InputDataSerializer.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#ifndef META_OCEAN_IO_SERIALIZATION_INPUT_DATA_SERIALIZER_H
#define META_OCEAN_IO_SERIALIZATION_INPUT_DATA_SERIALIZER_H
 
#include "ocean/io/serialization/Serialization.h"
#include "ocean/io/serialization/DataSerializer.h"
 
#include <functional>
 
namespace Ocean
{
 
namespace IO
{
 
namespace Serialization
{
 
/**
 * This class implements an input data serializer.
 * The input data serializer deserializes data samples from a stream (e.g., file or network).
 * @ingroup ioserialization
 */
class InputDataSerializer : public DataSerializer
{
    public:
 
        /// Definition of a factory function which creates a data sample based on a sample type.
        using FactoryFunction = std::function<UniqueDataSample(const std::string& sampleType)>;
 
        /**
         * Definition of a callback function which is invoked whenever a new channel is parsed.
         * @param channel The channel information
         */
        using ChannelEventFunction = std::function<void(const Channel& channel)>;
 
    protected:
 
        /**
         * This class implements an abstract stream for input data serializers.
         */
        class Stream
        {
            public:
 
                /**
                 * Destructs the stream.
                 */
                virtual ~Stream() = default;
 
                /**
                 * Returns the input bitstream.
                 * @return The input bitstream
                 */
                virtual InputBitstream& inputBitstream() = 0;
 
                /**
                 * Returns whether this stream is valid.
                 * @return True, if so
                 */
                virtual bool isValid() const = 0;
        };
 
        /// Definition of a unique pointer holding a stream.
        using UniqueStream = std::unique_ptr<Stream>;
 
        /// Definition of a map mapping sample types to factory functions.
        using FactoryFunctionMap = std::unordered_map<std::string, FactoryFunction>;
 
        /**
         * This class implements an extended channel with factory function.
         */
        class ExtendedChannel : public Channel
        {
            public:
 
                /**
                 * Creates a new invalid extended channel.
                 */
                ExtendedChannel() = default;
 
                /**
                 * Creates a new extended channel with given channel and factory function.
                 * @param channel The channel
                 * @param factoryFunction The factory function
                 */
                inline ExtendedChannel(const Channel& channel, const FactoryFunction& factoryFunction);
 
            public:
 
                /// The factory function for creating data samples.
                FactoryFunction factoryFunction_;
        };
 
        /// Definition of a map mapping channel ids to extended channels.
        using ExtendedChannelMap = std::unordered_map<ChannelId, ExtendedChannel>;
 
        /**
         * Comparator for SamplePair that orders by playback timestamp (min-heap).
         * Samples with smaller playback timestamps have higher priority.
         */
        struct SamplePairComparator
        {
            /**
             * Compares two sample pairs by their playback timestamps.
             * @param sampleA The first sample pair
             * @param sampleB The second sample pair
             * @return True if 'sampleA' should come after 'sampleB' (i.e., 'sampleA' has a larger timestamp)
             */
            inline bool operator()(const SamplePair& sampleA, const SamplePair& sampleB) const;
        };
 
        /**
         * A priority queue that allows moving elements out.
         * This extends std::priority_queue to provide access to the underlying container
         * for proper move semantics when popping elements.
         */
        class SampleQueue : public std::priority_queue<SamplePair, std::vector<SamplePair>, SamplePairComparator>
        {
            public:
 
                /**
                 * Pops the top element from the queue.
                 * @return The top element, moved out of the queue
                 */
                inline SamplePair popTop();
        };
 
    public:
 
        /**
         * Initializes the input data serializer.
         * The serializer will create the input stream and read the header.
         * Optionally, the serializer can pre-parse all channels before returning.
         * @param preparsedChannels Optional output parameter to receive all channels that were pre-parsed, nullptr if not of interest
         * @param isStreamCorrupted Optional output parameter to receive whether the stream is corrupted (missing end-of-stream indication), nullptr if not of interest
         * @return True, if succeeded
         */
        bool initialize(Channels* preparsedChannels = nullptr, bool* isStreamCorrupted = nullptr);
 
        /**
         * Starts the serializer.
         * @return True, if succeeded
         * @see DataSerializer::start().
         */
        bool start() override;
 
        /**
         * Stops the serializer.
         * This function sets a stopping flag and returns immediately; it does not wait for the serializer to actually stop.
         * The background thread will check the stopping flag at the beginning of each iteration and terminate.
         * @return True, if the stop request was accepted; False, if the serializer was not started
         * @see DataSerializer::stop(), stopAndWait(), hasStopped().
         */
        bool stop() override;
 
        /**
         * Returns whether the serializer has been started.
         * @return True, if so
         * @see DataSerializer::isStarted().
         */
        [[nodiscard]] bool isStarted() const override;
 
        /**
         * Returns whether the serializer has stopped and all remaining samples have been retrieved.
         * @return True, if so
         * @see DataSerializer::hasFinished().
         */
        [[nodiscard]] bool hasFinished() const override;
 
        /**
         * Registers a factory function for a given sample type.
         * The factory function will be used to create data samples when reading from the stream.
         * @param sampleType The sample type for which the factory function will be registered, must be non-empty
         * @param factoryFunction The factory function to register, must be valid
         * @return True, if succeeded
         */
        bool registerFactoryFunction(const std::string& sampleType, const FactoryFunction& factoryFunction);
 
        /**
         * Registers a factory function for a sample type T.
         * The sample type T must provide static functions `sampleType()` and `createSample()`.
         * This is a convenience function that calls `registerFactoryFunction(T::sampleType(), T::createSample)`.
         * @tparam T The sample type which must provide `static const std::string& sampleType()` and `static UniqueDataSample createSample(const std::string&)`
         * @return True, if succeeded
         */
        template <typename T>
        bool registerSample();
 
        /**
         * Registers a callback function that will be invoked whenever a new channel is parsed.
         * @param channelEventFunction The callback function to be invoked, must be valid
         * @return True if the callback was successfully registered, false otherwise
         */
        bool registerChannelEventFunction(const ChannelEventFunction& channelEventFunction);
 
        /**
         * Returns the next sample from the stream.
         * The sample will be removed from the internal queue and returned to the caller.
         * @param channelId The resulting channel id of the sample
         * @param speed The playback speed, with range (0, infinity), 0 to return samples as fast as possible, 1 for real-time playback
         * @return The sample, nullptr if no sample is available yet or if the stream has ended
         */
        [[nodiscard]] UniqueDataSample sample(ChannelId& channelId, const double speed = 1.0);
 
        /**
         * Returns the channel information for a given channel.
         * @param channelId The channel id to query
         * @return The channel information, an invalid channel if the channel doesn't exist
         */
        [[nodiscard]] ChannelConfiguration channelConfiguration(const ChannelId channelId) const;
 
        /**
         * Returns all channels that have been parsed so far.
         * @return The channels
         */
        [[nodiscard]] Channels channels() const;
 
    protected:
 
        /**
         * Creates the input stream.
         * @return The input stream, nullptr if the stream could not be created
         */
        virtual UniqueStream createStream() const = 0;
 
        /**
         * Reads the header from the input bitstream.
         * @param inputBitstream The input bitstream from which the header will be read
         * @return True, if succeeded
         */
        virtual bool readHeader(InputBitstream& inputBitstream);
 
        /**
         * The thread run function.
         * @see Thread::threadRun().
         */
        void threadRun() override;
 
    protected:
 
        /// The input stream.
        UniqueStream stream_;
 
        /// The map mapping sample types to factory functions.
        FactoryFunctionMap factoryFunctionMap_;
 
        /// The map mapping channel ids to extended channels (with factory function).
        ExtendedChannelMap extendedChannelMap_;
 
        /// The callback function which is invoked whenever a new channel is parsed.
        ChannelEventFunction channelEventFunction_;
 
        /// The priority queue holding samples which are pending to be retrieved, ordered by playback timestamp (smallest first).
        SampleQueue sampleQueue_;
 
        /// The maximum number of pending samples in the queue.
        static constexpr size_t maxPendingSampleQueueSize_ = 100;
};
 
/**
 * This class implements a file-based input data serializer.
 * @ingroup ioserialization
 */
class FileInputDataSerializer : public InputDataSerializer
{
    protected:
 
        /**
         * This class implements a file stream for file input data serializers.
         */
        class FileStream : public Stream
        {
            public:
 
                /**
                 * Creates a new file stream with given filename.
                 * @param filename The filename of the file to read, must be valid
                 */
                inline explicit FileStream(const std::string& filename);
 
                /**
                 * Destructs the file stream.
                 */
                inline ~FileStream() override;
 
                /**
                 * Returns the input bitstream.
                 * @return The input bitstream
                 * @see Stream::inputBitstream().
                 */
                inline InputBitstream& inputBitstream() override;
 
                /**
                 * Returns whether this stream is valid.
                 * @return True, if so
                 * @see Stream::isValid().
                 */
                inline bool isValid() const override;
 
            protected:
 
                /// The file stream.
                std::ifstream stream_;
 
                /// The input bitstream.
                InputBitstream inputBitstream_;
        };
 
    public:
 
        /**
         * Sets the filename of the file to read.
         * @param filename The filename of the file to read, must be non-empty
         * @return True, if succeeded
         */
        virtual bool setFilename(const std::string& filename);
 
    protected:
 
        /**
         * Creates the input stream.
         * @return The input stream, nullptr if the stream could not be created
         * @see InputDataSerializer::createStream().
         */
        UniqueStream createStream() const override;
 
    protected:
 
        /// The filename of the file to read.
        std::string filename_;
};
 
inline InputDataSerializer::ExtendedChannel::ExtendedChannel(const Channel& channel, const FactoryFunction& factoryFunction) :
    Channel(channel),
    factoryFunction_(factoryFunction)
{
    // nothing to do here
}
 
inline bool InputDataSerializer::SamplePairComparator::operator()(const SamplePair& sampleA, const SamplePair& sampleB) const
{
    return sampleA.second->playbackTimestamp() > sampleB.second->playbackTimestamp();
}
 
inline InputDataSerializer::SamplePair InputDataSerializer::SampleQueue::popTop()
{
    ocean_assert(!empty());
 
    std::pop_heap(c.begin(), c.end(), comp);
 
    SamplePair result = std::move(c.back());
    c.pop_back();
 
    return result;
}
 
inline FileInputDataSerializer::FileStream::FileStream(const std::string& filename) :
    stream_(filename.c_str(), std::ios::binary),
    inputBitstream_(stream_)
 
{
    // nothing to do here
}
 
inline FileInputDataSerializer::FileStream::~FileStream()
{
    stream_.close();
}
 
inline InputBitstream& FileInputDataSerializer::FileStream::inputBitstream()
{
    return inputBitstream_;
}
 
inline bool FileInputDataSerializer::FileStream::isValid() const
{
    return stream_.is_open() && !stream_.fail();
}
 
template <typename T>
bool InputDataSerializer::registerSample()
{
    return registerFactoryFunction(T::sampleType(), T::createSample);
}
 
}
 
}
 
}
 
#endif // META_OCEAN_IO_SERIALIZATION_INPUT_DATA_SERIALIZER_H