Improve Zip File Scanning on Mac

third_party/zlib/google/zip_reader.h

Index: third_party/zlib/google/zip_reader.h
diff --git a/third_party/zlib/google/zip_reader.h b/third_party/zlib/google/zip_reader.h
index c1b6fb3364abeba3c34231e9dd1fea500540029e..1ba76a7fcfc37e910ef03332f28664a43fa93817 100644
--- a/third_party/zlib/google/zip_reader.h
+++ b/third_party/zlib/google/zip_reader.h
@@ -162,6 +162,11 @@ class ZipReader {
   // 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,
+                                 size_t num_bytes) const;

[satorux1, 2017/07/14 01:00:53]

Could you add a unit test for this function to zip_reader_unittest.cc ?

[mortonm, 2017/07/14 17:08:45]

Done.

+
   // 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
@@ -217,6 +222,13 @@ class ZipReader {
       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 max_read_bytes,

[satorux1, 2017/07/14 01:00:53]

Ditto.

[mortonm, 2017/07/14 17:08:45]

Done.

+                                         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 {