mirror of
https://fuchsia.googlesource.com/third_party/pigweed.googlesource.com/pigweed/pigweed
synced 2024-09-20 13:51:05 +00:00
f298de4260
Bug: 350 Change-Id: Ia395cebedba24c9463e558059ebdb516759253e2 Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/38740 Commit-Queue: Wyatt Hepler <hepler@google.com> Reviewed-by: Keir Mierle <keir@google.com>
50 lines
1.8 KiB
C++
50 lines
1.8 KiB
C++
// Copyright 2021 The Pigweed 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
|
|
//
|
|
// https://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 "pw_multisink/drain.h"
|
|
|
|
namespace pw {
|
|
namespace multisink {
|
|
|
|
Result<ConstByteSpan> Drain::GetEntry(ByteSpan entry,
|
|
uint32_t& drop_count_out) {
|
|
uint32_t entry_sequence_id = 0;
|
|
drop_count_out = 0;
|
|
const Result<ConstByteSpan> result =
|
|
MultiSink::GetEntry(*this, entry, entry_sequence_id);
|
|
|
|
// Exit immediately if the result isn't OK or OUT_OF_RANGE, as the
|
|
// entry_sequence_id cannot be used for computation. Later invocations to
|
|
// GetEntry will permit readers to determine how far the sequence ID moved
|
|
// forward.
|
|
if (!result.ok() && !result.status().IsOutOfRange()) {
|
|
return result;
|
|
}
|
|
|
|
// Compute the drop count delta by comparing this entry's sequence ID with the
|
|
// last sequence ID this drain successfully read.
|
|
//
|
|
// The drop count calculation simply computes the difference between the
|
|
// current and last sequence IDs. Consecutive successful reads will always
|
|
// differ by one at least, so it is subtracted out. If the read was not
|
|
// successful, the difference is not adjusted.
|
|
drop_count_out =
|
|
entry_sequence_id - last_handled_sequence_id_ - (result.ok() ? 1 : 0);
|
|
|
|
last_handled_sequence_id_ = entry_sequence_id;
|
|
return result;
|
|
}
|
|
|
|
} // namespace multisink
|
|
} // namespace pw
|