[net] Change order of RequestPriority to natural: higher > lower

net/spdy/spdy_http_utils.cc

 // 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.
 
 #include "net/spdy/spdy_http_utils.h"
 
 #include <string>
 
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
@@ skipping 107 matching lines @@
     (*headers)[":version"] = kHttpProtocolVersion;
     (*headers)[":method"] = info.method;
     (*headers)[":host"] = GetHostAndOptionalPort(info.url);
     (*headers)[":scheme"] = info.url.scheme();
     (*headers)[":path"] = HttpUtil::PathForRequest(info.url);
     headers->erase("host"); // this is kinda insane, spdy 3 spec.
   }
 
 }
 
+COMPILE_ASSERT(HIGHEST - LOWEST < 4 &&
+               HIGHEST - MINIMUM_PRIORITY < 5,
+               request_priority_incompatible_with_spdy);

[szym, 2012/04/24 18:15:25]

Please, take a look at this assert and the mapping.

[Ryan Hamilton, 2012/04/24 18:45:35]

NICE!  Love this assert.

+
 SpdyPriority ConvertRequestPriorityToSpdyPriority(
     const RequestPriority priority,
     int protocol_version) {
-  DCHECK(HIGHEST <= priority && priority < NUM_PRIORITIES);
+  DCHECK_GE(priority, MINIMUM_PRIORITY);
+  DCHECK_LT(priority, NUM_PRIORITIES);
   if (protocol_version == 2) {
     // SPDY 2 only has 2 bits of priority, but we have 5 RequestPriorities.
-    if (priority < LOWEST) {
-      return priority;
+    // Map IDLE => 3, LOWEST => 2, LOW => 2, MEDIUM => 1, HIGHEST => 0.
+    if (priority > LOWEST) {
+      return static_cast<SpdyPriority>(HIGHEST - priority);
     } else {
-      DCHECK_GE(4, priority);
-      return priority - 1;
+      return static_cast<SpdyPriority>(HIGHEST - priority - 1);
     }
-  } else {
-    DCHECK_GE(7, priority);
-    return priority;
+  } else { // only valid
+    return static_cast<SpdyPriority>(HIGHEST - priority);
   }
 }
 
 GURL GetUrlFromHeaderBlock(const SpdyHeaderBlock& headers,
                            int protocol_version,
                            bool pushed) {
   // SPDY 2 server push urls are specified in a single "url" header.
   if (pushed && protocol_version == 2) {
       std::string url;
       SpdyHeaderBlock::const_iterator it;
@@ skipping 20 matching lines @@
   it = headers.find(path_header);
   if (it != headers.end())
     path = it->second;
 
   std::string url =  (scheme.empty() || host_port.empty() || path.empty())
       ? "" : scheme + "://" + host_port + path;
   return GURL(url);
 }
 
 }  // namespace net