writer.h

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/*
 * Copyright (c) 2015 Roc Streaming authors
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
 
//! @file roc_fec/writer.h
//! @brief FEC writer.
 
#ifndef ROC_FEC_WRITER_H_
#define ROC_FEC_WRITER_H_
 
#include "roc_core/array.h"
#include "roc_core/iarena.h"
#include "roc_core/noncopyable.h"
#include "roc_core/slice.h"
#include "roc_fec/iblock_encoder.h"
#include "roc_packet/icomposer.h"
#include "roc_packet/iwriter.h"
#include "roc_packet/packet.h"
#include "roc_packet/packet_factory.h"
 
namespace roc {
namespace fec {
 
//! FEC writer parameters.
struct WriterConfig {
    //! Number of data packets in block.
    size_t n_source_packets;
 
    //! Number of FEC packets in block.
    size_t n_repair_packets;
 
    WriterConfig()
        : n_source_packets(18)
        , n_repair_packets(10) {
    }
};
 
//! FEC writer.
class Writer : public packet::IWriter, public core::NonCopyable<> {
public:
    //! Initialize.
    //!
    //! @b Parameters
    //!  - @p config contains FEC scheme parameters
    //!  - @p encoder is used to encode repair packets
    //!  - @p writer is used to write source and repair packets
    //!  - @p source_composer is used to format source packets
    //!  - @p repair_composer is used to format repair packets
    //!  - @p packet_factory is used to allocate repair packets
    //!  - @p buffer_factory is used to allocate buffers for repair packets
    //!  - @p arena is used to initialize a packet array
    Writer(const WriterConfig& config,
           packet::FecScheme fec_scheme,
           IBlockEncoder& encoder,
           packet::IWriter& writer,
           packet::IComposer& source_composer,
           packet::IComposer& repair_composer,
           packet::PacketFactory& packet_factory,
           core::IArena& arena);
 
    //! Check if object is successfully constructed.
    bool is_valid() const;
 
    //! Check if writer is still working.
    bool is_alive() const;
 
    //! Set number of source packets per block.
    bool resize(size_t sblen, size_t rblen);
 
    //! Write packet.
    //! @remarks
    //!  - writes the given source packet to the output writer
    //!  - generates repair packets and also writes them to the output writer
    virtual ROC_ATTR_NODISCARD status::StatusCode write(const packet::PacketPtr&);
 
private:
    bool begin_block_(const packet::PacketPtr& pp);
    void end_block_();
    void next_block_();
 
    bool apply_sizes_(size_t sblen, size_t rblen, size_t payload_size);
 
    status::StatusCode write_source_packet_(const packet::PacketPtr&);
    void make_repair_packets_();
    packet::PacketPtr make_repair_packet_(packet::seqnum_t n);
    void encode_repair_packets_();
    void compose_repair_packets_();
    status::StatusCode write_repair_packets_();
    void fill_packet_fec_fields_(const packet::PacketPtr& packet, packet::seqnum_t n);
 
    void validate_fec_packet_(const packet::PacketPtr&);
    bool validate_source_packet_(const packet::PacketPtr&);
 
    size_t cur_sblen_;
    size_t next_sblen_;
 
    size_t cur_rblen_;
    size_t next_rblen_;
 
    size_t cur_payload_size_;
 
    IBlockEncoder& encoder_;
    packet::IWriter& writer_;
 
    packet::IComposer& source_composer_;
    packet::IComposer& repair_composer_;
 
    packet::PacketFactory& packet_factory_;
 
    core::Array<packet::PacketPtr> repair_block_;
 
    bool first_packet_;
 
    packet::blknum_t cur_sbn_;
    packet::seqnum_t cur_block_repair_sn_;
 
    size_t cur_packet_;
 
    const packet::FecScheme fec_scheme_;
 
    bool valid_;
    bool alive_;
};
 
} // namespace fec
} // namespace roc
 
#endif // ROC_FEC_WRITER_H_