1 files changed, 141 insertions, 0 deletions
diff --git a/src/main/java/org/glavo/javah/JNIGenerator.java b/src/main/java/org/glavo/javah/JNIGenerator.java
new file mode 100644
index 0000000..a00bc6c
--- /dev/null
+++ b/src/main/java/org/glavo/javah/JNIGenerator.java
@@ -0,0 +1,141 @@
+package org.glavo.javah;
+
+import org.objectweb.asm.*;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.UncheckedIOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class JNIGenerator extends ClassVisitor {
+    public static final String FILE_HEADER =
+            "/* DO NOT EDIT THIS FILE - it is machine generated */\n" +
+                    "#include <jni.h>\n";
+
+    public static final String FILE_END = "\n";
+
+    private final PrintWriter output;
+    private final Path classFile;
+
+    private String className;
+
+    private Map<String, Integer> methodNameCount = new HashMap<>();
+    private LinkedList<NativeMethod> methods = new LinkedList<>();
+    private LinkedList<ConstantField> constants = new LinkedList<>();
+
+    public JNIGenerator(PrintWriter output, Path classFile) {
+        super(Opcodes.ASM7);
+        Objects.requireNonNull(output);
+        Objects.requireNonNull(classFile);
+        this.output = output;
+        this.classFile = classFile;
+    }
+
+    public void generate() {
+        ClassReader cls = null;
+        try {
+            cls = new ClassReader(Files.readAllBytes(classFile));
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+        cls.accept(this, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES);
+
+        String name = Utils.encode(className).replace('/', '_');
+        String guard = "_Included_" + className;
+
+        output.println("/* Header for class " + className + " */\n\n");
+        output.println("#ifndef " + guard);
+        output.println("#define " + guard);
+        output.println("#ifdef __cplusplus");
+        output.println("extern \"C\" {");
+        output.println("#endif");
+
+        for (ConstantField constant : constants) {
+            String cm = name + "_" + Utils.encode(constant.name);
+            String value;
+            if (constant.value instanceof Float) {
+                value = constant.value.toString() + "f";
+            } else if (constant.value instanceof Long) {
+                value = constant.value.toString() + "i64";
+            } else {
+                value = constant.value.toString();
+            }
+            output.println("#undef " + cm);
+            output.println("#define " + cm + " " + value);
+        }
+        for (NativeMethod method : methods) {
+            String mm = "Java_" + name + "_" + Utils.encode(method.name);
+            if (methodNameCount.getOrDefault(method.name, 1) > 1) {
+                mm = mm + "__" + Utils.mangledArgSignature(method.type);
+            }
+            String r = Utils.mapToNativeType(method.type.getReturnType());
+            String args = Stream.concat(Stream.of("JNIEnv *", method.isStatic ? "jclass" : "jobject"),
+                    Arrays.stream(method.type.getArgumentTypes()).map(Utils::mapToNativeType))
+                    .collect(Collectors.joining(","));
+
+            output.println("/*");
+            output.println(" * Class:     " + name);
+            output.println(" * Method:    " + mm);
+            output.println(" * Signature: " + method.type);
+            output.println(" */");
+            output.println("JNIEXPORT " + r + " JNICALL " + mm);
+            output.println("  (" + args + ");");
+            output.println();
+        }
+
+        output.println("#ifdef __cplusplus");
+        output.println("}");
+        output.println("#endif");
+        output.println("#endif");
+    }
+
+    @Override
+    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+        className = name;
+    }
+
+    @Override
+    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+        if ((access & Opcodes.ACC_NATIVE) != 0) {
+            methodNameCount.put(name, methodNameCount.getOrDefault(name, 0) + 1);
+            methods.add(new NativeMethod(name, Type.getType(descriptor), (access & Opcodes.ACC_STATIC) != 0));
+        }
+        return null;
+    }
+
+    @Override
+    public FieldVisitor visitField(int access, String name, String descriptor, String signature, Object value) {
+        if (value != null && !(value instanceof String)) {
+            constants.add(new ConstantField(name, Type.getType(descriptor), value));
+        }
+        return null;
+    }
+
+    private static class NativeMethod {
+        String name;
+        Type type;
+        boolean isStatic;
+
+        public NativeMethod(String name, Type type, boolean isStatic) {
+            this.name = name;
+            this.type = type;
+            this.isStatic = isStatic;
+        }
+    }
+
+    private static class ConstantField {
+        String name;
+        Type type;
+        Object value;
+
+        public ConstantField(String name, Type type, Object value) {
+            this.name = name;
+            this.type = type;
+            this.value = value;
+        }
+    }
+}