Zipalign: Avoid unnecessary padding

Problem: Aligned entry always get padded to the next aligned slot.
Solution: Fix alignment test.

Bug: 199932309
Test: align_test.cpp
Change-Id: I1e61c67dcf45454dd782d0fcc6903f7e71954083

2 files changed, 30 insertions, 1 deletions

diff --git a/tools/zipalign/ZipFile.cpp b/tools/zipalign/ZipFile.cpp
index 6037d595da..f2f65a63bc 100644
--- a/tools/zipalign/ZipFile.cpp
+++ b/tools/zipalign/ZipFile.cpp
@@ -530,7 +530,7 @@ status_t ZipFile::alignEntry(android::ZipEntry* pEntry, uint32_t alignTo){
     // If the alignment is not what was requested, add some padding in the extra
     // so the payload ends up where is requested.
     uint64_t alignDiff = alignTo - (expectedPayloadOffset % alignTo);
-    if (alignDiff == 0)
+    if (alignDiff == alignTo)
         return OK;
 
     return pEntry->addPadding(alignDiff);
diff --git a/tools/zipalign/tests/src/align_test.cpp b/tools/zipalign/tests/src/align_test.cpp
index c79e791e41..96d4f7365f 100644
--- a/tools/zipalign/tests/src/align_test.cpp
+++ b/tools/zipalign/tests/src/align_test.cpp
@@ -9,6 +9,7 @@
 #include <android-base/file.h>
 
 using namespace android;
+using namespace base;
 
 static std::string GetTestPath(const std::string& filename) {
   static std::string test_data_dir = android::base::GetExecutableDirectory() + "/tests/data/";
@@ -26,6 +27,34 @@ TEST(Align, Unaligned) {
   ASSERT_EQ(0, verified);
 }
 
+TEST(Align, DoubleAligment) {
+  const std::string src = GetTestPath("unaligned.zip");
+  const std::string tmp = GetTestPath("da_aligned.zip");
+  const std::string dst = GetTestPath("da_d_aligner.zip");
+
+  int processed = process(src.c_str(), tmp.c_str(), 4, true, false, 4096);
+  ASSERT_EQ(0, processed);
+
+  int verified = verify(tmp.c_str(), 4, true, false);
+  ASSERT_EQ(0, verified);
+
+  // Align the result of the previous run. Essentially double aligning.
+  processed = process(tmp.c_str(), dst.c_str(), 4, true, false, 4096);
+  ASSERT_EQ(0, processed);
+
+  verified = verify(dst.c_str(), 4, true, false);
+  ASSERT_EQ(0, verified);
+
+  // Nothing should have changed between tmp and dst.
+  std::string tmp_content;
+  ASSERT_EQ(true, ReadFileToString(tmp, &tmp_content));
+
+  std::string dst_content;
+  ASSERT_EQ(true, ReadFileToString(dst, &dst_content));
+
+  ASSERT_EQ(tmp_content, dst_content);
+}
+
 // Align a zip featuring a hole at the beginning. The
 // hole in the archive is a delete entry in the Central
 // Directory.