From ed9b5cdfc648e86fd463bfa8d86b94c41671e14c Mon Sep 17 00:00:00 2001
From: jeff
Date: Sun, 8 Feb 2015 21:29:25 -0500
Subject: switch all classes to new signature/type system

---
 .../enigma/bytecode/MethodParametersAttribute.java | 85 ++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 src/cuchaz/enigma/bytecode/MethodParametersAttribute.java

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

diff --git a/src/cuchaz/enigma/bytecode/MethodParametersAttribute.java b/src/cuchaz/enigma/bytecode/MethodParametersAttribute.java
new file mode 100644
index 0000000..bf95956
--- /dev/null
+++ b/src/cuchaz/enigma/bytecode/MethodParametersAttribute.java
@@ -0,0 +1,85 @@
+/*******************************************************************************
+ * Copyright (c) 2014 Jeff Martin.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the GNU Public License v3.0
+ * which accompanies this distribution, and is available at
+ * http://www.gnu.org/licenses/gpl.html
+ * 
+ * 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://cr.openjdk.java.net/~mr/se/8/java-se-8-fr-spec-01/java-se-8-jvms-fr-diffs.pdf
+		// 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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