From f5b3a01e54d9b2e496f865e05b18f9455b0b8038 Mon Sep 17 00:00:00 2001
From: Adam Lesinski <adamlesinski@google.com>
Date: Tue, 18 Feb 2014 15:21:13 -0800
Subject: [PATCH] Add fastpath for single signature comparison

PackageManager does not need to create a hash set
when comparing two sets of signatures, where each set
contains one signature. This is the common case for
most applications.

Bug:13029313
Change-Id: I61883d85960db7b376e234d7abae6149c4d20245
---
 .../server/pm/PackageManagerService.java      | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index df83fd70c5ce7..da0c38d5152a8 100755
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -2546,15 +2546,41 @@ public class PackageManagerService extends IPackageManager.Stub {
         }
     }
 
+    /**
+     * Compares two sets of signatures. Returns:
+     * <br />
+     * {@link PackageManager#SIGNATURE_NEITHER_SIGNED}: if both signature sets are null,
+     * <br />
+     * {@link PackageManager#SIGNATURE_FIRST_NOT_SIGNED}: if the first signature set is null,
+     * <br />
+     * {@link PackageManager#SIGNATURE_SECOND_NOT_SIGNED}: if the second signature set is null,
+     * <br />
+     * {@link PackageManager#SIGNATURE_MATCH}: if the two signature sets are identical,
+     * <br />
+     * {@link PackageManager#SIGNATURE_NO_MATCH}: if the two signature sets differ.
+     */
     static int compareSignatures(Signature[] s1, Signature[] s2) {
         if (s1 == null) {
             return s2 == null
                     ? PackageManager.SIGNATURE_NEITHER_SIGNED
                     : PackageManager.SIGNATURE_FIRST_NOT_SIGNED;
         }
+
         if (s2 == null) {
             return PackageManager.SIGNATURE_SECOND_NOT_SIGNED;
         }
+
+        if (s1.length != s2.length) {
+            return PackageManager.SIGNATURE_NO_MATCH;
+        }
+
+        // Since both signature sets are of size 1, we can compare without HashSets.
+        if (s1.length == 1) {
+            return s1[0].equals(s2[0]) ?
+                    PackageManager.SIGNATURE_MATCH :
+                    PackageManager.SIGNATURE_NO_MATCH;
+        }
+
         HashSet<Signature> set1 = new HashSet<Signature>();
         for (Signature sig : s1) {
             set1.add(sig);