89 lines
3.9 KiB
C++
89 lines
3.9 KiB
C++
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <bitset>
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#include <list>
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#include <queue>
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#include "LogBuffer.h"
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#include "LogdLock.h"
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#include "SerializedLogChunk.h"
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#include "SerializedLogEntry.h"
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struct LogPosition {
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std::list<SerializedLogChunk>::iterator buffer_it;
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int read_offset;
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const SerializedLogEntry* log_entry() const { return buffer_it->log_entry(read_offset); }
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};
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struct LogWithId {
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log_id_t log_id;
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const SerializedLogEntry* entry;
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};
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// This class tracks the specific point where a FlushTo client has read through the logs. It
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// directly references the std::list<> iterators from the parent SerializedLogBuffer and the offset
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// into each log chunk where it has last read. All interactions with this class, except for its
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// construction, must be done with SerializedLogBuffer::lock_ held.
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class SerializedFlushToState : public FlushToState {
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public:
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// Initializes this state object. For each log buffer set in log_mask, this sets
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// logs_needed_from_next_position_.
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SerializedFlushToState(uint64_t start, LogMask log_mask, std::list<SerializedLogChunk>* logs)
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REQUIRES(logd_lock);
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// Decrease the reference of all referenced logs. This happens when a reader is disconnected.
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~SerializedFlushToState() override;
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// Updates the state of log_positions_ and logs_needed_from_next_position_ then returns true if
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// there are any unread logs, false otherwise.
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bool HasUnreadLogs() REQUIRES(logd_lock);
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// Returns the next unread log and sets logs_needed_from_next_position_ to indicate that we're
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// waiting for more logs from the associated log buffer.
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LogWithId PopNextUnreadLog() REQUIRES(logd_lock);
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// If the parent log buffer prunes logs, the reference that this class contains may become
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// invalid, so this must be called first to drop the reference to buffer_it, if any.
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void Prune(log_id_t log_id) REQUIRES(logd_lock);
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private:
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// Set logs_needed_from_next_position_[i] to indicate if log_positions_[i] points to an unread
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// log or to the point at which the next log will appear.
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void UpdateLogsNeeded(log_id_t log_id) REQUIRES(logd_lock);
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// Create a LogPosition object for the given log_id by searching through the log chunks for the
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// first chunk and then first log entry within that chunk that is greater or equal to start().
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void CreateLogPosition(log_id_t log_id) REQUIRES(logd_lock);
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// Checks to see if any log buffers set in logs_needed_from_next_position_ have new logs and
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// calls UpdateLogsNeeded() if so.
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void CheckForNewLogs() REQUIRES(logd_lock);
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std::list<SerializedLogChunk>* logs_ GUARDED_BY(logd_lock) = nullptr;
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// An optional structure that contains an iterator to the serialized log buffer and offset into
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// it that this logger should handle next.
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std::optional<LogPosition> log_positions_[LOG_ID_MAX] GUARDED_BY(logd_lock);
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// A bit for each log that is set if a given log_id has no logs or if this client has read all
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// of its logs. In order words: `logs_[i].empty() || (buffer_it == std::prev(logs_.end) &&
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// next_log_position == logs_write_position_)`. These will be re-checked in each
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// loop in case new logs came in.
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std::bitset<LOG_ID_MAX> logs_needed_from_next_position_ GUARDED_BY(logd_lock) = {};
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};
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