Fix issue where non-resource attributes would cause obtainStyleAttributes to fail

A sentinal value of 0x00000000 was used to mark the first time an AttributeFinder
was used. If the resource ID of an attribute was also 0x00000000 (which occurs with
non-resource attributes, like 'style'), then it would be mistaken as the sentinel
start value.

Bug:18421787
Change-Id: I4be353e0f8c940cb6f262d155129f048dcc444ae

2 files changed, 25 insertions, 3 deletions

diff --git a/include/androidfw/AttributeFinder.h b/include/androidfw/AttributeFinder.h
index a0ffeb3..acf7056 100644
--- a/include/androidfw/AttributeFinder.h
+++ b/include/androidfw/AttributeFinder.h
@@ -64,6 +64,7 @@ private:
     void jumpToClosestAttribute(uint32_t packageId);
     void markCurrentPackageId(uint32_t packageId);
 
+    bool mFirstTime;
     Iterator mBegin;
     Iterator mEnd;
     Iterator mCurrent;
@@ -81,7 +82,8 @@ private:
 
 template <typename Derived, typename Iterator> inline
 BackTrackingAttributeFinder<Derived, Iterator>::BackTrackingAttributeFinder(const Iterator& begin, const Iterator& end)
-    : mBegin(begin)
+    : mFirstTime(true)
+    , mBegin(begin)
     , mEnd(end)
     , mCurrent(begin)
     , mLargest(begin)
@@ -145,8 +147,11 @@ Iterator BackTrackingAttributeFinder<Derived, Iterator>::find(uint32_t attr) {
         return mEnd;
     }
 
-    if (mCurrentAttr == 0) {
-        // One-time initialization.
+    if (mFirstTime) {
+        // One-time initialization. We do this here instead of the constructor
+        // because the derived class we access in getAttribute() may not be
+        // fully constructed.
+        mFirstTime = false;
         mCurrentAttr = static_cast<const Derived*>(this)->getAttribute(mBegin);
         mLastPackageId = getPackage(mCurrentAttr);
         markCurrentPackageId(mLastPackageId);
diff --git a/libs/androidfw/tests/AttributeFinder_test.cpp b/libs/androidfw/tests/AttributeFinder_test.cpp
index 664709c..5054624 100644
--- a/libs/androidfw/tests/AttributeFinder_test.cpp
+++ b/libs/androidfw/tests/AttributeFinder_test.cpp
@@ -50,6 +50,10 @@ static const uint32_t packageUnsortedAttributes[] = {
         0x01010002, 0x01010004, 0x7f010001
 };
 
+static const uint32_t singlePackageAttributes[] = {
+        0x7f010007, 0x7f01000a, 0x7f01000d, 0x00000000
+};
+
 TEST(AttributeFinderTest, IteratesSequentially) {
     const int end = sizeof(sortedAttributes) / sizeof(*sortedAttributes);
     MockAttributeFinder finder(sortedAttributes, end);
@@ -109,3 +113,16 @@ TEST(AttributeFinderTest, FindAttributesInPackageUnsortedAttributeList) {
     EXPECT_EQ(1, finder.find(0x02010010));
     EXPECT_EQ(6, finder.find(0x7f010001));
 }
+
+TEST(AttributeFinderTest, FindAttributesInSinglePackageAttributeList) {
+    const int end = sizeof(singlePackageAttributes) / sizeof(*singlePackageAttributes);
+    MockAttributeFinder finder(singlePackageAttributes, end);
+
+    EXPECT_EQ(end, finder.find(0x010100f4));
+    EXPECT_EQ(end, finder.find(0x010100f5));
+    EXPECT_EQ(end, finder.find(0x010100f6));
+    EXPECT_EQ(end, finder.find(0x010100f7));
+    EXPECT_EQ(end, finder.find(0x010100f8));
+    EXPECT_EQ(end, finder.find(0x010100fa));
+    EXPECT_EQ(0, finder.find(0x7f010007));
+}