transformation.WasiSupportClassTransformer;
 import org.teavm.common.ServiceRepository;
 import org.teavm.dependency.ClassDependency;
 import org.teavm.dependency.DependencyAnalyzer;
@@ -199,6 +200,7 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
     private boolean obfuscated;
     private Set<MethodReference> asyncMethods;
     private boolean hasThreads;
+    private WasmRuntimeType runtimeType = WasmRuntimeType.TEAVM;
 
     @Override
     public void setController(TeaVMTargetController controller) {
@@ -233,6 +235,9 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         List<ClassHolderTransformer> transformers = new ArrayList<>();
         transformers.add(new ClassPatch());
         transformers.add(new WasmDependencyListener());
+        if (runtimeType == WasmRuntimeType.WASI) {
+            transformers.add(new WasiSupportClassTransformer());
+        }
         return transformers;
     }
 
@@ -291,6 +296,15 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         this.obfuscated = obfuscated;
     }
 
+    public void setRuntimeType(WasmRuntimeType runtimeType) {
+        this.runtimeType = runtimeType;
+    }
+
+    @Override
+    public WasmRuntimeType getRuntimeType() {
+        return runtimeType;
+    }
+
     @Override
     public void contributeDependencies(DependencyAnalyzer dependencyAnalyzer) {
         for (Class<?> type : Arrays.asList(int.class, long.class, float.class, double.class)) {
@@ -502,6 +516,7 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         module.add(initFunction);
         module.setStartFunction(initFunction);
         module.add(createStartFunction(names));
+        module.add(createStartCallerFunction());
 
         for (String functionName : classGenerator.getFunctionTable()) {
             WasmFunction function = module.getFunctions().get(functionName);
@@ -553,6 +568,17 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         return function;
     }
 
+    private WasmFunction createStartCallerFunction() {
+        WasmFunction function = new WasmFunction("teavm_call_start");
+        function.setExportName("_start");
+
+        WasmCall call = new WasmCall("teavm_start");
+        call.getArguments().add(new WasmInt32Constant(0));
+        function.getBody().add(call);
+
+        return function;
+    }
+
     private class IntrinsicFactoryContext implements WasmIntrinsicFactoryContext {
         @Override
         public ClassReaderSource getClassSource() {

core/src/main/java/org/teavm/backend/wasm/runtime/WasiBuffer.java

@@ -0,0 +1,33 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.runtime;
+
+import org.teavm.interop.Address;
+
+public final class WasiBuffer {
+    private static byte[] argBuffer = new byte[256];
+
+    private WasiBuffer() {
+    }
+
+    public static int getBufferSize() {
+        return argBuffer.length;
+    }
+
+    public static Address getBuffer() {
+        return Address.ofData(argBuffer);
+    }
+}

core/src/main/java/org/teavm/backend/wasm/runtime/WasiSupport.java

@@ -0,0 +1,95 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.runtime;
+
+import org.teavm.backend.wasm.wasi.IOVec;
+import org.teavm.backend.wasm.wasi.LongResult;
+import org.teavm.backend.wasm.wasi.SizeResult;
+import org.teavm.backend.wasm.wasi.Wasi;
+import org.teavm.interop.Address;
+import org.teavm.interop.Structure;
+import org.teavm.interop.Unmanaged;
+
+@Unmanaged
+public class WasiSupport {
+    private WasiSupport() {
+    }
+
+    @Unmanaged
+    public static void putCharsStdout(Address address, int count) {
+        putChars(1, address, count);
+    }
+
+    @Unmanaged
+    public static void putCharsStderr(Address address, int count) {
+        putChars(2, address, count);
+    }
+
+    @Unmanaged
+    public static void putChars(int fd, Address address, int count) {
+        Address argsAddress = WasiBuffer.getBuffer();
+        IOVec ioVec = argsAddress.toStructure();
+        SizeResult result = argsAddress.add(Structure.sizeOf(IOVec.class)).toStructure();
+        ioVec.buffer = address;
+        ioVec.bufferLength = count;
+        Wasi.fdWrite(fd, ioVec, 1, result);
+    }
+
+    @Unmanaged
+    public static long currentTimeMillis() {
+        Address argsAddress = WasiBuffer.getBuffer();
+        LongResult result = argsAddress.toStructure();
+        Wasi.clockTimeGet(Wasi.CLOCKID_REALTIME, 10, result);
+        return result.value;
+    }
+
+    @Unmanaged
+    public static void printString(String s) {
+        int charsInChunk = 128;
+        int offsetInBuffer = 128;
+        Address buffer = WasiBuffer.getBuffer().add(offsetInBuffer);
+        for (int i = 0; i < s.length(); i += charsInChunk) {
+            int end = Math.min(s.length(), i + charsInChunk);
+            int count = end - i;
+            for (int j = 0; j < count; ++j) {
+                buffer.add(offsetInBuffer + j).putByte((byte) s.charAt(j));
+            }
+            putCharsStderr(buffer, count);
+        }
+    }
+
+    @Unmanaged
+    public static void printInt(int i) {
+        int count = 0;
+        Address buffer = WasiBuffer.getBuffer().add(WasiBuffer.getBufferSize());
+        do {
+            ++count;
+            buffer = buffer.add(-1);
+            buffer.putByte((byte) ((i % 10) + (int) '0'));
+            i /= 10;
+        } while (i > 0);
+        putCharsStderr(buffer, count);
+    }
+
+    @Unmanaged
+    public static void printOutOfMemory() {
+        printString("Out of memory");
+    }
+
+    @Unmanaged
+    public static void initHeapTrace(int maxHeap) {
+    }
+}

core/src/main/java/org/teavm/backend/wasm/runtime/WasmSupport.java

@@ -0,0 +1,52 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.runtime;
+
+import org.teavm.interop.Address;
+import org.teavm.interop.Import;
+
+public class WasmSupport {
+    private WasmSupport() {
+    }
+
+    @Import(name = "putwcharsOut", module = "teavm")
+    public static native void putCharsStderr(Address address, int count);
+
+    @Import(name = "putwcharsErr", module = "teavm")
+    public static native void putCharsStdout(Address address, int count);
+
+    public static long currentTimeMillis() {
+        return (long) currentTimeMillisImpl();
+    }
+
+    @Import(name = "currentTimeMillis", module = "teavm")
+    private static native double currentTimeMillisImpl();
+
+    @Import(name = "print", module = "spectest")
+    public static native void print(int a);
+
+    @Import(name = "logString", module = "teavm")
+    public static native void printString(String s);
+
+    @Import(name = "logInt", module = "teavm")
+    public static native void printInt(int i);
+
+    @Import(name = "logOutOfMemory", module = "teavm")
+    public static native void printOutOfMemory();
+
+    @Import(name = "init", module = "teavmHeapTrace")
+    public static native void initHeapTrace(int maxHeap);
+}

core/src/main/java/org/teavm/backend/wasm/transformation/WasiSupportClassTransformer.java

@@ -0,0 +1,62 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.transformation;
+
+import org.teavm.backend.wasm.runtime.WasiSupport;
+import org.teavm.backend.wasm.runtime.WasmSupport;
+import org.teavm.model.ClassHierarchy;
+import org.teavm.model.ClassHolder;
+import org.teavm.model.ClassHolderTransformer;
+import org.teavm.model.ClassHolderTransformerContext;
+import org.teavm.model.ClassReader;
+import org.teavm.model.ElementModifier;
+import org.teavm.model.MethodHolder;
+import org.teavm.model.MethodReader;
+import org.teavm.model.ValueType;
+import org.teavm.model.emit.ProgramEmitter;
+import org.teavm.model.emit.ValueEmitter;
+
+public class WasiSupportClassTransformer implements ClassHolderTransformer {
+    @Override
+    public void transformClass(ClassHolder cls, ClassHolderTransformerContext context) {
+        if (cls.getName().equals(WasmSupport.class.getName())) {
+            transformWasm(cls, context.getHierarchy());
+        }
+    }
+
+    private void transformWasm(ClassHolder cls, ClassHierarchy classHierarchy) {
+        ClassReader sourceCls = classHierarchy.getClassSource().get(WasiSupport.class.getName());
+        for (MethodHolder method : cls.getMethods()) {
+            MethodReader sourceMethod = sourceCls.getMethod(method.getDescriptor());
+            if (sourceMethod != null) {
+                if (method.hasModifier(ElementModifier.NATIVE)) {
+                    method.getModifiers().remove(ElementModifier.NATIVE);
+                }
+                ProgramEmitter pe = ProgramEmitter.create(method, classHierarchy);
+                ValueEmitter[] args = new ValueEmitter[method.parameterCount()];
+                for (int i = 0; i < args.length; ++i) {
+                    args[i] = pe.var(i + 1, method.parameterType(i));
+                }
+                ValueEmitter result = pe.invoke(sourceMethod.getReference(), args);
+                if (method.getResultType() != ValueType.VOID) {
+                    result.returnValue();
+                } else {
+                    pe.exit();
+                }
+            }
+        }
+    }
+}

core/src/main/java/org/teavm/backend/wasm/wasi/IOVec.java

@@ -0,0 +1,24 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.wasi;
+
+import org.teavm.interop.Address;
+import org.teavm.interop.Structure;
+
+public class IOVec extends Structure {
+    public Address buffer;
+    public int bufferLength;
+}

core/src/main/java/org/teavm/backend/wasm/wasi/LongResult.java

@@ -0,0 +1,22 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.wasi;
+
+import org.teavm.interop.Structure;
+
+public class LongResult extends Structure {
+    public long value;
+}

core/src/main/java/org/teavm/backend/wasm/wasi/SizeResult.java

@@ -0,0 +1,22 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.wasi;
+
+import org.teavm.interop.Structure;
+
+public class SizeResult extends Structure {
+    public int value;
+}

core/src/main/java/org/teavm/backend/wasm/wasi/Wasi.java

@@ -0,0 +1,31 @@
+/*
+ *  Copyright 2022 Alexey Andreev.
+ *
+ *  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.
+ */
+package org.teavm.backend.wasm.wasi;
+
+import org.teavm.interop.Import;
+
+public final class Wasi {
+    public static final int CLOCKID_REALTIME = 0;
+
+    private Wasi() {
+    }
+
+    @Import(name = "fd_write", module = "wasi_snapshot_preview1")
+    public static native short fdWrite(int fd, IOVec vectors, int vectorsCont, SizeResult result);
+
+    @Import(name = "clock_time_get", module = "wasi_snapshot_preview1")
+    public static native short clockTimeGet(int clockId, long precision, LongResult result);
+}

core/src/main/resources/org/teavm/backend/wasm/wasm-runtime.js

@@ -31,6 +31,14 @@ TeaVM.wasm = function() {
             lineBuffer += String.fromCharCode(charCode);
         }
     }
+    function putwchars(buffer, count) {
+        let instance = controller.instance;
+        let memory = instance.exports.memory.buffer;
+        for (let i = 0; i < count; ++i) {
+            // TODO: support UTF-8
+            putwchar(memory[buffer++]);
+        }
+    }
     function towlower(code) {
         return String.fromCharCode(code).toLowerCase().charCodeAt(0);
     }
@@ -90,7 +98,8 @@ TeaVM.wasm = function() {
             teavm_getNaN: function() { return NaN; },
             isinf: function(n) { return !isFinite(n) },
             isfinite: isFinite,
-            putwchar: putwchar,
+            putwcharsOut: (chars, count) => putwchars(controller, chars, count),
+            putwcharsErr: (chars, count) => putwchars(controller, chars, count),
             towlower: towlower,
             towupper: towupper,
             getNativeOffset: getNativeOffset,

tools/cli/src/main/java/org/teavm/cli/TeaVMRunner.java

@@ -58,7 +58,7 @@ public final class TeaVMRunner {
         options.addOption(Option.builder("t")
                 .argName("target")
                 .hasArg()
-                .desc("target type (javascript/js, webassembly/wasm, C)")
+                .desc("target type (javascript/js, webassembly/wasm, webassembly-wasi/wasm-wasi/wasi, C)")
                 .build());
         options.addOption(Option.builder("d")
                 .argName("directory")
@@ -220,6 +220,11 @@ public final class TeaVMRunner {
                 case "wasm":
                     tool.setTargetType(TeaVMTargetType.WEBASSEMBLY);
                     break;
+                case "webassembly-wasi":
+                case "wasm-wasi":
+                case "wasi":
+                    tool.setTargetType(TeaVMTargetType.WEBASSEMBLY);
+                    break;
                 case "c":
                     tool.setTargetType(TeaVMTargetType.C);
                     break;

tools/core/src/main/java/org/teavm/tooling/TeaVMTargetType.java

@@ -18,5 +18,6 @@ package org.teavm.tooling;
 public enum TeaVMTargetType {
     JAVASCRIPT,
     WEBASSEMBLY,
+    WEBASSEMBLY_WASI,
     C
 }

tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java

@@ -37,6 +37,7 @@ import org.teavm.backend.c.generate.CNameProvider;
 import org.teavm.backend.c.generate.ShorteningFileNameProvider;
 import org.teavm.backend.c.generate.SimpleFileNameProvider;
 import org.teavm.backend.javascript.JavaScriptTarget;
+import org.teavm.backend.wasm.WasmRuntimeType;
 import org.teavm.backend.wasm.WasmTarget;
 import org.teavm.backend.wasm.render.WasmBinaryVersion;
 import org.teavm.cache.AlwaysStaleCacheStatus;
@@ -315,7 +316,9 @@ public class TeaVMTool {
             case JAVASCRIPT:
                 return prepareJavaScriptTarget();
             case WEBASSEMBLY:
-                return prepareWebAssemblyTarget();
+                return prepareWebAssemblyDefaultTarget();
+            case WEBASSEMBLY_WASI:
+                return prepareWebAssemblyWasiTarget();
             case C:
                 return prepareCTarget();
         }
@@ -347,6 +350,18 @@ public class TeaVMTool {
         return webAssemblyTarget;
     }
 
+    private WasmTarget prepareWebAssemblyDefaultTarget() {
+        WasmTarget target = prepareWebAssemblyTarget();
+        target.setRuntimeType(WasmRuntimeType.TEAVM);
+        return target;
+    }
+
+    private WasmTarget prepareWebAssemblyWasiTarget() {
+        WasmTarget target = prepareWebAssemblyTarget();
+        target.setRuntimeType(WasmRuntimeType.WASI);
+        return target;
+    }
+
     private CTarget prepareCTarget() {
         cTarget = new CTarget(new CNameProvider());
         cTarget.setMinHeapSize(minHeapSize);