Parsing of encoded duration for unencrypted opus streams.

media/base/media_log.h

Index: media/base/media_log.h
diff --git a/media/base/media_log.h b/media/base/media_log.h
index 1a76cbf5f01ed68e67479f523e4119bd365b3dc8..5ac733c20a42b40af4e70929914947ced1959db9 100644
--- a/media/base/media_log.h
+++ b/media/base/media_log.h
@@ -8,6 +8,7 @@
 #include <sstream>
 #include <string>
 
+#include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
@@ -36,6 +37,11 @@ class LogHelper {
 
 #define MEDIA_LOG(log_cb) LogHelper(log_cb).stream()
 
+// Logs only while count < max. Increments count for each log. Use LAZY_STREAM
+// to avoid wasteful evaluation of subsequent stream arguments.
+#define LIMITED_MEDIA_LOG(log_cb, count, max) \
+  LAZY_STREAM(MEDIA_LOG(log_cb), count <= max && count++)

[wolenetz, 2015/02/05 23:04:59]

macros-r-fun :)

s/<=/</. Also, caller might have funky count and max. Consider count=-1, max=1.
count++ would be 0, resulting in false evaluation for the macro's |condition| on
first evaluation.
Also, wrap the params inside () to make evaluation order explicit.

Therefore, I think a better |condition| expression would be (count) < (max) &&
((count++) || 1).

I think it is understood by both users and implementors of LAZY_STREAM that
|condition| should only be evaluated once. However, I could be wrong. In that
case, the side-effect of incrementing count for every evaluation of |condition|
within LAZY_STREAM (when count is still < max) would result in unexpected
behavior if LAZY_STREAM implementation change is modified to perhaps evaluate
|condition| N times, where N is not always 1. I'm not sure the best way to
account for this, but a starting point would be to add to LAZY_STREAM's
implementation documentation (and get appropriate OWNER l*tm) that |condition|
must only be evaluated once within the implementation, as part of this CL.

[chcunningham, 2015/02/06 03:20:09]

Done. Adding akalin@chromium.org to review this change to LAZY_STREAM
documentation.

+
 class MEDIA_EXPORT MediaLog : public base::RefCountedThreadSafe<MediaLog> {
  public:
   // Convert various enums to strings.