zip_archive: generalize deflate method.

Remove dependencies on zip_archive specific data structures. In follow
up changes, this method will be promoted to a public API and used from
androidfw/ZipUtils as well as tools/zipalign, thereby allowing us to
remove a near-exact copy of this code and to simplify depdencies.

Test: zip_archive_test
Bug: 35246701
Change-Id: If24a9965fbd6fff308c8758859026684fd2af3b9

libziparchive/zip_archive.cc

@@ -848,6 +848,34 @@ class FileWriter : public Writer {
   size_t total_bytes_written_;
 };
 
+class Reader {
+ public:
+  virtual bool ReadAtOffset(uint8_t* buf, size_t len, uint32_t offset) const = 0;
+  virtual ~Reader() {}
+
+ protected:
+  Reader() = default;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Reader);
+};
+
+class EntryReader : public Reader {
+ public:
+  EntryReader(const MappedZipFile& zip_file, const ZipEntry* entry)
+      : Reader(), zip_file_(zip_file), entry_(entry) {}
+
+  virtual bool ReadAtOffset(uint8_t* buf, size_t len, uint32_t offset) const {
+    return zip_file_.ReadAtOffset(buf, len, entry_->offset + offset);
+  }
+
+  virtual ~EntryReader() {}
+
+ private:
+  const MappedZipFile& zip_file_;
+  const ZipEntry* entry_;
+};
+
 // This method is using libz macros with old-style-casts
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wold-style-cast"
@@ -856,8 +884,9 @@ static inline int zlib_inflateInit2(z_stream* stream, int window_bits) {
 }
 #pragma GCC diagnostic pop
 
-static int32_t InflateEntryToWriter(MappedZipFile& mapped_zip, const ZipEntry* entry,
-                                    Writer* writer, uint64_t* crc_out) {
+static int32_t InflateReaderToWriter(const Reader& reader, const uint32_t compressed_length,
+                                     const uint32_t uncompressed_length, Writer* writer,
+                                     uint64_t* crc_out) {
   const size_t kBufSize = 32768;
   std::vector<uint8_t> read_buf(kBufSize);
   std::vector<uint8_t> write_buf(kBufSize);
@@ -898,25 +927,23 @@ static int32_t InflateEntryToWriter(MappedZipFile& mapped_zip, const ZipEntry* e
 
   std::unique_ptr<z_stream, decltype(zstream_deleter)> zstream_guard(&zstream, zstream_deleter);
 
-  const uint32_t uncompressed_length = entry->uncompressed_length;
-
   uint64_t crc = 0;
-  uint32_t compressed_length = entry->compressed_length;
+  uint32_t remaining_bytes = compressed_length;
   do {
     /* read as much as we can */
     if (zstream.avail_in == 0) {
-      const size_t getSize = (compressed_length > kBufSize) ? kBufSize : compressed_length;
-      off64_t offset = entry->offset + (entry->compressed_length - compressed_length);
+      const size_t read_size = (remaining_bytes > kBufSize) ? kBufSize : remaining_bytes;
+      const uint32_t offset = (compressed_length - remaining_bytes);
       // Make sure to read at offset to ensure concurrent access to the fd.
-      if (!mapped_zip.ReadAtOffset(read_buf.data(), getSize, offset)) {
-        ALOGW("Zip: inflate read failed, getSize = %zu: %s", getSize, strerror(errno));
+      if (!reader.ReadAtOffset(read_buf.data(), read_size, offset)) {
+        ALOGW("Zip: inflate read failed, getSize = %zu: %s", read_size, strerror(errno));
         return kIoError;
       }
 
-      compressed_length -= getSize;
+      remaining_bytes -= read_size;
 
       zstream.next_in = &read_buf[0];
-      zstream.avail_in = getSize;
+      zstream.avail_in = read_size;
     }
 
     /* uncompress the data */
@@ -952,7 +979,7 @@ static int32_t InflateEntryToWriter(MappedZipFile& mapped_zip, const ZipEntry* e
   // the same manner that we have above.
   *crc_out = crc;
 
-  if (zstream.total_out != uncompressed_length || compressed_length != 0) {
+  if (zstream.total_out != uncompressed_length || remaining_bytes != 0) {
     ALOGW("Zip: size mismatch on inflated file (%lu vs %" PRIu32 ")", zstream.total_out,
           uncompressed_length);
     return kInconsistentInformation;
@@ -961,6 +988,14 @@ static int32_t InflateEntryToWriter(MappedZipFile& mapped_zip, const ZipEntry* e
   return 0;
 }
 
+static int32_t InflateEntryToWriter(MappedZipFile& mapped_zip, const ZipEntry* entry,
+                                    Writer* writer, uint64_t* crc_out) {
+  const EntryReader reader(mapped_zip, entry);
+
+  return InflateReaderToWriter(reader, entry->compressed_length, entry->uncompressed_length, writer,
+                               crc_out);
+}
+
 static int32_t CopyEntryToWriter(MappedZipFile& mapped_zip, const ZipEntry* entry, Writer* writer,
                                  uint64_t* crc_out) {
   static const uint32_t kBufSize = 32768;
@@ -1118,7 +1153,7 @@ off64_t MappedZipFile::GetFileLength() const {
 }
 
 // Attempts to read |len| bytes into |buf| at offset |off|.
-bool MappedZipFile::ReadAtOffset(uint8_t* buf, size_t len, off64_t off) {
+bool MappedZipFile::ReadAtOffset(uint8_t* buf, size_t len, off64_t off) const {
   if (has_fd_) {
     if (!android::base::ReadFullyAtOffset(fd_, buf, len, off)) {
       ALOGE("Zip: failed to read at offset %" PRId64 "\n", off);

libziparchive/zip_archive_private.h

@@ -106,7 +106,7 @@ class MappedZipFile {
 
   off64_t GetFileLength() const;
 
-  bool ReadAtOffset(uint8_t* buf, size_t len, off64_t off);
+  bool ReadAtOffset(uint8_t* buf, size_t len, off64_t off) const;
 
  private:
   // If has_fd_ is true, fd is valid and we'll read contents of a zip archive