DataSerializer.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_DATA_SERIALIZER_H
#define META_OCEAN_IO_SERIALIZATION_DATA_SERIALIZER_H
 
#include "ocean/io/serialization/Serialization.h"
 
#include "ocean/base/Timestamp.h"
#include "ocean/base/Thread.h"
 
#include "ocean/io/Bitstream.h"
#include "ocean/io/serialization/DataTimestamp.h"
#include "ocean/io/serialization/DataSample.h"
 
namespace Ocean
{
 
namespace IO
{
 
namespace Serialization
{
 
/**
 * This class implements the base class for data serializers.
 * Data serializers are used to serialize and deserialize data samples across multiple channels.<br>
 * Each channel can have a different sample type, name, and content type, allowing heterogeneous data to be organized and streamed together.<br>
 * The class provides a thread-based architecture where the actual serialization/deserialization happens asynchronously in a background thread.<br>
 * Derived classes (InputDataSerializer and OutputDataSerializer) implement the specific read or write functionality.
 * @ingroup ioserialization
 */
class OCEAN_IO_SERIALIZATION_EXPORT DataSerializer : protected Thread
{
    public:
 
        /// Definition of a channel id.
        using ChannelId = uint32_t;
 
        /**
         * Returns an invalid channel id.
         * @return The invalid channel id
         */
        static constexpr ChannelId invalidChannelId();
 
        /**
         * This class holds channel configuration (sample type, name, and content type).
         * A channel configuration uniquely identifies the type and purpose of a data channel without including the runtime channel id.<br>
         * The sample type describes the class type of data samples (e.g., "DataSampleFrame"), the name provides a user-friendly identifier (e.g., "camera_left"), and the content type describes the semantic meaning of the data (e.g., "RGB_FRAME").
         */
        class ChannelConfiguration
        {
            public:
 
                /**
                 * Definition of a hash function for ChannelConfiguration objects.
                 */
                struct Hash
                {
                    /**
                     * Calculates the hash value for a given channel configuration.
                     * @param channelConfiguration The channel configuration for which the hash will be calculated
                     * @return The hash value
                     */
                    inline size_t operator()(const ChannelConfiguration& channelConfiguration) const;
                };
 
            public:
 
                /**
                 * Creates a new invalid channel configuration.
                 */
                ChannelConfiguration() = default;
 
                /**
                 * Creates a new channel configuration with given sample type, name, and content type.
                 * @param sampleType The sample type
                 * @param name The name of the channel
                 * @param contentType The content type
                 */
                inline ChannelConfiguration(const std::string& sampleType, const std::string& name, const std::string& contentType);
 
                /**
                 * Returns the sample type.
                 * @return The sample type
                 */
                inline const std::string& sampleType() const;
 
                /**
                 * Returns the name of the channel.
                 * @return The channel name
                 */
                inline const std::string& name() const;
 
                /**
                 * Returns the content type.
                 * @return The content type
                 */
                inline const std::string& contentType() const;
 
                /**
                 * Returns whether this channel configuration is valid.
                 * @return True, if all fields (sample type, name, and content type) are non-empty
                 */
                inline bool isValid() const;
 
                /**
                 * Returns whether two channel configurations are equal.
                 * @param channelConfiguration The second channel configuration to compare
                 * @return True, if both configurations are equal
                 */
                inline bool operator==(const ChannelConfiguration& channelConfiguration) const;
 
            protected:
 
                /// The sample type.
                std::string sampleType_;
 
                /// The name of the channel.
                std::string name_;
 
                /// The content type.
                std::string contentType_;
        };
 
        /**
         * This class implements a channel with configuration and channel id.
         * A channel extends ChannelConfiguration by adding a unique channel id that is assigned at runtime during serialization.<br>
         * The channel id is used to efficiently identify and route data samples within the serialization stream.
         */
        class OCEAN_IO_SERIALIZATION_EXPORT Channel : public ChannelConfiguration
        {
            public:
 
                /**
                 * Definition of a hash function for Channel objects.
                 */
                struct Hash
                {
                    /**
                     * Calculates the hash value for a given channel.
                     * @param channel The channel for which the hash will be calculated
                     * @return The hash value
                     */
                    inline size_t operator()(const Channel& channel) const;
                };
 
            public:
 
                /**
                 * Creates a new invalid channel.
                 */
                Channel() = default;
 
                /**
                 * Creates a new channel with given configuration and channel id.
                 * @param channelConfiguration The channel configuration
                 * @param channelId The channel id
                 */
                inline Channel(const ChannelConfiguration& channelConfiguration, const ChannelId channelId);
 
                /**
                 * Returns the channel id.
                 * @return The channel id
                 */
                inline ChannelId channelId() const;
 
                /**
                 * Returns whether this channel is valid.
                 * @return True, if the channel id is valid and the configuration is valid
                 */
                inline bool isValid() const;
 
                /**
                 * Returns whether two channels are equal.
                 * @param channel The second channel to compare
                 * @return True, if both channels are equal
                 */
                inline bool operator==(const Channel& channel) const;
 
            protected:
 
                /// The channel id.
                ChannelId channelId_ = invalidChannelId();
        };
 
        /// Definition of a vector holding channels.
        using Channels = std::vector<Channel>;
 
    protected:
 
        /**
         * Definition of individual states the serializer can have.
         */
        enum State
        {
            /// The serializer has not yet been initialized or started.
            S_IDLE,
            /// The serializer has been initialized and is ready to start.
            S_INITIALIZED,
            /// The serializer has been started and is currently actively processing data samples.
            S_STARTED,
            /// The serializer is currently stopping but may still process remaining data samples.
            S_STOPPING,
            /// The serializer has been stopped and all active processing of data samples has finished. However, there may still be samples left which could be requested by the user.
            S_STOPPED
        };
 
        /// Definition of a map mapping channel configurations to channel ids.
        using ChannelConfigurationMap = std::unordered_map<ChannelConfiguration, ChannelId, ChannelConfiguration::Hash>;
 
        /// Definition of a pair holding a channel id and a unique data sample.
        using SamplePair = std::pair<ChannelId, UniqueDataSample>;
 
        /**
         * This class implements a data sample holding channel configuration information.
         * This internal class is used to serialize channel configuration as a special sample type, allowing the configuration to be embedded in the data stream alongside regular samples.<br>
         * When a new channel is encountered during playback, the configuration sample is read first to establish the channel's metadata.
         */
        class DataSampleChannelConfiguration :
            public DataSample,
            public ChannelConfiguration
        {
            public:
 
                /**
                 * Creates a new invalid data sample channel configuration.
                 */
                DataSampleChannelConfiguration() = default;
 
                /**
                 * Creates a new data sample channel configuration from a data sample and channel configuration.
                 * @param sample The data sample
                 * @param channelConfiguration The channel configuration
                 */
                inline explicit DataSampleChannelConfiguration(const DataSample& sample, const ChannelConfiguration& channelConfiguration);
 
                /**
                 * Creates a new data sample channel configuration from a data timestamp and channel configuration.
                 * @param dataTimestamp The data timestamp
                 * @param channelConfiguration The channel configuration
                 * @param sampleCreationTimestamp The timestamp when the sample was created, this timestamp is not serialized and is only used to automatically determine the playback timestamp
                 */
                inline explicit DataSampleChannelConfiguration(const DataTimestamp& dataTimestamp, const ChannelConfiguration& channelConfiguration, const Timestamp sampleCreationTimestamp = Timestamp(true));
 
                /**
                 * Reads the sample from an input bitstream.
                 * @param inputBitstream The input bitstream from which the sample will be read
                 * @return True, if succeeded
                 */
                inline bool readSample(InputBitstream& inputBitstream) override;
 
                /**
                 * Writes the sample to an output bitstream.
                 * @param outputBitstream The output bitstream to which the sample will be written
                 * @return True, if succeeded
                 */
                inline bool writeSample(OutputBitstream& outputBitstream) const override;
 
                /**
                 * Returns the type of the sample.
                 * @return The sample type
                 */
                inline const std::string& type() const override;
        };
 
    public:
 
        /**
         * Destructs the data serializer.
         */
        virtual ~DataSerializer() = default;
 
        /**
         * Starts the serializer.
         * @return True, if succeeded
         */
        virtual bool start() = 0;
 
        /**
         * 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 and terminate asynchronously.
         * Use stopAndWait() to wait until the serializer has fully stopped, or poll hasStopped() to check if it has stopped.
         * @return True, if the stop request was accepted; False, if the serializer was not started
         * @see stopAndWait(), hasStopped().
         */
        virtual bool stop() = 0;
 
        /**
         * Stops the serializer and waits until the serializer has stopped.
         * @param timeout The timeout in seconds, with range (0, infinity)
         * @return True, if the serializer stopped within the given timeout
         */
        virtual bool stopAndWait(const double timeout = 60.0);
 
        /**
         * Returns whether the serializer has been started.
         * @return True, if so
         */
        [[nodiscard]] virtual bool isStarted() const = 0;
 
        /**
         * Returns whether the serializer has stopped but does not check wehther remaining samples have not yet been processed or retrieved.
         * @return True, if so
         */
        [[nodiscard]] virtual bool hasStopped() const;
 
        /**
         * Returns whether the serializer has stopped and all remaining samples have been processed or retrieved.
         * @return True, if so
         * @see DataSerializer::hasFinished().
         */
        [[nodiscard]] virtual bool hasFinished() const = 0;
 
    protected:
 
        /**
         * Returns whether the given channel value has the configuration bit set.
         * @param channelValue The channel value to check
         * @return True, if the channel value is a configuration channel id
         */
        [[nodiscard]] static constexpr bool isConfigurationChannelId(const uint32_t channelValue);
 
        /**
         * Creates a configuration channel id from a regular channel id by setting the highest bit.
         * @param channelId The channel id
         * @return The configuration channel id
         */
        [[nodiscard]] static constexpr uint32_t makeConfigurationChannelId(const ChannelId channelId);
 
        /**
         * Extracts the channel id from a channel value by clearing the configuration bit.
         * @param channelValue The channel value
         * @return The channel id
         */
        [[nodiscard]] static constexpr ChannelId extractChannelId(const uint32_t channelValue);
 
    protected:
 
        /// The timestamp when the serializer was started.
        Timestamp startTimestamp_;
 
        /// The current state of the serializer.
        State state_ = S_IDLE;
 
        /// True, if the serializer succeeded; False, if an error occurred.
        bool succeeded_ = true;
 
        /// The lock for thread-safe access.
        mutable Lock lock_;
};
 
constexpr DataSerializer::ChannelId DataSerializer::invalidChannelId()
{
    return ChannelId(-1);
}
 
inline size_t DataSerializer::ChannelConfiguration::Hash::operator()(const ChannelConfiguration& channelConfiguration) const
{
    size_t seed = std::hash<std::string>()(channelConfiguration.sampleType_);
    seed ^= std::hash<std::string>{}(channelConfiguration.name_) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
    seed ^= std::hash<std::string>{}(channelConfiguration.contentType_) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
    return seed;
}
 
inline DataSerializer::ChannelConfiguration::ChannelConfiguration(const std::string& sampleType, const std::string& name, const std::string& contentType) :
    sampleType_(sampleType),
    name_(name),
    contentType_(contentType)
{
    // nothing to do here
}
 
inline const std::string& DataSerializer::ChannelConfiguration::sampleType() const
{
    return sampleType_;
}
 
inline const std::string& DataSerializer::ChannelConfiguration::name() const
{
    return name_;
}
 
inline const std::string& DataSerializer::ChannelConfiguration::contentType() const
{
    return contentType_;
}
 
inline bool DataSerializer::ChannelConfiguration::isValid() const
{
    return !sampleType_.empty() && !name_.empty() && !contentType_.empty();
}
 
inline bool DataSerializer::ChannelConfiguration::operator==(const ChannelConfiguration& channelConfiguration) const
{
    return sampleType_ == channelConfiguration.sampleType_ && name_ == channelConfiguration.name_ && contentType_ == channelConfiguration.contentType_;
}
 
inline size_t DataSerializer::Channel::Hash::operator()(const Channel& channel) const
{
    size_t seed = std::hash<uint32_t>()(channel.channelId_);
    seed ^= ChannelConfiguration::Hash{}(channel) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 
    return seed;
}
 
inline DataSerializer::Channel::Channel(const ChannelConfiguration& channelConfiguration, const ChannelId channelId) :
    ChannelConfiguration(channelConfiguration),
    channelId_(channelId)
{
    // nothing to do here
}
 
inline DataSerializer::ChannelId DataSerializer::Channel::channelId() const
{
    return channelId_;
}
 
inline bool DataSerializer::Channel::isValid() const
{
    return channelId_ != invalidChannelId() && ChannelConfiguration::isValid();
}
 
inline bool DataSerializer::Channel::operator==(const Channel& channel) const
{
    return channelId_ == channel.channelId_ && ChannelConfiguration::operator==(channel);
}
 
constexpr bool DataSerializer::isConfigurationChannelId(const uint32_t channelValue)
{
    constexpr uint32_t highestBit = 1u << 31u;
 
    return channelValue & highestBit;
}
 
constexpr uint32_t DataSerializer::makeConfigurationChannelId(const ChannelId channelId)
{
    ocean_assert(channelId != invalidChannelId());
    ocean_assert(!isConfigurationChannelId(channelId));
 
    constexpr uint32_t highestBit = 1u << 31u;
 
    return channelId | highestBit;
}
 
constexpr DataSerializer::ChannelId DataSerializer::extractChannelId(const uint32_t channelValue)
{
    constexpr uint32_t highestBit = 1u << 31u;
 
    return ChannelId(channelValue & ~highestBit);
}
 
inline DataSerializer::DataSampleChannelConfiguration::DataSampleChannelConfiguration(const DataSample& sample, const ChannelConfiguration& channelConfiguration) :
    DataSample(sample),
    ChannelConfiguration(channelConfiguration)
{
    // nothing to do here
}
 
inline DataSerializer::DataSampleChannelConfiguration::DataSampleChannelConfiguration(const DataTimestamp& dataTimestamp, const ChannelConfiguration& channelConfiguration, const Timestamp sampleCreationTimestamp) :
    DataSample(dataTimestamp, sampleCreationTimestamp),
    ChannelConfiguration(channelConfiguration)
{
    // nothing to do here
}
 
inline bool DataSerializer::DataSampleChannelConfiguration::readSample(InputBitstream& inputBitstream)
{
    if (!DataSample::readSample(inputBitstream))
    {
        return false;
    }
 
    return inputBitstream.read<std::string>(sampleType_) && inputBitstream.read<std::string>(name_) && inputBitstream.read<std::string>(contentType_);
}
 
inline bool DataSerializer::DataSampleChannelConfiguration::writeSample(OutputBitstream& outputBitstream) const
{
    if (!DataSample::writeSample(outputBitstream))
    {
        return false;
    }
 
    return outputBitstream.write<std::string>(sampleType_) && outputBitstream.write<std::string>(name_) && outputBitstream.write<std::string>(contentType_);
}
 
inline const std::string& DataSerializer::DataSampleChannelConfiguration::type() const
{
    return sampleType_;
}
 
}
 
}
 
}
 
#endif // META_OCEAN_IO_SERIALIZATION_DATA_SERIALIZER_H