1 files changed, 86 insertions, 0 deletions
diff --git a/grpc/src/core/ext/transport/chttp2/transport/hpack_encoder_table.cc b/grpc/src/core/ext/transport/chttp2/transport/hpack_encoder_table.cc
new file mode 100644
index 00000000..ef31a019
--- /dev/null
+++ b/grpc/src/core/ext/transport/chttp2/transport/hpack_encoder_table.cc
@@ -0,0 +1,86 @@
+// Copyright 2021 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <grpc/support/port_platform.h>
+
+#include "src/core/ext/transport/chttp2/transport/hpack_encoder_table.h"
+
+#include <grpc/support/log.h>
+
+namespace grpc_core {
+
+uint32_t HPackEncoderTable::AllocateIndex(size_t element_size) {
+  uint32_t new_index = tail_remote_index_ + table_elems_ + 1;
+  GPR_DEBUG_ASSERT(element_size <= MaxEntrySize());
+
+  if (element_size > max_table_size_) {
+    while (table_size_ > 0) {
+      EvictOne();
+    }
+    return 0;
+  }
+
+  // Reserve space for this element in the remote table: if this overflows
+  // the current table, drop elements until it fits, matching the decompressor
+  // algorithm.
+  while (table_size_ + element_size > max_table_size_) {
+    EvictOne();
+  }
+  GPR_ASSERT(table_elems_ < elem_size_.size());
+  elem_size_[new_index % elem_size_.size()] =
+      static_cast<uint16_t>(element_size);
+  table_size_ += element_size;
+  table_elems_++;
+
+  return new_index;
+}
+
+bool HPackEncoderTable::SetMaxSize(uint32_t max_table_size) {
+  if (max_table_size == max_table_size_) {
+    return false;
+  }
+  while (table_size_ > 0 && table_size_ > max_table_size) {
+    EvictOne();
+  }
+  max_table_size_ = max_table_size;
+  const size_t max_table_elems =
+      hpack_constants::EntriesForBytes(max_table_size);
+  // TODO(ctiller): integrate with ResourceQuota to rebuild smaller when we can.
+  if (max_table_elems > elem_size_.size()) {
+    Rebuild(std::max(max_table_elems, 2 * elem_size_.size()));
+  }
+  return true;
+}
+
+void HPackEncoderTable::EvictOne() {
+  tail_remote_index_++;
+  GPR_ASSERT(tail_remote_index_ > 0);
+  GPR_ASSERT(table_elems_ > 0);
+  auto removing_size = elem_size_[tail_remote_index_ % elem_size_.size()];
+  GPR_ASSERT(table_size_ >= removing_size);
+  table_size_ -= removing_size;
+  table_elems_--;
+}
+
+void HPackEncoderTable::Rebuild(uint32_t capacity) {
+  decltype(elem_size_) new_elem_size(capacity);
+  GPR_ASSERT(table_elems_ <= capacity);
+  for (uint32_t i = 0; i < table_elems_; i++) {
+    uint32_t ofs = tail_remote_index_ + i + 1;
+    new_elem_size[ofs % capacity] = elem_size_[ofs % elem_size_.size()];
+  }
+  elem_size_.swap(new_elem_size);
+}
+
+}  // namespace grpc_core