commit ec095767e6fd0b622a8d0610b5809b682d435f7a
author renjietang <renjietang@google.com> Wed Jun 19 14:35:02 2019 -0700
committer Copybara-Service <copybara-worker@google.com> Thu Jun 20 07:03:43 2019 -0700
tree 4fbb17bcef8921c21fffbedf66e1cbb99840cb37
parent c1cab06be6b47a0f96c7dff58802680b2b583b88

Make writing Prioritized Element ID and Element Dependency ID optional when handling priority.

These fields are specified to be absent when priority type or dependency type is ROOT_OF_TREE.

On the decoding side, the absent fields will be parsed as 0 for default value. Those fields won't be used when later the frame is processed.

gfe-relnote: v99 only, not flag protected.
PiperOrigin-RevId: 254072432
Change-Id: I336e06b39d89ff01507e54818dafa67923e96e4c

quic/core/http/http_encoder.cc

diff --git a/quic/core/http/http_encoder.cc b/quic/core/http/http_encoder.cc
index 4505dc7..2b8be8e 100644
--- a/quic/core/http/http_encoder.cc
+++ b/quic/core/http/http_encoder.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "net/third_party/quiche/src/quic/core/http/http_encoder.h"
+
 #include "net/third_party/quiche/src/quic/core/quic_data_writer.h"
 
 namespace quic {
@@ -43,6 +44,8 @@
 static const size_t kPriorityWeightLength = 1;
 // Length of a priority frame's first byte.
 static const size_t kPriorityFirstByteLength = 1;
+// The bit that indicates Priority frame is exclusive.
+static const uint8_t kPriorityExclusiveBit = 1;
 
 }  // namespace
 
@@ -95,8 +98,12 @@
     std::unique_ptr<char[]>* output) {
   QuicByteCount payload_length =
       kPriorityFirstByteLength +
-      QuicDataWriter::GetVarInt62Len(priority.prioritized_element_id) +
-      QuicDataWriter::GetVarInt62Len(priority.element_dependency_id) +
+      (priority.prioritized_type == ROOT_OF_TREE
+           ? 0
+           : QuicDataWriter::GetVarInt62Len(priority.prioritized_element_id)) +
+      (priority.dependency_type == ROOT_OF_TREE
+           ? 0
+           : QuicDataWriter::GetVarInt62Len(priority.element_dependency_id)) +
       kPriorityWeightLength;
   QuicByteCount total_length =
       GetTotalLength(payload_length, HttpFrameType::PRIORITY);
@@ -111,16 +118,14 @@
   }
 
   // Set the first byte of the payload.
-  uint8_t bits = 0;
-  bits = SetPriorityFields(bits, priority.prioritized_type, true);
-  bits = SetPriorityFields(bits, priority.dependency_type, false);
+  uint8_t firstByte = 0;
+  firstByte = SetPriorityFields(firstByte, priority.prioritized_type, true);
+  firstByte = SetPriorityFields(firstByte, priority.dependency_type, false);
   if (priority.exclusive) {
-    bits |= 1;
+    firstByte |= kPriorityExclusiveBit;
   }
 
-  if (writer.WriteUInt8(bits) &&
-      writer.WriteVarInt62(priority.prioritized_element_id) &&
-      writer.WriteVarInt62(priority.element_dependency_id) &&
+  if (writer.WriteUInt8(firstByte) && MaybeWriteIds(priority, &writer) &&
       writer.WriteUInt8(priority.weight)) {
     return total_length;
   }
@@ -282,4 +287,27 @@
          payload_length;
 }
 
+bool HttpEncoder::MaybeWriteIds(const PriorityFrame& priority,
+                                QuicDataWriter* writer) {
+  if (priority.prioritized_type != ROOT_OF_TREE) {
+    if (!writer->WriteVarInt62(priority.prioritized_element_id)) {
+      return false;
+    }
+  } else {
+    DCHECK_EQ(0u, priority.prioritized_element_id)
+        << "Prioritized element id should be 0 when prioritized type is "
+           "ROOT_OF_TREE";
+  }
+  if (priority.dependency_type != ROOT_OF_TREE) {
+    if (!writer->WriteVarInt62(priority.element_dependency_id)) {
+      return false;
+    }
+  } else {
+    DCHECK_EQ(0u, priority.element_dependency_id)
+        << "Element dependency id should be 0 when dependency type is "
+           "ROOT_OF_TREE";
+  }
+  return true;
+}
+
 }  // namespace quic