Refactoring media mime type and supported codec checks

net/base/mime_util.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_BASE_MIME_UTIL_H__
 #define NET_BASE_MIME_UTIL_H__
 
 // This file defines MIME utility functions. All of them assume the MIME type
 // to be of the format specified by rfc2045. According to it, MIME types are
 // case strongly insensitive except parameter values, which may or may not be
 // case sensitive.
 //
 // These utilities perform a *case-sensitive* matching for  parameter values,
 // which may produce some false negatives. Except that, matching is
 // case-insensitive.
 //
 // All constants in mime_util.cc must be written in lower case, except parameter
 // values, which can be any case.
 
 #include <string>
 #include <vector>
 
+#include "base/callback.h"
 #include "base/files/file_path.h"
 #include "net/base/net_export.h"
 
 namespace net {
 
 // Get the mime type (if any) that is associated with the given file extension.
 // Returns true if a corresponding mime type exists.
 NET_EXPORT bool GetMimeTypeFromExtension(const base::FilePath::StringType& ext,
                                          std::string* mime_type);
 
@@ skipping 61 matching lines @@
 
 // Parses a codec string, populating |codecs_out| with the prefix of each codec
 // in the string |codecs_in|. For example, passed "aaa.b.c,dd.eee", if
 // |strip| == true |codecs_out| will contain {"aaa", "dd"}, if |strip| == false
 // |codecs_out| will contain {"aaa.b.c", "dd.eee"}.
 // See http://www.ietf.org/rfc/rfc4281.txt.
 NET_EXPORT void ParseCodecString(const std::string& codecs,
                                  std::vector<std::string>* codecs_out,
                                  bool strip);
 
+// Returns true if the given |codec_id|, identified by a codec id string
+// described in RFC 6381, is supported. Returns false if the codec id is not
+// recognized or if that codec is not supported.
+NET_EXPORT bool IsCodecSupported(const std::string& codec_id);
+
+// The default implementation of IsCodecSupported, it can be overridden by
+// providing a custom callback via SetIsCodecSupportedCB.
+NET_EXPORT bool DefaultIsCodecSupported(const std::string& codec_id);
+
+// Provides a custom, platform-specific implementation of IsCodecSupported.
+typedef base::Callback<bool(const std::string&)> IsCodecSupportedCB;
+NET_EXPORT void SetIsCodecSupportedCB(IsCodecSupportedCB is_codec_supported_cb);

[Ryan Sleevi, 2015/04/21 13:23:29]

STYLE: Callbacks should *always* be passed as const-ref

DESIGN: Is the typedef actually necessary? It seems cleaner (e.g. avoiding
namespace polution) to avoid it.

[servolk, 2015/04/21 22:09:02]

Changed to const-ref. Re typedef - I've posted my reasoning in an earlier
comment, let me know which you prefer.

+
 // Check to see if a particular MIME type is in our list which only supports a
 // certain subset of codecs.
 NET_EXPORT bool IsStrictMediaMimeType(const std::string& mime_type);
 
 // Indicates that the MIME type and (possible codec string) are supported by the
 // underlying platform.
 enum SupportsType {
   // The underlying platform is known not to support the given MIME type and
   // codec combination.
   IsNotSupported,
@@ skipping 59 matching lines @@
                                            std::string* post_data);
 
 // Adds the final delimiter to a multi-part upload request.
 NET_EXPORT void AddMultipartFinalDelimiterForUpload(
     const std::string& mime_boundary,
     std::string* post_data);
 
 }  // namespace net
 
 #endif  // NET_BASE_MIME_UTIL_H__