Add non-blocking peek for the syncsocket

- Windows only

BUG=none
TEST=unit test included


Review URL: http://codereview.chromium.org/464020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@33876 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 18 insertions, 0 deletions

diff --git a/base/sync_socket.h b/base/sync_socket.h
index ad181ff..a44c445 100644
--- a/base/sync_socket.h
+++ b/base/sync_socket.h
@@ -51,6 +51,12 @@ class SyncSocket {
   // Returns the number of bytes received, or 0 upon failure.
   size_t Receive(void* buffer, size_t length);
 
+  // Returns the number of bytes available. If non-zero, Receive() will not
+  // not block when called. NOTE: Some implementations cannot reliably
+  // determine the number of bytes available so avoid using the returned
+  // size as a promise and simply test against zero.
+  size_t Peek();
+
   // Extracts the contained handle.  Used for transferring between
   // processes.
   Handle handle() const { return handle_; }
diff --git a/base/sync_socket_posix.cc b/base/sync_socket_posix.cc
index 35d53b2..5390c7d 100644
--- a/base/sync_socket_posix.cc
+++ b/base/sync_socket_posix.cc
@@ -98,4 +98,10 @@ size_t SyncSocket::Receive(void* buffer, size_t length) {
   }
 }
 
+// TODO(port). Some kind of select?
+size_t SyncSocket::Peek() {
+  NOTIMPLEMENTED();
+  return 0;
+}
+
 }  // namespace base
diff --git a/base/sync_socket_win.cc b/base/sync_socket_win.cc
index b591bb0..4e3c35f 100644
--- a/base/sync_socket_win.cc
+++ b/base/sync_socket_win.cc
@@ -141,4 +141,10 @@ size_t SyncSocket::Receive(void* buffer, size_t length) {
   return count;
 }
 
+size_t SyncSocket::Peek() {
+  DWORD available = 0;
+  PeekNamedPipe(handle_, NULL, 0, NULL, &available, NULL);
+  return available;
+}
+
 }  // namespace base