blob: b5909576142c97e9a33c715086ca004b632988c9 [file] [log] [blame]
// 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/multisink.h"
#include <cstring>
#include "pw_assert/check.h"
#include "pw_status/try.h"
#include "pw_varint/varint.h"
namespace pw {
namespace multisink {
void MultiSink::HandleEntry(ConstByteSpan entry) {
std::lock_guard lock(lock_);
PW_DCHECK_OK(ring_buffer_.PushBack(entry, sequence_id_++));
NotifyListeners();
}
void MultiSink::HandleDropped(uint32_t drop_count) {
std::lock_guard lock(lock_);
sequence_id_ += drop_count;
NotifyListeners();
}
Result<ConstByteSpan> MultiSink::GetEntry(Drain& drain,
ByteSpan buffer,
uint32_t& drop_count_out) {
size_t bytes_read = 0;
uint32_t entry_sequence_id = 0;
drop_count_out = 0;
std::lock_guard lock(lock_);
PW_DCHECK_PTR_EQ(drain.multisink_, this);
const Status peek_status = drain.reader_.PeekFrontWithPreamble(
buffer, entry_sequence_id, bytes_read);
if (peek_status.IsOutOfRange()) {
// If the drain has caught up, report the last handled sequence ID so that
// it can still process any dropped entries.
entry_sequence_id = sequence_id_ - 1;
} else if (!peek_status.ok()) {
// Exit immediately if the result isn't OK or OUT_OF_RANGE, as the
// entry_entry_sequence_id cannot be used for computation. Later invocations
// to GetEntry will permit readers to determine how far the sequence ID
// moved forward.
return peek_status;
}
// 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 - drain.last_handled_sequence_id_ -
(peek_status.ok() ? 1 : 0);
drain.last_handled_sequence_id_ = entry_sequence_id;
// The Peek above may have failed due to OutOfRange, now that we've set the
// drop count see if we should return before attempting to pop.
if (peek_status.IsOutOfRange()) {
return peek_status;
}
// Success, pop the oldest entry!
PW_CHECK(drain.reader_.PopFront().ok());
return std::as_bytes(buffer.first(bytes_read));
}
void MultiSink::AttachDrain(Drain& drain) {
std::lock_guard lock(lock_);
PW_DCHECK_PTR_EQ(drain.multisink_, nullptr);
drain.multisink_ = this;
drain.last_handled_sequence_id_ = sequence_id_ - 1;
PW_CHECK_OK(ring_buffer_.AttachReader(drain.reader_));
}
void MultiSink::DetachDrain(Drain& drain) {
std::lock_guard lock(lock_);
PW_DCHECK_PTR_EQ(drain.multisink_, this);
drain.multisink_ = nullptr;
PW_CHECK_OK(ring_buffer_.DetachReader(drain.reader_),
"The drain wasn't already attached.");
}
void MultiSink::AttachListener(Listener& listener) {
std::lock_guard lock(lock_);
listeners_.push_back(listener);
}
void MultiSink::DetachListener(Listener& listener) {
std::lock_guard lock(lock_);
[[maybe_unused]] bool was_detached = listeners_.remove(listener);
PW_DCHECK(was_detached, "The listener was already attached.");
}
void MultiSink::Clear() {
std::lock_guard lock(lock_);
ring_buffer_.Clear();
}
void MultiSink::NotifyListeners() {
for (auto& listener : listeners_) {
listener.OnNewEntryAvailable();
}
}
Result<ConstByteSpan> MultiSink::Drain::GetEntry(ByteSpan buffer,
uint32_t& drop_count_out) {
PW_DCHECK_NOTNULL(multisink_);
return multisink_->GetEntry(*this, buffer, drop_count_out);
}
} // namespace multisink
} // namespace pw