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..0a5105e1f5daa586a6fcc689ca7e754a0394d8e0 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,

[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
@@ -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 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 {