text: /*
   * ngtcp2
   *
   * Copyright (c) 2017 ngtcp2 contributors
   *
   * Permission is hereby granted, free of charge, to any person obtaining
   * a copy of this software and associated documentation files (the
   * "Software"), to deal in the Software without restriction, including
   * without limitation the rights to use, copy, modify, merge, publish,
   * distribute, sublicense, and/or sell copies of the Software, and to
   * permit persons to whom the Software is furnished to do so, subject to
   * the following conditions:
   *
   * The above copyright notice and this permission notice shall be
   * included in all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
   * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   */
  #ifndef NGTCP2_PKT_H
  #define NGTCP2_PKT_H
  
  #ifdef HAVE_CONFIG_H
  #  include <config.h>
  #endif /* HAVE_CONFIG_H */
  
  #include <ngtcp2/ngtcp2.h>
  
  /* QUIC header macros */
  #define NGTCP2_HEADER_FORM_BIT 0x80
  #define NGTCP2_FIXED_BIT_MASK 0x40
  #define NGTCP2_PKT_NUMLEN_MASK 0x03
  
  /* Long header specific macros */
  #define NGTCP2_LONG_TYPE_MASK 0x30
  #define NGTCP2_LONG_RESERVED_BIT_MASK 0x0c
  
  /* Short header specific macros */
  #define NGTCP2_SHORT_SPIN_BIT_MASK 0x20
  #define NGTCP2_SHORT_RESERVED_BIT_MASK 0x18
  #define NGTCP2_SHORT_KEY_PHASE_BIT 0x04
  
  /* NGTCP2_SR_TYPE is a Type field of Stateless Reset. */
  #define NGTCP2_SR_TYPE 0x1f
  
  /* NGTCP2_MIN_LONG_HEADERLEN is the minimum length of long header.
     That is (1|1|TT|RR|PP)<1> + VERSION<4> + DCIL<1> + SCIL<1> +
     LENGTH<1> + PKN<1> */
  #define NGTCP2_MIN_LONG_HEADERLEN (1 + 4 + 1 + 1 + 1 + 1)
  
  #define NGTCP2_STREAM_FIN_BIT 0x01
  #define NGTCP2_STREAM_LEN_BIT 0x02
  #define NGTCP2_STREAM_OFF_BIT 0x04
  
  /* NGTCP2_STREAM_OVERHEAD is the maximum number of bytes required
     other than payload for STREAM frame.  That is from type field to
     the beginning of the payload. */
  #define NGTCP2_STREAM_OVERHEAD (1 + 8 + 8 + 8)
  
  /* NGTCP2_CRYPTO_OVERHEAD is the maximum number of bytes required
     other than payload for CRYPTO frame.  That is from type field to
     the beginning of the payload. */
  #define NGTCP2_CRYPTO_OVERHEAD (1 + 8 + 8)
  
  /* NGTCP2_MIN_FRAME_PAYLOADLEN is the minimum frame payload length. */
  #define NGTCP2_MIN_FRAME_PAYLOADLEN 16
  
  /* NGTCP2_MAX_VARINT is the maximum value which can be encoded in
     variable-length integer encoding */
  #define NGTCP2_MAX_VARINT ((1ULL << 62) - 1)
  
  /* NGTCP2_MAX_SERVER_STREAM_ID_BIDI is the maximum bidirectional
     server stream ID. */
  #define NGTCP2_MAX_SERVER_STREAM_ID_BIDI ((int64_t)0x3ffffffffffffffdll)
  /* NGTCP2_MAX_CLIENT_STREAM_ID_BIDI is the maximum bidirectional
     client stream ID. */
  #define NGTCP2_MAX_CLIENT_STREAM_ID_BIDI ((int64_t)0x3ffffffffffffffcll)
  /* NGTCP2_MAX_SERVER_STREAM_ID_UNI is the maximum unidirectional
     server stream ID. */
  #define NGTCP2_MAX_SERVER_STREAM_ID_UNI ((int64_t)0x3fffffffffffffffll)
  /* NGTCP2_MAX_CLIENT_STREAM_ID_UNI is the maximum unidirectional
     client stream ID. */
  #define NGTCP2_MAX_CLIENT_STREAM_ID_UNI ((int64_t)0x3ffffffffffffffell)
  
  /* NGTCP2_MAX_NUM_ACK_BLK is the maximum number of Additional ACK
     blocks which this library can create, or decode. */
  #define NGTCP2_MAX_ACK_BLKS 32
  
  /* NGTCP2_MAX_PKT_NUM is the maximum packet number. */
  #define NGTCP2_MAX_PKT_NUM ((int64_t)((1ll << 62) - 1))
  
  /* NGTCP2_MIN_PKT_EXPANDLEN is the minimum packet size expansion in
     addition to the minimum DCID length to hide/trigger Stateless
     Reset. */
  #define NGTCP2_MIN_PKT_EXPANDLEN 22
  
  /* NGTCP2_RETRY_TAGLEN is the length of Retry packet integrity tag. */
  #define NGTCP2_RETRY_TAGLEN 16
  
  typedef struct ngtcp2_pkt_retry {
    ngtcp2_cid odcid;
    ngtcp2_vec token;
    uint8_t tag[NGTCP2_RETRY_TAGLEN];
  } ngtcp2_pkt_retry;
  
  typedef enum {
    NGTCP2_FRAME_PADDING = 0x00,
    NGTCP2_FRAME_PING = 0x01,
    NGTCP2_FRAME_ACK = 0x02,
    NGTCP2_FRAME_ACK_ECN = 0x03,
    NGTCP2_FRAME_RESET_STREAM = 0x04,
    NGTCP2_FRAME_STOP_SENDING = 0x05,
    NGTCP2_FRAME_CRYPTO = 0x06,
    NGTCP2_FRAME_NEW_TOKEN = 0x07,
    NGTCP2_FRAME_STREAM = 0x08,
    NGTCP2_FRAME_MAX_DATA = 0x10,
    NGTCP2_FRAME_MAX_STREAM_DATA = 0x11,
    NGTCP2_FRAME_MAX_STREAMS_BIDI = 0x12,
    NGTCP2_FRAME_MAX_STREAMS_UNI = 0x13,
    NGTCP2_FRAME_DATA_BLOCKED = 0x14,
    NGTCP2_FRAME_STREAM_DATA_BLOCKED = 0x15,
    NGTCP2_FRAME_STREAMS_BLOCKED_BIDI = 0x16,
    NGTCP2_FRAME_STREAMS_BLOCKED_UNI = 0x17,
    NGTCP2_FRAME_NEW_CONNECTION_ID = 0x18,
    NGTCP2_FRAME_RETIRE_CONNECTION_ID = 0x19,
    NGTCP2_FRAME_PATH_CHALLENGE = 0x1a,
    NGTCP2_FRAME_PATH_RESPONSE = 0x1b,
    NGTCP2_FRAME_CONNECTION_CLOSE = 0x1c,
    NGTCP2_FRAME_CONNECTION_CLOSE_APP = 0x1d,
    NGTCP2_FRAME_HANDSHAKE_DONE = 0x1e,
  } ngtcp2_frame_type;
  
  typedef struct ngtcp2_stream {
    uint8_t type;
    /**
     * flags of decoded STREAM frame.  This gets ignored when encoding
     * STREAM frame.
     */
    uint8_t flags;
    uint8_t fin;
    int64_t stream_id;
    uint64_t offset;
    /* datacnt is the number of elements that data contains.  Although
       the length of data is 1 in this definition, the library may
       allocate extra bytes to hold more elements. */
    size_t datacnt;
    /* data is the array of ngtcp2_vec which references data. */
    ngtcp2_vec data[1];
  } ngtcp2_stream;
  
  typedef struct ngtcp2_ack_blk {
    uint64_t gap;
    uint64_t blklen;
  } ngtcp2_ack_blk;
  
  typedef struct ngtcp2_ack {
    uint8_t type;
    int64_t largest_ack;
    uint64_t ack_delay;
    /**
     * ack_delay_unscaled is an ack_delay multiplied by
     * 2**ack_delay_component * NGTCP2_MICROSECONDS.
     */
    ngtcp2_duration ack_delay_unscaled;
    struct {
      uint64_t ect0;
      uint64_t ect1;
      uint64_t ce;
    } ecn;
    uint64_t first_ack_blklen;
    size_t num_blks;
    ngtcp2_ack_blk blks[1];
  } ngtcp2_ack;
  
  typedef struct ngtcp2_padding {
    uint8_t type;
    /**
     * The length of contiguous PADDING frames.
     */
    size_t len;
  } ngtcp2_padding;
  
  typedef struct ngtcp2_reset_stream {
    uint8_t type;
    int64_t stream_id;
    uint64_t app_error_code;
    uint64_t final_size;
  } ngtcp2_reset_stream;
  
  typedef struct ngtcp2_connection_close {
    uint8_t type;
    uint64_t error_code;
    uint64_t frame_type;
    size_t reasonlen;
    uint8_t *reason;
  } ngtcp2_connection_close;
  
  typedef struct ngtcp2_max_data {
    uint8_t type;
    /**
     * max_data is Maximum Data.
     */
    uint64_t max_data;
  } ngtcp2_max_data;
  
  typedef struct ngtcp2_max_stream_data {
    uint8_t type;
    int64_t stream_id;
    uint64_t max_stream_data;
  } ngtcp2_max_stream_data;
  
  typedef struct ngtcp2_max_streams {
    uint8_t type;
    uint64_t max_streams;
  } ngtcp2_max_streams;
  
  typedef struct ngtcp2_ping {
    uint8_t type;
  } ngtcp2_ping;
  
  typedef struct ngtcp2_data_blocked {
    uint8_t type;
    uint64_t offset;
  } ngtcp2_data_blocked;
  
  typedef struct ngtcp2_stream_data_blocked {
    uint8_t type;
    int64_t stream_id;
    uint64_t offset;
  } ngtcp2_stream_data_blocked;
  
  typedef struct ngtcp2_streams_blocked {
    uint8_t type;
    uint64_t max_streams;
  } ngtcp2_streams_blocked;
  
  typedef struct ngtcp2_new_connection_id {
    uint8_t type;
    uint64_t seq;
    uint64_t retire_prior_to;
    ngtcp2_cid cid;
    uint8_t stateless_reset_token[NGTCP2_STATELESS_RESET_TOKENLEN];
  } ngtcp2_new_connection_id;
  
  typedef struct ngtcp2_stop_sending {
    uint8_t type;
    int64_t stream_id;
    uint64_t app_error_code;
  } ngtcp2_stop_sending;
  
  typedef struct ngtcp2_path_challenge {
    uint8_t type;
    uint8_t data[8];
  } ngtcp2_path_challenge;
  
  typedef struct ngtcp2_path_response {
    uint8_t type;
    uint8_t data[8];
  } ngtcp2_path_response;
  
  typedef struct ngtcp2_crypto {
    uint8_t type;
    uint64_t offset;
    /* datacnt is the number of elements that data contains.  Although
       the length of data is 1 in this definition, the library may
       allocate extra bytes to hold more elements. */
    size_t datacnt;
    /* data is the array of ngtcp2_vec which references data. */
    ngtcp2_vec data[1];
  } ngtcp2_crypto;
  
  typedef struct ngtcp2_new_token {
    uint8_t type;
    ngtcp2_vec token;
  } ngtcp2_new_token;
  
  typedef struct ngtcp2_retire_connection_id {
    uint8_t type;
    uint64_t seq;
  } ngtcp2_retire_connection_id;
  
  typedef struct ngtcp2_handshake_done {
    uint8_t type;
  } ngtcp2_handshake_done;
  
  typedef union ngtcp2_frame {
    uint8_t type;
    ngtcp2_stream stream;
    ngtcp2_ack ack;
    ngtcp2_padding padding;
    ngtcp2_reset_stream reset_stream;
    ngtcp2_connection_close connection_close;
    ngtcp2_max_data max_data;
    ngtcp2_max_stream_data max_stream_data;
    ngtcp2_max_streams max_streams;
    ngtcp2_ping ping;
    ngtcp2_data_blocked data_blocked;
    ngtcp2_stream_data_blocked stream_data_blocked;
    ngtcp2_streams_blocked streams_blocked;
    ngtcp2_new_connection_id new_connection_id;
    ngtcp2_stop_sending stop_sending;
    ngtcp2_path_challenge path_challenge;
    ngtcp2_path_response path_response;
    ngtcp2_crypto crypto;
    ngtcp2_new_token new_token;
    ngtcp2_retire_connection_id retire_connection_id;
    ngtcp2_handshake_done handshake_done;
  } ngtcp2_frame;
  
  typedef struct ngtcp2_pkt_chain ngtcp2_pkt_chain;
  
  /*
   * ngtcp2_pkt_chain is the chain of incoming packets buffered.
   */
  struct ngtcp2_pkt_chain {
    ngtcp2_path_storage path;
    ngtcp2_pkt_info pi;
    ngtcp2_pkt_chain *next;
    uint8_t *pkt;
    /* pktlen is length of a QUIC packet. */
    size_t pktlen;
    /* dgramlen is length of UDP datagram that a QUIC packet is
       included. */
    size_t dgramlen;
    ngtcp2_tstamp ts;
  };
  
  /*
   * ngtcp2_pkt_chain_new allocates ngtcp2_pkt_chain objects, and
   * assigns its pointer to |*ppc|.  The content of buffer pointed by
   * |pkt| of length |pktlen| is copied into |*ppc|.  The packet is
   * obtained via the network |path|.  The values of path->local and
   * path->remote are copied into |*ppc|.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_NOMEM
   *     Out of memory.
   */
  int ngtcp2_pkt_chain_new(ngtcp2_pkt_chain **ppc, const ngtcp2_path *path,
                           const ngtcp2_pkt_info *pi, const uint8_t *pkt,
                           size_t pktlen, size_t dgramlen, ngtcp2_tstamp ts,
                           const ngtcp2_mem *mem);
  
  /*
   * ngtcp2_pkt_chain_del deallocates |pc|.  It also frees the memory
   * pointed by |pc|.
   */
  void ngtcp2_pkt_chain_del(ngtcp2_pkt_chain *pc, const ngtcp2_mem *mem);
  
  /*
   * ngtcp2_pkt_hd_init initializes |hd| with the given values.  If
   * |dcid| and/or |scid| is NULL, DCID and SCID of |hd| is empty
   * respectively.  |pkt_numlen| is the number of bytes used to encode
   * |pkt_num| and either 1, 2, or 4.  |version| is QUIC version for
   * long header.  |len| is the length field of Initial, 0RTT, and
   * Handshake packets.
   */
  void ngtcp2_pkt_hd_init(ngtcp2_pkt_hd *hd, uint8_t flags, uint8_t type,
                          const ngtcp2_cid *dcid, const ngtcp2_cid *scid,
                          int64_t pkt_num, size_t pkt_numlen, uint32_t version,
                          size_t len);
  
  /*
   * ngtcp2_pkt_encode_hd_long encodes |hd| as QUIC long header into
   * |out| which has length |outlen|.  It returns the number of bytes
   * written into |outlen| if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer is too short
   */
  ngtcp2_ssize ngtcp2_pkt_encode_hd_long(uint8_t *out, size_t outlen,
                                         const ngtcp2_pkt_hd *hd);
  
  /*
   * ngtcp2_pkt_encode_hd_short encodes |hd| as QUIC short header into
   * |out| which has length |outlen|.  It returns the number of bytes
   * written into |outlen| if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer is too short
   */
  ngtcp2_ssize ngtcp2_pkt_encode_hd_short(uint8_t *out, size_t outlen,
                                          const ngtcp2_pkt_hd *hd);
  
  /**
   * @function
   *
   * `ngtcp2_pkt_decode_frame` decodes a QUIC frame from the buffer
   * pointed by |payload| whose length is |payloadlen|.
   *
   * This function returns the number of bytes read to decode a single
   * frame if it succeeds, or one of the following negative error codes:
   *
   * :enum:`NGTCP2_ERR_FRAME_ENCODING`
   *     Frame is badly formatted; or frame type is unknown.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_frame(ngtcp2_frame *dest, const uint8_t *payload,
                                       size_t payloadlen);
  
  /**
   * @function
   *
   * `ngtcp2_pkt_encode_frame` encodes a frame |fm| into the buffer
   * pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written to the buffer, or
   * one of the following negative error codes:
   *
   * :enum:`NGTCP2_ERR_NOBUF`
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_frame(uint8_t *out, size_t outlen,
                                       ngtcp2_frame *fr);
  
  /*
   * ngtcp2_pkt_decode_version_negotiation decodes Version Negotiation
   * packet payload |payload| of length |payloadlen|, and stores the
   * result in |dest|.  |dest| must have enough capacity to store the
   * result.  |payloadlen| also must be a multiple of sizeof(uint32_t).
   *
   * This function returns the number of versions written in |dest|.
   */
  size_t ngtcp2_pkt_decode_version_negotiation(uint32_t *dest,
                                               const uint8_t *payload,
                                               size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_stateless_reset decodes Stateless Reset payload
   * |payload| of length |payloadlen|.  The |payload| must start with
   * Stateless Reset Token.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_INVALID_ARGUMENT
   *     Payloadlen is too short.
   */
  int ngtcp2_pkt_decode_stateless_reset(ngtcp2_pkt_stateless_reset *sr,
                                        const uint8_t *payload,
                                        size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_retry decodes Retry packet payload |payload| of
   * length |payloadlen|.  The |payload| must start with Retry token
   * field.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_INVALID_ARGUMENT
   *     Payloadlen is too short.
   */
  int ngtcp2_pkt_decode_retry(ngtcp2_pkt_retry *dest, const uint8_t *payload,
                              size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_stream_frame decodes STREAM frame from |payload|
   * of length |payloadlen|.  The result is stored in the object pointed
   * by |dest|.  STREAM frame must start at payload[0].  This function
   * finishes when it decodes one STREAM frame, and returns the exact
   * number of bytes read to decode a frame if it succeeds, or one of
   * the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include STREAM frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_stream_frame(ngtcp2_stream *dest,
                                              const uint8_t *payload,
                                              size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_ack_frame decodes ACK frame from |payload| of
   * length |payloadlen|.  The result is stored in the object pointed by
   * |dest|.  ACK frame must start at payload[0].  This function
   * finishes when it decodes one ACK frame, and returns the exact
   * number of bytes read to decode a frame if it succeeds, or one of
   * the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include ACK frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_ack_frame(ngtcp2_ack *dest,
                                           const uint8_t *payload,
                                           size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_padding_frame decodes contiguous PADDING frames
   * from |payload| of length |payloadlen|.  It continues to parse
   * frames as long as the frame type is PADDING.  This finishes when it
   * encounters the frame type which is not PADDING, or all input data
   * is read.  The first byte (payload[0]) must be NGTCP2_FRAME_PADDING.
   * This function returns the exact number of bytes read to decode
   * PADDING frames.
   */
  size_t ngtcp2_pkt_decode_padding_frame(ngtcp2_padding *dest,
                                         const uint8_t *payload,
                                         size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_reset_stream_frame decodes RESET_STREAM frame
   * from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  RESET_STREAM frame must start at
   * payload[0].  This function finishes when it decodes one
   * RESET_STREAM frame, and returns the exact number of bytes read to
   * decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include RESET_STREAM frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_reset_stream_frame(ngtcp2_reset_stream *dest,
                                                    const uint8_t *payload,
                                                    size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_connection_close_frame decodes CONNECTION_CLOSE
   * frame from |payload| of length |payloadlen|.  The result is stored
   * in the object pointed by |dest|.  CONNECTION_CLOSE frame must start
   * at payload[0].  This function finishes it decodes one
   * CONNECTION_CLOSE frame, and returns the exact number of bytes read
   * to decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include CONNECTION_CLOSE frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_connection_close_frame(
      ngtcp2_connection_close *dest, const uint8_t *payload, size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_max_data_frame decodes MAX_DATA frame from
   * |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  MAX_DATA frame must start at payload[0].
   * This function finishes when it decodes one MAX_DATA frame, and
   * returns the exact number of bytes read to decode a frame if it
   * succeeds, or one of the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include MAX_DATA frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_max_data_frame(ngtcp2_max_data *dest,
                                                const uint8_t *payload,
                                                size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_max_stream_data_frame decodes MAX_STREAM_DATA
   * frame from |payload| of length |payloadlen|.  The result is stored
   * in the object pointed by |dest|.  MAX_STREAM_DATA frame must start
   * at payload[0].  This function finishes when it decodes one
   * MAX_STREAM_DATA frame, and returns the exact number of bytes read
   * to decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include MAX_STREAM_DATA frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_max_stream_data_frame(
      ngtcp2_max_stream_data *dest, const uint8_t *payload, size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_max_streams_frame decodes MAX_STREAMS frame from
   * |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  MAX_STREAMS frame must start at
   * payload[0].  This function finishes when it decodes one MAX_STREAMS
   * frame, and returns the exact number of bytes read to decode a frame
   * if it succeeds, or one of the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include MAX_STREAMS frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_max_streams_frame(ngtcp2_max_streams *dest,
                                                   const uint8_t *payload,
                                                   size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_ping_frame decodes PING frame from |payload| of
   * length |payloadlen|.  The result is stored in the object pointed by
   * |dest|.  PING frame must start at payload[0].  This function
   * finishes when it decodes one PING frame, and returns the exact
   * number of bytes read to decode a frame if it succeeds, or one of
   * the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include PING frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_ping_frame(ngtcp2_ping *dest,
                                            const uint8_t *payload,
                                            size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_data_blocked_frame decodes DATA_BLOCKED frame
   * from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  DATA_BLOCKED frame must start at
   * payload[0].  This function finishes when it decodes one
   * DATA_BLOCKED frame, and returns the exact number of bytes read to
   * decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include DATA_BLOCKED frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_data_blocked_frame(ngtcp2_data_blocked *dest,
                                                    const uint8_t *payload,
                                                    size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_stream_data_blocked_frame decodes
   * STREAM_DATA_BLOCKED frame from |payload| of length |payloadlen|.
   * The result is stored in the object pointed by |dest|.
   * STREAM_DATA_BLOCKED frame must start at payload[0].  This function
   * finishes when it decodes one STREAM_DATA_BLOCKED frame, and returns
   * the exact number of bytes read to decode a frame if it succeeds, or
   * one of the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include STREAM_DATA_BLOCKED frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_decode_stream_data_blocked_frame(ngtcp2_stream_data_blocked *dest,
                                              const uint8_t *payload,
                                              size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_streams_blocked_frame decodes STREAMS_BLOCKED
   * frame from |payload| of length |payloadlen|.  The result is stored
   * in the object pointed by |dest|.  STREAMS_BLOCKED frame must start
   * at payload[0].  This function finishes when it decodes one
   * STREAMS_BLOCKED frame, and returns the exact number of bytes read
   * to decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include STREAMS_BLOCKED frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_streams_blocked_frame(
      ngtcp2_streams_blocked *dest, const uint8_t *payload, size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_new_connection_id_frame decodes NEW_CONNECTION_ID
   * frame from |payload| of length |payloadlen|.  The result is stored
   * in the object pointed by |dest|.  NEW_CONNECTION_ID frame must
   * start at payload[0].  This function finishes when it decodes one
   * NEW_CONNECTION_ID frame, and returns the exact number of bytes read
   * to decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include NEW_CONNECTION_ID frame; or the
   *     length of CID is strictly less than NGTCP2_MIN_CIDLEN or
   *     greater than NGTCP2_MAX_CIDLEN.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_new_connection_id_frame(
      ngtcp2_new_connection_id *dest, const uint8_t *payload, size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_stop_sending_frame decodes STOP_SENDING frame
   * from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  STOP_SENDING frame must start at
   * payload[0].  This function finishes when it decodes one
   * STOP_SENDING frame, and returns the exact number of bytes read to
   * decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include STOP_SENDING frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_stop_sending_frame(ngtcp2_stop_sending *dest,
                                                    const uint8_t *payload,
                                                    size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_path_challenge_frame decodes PATH_CHALLENGE frame
   * from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  PATH_CHALLENGE frame must start at
   * payload[0].  This function finishes when it decodes one
   * PATH_CHALLENGE frame, and returns the exact number of bytes read to
   * decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include PATH_CHALLENGE frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_path_challenge_frame(ngtcp2_path_challenge *dest,
                                                      const uint8_t *payload,
                                                      size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_path_response_frame decodes PATH_RESPONSE frame
   * from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  PATH_RESPONSE frame must start at
   * payload[0].  This function finishes when it decodes one
   * PATH_RESPONSE frame, and returns the exact number of bytes read to
   * decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include PATH_RESPONSE frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_path_response_frame(ngtcp2_path_response *dest,
                                                     const uint8_t *payload,
                                                     size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_crypto_frame decodes CRYPTO frame from |payload|
   * of length |payloadlen|.  The result is stored in the object pointed
   * by |dest|.  CRYPTO frame must start at payload[0].  This function
   * finishes when it decodes one CRYPTO frame, and returns the exact
   * number of bytes read to decode a frame if it succeeds, or one of
   * the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include CRYPTO frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_crypto_frame(ngtcp2_crypto *dest,
                                              const uint8_t *payload,
                                              size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_new_token_frame decodes NEW_TOKEN frame from
   * |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  NEW_TOKEN frame must start at
   * payload[0].  This function finishes when it decodes one NEW_TOKEN
   * frame, and returns the exact number of bytes read to decode a frame
   * if it succeeds, or one of the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include NEW_TOKEN frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_new_token_frame(ngtcp2_new_token *dest,
                                                 const uint8_t *payload,
                                                 size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_retire_connection_id_frame decodes RETIRE_CONNECTION_ID
   * frame from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  RETIRE_CONNECTION_ID frame must start at
   * payload[0].  This function finishes when it decodes one RETIRE_CONNECTION_ID
   * frame, and returns the exact number of bytes read to decode a frame
   * if it succeeds, or one of the following negative error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include RETIRE_CONNECTION_ID frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_decode_retire_connection_id_frame(ngtcp2_retire_connection_id *dest,
                                               const uint8_t *payload,
                                               size_t payloadlen);
  
  /*
   * ngtcp2_pkt_decode_handshake_done_frame decodes HANDSHAKE_DONE frame
   * from |payload| of length |payloadlen|.  The result is stored in the
   * object pointed by |dest|.  HANDSHAKE_DONE frame must start at
   * payload[0].  This function finishes when it decodes one
   * HANDSHAKE_DONE frame, and returns the exact number of bytes read to
   * decode a frame if it succeeds, or one of the following negative
   * error codes:
   *
   * NGTCP2_ERR_FRAME_ENCODING
   *     Payload is too short to include HANDSHAKE_DONE frame.
   */
  ngtcp2_ssize ngtcp2_pkt_decode_handshake_done_frame(ngtcp2_handshake_done *dest,
                                                      const uint8_t *payload,
                                                      size_t payloadlen);
  
  /*
   * ngtcp2_pkt_encode_stream_frame encodes STREAM frame |fr| into the
   * buffer pointed by |out| of length |outlen|.
   *
   * This function assigns <the serialized frame type> &
   * ~NGTCP2_FRAME_STREAM to fr->flags.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_stream_frame(uint8_t *out, size_t outlen,
                                              ngtcp2_stream *fr);
  
  /*
   * ngtcp2_pkt_encode_ack_frame encodes ACK frame |fr| into the buffer
   * pointed by |out| of length |outlen|.
   *
   * This function assigns <the serialized frame type> &
   * ~NGTCP2_FRAME_ACK to fr->flags.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_ack_frame(uint8_t *out, size_t outlen,
                                           ngtcp2_ack *fr);
  
  /*
   * ngtcp2_pkt_encode_padding_frame encodes PADDING frame |fr| into the
   * buffer pointed by |out| of length |outlen|.
   *
   * This function encodes consecutive fr->len PADDING frames.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write frame(s).
   */
  ngtcp2_ssize ngtcp2_pkt_encode_padding_frame(uint8_t *out, size_t outlen,
                                               const ngtcp2_padding *fr);
  
  /*
   * ngtcp2_pkt_encode_reset_stream_frame encodes RESET_STREAM frame
   * |fr| into the buffer pointed by |out| of length |buflen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_reset_stream_frame(uint8_t *out, size_t outlen,
                                       const ngtcp2_reset_stream *fr);
  
  /*
   * ngtcp2_pkt_encode_connection_close_frame encodes CONNECTION_CLOSE
   * frame |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_connection_close_frame(uint8_t *out, size_t outlen,
                                           const ngtcp2_connection_close *fr);
  
  /*
   * ngtcp2_pkt_encode_max_data_frame encodes MAX_DATA frame |fr| into
   * the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_max_data_frame(uint8_t *out, size_t outlen,
                                                const ngtcp2_max_data *fr);
  
  /*
   * ngtcp2_pkt_encode_max_stream_data_frame encodes MAX_STREAM_DATA
   * frame |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_max_stream_data_frame(uint8_t *out, size_t outlen,
                                          const ngtcp2_max_stream_data *fr);
  
  /*
   * ngtcp2_pkt_encode_max_streams_frame encodes MAX_STREAMS
   * frame |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_max_streams_frame(uint8_t *out, size_t outlen,
                                                   const ngtcp2_max_streams *fr);
  
  /*
   * ngtcp2_pkt_encode_ping_frame encodes PING frame |fr| into the
   * buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_ping_frame(uint8_t *out, size_t outlen,
                                            const ngtcp2_ping *fr);
  
  /*
   * ngtcp2_pkt_encode_data_blocked_frame encodes DATA_BLOCKED frame
   * |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_data_blocked_frame(uint8_t *out, size_t outlen,
                                       const ngtcp2_data_blocked *fr);
  
  /*
   * ngtcp2_pkt_encode_stream_data_blocked_frame encodes
   * STREAM_DATA_BLOCKED frame |fr| into the buffer pointed by |out| of
   * length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_stream_data_blocked_frame(
      uint8_t *out, size_t outlen, const ngtcp2_stream_data_blocked *fr);
  
  /*
   * ngtcp2_pkt_encode_streams_blocked_frame encodes STREAMS_BLOCKED
   * frame |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_streams_blocked_frame(uint8_t *out, size_t outlen,
                                          const ngtcp2_streams_blocked *fr);
  
  /*
   * ngtcp2_pkt_encode_new_connection_id_frame encodes NEW_CONNECTION_ID
   * frame |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_new_connection_id_frame(uint8_t *out, size_t outlen,
                                            const ngtcp2_new_connection_id *fr);
  
  /*
   * ngtcp2_pkt_encode_stop_sending_frame encodes STOP_SENDING frame
   * |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_stop_sending_frame(uint8_t *out, size_t outlen,
                                       const ngtcp2_stop_sending *fr);
  
  /*
   * ngtcp2_pkt_encode_path_challenge_frame encodes PATH_CHALLENGE frame
   * |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_path_challenge_frame(uint8_t *out, size_t outlen,
                                         const ngtcp2_path_challenge *fr);
  
  /*
   * ngtcp2_pkt_encode_path_response_frame encodes PATH_RESPONSE frame
   * |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_path_response_frame(uint8_t *out, size_t outlen,
                                        const ngtcp2_path_response *fr);
  
  /*
   * ngtcp2_pkt_encode_crypto_frame encodes CRYPTO frame |fr| into the
   * buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_crypto_frame(uint8_t *out, size_t outlen,
                                              const ngtcp2_crypto *fr);
  
  /*
   * ngtcp2_pkt_encode_new_token_frame encodes NEW_TOKEN frame |fr| into
   * the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_new_token_frame(uint8_t *out, size_t outlen,
                                                 const ngtcp2_new_token *fr);
  
  /*
   * ngtcp2_pkt_encode_retire_connection_id_frame encodes RETIRE_CONNECTION_ID
   * frame |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_retire_connection_id_frame(
      uint8_t *out, size_t outlen, const ngtcp2_retire_connection_id *fr);
  
  /*
   * ngtcp2_pkt_encode_handshake_done_frame encodes HANDSHAKE_DONE frame
   * |fr| into the buffer pointed by |out| of length |outlen|.
   *
   * This function returns the number of bytes written if it succeeds,
   * or one of the following negative error codes:
   *
   * NGTCP2_ERR_NOBUF
   *     Buffer does not have enough capacity to write a frame.
   */
  ngtcp2_ssize
  ngtcp2_pkt_encode_handshake_done_frame(uint8_t *out, size_t outlen,
                                         const ngtcp2_handshake_done *fr);
  
  /*
   * ngtcp2_pkt_adjust_pkt_num find the full 64 bits packet number for
   * |pkt_num|, which is expected to be least significant |n| bits.  The
   * |max_pkt_num| is the highest successfully authenticated packet
   * number.
   */
  int64_t ngtcp2_pkt_adjust_pkt_num(int64_t max_pkt_num, int64_t pkt_num,
                                    size_t n);
  
  /*
   * ngtcp2_pkt_validate_ack checks that ack is malformed or not.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_ACK_FRAME
   *     ACK frame is malformed
   */
  int ngtcp2_pkt_validate_ack(ngtcp2_ack *fr);
  
  /*
   * ngtcp2_pkt_stream_max_datalen returns the maximum number of bytes
   * which can be sent for stream denoted by |stream_id|.  |offset| is
   * an offset of within the stream.  |len| is the estimated number of
   * bytes to be sent.  |left| is the size of buffer.  If |left| is too
   * small to write STREAM frame, this function returns (size_t)-1.
   */
  size_t ngtcp2_pkt_stream_max_datalen(int64_t stream_id, uint64_t offset,
                                       size_t len, size_t left);
  
  /*
   * ngtcp2_pkt_crypto_max_datalen returns the maximum number of bytes
   * which can be sent for crypto stream.  |offset| is an offset of
   * within the crypto stream.  |len| is the estimated number of bytes
   * to be sent.  |left| is the size of buffer.  If |left| is too small
   * to write CRYPTO frame, this function returns (size_t)-1.
   */
  size_t ngtcp2_pkt_crypto_max_datalen(uint64_t offset, size_t len, size_t left);
  
  /*
   * ngtcp2_pkt_verify_reserved_bits verifies that the first byte |c| of
   * the packet header has the correct reserved bits.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_PROTO
   *     Reserved bits has wrong value.
   */
  int ngtcp2_pkt_verify_reserved_bits(uint8_t c);
  
  /*
   * ngtcp2_pkt_encode_pseudo_retry encodes Retry pseudo-packet in the
   * buffer pointed by |dest| of length |destlen|.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_BUF
   *     Buffer is too short.
   */
  ngtcp2_ssize ngtcp2_pkt_encode_pseudo_retry(
      uint8_t *dest, size_t destlen, const ngtcp2_pkt_hd *hd, uint8_t unused,
      const ngtcp2_cid *odcid, const uint8_t *token, size_t tokenlen);
  
  /*
   * ngtcp2_pkt_verify_retry_tag verifies Retry packet.  The buffer
   * pointed by |pkt| of length |pktlen| must contain Retry packet
   * including packet header.  The odcid and tag fields of |retry| must
   * be specified.  |aead| must be AEAD_AES_128_GCM.
   *
   * This function returns 0 if it succeeds, or one of the following
   * negative error codes:
   *
   * NGTCP2_ERR_PROTO
   *     Verification failed.
   */
  int ngtcp2_pkt_verify_retry_tag(const ngtcp2_pkt_retry *retry,
                                  const uint8_t *pkt, size_t pktlen,
                                  ngtcp2_encrypt encrypt,
                                  const ngtcp2_crypto_aead *aead,
                                  const ngtcp2_crypto_aead_ctx *aead_ctx);
  
  /**
   * @function
   *
   * `ngtcp2_pkt_get_type_long` returns the long packet type.  |c| is
   * the first byte of Long packet header.
   */
  uint8_t ngtcp2_pkt_get_type_long(uint8_t c);
  
  #endif /* NGTCP2_PKT_H */
  