From 4be005617b3b8c3578cca07c5d085d12916f0d1d Mon Sep 17 00:00:00 2001
From: lclc98
Date: Thu, 30 Jun 2016 00:49:21 +1000
Subject: Json format (#2)

* Added new format

* Fixed bug

* Updated Version
---
 .../enigma/bytecode/MethodParametersAttribute.java | 86 ++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 src/main/java/cuchaz/enigma/bytecode/MethodParametersAttribute.java

(limited to 'src/main/java/cuchaz/enigma/bytecode/MethodParametersAttribute.java')

diff --git a/src/main/java/cuchaz/enigma/bytecode/MethodParametersAttribute.java b/src/main/java/cuchaz/enigma/bytecode/MethodParametersAttribute.java
new file mode 100644
index 0000000..ee7ed87
--- /dev/null
+++ b/src/main/java/cuchaz/enigma/bytecode/MethodParametersAttribute.java
@@ -0,0 +1,86 @@
+/*******************************************************************************
+ * Copyright (c) 2015 Jeff Martin.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the GNU Lesser General Public
+ * License v3.0 which accompanies this distribution, and is available at
+ * http://www.gnu.org/licenses/lgpl.html
+ * <p>
+ * Contributors:
+ * Jeff Martin - initial API and implementation
+ ******************************************************************************/
+package cuchaz.enigma.bytecode;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import javassist.bytecode.AttributeInfo;
+import javassist.bytecode.ConstPool;
+import javassist.bytecode.MethodInfo;
+
+public class MethodParametersAttribute extends AttributeInfo {
+
+    private MethodParametersAttribute(ConstPool pool, List<Integer> parameterNameIndices) {
+        super(pool, "MethodParameters", writeStruct(parameterNameIndices));
+    }
+
+    public static void updateClass(MethodInfo info, List<String> names) {
+
+        // add the names to the class const pool
+        ConstPool constPool = info.getConstPool();
+        List<Integer> parameterNameIndices = new ArrayList<Integer>();
+        for (String name : names) {
+            if (name != null) {
+                parameterNameIndices.add(constPool.addUtf8Info(name));
+            } else {
+                parameterNameIndices.add(0);
+            }
+        }
+
+        // add the attribute to the method
+        info.addAttribute(new MethodParametersAttribute(constPool, parameterNameIndices));
+    }
+
+    private static byte[] writeStruct(List<Integer> parameterNameIndices) {
+        // JVM 8 Spec says the struct looks like this:
+        // http://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.24
+        // uint8 num_params
+        // for each param:
+        // uint16 name_index -> points to UTF8 entry in constant pool, or 0 for no entry
+        // uint16 access_flags -> don't care, just set to 0
+
+        ByteArrayOutputStream buf = new ByteArrayOutputStream();
+        DataOutputStream out = new DataOutputStream(buf);
+
+        // NOTE: java hates unsigned integers, so we have to be careful here
+        // the writeShort(), writeByte() methods will read 16,8 low-order bits from the int argument
+        // as long as the int argument is in range of the unsigned short/byte type, it will be written as an unsigned short/byte
+        // if the int is out of range, the byte stream won't look the way we want and weird things will happen
+        final int SIZEOF_UINT8 = 1;
+        final int SIZEOF_UINT16 = 2;
+        final int MAX_UINT8 = (1 << 8) - 1;
+        final int MAX_UINT16 = (1 << 16) - 1;
+
+        try {
+            assert (parameterNameIndices.size() >= 0 && parameterNameIndices.size() <= MAX_UINT8);
+            out.writeByte(parameterNameIndices.size());
+
+            for (Integer index : parameterNameIndices) {
+                assert (index >= 0 && index <= MAX_UINT16);
+                out.writeShort(index);
+
+                // just write 0 for the access flags
+                out.writeShort(0);
+            }
+
+            out.close();
+            byte[] data = buf.toByteArray();
+            assert (data.length == SIZEOF_UINT8 + parameterNameIndices.size() * (SIZEOF_UINT16 + SIZEOF_UINT16));
+            return data;
+        } catch (IOException ex) {
+            throw new Error(ex);
+        }
+    }
+}
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