Refactor Pickle Read methods to use higher performance PickleIterator.

There was a lot of redundant error checking and initialization code in all Pickle Read methods because of the void** iterator type. This change replaces the void* iterator with PickleIterator, which encapsulates the read pointer so that less error checking and initialization code is needed for reading.

PickleIterator has all the necessary data to do the actual reading. The advantage of having it provide Read methods (as opposed to leaving them solely in the Pickle interface) is that the callers do not need to pass around the const Pickle* once they have a PickleIterator.

Followup CLs will refactor the call sites to remove const Pickle* arguments where they are now unnecessary. Then the Pickle::Read* methods can be removed entirely.

The alternative approach would have been to change the Pickle::Read methods to non-const and remove the iterator parameter (making Read methods advance an internal read pointer). Unfortunately, the const Read with iterator design is entrenched throughout the chromium code, making this a much more complex change with the same performance outcome.

BUG=13108

Review URL: https://chromiumcodereview.appspot.com/9447084

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@125447 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 2 insertions, 1 deletions

diff --git a/net/http/http_response_headers.h b/net/http/http_response_headers.h
index 0ab162e..6fbc0bb 100644
--- a/net/http/http_response_headers.h
+++ b/net/http/http_response_headers.h
@@ -16,6 +16,7 @@
 #include "net/http/http_version.h"
 
 class Pickle;
+class PickleIterator;
 
 namespace base {
 class Time;
@@ -52,7 +53,7 @@ class NET_EXPORT HttpResponseHeaders
   // Initializes from the representation stored in the given pickle.  The data
   // for this object is found relative to the given pickle_iter, which should
   // be passed to the pickle's various Read* methods.
-  HttpResponseHeaders(const Pickle& pickle, void** pickle_iter);
+  HttpResponseHeaders(const Pickle& pickle, PickleIterator* pickle_iter);
 
   // Appends a representation of this object to the given pickle.
   // The options argument can be a combination of PersistOptions.