Improve Zip File Scanning on Mac

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 <stddef.h>
 #include <stdint.h>
 
 #include <memory>
@@ skipping 144 matching lines @@
   bool OpenCurrentEntryInZip();
 
   // 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 in chunks to |delegate|.
   bool ExtractCurrentEntry(WriterDelegate* delegate) const;
 
+  // Extracts part of the current entry to |delegate|, starting from the
+  // beginning of the entry.
+  bool ExtractPartOfCurrentEntry(WriterDelegate* delegate,

[satorux1, 2017/07/18 07:46:38]

Part -> Head/Prefix/Beinning to make it clear that it extracts the beginning of
the entry?

[mortonm, 2017/07/18 19:58:49]

Done.

[mortonm, 2017/07/18 19:58:49]

Done.

+                                 size_t num_bytes_to_extract) const;
+
   // 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 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) const;
 
@@ skipping 35 matching lines @@
   // passing it around by value, but by reference or pointer.
   // Note: the value returned by EntryInfo::original_size() cannot be
   // trusted, so the real size of the uncompressed contents can be different.
   // Use max_read_bytes to limit the ammount of memory used to carry the entry.
   // If the real size of the uncompressed data is bigger than max_read_bytes
   // then false is returned. |max_read_bytes| must be non-zero.
   bool ExtractCurrentEntryToString(
       size_t max_read_bytes,
       std::string* output) const;
 
+  // Same as ExtractCurrentEntryToString(), except specifies the number of bytes
+  // to read into the string so that it is possible to only read a partial
+  // amount of the entry into a string. This is used to infer the type of
+  // MachO files on Mac by sniffing their magic number in the header.
+  bool ExtractPartOfCurrentEntryToString(size_t num_bytes_to_extract,
+                                         std::string* output) const;
+
   // Returns the current entry info. Returns NULL if the current entry is
   // not yet opened. OpenCurrentEntryInZip() must be called beforehand.
   EntryInfo* current_entry_info() const {
     return current_entry_info_.get();
   }
 
   // Returns the number of entries in the zip file.
   // Open() must be called beforehand.
   int num_entries() const { return num_entries_; }
 
@@ skipping 42 matching lines @@
  private:
   base::File* file_;
   int64_t file_length_;
 
   DISALLOW_COPY_AND_ASSIGN(FileWriterDelegate);
 };
 
 }  // namespace zip
 
 #endif  // THIRD_PARTY_ZLIB_GOOGLE_ZIP_READER_H_