From 40bbf5c347fde4ccba4b1875e63e94a84354b7af Mon Sep 17 00:00:00 2001
From: Alex Light <allight@google.com>
Date: Fri, 1 Apr 2016 14:24:48 -0700
Subject: [PATCH] Dex version 37 support

Make dexlib able to read and write version 37 dex files.

Bug: 27809626

Change-Id: I3d0ca6201c7abe7763d2fb925e9ee1edbef24230
---
 .../jf/dexlib2/dexbacked/raw/HeaderItem.java  | 24 +++++++++++++++++--
 .../java/org/jf/dexlib2/writer/DexWriter.java |  4 ++--
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/raw/HeaderItem.java b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/raw/HeaderItem.java
index 3499eadca..531ff4614 100644
--- a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/raw/HeaderItem.java
+++ b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/raw/HeaderItem.java
@@ -42,9 +42,14 @@
 public class HeaderItem {
     public static final int ITEM_SIZE = 0x70;
 
+    /**
+     * The magic numbers for dex files.
+     *
+     * They are: "dex\n035\0" and "dex\n037\0".
+     */
     public static final byte[][] MAGIC_VALUES= new byte[][] {
             new byte[]{0x64, 0x65, 0x78, 0x0a, 0x30, 0x33, 0x35, 0x00},
-            new byte[]{0x64, 0x65, 0x78, 0x0a, 0x30, 0x33, 0x36, 0x00}};
+            new byte[]{0x64, 0x65, 0x78, 0x0a, 0x30, 0x33, 0x37, 0x00}};
 
     public static final int LITTLE_ENDIAN_TAG = 0x12345678;
     public static final int BIG_ENDIAN_TAG = 0x78563412;
@@ -225,6 +230,21 @@ private static String getEndianText(int endianTag) {
         return "Invalid";
     }
 
+
+    /**
+     * Get the higest magic number supported by Android for this api level.
+     * @return The dex file magic number
+     */
+    public static byte[] getMagicForApi(int api) {
+        if (api < 24) {
+            // Prior to Android N we only support dex version 035.
+            return HeaderItem.MAGIC_VALUES[0];
+        } else {
+            // On android N and later we support dex version 037.
+            return HeaderItem.MAGIC_VALUES[1];
+        }
+    }
+
     private static int getVersion(byte[] buf, int offset) {
         if (buf.length - offset < 8) {
             return 0;
@@ -241,7 +261,7 @@ private static int getVersion(byte[] buf, int offset) {
                 }
             }
             if (matches) {
-                return i==0?35:36;
+                return i==0?35:37;
             }
         }
         return 0;
diff --git a/dexlib2/src/main/java/org/jf/dexlib2/writer/DexWriter.java b/dexlib2/src/main/java/org/jf/dexlib2/writer/DexWriter.java
index 9d353982e..4e81f7fa6 100644
--- a/dexlib2/src/main/java/org/jf/dexlib2/writer/DexWriter.java
+++ b/dexlib2/src/main/java/org/jf/dexlib2/writer/DexWriter.java
@@ -1221,8 +1221,8 @@ private void writeMapItem(@Nonnull DexDataWriter writer, int type, int size, int
     }
 
     private void writeHeader(@Nonnull DexDataWriter writer, int dataOffset, int fileSize) throws IOException {
-        // always write the 035 version, there's no reason to use the 036 version for now
-        writer.write(HeaderItem.MAGIC_VALUES[0]);
+        // Write the appropriate header.
+        writer.write(HeaderItem.getMagicForApi(opcodes.api));
 
         // checksum placeholder
         writer.writeInt(0);