Wasm: support command line args in WASI

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

@@ -104,6 +104,7 @@ import org.teavm.backend.wasm.render.WasmBinaryVersion;
 import org.teavm.backend.wasm.render.WasmBinaryWriter;
 import org.teavm.backend.wasm.render.WasmCRenderer;
 import org.teavm.backend.wasm.render.WasmRenderer;
+import org.teavm.backend.wasm.runtime.WasmSupport;
 import org.teavm.backend.wasm.transformation.IndirectCallTraceTransformation;
 import org.teavm.backend.wasm.transformation.MemoryAccessTraceTransformation;
 import org.teavm.backend.wasm.transformation.WasiSupportClassTransformer;
@@ -388,6 +389,7 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         dependencyAnalyzer.linkMethod(new MethodReference(EventQueue.class, "isStopped", boolean.class)).use();
         dependencyAnalyzer.linkMethod(new MethodReference(Thread.class, "setCurrentThread", Thread.class,
                 void.class)).use();
+        dependencyAnalyzer.linkMethod(new MethodReference(WasmSupport.class, "getArgs", String[].class)).use();
 
         ClassReader fiberClass = dependencyAnalyzer.getClassSource().get(Fiber.class.getName());
         for (MethodReader method : fiberClass.getMethods()) {
@@ -516,7 +518,7 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         module.add(initFunction);
         module.setStartFunction(initFunction);
         module.add(createStartFunction(names));
-        module.add(createStartCallerFunction());
+        module.add(createStartCallerFunction(names));
 
         for (String functionName : classGenerator.getFunctionTable()) {
             WasmFunction function = module.getFunctions().get(functionName);
@@ -568,12 +570,14 @@ public class WasmTarget implements TeaVMTarget, TeaVMWasmHost {
         return function;
     }
 
-    private WasmFunction createStartCallerFunction() {
+    private WasmFunction createStartCallerFunction(NameProvider names) {
         WasmFunction function = new WasmFunction("teavm_call_start");
         function.setExportName("_start");
 
+        WasmCall argsCall = new WasmCall(names.forMethod(new MethodReference(WasmSupport.class,
+                "getArgs", String[].class)));
         WasmCall call = new WasmCall("teavm_start");
-        call.getArguments().add(new WasmInt32Constant(0));
+        call.getArguments().add(argsCall);
         function.getBody().add(call);
 
         return function;

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

@@ -15,6 +15,7 @@
  */
 package org.teavm.backend.wasm.runtime;
 
+import java.nio.charset.StandardCharsets;
 import org.teavm.backend.wasm.wasi.IOVec;
 import org.teavm.backend.wasm.wasi.LongResult;
 import org.teavm.backend.wasm.wasi.SizeResult;
@@ -65,7 +66,7 @@ public class WasiSupport {
             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));
+                buffer.add(j).putByte((byte) s.charAt(i + j));
             }
             putCharsStderr(buffer, count);
         }
@@ -74,6 +75,8 @@ public class WasiSupport {
     @Unmanaged
     public static void printInt(int i) {
         int count = 0;
+        boolean negative = i < 0;
+        i = Math.abs(i);
         Address buffer = WasiBuffer.getBuffer().add(WasiBuffer.getBufferSize());
         do {
             ++count;
@@ -81,6 +84,11 @@ public class WasiSupport {
             buffer.putByte((byte) ((i % 10) + (int) '0'));
             i /= 10;
         } while (i > 0);
+        if (negative) {
+            ++count;
+            buffer = buffer.add(-1);
+            buffer.putByte((byte) '-');
+        }
         putCharsStderr(buffer, count);
     }
 
@@ -92,4 +100,34 @@ public class WasiSupport {
     @Unmanaged
     public static void initHeapTrace(int maxHeap) {
     }
+
+    public static String[] getArgs() {
+        Address buffer = WasiBuffer.getBuffer();
+        SizeResult sizesReceiver = buffer.toStructure();
+        SizeResult bufferSizeReceiver = buffer.add(Structure.sizeOf(SizeResult.class)).toStructure();
+        short errno = Wasi.argsSizesGet(sizesReceiver, bufferSizeReceiver);
+
+        if (errno != Wasi.ERRNO_SUCCESS) {
+            throw new RuntimeException("Could not get command line arguments");
+        }
+        int argvSize = sizesReceiver.value;
+        int argvBufSize = bufferSizeReceiver.value;
+
+        int[] argvOffsets = new int[argvSize];
+        byte[] argvBuffer = new byte[argvBufSize];
+        errno = Wasi.argsGet(Address.ofData(argvOffsets), Address.ofData(argvBuffer));
+
+        if (errno != Wasi.ERRNO_SUCCESS) {
+            throw new RuntimeException("Could not get command line arguments");
+        }
+
+        String[] args = new String[argvSize - 1];
+        for (int i = 1; i < argvSize; ++i) {
+            int offset = argvOffsets[i] - Address.ofData(argvBuffer).toInt();
+            int length = (i == argvSize - 1 ? argvBufSize - offset : argvOffsets[i + 1] - argvOffsets[i]) - 1;
+            args[i - 1] = new String(argvBuffer, offset, length, StandardCharsets.UTF_8);
+        }
+
+        return args;
+    }
 }

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

@@ -49,4 +49,8 @@ public class WasmSupport {
 
     @Import(name = "init", module = "teavmHeapTrace")
     public static native void initHeapTrace(int maxHeap);
+
+    public static String[] getArgs() {
+        return new String[0];
+    }
 }

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

@@ -15,10 +15,12 @@
  */
 package org.teavm.backend.wasm.wasi;
 
+import org.teavm.interop.Address;
 import org.teavm.interop.Import;
 
 public final class Wasi {
     public static final int CLOCKID_REALTIME = 0;
+    public static final short ERRNO_SUCCESS = 0;
 
     private Wasi() {
     }
@@ -28,4 +30,10 @@ public final class Wasi {
 
     @Import(name = "clock_time_get", module = "wasi_snapshot_preview1")
     public static native short clockTimeGet(int clockId, long precision, LongResult result);
+
+    @Import(name = "args_sizes_get", module = "wasi_snapshot_preview1")
+    public static native short argsSizesGet(SizeResult argvSize, SizeResult argvBufSize);
+
+    @Import(name = "args_get", module = "wasi_snapshot_preview1")
+    public static native short argsGet(Address argv, Address argvBuf);
 }