Always compile with -pthread.

[cubemap] / stream.h

#ifndef _STREAM_H
#define _STREAM_H 1

// Representation of a single, muxed (we only really care about bytes/blocks) stream.
// Fed by Input, sent out by Server (to Client).

#include <stddef.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <deque>
#include <memory>
#include <mutex>
#include <string>
#include <vector>

#include "metacube2.h"

class StreamProto;
struct Client;

// metacube2_pts_packet except the type and byteswapping.
struct RationalPTS {
        int64_t pts = 0;
        uint64_t timebase_num = 0, timebase_den = 0;  // 0/0 for unknown PTS.
};

struct Stream {
        // Must be in sync with StreamConfig::Encoding.
        enum Encoding { STREAM_ENCODING_RAW = 0, STREAM_ENCODING_METACUBE };

        Stream(const std::string &url,
               size_t backlog_size,
               uint64_t prebuffering_bytes,
               Encoding encoding,
               Encoding src_encoding,
               unsigned hls_frag_duration,
               size_t hls_backlog_margin,
               const std::string &allow_origin);
        ~Stream();

        // Serialization/deserialization.
        Stream(const StreamProto &serialized, int data_fd);
        StreamProto serialize();

        // Changes the backlog size, restructuring the data as needed.
        void set_backlog_size(size_t new_size);

        // You should hold the owning Server's <mutex>, since it calls add_data_raw().
        // Sets unavailable to false.
        void set_header(const std::string &new_http_header, const std::string &new_stream_header);

        void set_unavailable() {
                unavailable = true;
        }

        // Mutex protecting <queued_data> and <queued_data_last_starting_point>.
        // Note that if you want to hold both this and the owning server's
        // <mutex> you will need to take <mutex> before this one.
        mutable std::mutex queued_data_mutex;

        std::string url;

        // If true, the backend is not completely connected, and thus, we cannot serve
        // clients (except for historic HLS fragments).
        bool unavailable = true;

        // The HTTP response header, without the trailing double newline.
        std::string http_header;

        // The video stream header (if any).
        std::string stream_header;

        // What encoding we apply to the outgoing data (usually raw, but can also
        // be Metacube, for reflecting to another Cubemap instance).
        Encoding encoding;

        // What encoding we expect the incoming data to be in (usually Metacube).
        Encoding src_encoding;

        // Contents of CORS header (Access-Control-Allow-Origin), if any.
        std::string allow_origin;

        // The stream data itself, stored in a circular buffer.
        //
        // We store our data in a file, so that we can send the data to the
        // kernel only once (with write()). We then use sendfile() for each
        // client, which effectively zero-copies it out of the kernel's buffer
        // cache. This is significantly more efficient than doing write() from
        // a userspace memory buffer, since the latter makes the kernel copy
        // the same data from userspace many times.
        int data_fd;

        // How many bytes <data_fd> can hold (the buffer size).
        size_t backlog_size;

        // How many bytes we need to have in the backlog before we start
        // sending (in practice, we will then send all of them at once,
        // and then start sending at the normal rate thereafter).
        // This is basically to force a buffer on the client, which can help
        // if the client expects us to be able to fill up the buffer much
        // faster than realtime (ie., it expects a static file).
        uint64_t prebuffering_bytes;

        // How many bytes this stream have received. Can very well be larger
        // than <backlog_size>, since the buffer wraps.
        uint64_t bytes_received = 0;

        // A list of points in the stream that is suitable to start new clients at
        // (after having sent the header). Empty if no such point exists yet.
        std::deque<uint64_t> suitable_starting_points;

        // A list of HLS fragment boundaries currently in the backlog; the first fragment
        // is between point 0 and 1, the second is between 1 and 2, and so on.
        // This roughly mirrors suitable_starting_points, but we generally make much
        // larger fragments (we try to get as close as possible without exceeding
        // <hls_frag_duration> seconds by too much).
        //
        // We keep this list even if we don't have HLS, given that we have pts data
        // from the input stream.
        //
        // NOTE: The last fragment is an in-progress fragment, which can still be
        // extended and thus should not be output. So the last fragment output is
        // from points N-3..N-2.
        struct FragmentStart {
                uint64_t byte_position;
                double pts;  // Unused if begins_header is true.

                // Whether the fragment started at this position is a stream header or not.
                // Note that headers are stored _after_ the fragments they are headers for,
                // so that they rotate out of the backlog last (and also because they are
                // conveniently written then). The most current header is _not_ stored
                // in the backlog; it is stored in stream_header. Only when replaced
                // is it committed to the backlog and gets an entry here.
                bool begins_header;
        };
        std::deque<FragmentStart> fragments;
        uint64_t first_fragment_index = 0, discontinuity_counter = 0;

        // HLS target duration, in seconds.
        unsigned hls_frag_duration = 6;

        // Don't advertise new HLS fragments beginning before this point after the
        // start of the backlog, so that we're reasonably sure that we can actually
        // serve them even if the client can't completely keep up.
        size_t hls_backlog_margin = 0;

        // HLS playlists for this stream, in the form of a HTTP response, with
        // headers and all. These are created on-demand, re-used by clients as
        // needed, and cleared when they are no longer valid (e.g., when new fragments
        // are added).
        std::shared_ptr<const std::string> hls_playlist_http10;
        std::shared_ptr<const std::string> hls_playlist_http11_close;
        std::shared_ptr<const std::string> hls_playlist_http11_persistent;

        // Clients that are in SENDING_DATA, but that we don't listen on,
        // because we currently don't have any data for them.
        // See put_client_to_sleep() and wake_up_all_clients().
        std::vector<Client *> sleeping_clients;

        // Clients that we recently got data for (when they were in
        // <sleeping_clients>).
        std::vector<Client *> to_process;

        // Maximum pacing rate for the stream.
        uint32_t pacing_rate = ~0U;

        // Queued data, if any. Protected by <queued_data_mutex>.
        // The data pointers in the iovec are owned by us.
        struct DataElement {
                iovec data;
                uint16_t metacube_flags;
                RationalPTS pts;
        };
        std::vector<DataElement> queued_data;

        // Put client to sleep, since there is no more data for it; we will on
        // longer listen on POLLOUT until we get more data. Also, it will be put
        // in the list of clients to wake up when we do.
        void put_client_to_sleep(Client *client);

        // Add more data to <queued_data>, adding Metacube headers if needed.
        // Does not take ownership of <data>.
        void add_data_deferred(const char *data, size_t bytes, uint16_t metacube_flags, const RationalPTS &pts);

        // Add queued data to the stream, if any.
        // You should hold the owning Server's <mutex>.
        void process_queued_data();

        // Generate a HLS playlist based on the current state, including HTTP headers.
        std::shared_ptr<const std::string> generate_hls_playlist(bool http_11, bool close_after_response);

        void clear_hls_playlist_cache();

private:
        Stream(const Stream& other);

        // Adds data directly to the stream file descriptor, without adding headers or
        // going through <queued_data>.
        // You should hold the owning Server's <mutex>, and probably call
        // remove_obsolete_starting_points() afterwards.
        void add_data_raw(const std::vector<DataElement> &data);

        // Remove points from <suitable_starting_points> that are no longer
        // in the backlog.
        // You should hold the owning Server's <mutex>.
        void remove_obsolete_starting_points();

        // Extend the in-progress fragment to the given position, or finish it and start
        // a new one if that would make it too long. Returns true if a new fragment
        // was created (ie., the HLS playlists need to be regenerated).
        bool add_fragment_boundary(size_t byte_position, const RationalPTS &pts);
};

#endif  // !defined(_STREAM_H)