Preserve modification timestamp when zipping files.

third_party/zlib/google/zip_reader.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef THIRD_PARTY_ZLIB_GOOGLE_ZIP_READER_H_
 #define THIRD_PARTY_ZLIB_GOOGLE_ZIP_READER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 39 matching lines @@
               const unz_file_info& raw_file_info);
 
     // Returns the file path. The path is usually relative like
     // "foo/bar.txt", but if it's absolute, is_unsafe() returns true.
     const base::FilePath& file_path() const { return file_path_; }
 
     // Returns the size of the original file (i.e. after uncompressed).
     // Returns 0 if the entry is a directory.
     int64 original_size() const { return original_size_; }
 
-    // Returns the last modified time.
+    // Returns the last modified time. If the time stored in the zip file was
+    // not valid, the unix epoch will be returned.
+    //
+    // The time stored in the zip archive uses the MS-DOS date and time format.
+    // http://msdn.microsoft.com/en-us/library/ms724247(v=vs.85).aspx
+    // As such the following limitations apply:
+    // * only years from 1980 to 2107 can be represented.
+    // * the time stamp has a 2 second resolution.
+    // * there's no timezone information, so the time is interpreted as local.
     base::Time last_modified() const { return last_modified_; }
 
     // Returns true if the entry is a directory.
     bool is_directory() const { return is_directory_; }
 
     // Returns true if the entry is unsafe, like having ".." or invalid
     // UTF-8 characters in its file name, or the file path is absolute.
     bool is_unsafe() const { return is_unsafe_; }
 
    private:
@@ skipping 49 matching lines @@
   // Locates an entry in the zip file and opens it. Returns true on
   // success. This function internally calls OpenCurrentEntryInZip() on
   // success. On failure, current_entry_info() becomes NULL.
   bool LocateAndOpenEntry(const base::FilePath& path_in_zip);
 
   // Extracts the current entry to the given output file path. If the
   // current file is a directory, just creates a directory
   // instead. Returns true on success. OpenCurrentEntryInZip() must be
   // called beforehand.
   //
-  // This function does not preserve the timestamp of the original entry.
+  // This function preserves the timestamp of the original entry. If that
+  // timestamp is not valid, the timestamp will be set to the current time.
   bool ExtractCurrentEntryToFilePath(const base::FilePath& output_file_path);
 
   // Extracts the current entry to the given output directory path using
   // ExtractCurrentEntryToFilePath(). Sub directories are created as needed
   // based on the file path of the current entry. For example, if the file
   // path in zip is "foo/bar.txt", and the output directory is "output",
   // "output/foo/bar.txt" will be created.
   //
   // Returns true on success. OpenCurrentEntryInZip() must be called
   // beforehand.
+  //
+  // This function preserves the timestamp of the original entry. If that
+  // timestamp is not valid, the timestamp will be set to the current time.
   bool ExtractCurrentEntryIntoDirectory(
       const base::FilePath& output_directory_path);
 
 #if defined(OS_POSIX)
   // Extracts the current entry by writing directly to a file descriptor.
   // Does not close the file descriptor. Returns true on success.
   bool ExtractCurrentEntryToFd(int fd);
 #endif
 
   // Returns the current entry info. Returns NULL if the current entry is
@@ skipping 17 matching lines @@
   int num_entries_;
   bool reached_end_;
   scoped_ptr<EntryInfo> current_entry_info_;
 
   DISALLOW_COPY_AND_ASSIGN(ZipReader);
 };
 
 }  // namespace zip
 
 #endif  // THIRD_PARTY_ZLIB_GOOGLE_ZIP_READER_H_