From 30efaaed9507981a9c051096e3665c79d0a3eeb9 Mon Sep 17 00:00:00 2001
From: Volker Berlin <volker.berlin@googlemail.com>
Date: Sat, 18 May 2019 21:37:19 +0200
Subject: [PATCH] pass virtual function index

---
 .../jwebassembly/binary/BinaryModuleWriter.java        | 10 +++++++++-
 .../inetsoftware/jwebassembly/module/ModuleWriter.java |  6 ++++--
 .../module/WasmCallIndirectInstruction.java            |  6 ++++--
 .../jwebassembly/text/TextModuleWriter.java            |  8 ++++++--
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
index 616b195..9a14593 100644
--- a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
@@ -1001,8 +1001,16 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
      * {@inheritDoc}
      */
     @Override
-    protected void writeFunctionCallIndirect( FunctionName name ) throws IOException {
+    protected void writeVirtualFunctionCall( FunctionName name, int virtualFunctionIdx ) throws IOException {
         callIndirect = true;
+        codeStream.writeOpCode( STRUCT_GET );
+        codeStream.writeValueType( ValueType.i32 );
+        codeStream.writeVaruint32( 0 ); // vtable is ever on position 0
+
+        codeStream.writeOpCode( I32_LOAD );
+        codeStream.write( 2 ); // 32 alignment
+        codeStream.writeVaruint32( virtualFunctionIdx * 4 );
+
         Function func = getFunction( name );
         codeStream.writeOpCode( CALL_INDIRECT );
         codeStream.writeVaruint32( func.typeId );
diff --git a/src/de/inetsoftware/jwebassembly/module/ModuleWriter.java b/src/de/inetsoftware/jwebassembly/module/ModuleWriter.java
index 8a4bcdd..62d9dae 100644
--- a/src/de/inetsoftware/jwebassembly/module/ModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/module/ModuleWriter.java
@@ -225,14 +225,16 @@ public abstract class ModuleWriter implements Closeable {
     protected abstract void writeFunctionCall( FunctionName name ) throws IOException;
 
     /**
-     * Write a call indirect to a function.
+     * Write a function call to an instance function. On the stack there must be the object.
      * 
      * @param name
      *            the function name
+     * @param virtualFunctionIdx
+     *            the index of the virtual method in the object. If the value < 0 a direct call should be used. 
      * @throws IOException
      *             if any I/O error occur
      */
-    protected abstract void writeFunctionCallIndirect( FunctionName name ) throws IOException;
+    protected abstract void writeVirtualFunctionCall( FunctionName name, int virtualFunctionIdx ) throws IOException;
 
     /**
      * Write a block/branch code
diff --git a/src/de/inetsoftware/jwebassembly/module/WasmCallIndirectInstruction.java b/src/de/inetsoftware/jwebassembly/module/WasmCallIndirectInstruction.java
index a8a6de2..03c1fd3 100644
--- a/src/de/inetsoftware/jwebassembly/module/WasmCallIndirectInstruction.java
+++ b/src/de/inetsoftware/jwebassembly/module/WasmCallIndirectInstruction.java
@@ -28,6 +28,8 @@ import javax.annotation.Nonnull;
  */
 class WasmCallIndirectInstruction extends WasmCallInstruction {
 
+    private int virtualFunctionIdx = -1;
+
     /**
      * Create an instance of a function call instruction
      * 
@@ -55,10 +57,10 @@ class WasmCallIndirectInstruction extends WasmCallInstruction {
      */
     @Override
     public void writeTo( @Nonnull ModuleWriter writer ) throws IOException {
-        if( true ) { // TODO
+        if( virtualFunctionIdx < 0 ) {
             super.writeTo( writer );
         } else {
-            writer.writeFunctionCallIndirect( getFunctionName() );
+            writer.writeVirtualFunctionCall( getFunctionName(), virtualFunctionIdx );
         }
     }
 
diff --git a/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java b/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
index 18246e7..c1396b3 100644
--- a/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
@@ -529,10 +529,14 @@ public class TextModuleWriter extends ModuleWriter {
      * {@inheritDoc}
      */
     @Override
-    protected void writeFunctionCallIndirect( FunctionName name ) throws IOException {
+    protected void writeVirtualFunctionCall( FunctionName name, int virtualFunctionIdx ) throws IOException {
         callIndirect = true;
         newline( methodOutput );
-        methodOutput.append( "call_indirect $" ).append( normalizeName( name ) );
+        methodOutput.append( "struct.get i32 0 ;;vtable" ); // vtable is ever on position 0
+        newline( methodOutput );
+        methodOutput.append( "i32.load offset=" ).append( virtualFunctionIdx * 4 ); // use default alignment
+        newline( methodOutput );
+        methodOutput.append( "call_indirect (type $" ).append( normalizeName( name ) ).append( ')' );
     }
 
     /**