implements support for static class constructors

README.md

@@ -35,7 +35,7 @@ The project is currently not production ready but you can run already some tests
 * [x] invoke default method calls
 * [x] String support
 * [x] Simple Class object support
-* [ ] static constructors
+* [x] static constructors
 * [x] Optimizer - Optimize the WASM output of a single method after transpiling before writing to output
 * [x] Hello World sample [(live)](https://i-net-software.github.io/JWebAssembly/samples/HelloWorld/HelloWorld.html), [(source code)](https://github.com/i-net-software/JWebAssembly/blob/master/docs/samples/HelloWorld/HelloWorld.java)
 

src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java

@@ -91,6 +91,8 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
 
     private boolean                     callIndirect;
 
+    private FunctionName                startFunction;
+
     /**
      * Create new instance.
      * 
@@ -133,6 +135,7 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
         writeEventSection();
         writeSection( SectionType.Global, globals.values() );
         writeSection( SectionType.Export, exports );
+        writeStartSection();
         writeElementSection();
         writeCodeSection();
         writeDataSection();
@@ -253,6 +256,22 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
         }
     }
 
+    /**
+     * Write a start section. The id of the function that should be automatically executed.
+     * 
+     * @throws IOException
+     *             if any I/O error occur
+     */
+    private void writeStartSection() throws IOException {
+        if( startFunction == null ) {
+            return;
+        }
+        int id = getFunction( startFunction ).id;
+        WasmOutputStream stream = new WasmOutputStream();
+        stream.writeVaruint32( id );
+        wasm.writeSection( SectionType.Start, stream );
+    }
+
     /**
      * Write element section. This section create a matching between direct and indirect function call IDs.
      * 
@@ -518,10 +537,15 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
      */
     @Override
     protected void writeMethodParamStart( FunctionName name, FunctionType funcType ) throws IOException {
-        if( funcType == FunctionType.Abstract ) {
-            abstracts.put( name.signatureName, function = new Function() );
-        } else {
-            function = getFunction( name );
+        switch( funcType ) {
+            case Abstract:
+                abstracts.put( name.signatureName, function = new Function() );
+                break;
+            case Start:
+                startFunction = name;
+                //$FALL-THROUGH$
+            default:
+                function = getFunction( name );
         }
         functionType = new FunctionTypeEntry();
         locals.clear();

src/de/inetsoftware/jwebassembly/module/FunctionManager.java

@@ -37,9 +37,9 @@ import de.inetsoftware.jwebassembly.WasmException;
  */
 class FunctionManager {
 
-    private final Map<FunctionName, FunctionState> states           = new LinkedHashMap<>();
+    private final Map<FunctionName, FunctionState> states            = new LinkedHashMap<>();
 
-    private final Map<String, FunctionName>        classesWithCInit = new HashMap<>();
+    private final Map<String, FunctionName>        classesWithClinit = new HashMap<>();
 
     private boolean isFinish;
 
@@ -90,10 +90,10 @@ class FunctionManager {
      * Mark that a class has static initializer.
      * 
      * @param name
-     *            the function name
+     *            the "&lt;clinit&gt;" function name
      */
-    void markClassWithCInit( FunctionName name ) {
-        classesWithCInit.put( name.className, name );
+    void markClassWithClinit( FunctionName name ) {
+        classesWithClinit.put( name.className, name );
     }
 
     /**
@@ -152,7 +152,7 @@ class FunctionManager {
             }
             state.state = State.Needed;
             JWebAssembly.LOGGER.fine( "\t\tcall: " + name.signatureName );
-            FunctionName cInit = classesWithCInit.get( name.className );
+            FunctionName cInit = classesWithClinit.get( name.className );
             if( cInit != null ) {
                 markAsNeeded( cInit );
             }
@@ -243,10 +243,23 @@ class FunctionManager {
         return null;
     }
 
+    /**
+     * Get all static constructor FunctionName of used classes.
+     * 
+     * @return an iterator
+     */
+    @Nullable
+    Iterator<FunctionName> getWriteLaterClinit() {
+        return classesWithClinit.values().stream().filter( ( name ) -> {
+            FunctionState state = states.get( name );
+            return state != null && (state.state == State.Needed || state.state == State.Scanned);
+        } ).iterator();
+    }
+
     /**
      * Get all FunctionName that is required but was not written.
      * 
-     * @return the FunctionName or null
+     * @return an iterator
      */
     @Nullable
     Iterator<FunctionName> getWriteLater() {

src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java

@@ -299,6 +299,9 @@ public class ModuleGenerator {
             javaScript.addImport( importModule, importName, importAnannotation );
         }
 
+        // add a start method for the static class constructors
+        prepareStartFunction();
+
         // init/write the function types
         for( Iterator<FunctionName> iterator = functions.getWriteLater(); iterator.hasNext(); ) {
             FunctionName name = iterator.next();
@@ -318,6 +321,39 @@ public class ModuleGenerator {
         writer.prepareFinish();
     }
 
+    /**
+     * Add a start method for the static class constructors
+     * 
+     * @throws IOException
+     *             if any I/O error occur
+     */
+    private void prepareStartFunction() throws IOException {
+        // add the start function/section only if there are static code
+        Iterator<FunctionName> iterator = functions.getWriteLaterClinit();
+        if( iterator.hasNext() ) {
+            FunctionName cinit = new SyntheticFunctionName( "", "<clinit>", "()V" ) {
+                @Override
+                protected boolean hasWasmCode() {
+                    return true;
+                }
+
+                @Override
+                protected WasmCodeBuilder getCodeBuilder( WatParser watParser ) {
+                    watParser.reset( null, null, getSignature( null ) );
+
+                    while( iterator.hasNext() ) {
+                        FunctionName name = iterator.next();
+                        //TODO if not in the debug mode then inlining would produce smaller output and should be faster
+                        watParser.addCallInstruction( name, 0, -1 );
+                    }
+                    return watParser;
+                }
+            };
+            functions.markAsNeeded( cinit );
+            writeMethodSignature( cinit, FunctionType.Start, null );
+        }
+    }
+
     /**
      * Finish the code generation.
      * 
@@ -405,7 +441,7 @@ public class ModuleGenerator {
         try {
             FunctionName name = new FunctionName( method );
             if( "<clinit>".equals( name.methodName ) ) {
-                functions.markClassWithCInit( name );
+                functions.markClassWithClinit( name );
             }
             if( functions.isKnown( name ) ) {
                 return;

src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java

@@ -329,8 +329,14 @@ public class TextModuleWriter extends ModuleWriter {
      */
     @Override
     protected void writeMethodParamStart( @Nonnull FunctionName name, FunctionType funcType ) throws IOException {
-        if( funcType == FunctionType.Abstract ) {
-            abstracts.put( name.signatureName, new Function() );
+        switch( funcType ) {
+            case Abstract:
+                abstracts.put( name.signatureName, new Function() );
+                break;
+            case Start:
+                newline( imports );
+                imports.append( "(start $" ).append( normalizeName( name ) ).append( ")" );
+                break;
         }
         typeOutput.setLength( 0 );
         methodParamNames.clear();

src/de/inetsoftware/jwebassembly/wasm/FunctionType.java

@@ -26,5 +26,7 @@ public enum FunctionType {
     /** has real code */
     Code,
     /** abstract or interface, only used for indirrect call */
-    Abstract;
+    Abstract,
+    /** the function of start section, should occur only once */
+    Start,
 }