Avoid using data descriptors in ZIP files when possible.
These add 16 bytes per ZIP entry, and are usually avoidable. APKs contain thousands of
deflated entries, so this overhead adds up to tens of kilobytes.
Bug: 135470635
Change-Id: Ib928aa41dd55cacc41f7394c218c4340d3bbd570
diff --git a/libziparchive/Android.bp b/libziparchive/Android.bp
index 3843252..0253f2f 100644
--- a/libziparchive/Android.bp
+++ b/libziparchive/Android.bp
@@ -76,6 +76,10 @@
"liblog",
],
+ // for FRIEND_TEST
+ static_libs: ["libgtest_prod"],
+ export_static_lib_headers: ["libgtest_prod"],
+
export_include_dirs: ["include"],
}
diff --git a/libziparchive/include/ziparchive/zip_writer.h b/libziparchive/include/ziparchive/zip_writer.h
index a2a0dbf..d68683d 100644
--- a/libziparchive/include/ziparchive/zip_writer.h
+++ b/libziparchive/include/ziparchive/zip_writer.h
@@ -19,6 +19,7 @@
#include <cstdio>
#include <ctime>
+#include <gtest/gtest_prod.h>
#include <memory>
#include <string>
#include <string_view>
@@ -165,6 +166,7 @@
int32_t StoreBytes(FileEntry* file, const void* data, uint32_t len);
int32_t CompressBytes(FileEntry* file, const void* data, uint32_t len);
int32_t FlushCompressedBytes(FileEntry* file);
+ bool ShouldUseDataDescriptor() const;
enum class State {
kWritingZip,
@@ -182,4 +184,6 @@
std::unique_ptr<z_stream, void (*)(z_stream*)> z_stream_;
std::vector<uint8_t> buffer_;
+
+ FRIEND_TEST(zipwriter, WriteToUnseekableFile);
};
diff --git a/libziparchive/zip_writer.cc b/libziparchive/zip_writer.cc
index 198154b..67279a6 100644
--- a/libziparchive/zip_writer.cc
+++ b/libziparchive/zip_writer.cc
@@ -455,6 +455,11 @@
return kNoError;
}
+bool ZipWriter::ShouldUseDataDescriptor() const {
+ // Only use a trailing "data descriptor" if the output isn't seekable.
+ return !seekable_;
+}
+
int32_t ZipWriter::FinishEntry() {
if (state_ != State::kWritingEntry) {
return kInvalidState;
@@ -467,7 +472,7 @@
}
}
- if ((current_file_entry_.compression_method & kCompressDeflated) || !seekable_) {
+ if (ShouldUseDataDescriptor()) {
// Some versions of ZIP don't allow STORED data to have a trailing DataDescriptor.
// If this file is not seekable, or if the data is compressed, write a DataDescriptor.
const uint32_t sig = DataDescriptor::kOptSignature;
@@ -515,7 +520,7 @@
for (FileEntry& file : files_) {
CentralDirectoryRecord cdr = {};
cdr.record_signature = CentralDirectoryRecord::kSignature;
- if ((file.compression_method & kCompressDeflated) || !seekable_) {
+ if (ShouldUseDataDescriptor()) {
cdr.gpb_flags |= kGPBDDFlagMask;
}
cdr.compression_method = file.compression_method;
diff --git a/libziparchive/zip_writer_test.cc b/libziparchive/zip_writer_test.cc
index c3da23c..d324d4b 100644
--- a/libziparchive/zip_writer_test.cc
+++ b/libziparchive/zip_writer_test.cc
@@ -243,6 +243,7 @@
ZipEntry data;
ASSERT_EQ(0, FindEntry(handle, "file.txt", &data));
EXPECT_EQ(kCompressDeflated, data.method);
+ EXPECT_EQ(0u, data.has_data_descriptor);
ASSERT_EQ(4u, data.uncompressed_length);
ASSERT_TRUE(AssertFileEntryContentsEq("helo", handle, &data));
@@ -351,6 +352,29 @@
CloseArchive(handle);
}
+TEST_F(zipwriter, WriteToUnseekableFile) {
+ const char* expected = "hello";
+ ZipWriter writer(file_);
+ writer.seekable_ = false;
+
+ ASSERT_EQ(0, writer.StartEntry("file.txt", 0));
+ ASSERT_EQ(0, writer.WriteBytes(expected, strlen(expected)));
+ ASSERT_EQ(0, writer.FinishEntry());
+ ASSERT_EQ(0, writer.Finish());
+ ASSERT_GE(0, lseek(fd_, 0, SEEK_SET));
+
+ ZipArchiveHandle handle;
+ ASSERT_EQ(0, OpenArchiveFd(fd_, "temp", &handle, false));
+ ZipEntry data;
+ ASSERT_EQ(0, FindEntry(handle, "file.txt", &data));
+ EXPECT_EQ(kCompressStored, data.method);
+ EXPECT_EQ(1u, data.has_data_descriptor);
+ EXPECT_EQ(strlen(expected), data.compressed_length);
+ ASSERT_EQ(strlen(expected), data.uncompressed_length);
+ ASSERT_TRUE(AssertFileEntryContentsEq(expected, handle, &data));
+ CloseArchive(handle);
+}
+
TEST_F(zipwriter, TruncateFileAfterBackup) {
ZipWriter writer(file_);