1 files changed, 40 insertions, 0 deletions
diff --git a/src/main/javassist/bytecode/LineNumberAttributeBuilder.java b/src/main/javassist/bytecode/LineNumberAttributeBuilder.java
new file mode 100644
index 00000000..52d9d0c8
--- /dev/null
+++ b/src/main/javassist/bytecode/LineNumberAttributeBuilder.java
@@ -0,0 +1,40 @@
+package javassist.bytecode;
+
+import javassist.compiler.ast.ASTree;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+public class LineNumberAttributeBuilder {
+    private final HashMap<Integer, Integer> map = new HashMap<>();
+
+    public void put(int newPc, ASTree tree) {
+        if (tree != null)
+            put(newPc, tree.getLineNumber());
+    }
+
+    private void put(int newPc, int lineNum) {
+        Integer pc = map.get(lineNum);
+        if (pc == null || newPc < pc) {
+            map.put(lineNum, newPc);
+        }
+    }
+
+    public LineNumberAttribute build(ConstPool cp) {
+        int size = map.size();
+        try (ByteArrayOutputStream bos = new ByteArrayOutputStream(size * 4 + 2);
+             DataOutputStream dos = new DataOutputStream(bos)) {
+            dos.writeShort(size);
+            for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
+                dos.writeShort(entry.getValue());
+                dos.writeShort(entry.getKey());
+            }
+            return new LineNumberAttribute(cp, bos.toByteArray());
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}