add field counter

Author: ar.r.lysenko

src/main/java/org/example/Analyzer.java

@@ -0,0 +1,45 @@
+package org.example;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Path;
+import java.util.jar.JarFile;
+import org.example.visitor.ClassStatisticVisitor;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassVisitor;
+
+public class Analyzer {
+
+    public static void main(String[] args) throws IOException {
+        var path = Path.of("src/main/resources/sample.jar");
+        var analyzer = new Analyzer();
+
+        analyzer.analyzeJar(path);
+    }
+
+    public void analyzeJar(Path path) throws IOException {
+        try (JarFile jar = new JarFile(path.toFile())) {
+
+            Statistic statistic = new Statistic();
+
+            jar.stream()
+                    .filter(entry -> entry.getName().endsWith(".class"))
+                    .forEach(entry -> {
+                                // Should be safe for Java classes, since they always in the class with same name
+                                // unlike kotlin classes
+                                String className = entry.getName().replace(".class", "");
+
+                                try (InputStream is = jar.getInputStream(entry)) {
+                                    ClassReader cr = new ClassReader(is);
+                                    ClassVisitor visitor = new ClassStatisticVisitor(statistic);
+                                    cr.accept(visitor, 0);
+                                } catch (IOException e) {
+                                    throw new RuntimeException(e);
+                                }
+                            }
+                    );
+
+            statistic.printStatistic();
+        }
+    }
+}

src/main/java/org/example/Example.java

@@ -0,0 +1,16 @@
+package org.example;
+
+import org.example.util.AverageHolder;
+
+public class Statistic {
+
+    private final AverageHolder fieldAverageHolder = new AverageHolder();
+
+    public void updateFieldStatistic(Integer fieldCount) {
+        fieldAverageHolder.updateAverage(fieldCount);
+    }
+
+    public void printStatistic() {
+        System.out.print("Average: " + fieldAverageHolder.getAverage());
+    }
+}

src/main/java/org/example/Statistic.java

@@ -0,0 +1,18 @@
+package org.example.util;
+
+public class AverageHolder {
+    private final Object lock = new Object();
+    private Integer sum = 0;
+    private Integer count = 0;
+
+    public Double getAverage() {
+        return count.equals(0) ? 0.0 : sum.doubleValue() / count;
+    }
+
+    public void updateAverage(Integer value) {
+        synchronized (lock) {
+            sum += value;
+            count++;
+        }
+    }
+}

src/main/java/org/example/example/BubbleSort.java

@@ -0,0 +1,55 @@
+package org.example.visitor;
+
+import org.example.Statistic;
+import org.objectweb.asm.AnnotationVisitor;
+import org.objectweb.asm.Attribute;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.FieldVisitor;
+import org.objectweb.asm.MethodVisitor;
+import static org.objectweb.asm.Opcodes.ASM8;
+
+public class ClassStatisticVisitor extends ClassVisitor {
+
+    private final Statistic statistic;
+
+    private Integer fieldCount = 0;
+
+    public ClassStatisticVisitor(Statistic statistic) {
+        super(ASM8);
+        this.statistic = statistic;
+    }
+
+    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+    }
+
+    public void visitSource(String source, String debug) {
+    }
+
+    public void visitOuterClass(String owner, String name, String desc) {
+    }
+
+    public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
+        return super.visitAnnotation(desc, visible);
+    }
+
+    public void visitAttribute(Attribute attr) {
+    }
+
+    // todo also visit inner classes
+    public void visitInnerClass(String name, String outerName, String innerName, int access) {
+    }
+
+    public FieldVisitor visitField(int access, String name, String desc, String signature, Object value) {
+        fieldCount++;
+        return super.visitField(access, name, desc, signature, value);
+    }
+
+    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
+        return super.visitMethod(access, name, desc, signature, exceptions);
+    }
+
+    public void visitEnd() {
+        statistic.updateFieldStatistic(fieldCount);
+    }
+}
+