blob: 6e17b24d5778ce7f13ec0dd2fee9d3cf8993ac85 [file] [log] [blame]
// Copyright (c) 2019 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 "quic/core/qpack/qpack_required_insert_count.h"
#include <limits>
#include "quic/platform/api/quic_logging.h"
namespace quic {
uint64_t QpackEncodeRequiredInsertCount(uint64_t required_insert_count,
uint64_t max_entries) {
if (required_insert_count == 0) {
return 0;
}
return required_insert_count % (2 * max_entries) + 1;
}
bool QpackDecodeRequiredInsertCount(uint64_t encoded_required_insert_count,
uint64_t max_entries,
uint64_t total_number_of_inserts,
uint64_t* required_insert_count) {
if (encoded_required_insert_count == 0) {
*required_insert_count = 0;
return true;
}
// |max_entries| is calculated by dividing an unsigned 64-bit integer by 32,
// precluding all calculations in this method from overflowing.
QUICHE_DCHECK_LE(max_entries, std::numeric_limits<uint64_t>::max() / 32);
if (encoded_required_insert_count > 2 * max_entries) {
return false;
}
*required_insert_count = encoded_required_insert_count - 1;
QUICHE_DCHECK_LT(*required_insert_count,
std::numeric_limits<uint64_t>::max() / 16);
uint64_t current_wrapped = total_number_of_inserts % (2 * max_entries);
QUICHE_DCHECK_LT(current_wrapped, std::numeric_limits<uint64_t>::max() / 16);
if (current_wrapped >= *required_insert_count + max_entries) {
// Required Insert Count wrapped around 1 extra time.
*required_insert_count += 2 * max_entries;
} else if (current_wrapped + max_entries < *required_insert_count) {
// Decoder wrapped around 1 extra time.
current_wrapped += 2 * max_entries;
}
if (*required_insert_count >
std::numeric_limits<uint64_t>::max() - total_number_of_inserts) {
return false;
}
*required_insert_count += total_number_of_inserts;
// Prevent underflow, also disallow invalid value 0 for Required Insert Count.
if (current_wrapped >= *required_insert_count) {
return false;
}
*required_insert_count -= current_wrapped;
return true;
}
} // namespace quic