Break rtp_rtcp_format out of rtp_rtcp, to resolve circular dependencies

webrtc/modules/rtp_rtcp/source/byte_io.h

Index: webrtc/modules/rtp_rtcp/source/byte_io.h
diff --git a/webrtc/modules/rtp_rtcp/source/byte_io.h b/webrtc/modules/rtp_rtcp/source/byte_io.h
index 1724bb0a2e5951fb29472049f535be627cf0835b..cd2a2bea542a4807c9161a37a4616c3458f1b333 100644
--- a/webrtc/modules/rtp_rtcp/source/byte_io.h
+++ b/webrtc/modules/rtp_rtcp/source/byte_io.h
@@ -36,9 +36,10 @@
 // it easy for the compiler to completely inline the reading/writing.
 
 
-#include <limits>
+#include <stddef.h>

[eladalon, 2017/09/12 14:45:07]

By the way, for my information, don't we prefer to include webrtc/typedefs.h?

[danilchap, 2017/09/12 15:17:18]

I've reverted this file alltogether,
but generally I think we do not:
typedefs.h defines macros like NO_RETURN/FALLTHROUGH etc.
this file doesn't need those macros so it shouldn't include it instead of c
header that it actually need (for uintX_t types)

Can't find rule that explicitly direct one way or another. So following generic
guidance 'include as little as you actually need'

[eladalon, 2017/09/12 15:25:24]

Acknowledged.

+#include <stdint.h>
 
-#include "webrtc/typedefs.h"
+#include <limits>
 
 namespace webrtc {
 
@@ -403,6 +404,12 @@ class ByteWriter<T, 8, false> {
   }
 };
 
+// Round up to the nearest size that is a multiple of 4.
+inline size_t Word32Align(size_t size) {
+  // Same as increment by 3 and clear last two bits.
+  return (size + 3) & ~0x3;

[eladalon, 2017/09/12 14:45:07]

Is this the safest way to do this?
1. There are some implicit conversions in play, and I am not 100% comfortable
with them. Given that size_t is always unsigned, perhaps we could take the
maximum value of it and subtract three instead? You get the same value us ~0x3,
but without any conversions.
2. Speaking of maximum values, what if (size+3) overflows?

[danilchap, 2017/09/12 15:17:17]

2. Moved inside rtp_header_extension_map where size is obviously way below
maximum value.

1. Changed to safer + and % from treating size_t as bitmask.

+}
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_BYTE_IO_H_