Add Socket::ReadIfReady()

net/spdy/spdy_session.cc

Index: net/spdy/spdy_session.cc
diff --git a/net/spdy/spdy_session.cc b/net/spdy/spdy_session.cc
index 431022624477c12cdb079655abc77cb9b7723f39..edf73acd901451398456d6149d6cb08ebc2e053e 100644
--- a/net/spdy/spdy_session.cc
+++ b/net/spdy/spdy_session.cc
@@ -11,6 +11,7 @@
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
+#include "base/feature_list.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ -45,6 +46,7 @@
 #include "net/log/net_log_source_type.h"
 #include "net/log/net_log_with_source.h"
 #include "net/proxy/proxy_server.h"
+#include "net/socket/socket.h"
 #include "net/socket/ssl_client_socket.h"
 #include "net/spdy/platform/api/spdy_estimate_memory_usage.h"
 #include "net/spdy/spdy_buffer_producer.h"
@@ -1804,6 +1806,32 @@ void SpdySession::PumpReadLoop(ReadState expected_read_state, int result) {
   ignore_result(DoReadLoop(expected_read_state, result));
 }
 
+int SpdySession::DoRead() {

[Bence, 2017/03/03 16:33:41]

Oh no, I just reordered methods in https://crrev.com/2683643002 so that the
order is consistent between spdy_session.h and spdy_session.cc.  If you want to
swap DoRead() and DoReadLoop(), could you please also do that in the header
file?

[xunjieli, 2017/03/03 19:41:06]

Done.

+  CHECK(in_io_loop_);
+
+  CHECK(connection_);
+  CHECK(connection_->socket());

[Bence, 2017/03/03 16:33:42]

Do you think this would flow more naturally?

if (base::FeatureList::IsEnabled(Socket::kReadIfReadyExperiment)) {
  int rv = connection_->socket()->ReadIfReady(
      read_buffer_.get(), kReadBufferSize,
      base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
                 READ_STATE_DO_READ));
  // TODO(xunjieli): Follow-up CL to release |read_buffer_|.
  // https://crbug.com/524258
  if (rv == ERR_IO_PENDING) {
    read_state_ = READ_STATE_DO_READ;
    return rv;
  }
  if (rv != ERR_READ_IF_READY_NOT_IMPLEMENTED) {
    read_state_ = READ_STATE_DO_READ_COMPLETE;
    return rv;
  }
}
// Fallback to regular Read().
read_state_ = READ_STATE_DO_READ_COMPLETE;
return connection_->socket()->Read(
    read_buffer_.get(), kReadBufferSize,
    base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
               READ_STATE_DO_READ_COMPLETE));

[xunjieli, 2017/03/03 19:41:06]

I may be biased, but I like my verson better. Fewer lines of code and the state
change is easier to read -- default to READ_STATE_DO_READ_COMPLETED but for
async ReadIfReady() case go to READ_STATE_DO_READ.

[Bence, 2017/03/06 23:43:14]

It's okay to be biased, you are the author.  :)

+  read_state_ = READ_STATE_DO_READ_COMPLETE;
+  int rv = ERR_READ_IF_READY_NOT_IMPLEMENTED;
+  if (base::FeatureList::IsEnabled(Socket::kReadIfReadyExperiment)) {
+    rv = connection_->socket()->ReadIfReady(
+        read_buffer_.get(), kReadBufferSize,
+        base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
+                   READ_STATE_DO_READ));
+    // TODO(xunjieli): Follow-up CL to release |read_buffer_|. crbug.com/524258.

[Bence, 2017/03/03 16:33:42]

Optional: use https:// prefix for crbug, because some viewers/editors need that
to make this a clickable link (for example, gnome-terminal, when text is output
using cat, less, diff, grep etc.).

[xunjieli, 2017/03/03 19:41:06]

Done. I personally avoid the https:// prefix because that's extra 8 characters
and makes one line into two. 

[Bence, 2017/03/06 23:43:14]

I guess then you are not using vim in gnome-terminal to write code.  :)

+  }
+  if (rv == ERR_READ_IF_READY_NOT_IMPLEMENTED) {
+    // Fallback to regular Read().
+    return connection_->socket()->Read(
+        read_buffer_.get(), kReadBufferSize,
+        base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
+                   READ_STATE_DO_READ_COMPLETE));
+  }
+  if (rv == ERR_IO_PENDING)
+    read_state_ = READ_STATE_DO_READ;
+  return rv;
+}
+
 int SpdySession::DoReadLoop(ReadState expected_read_state, int result) {
   CHECK(!in_io_loop_);
   CHECK_EQ(read_state_, expected_read_state);
@@ -1857,18 +1885,6 @@ int SpdySession::DoReadLoop(ReadState expected_read_state, int result) {
   return result;
 }
 
-int SpdySession::DoRead() {
-  CHECK(in_io_loop_);
-
-  CHECK(connection_);
-  CHECK(connection_->socket());
-  read_state_ = READ_STATE_DO_READ_COMPLETE;
-  return connection_->socket()->Read(
-      read_buffer_.get(), kReadBufferSize,
-      base::Bind(&SpdySession::PumpReadLoop, weak_factory_.GetWeakPtr(),
-                 READ_STATE_DO_READ_COMPLETE));
-}
-
 int SpdySession::DoReadComplete(int result) {
   CHECK(in_io_loop_);