text: /*
   * Copyright (C) Nginx, Inc.
   * Copyright (C) Valentin V. Bartenev
   */
  
  
  #ifndef _NGX_HTTP_V2_H_INCLUDED_
  #define _NGX_HTTP_V2_H_INCLUDED_
  
  
  #include <ngx_config.h>
  #include <ngx_core.h>
  #include <ngx_http.h>
  
  
  #define NGX_HTTP_V2_ALPN_ADVERTISE       "\x02h2"
  #define NGX_HTTP_V2_NPN_ADVERTISE        NGX_HTTP_V2_ALPN_ADVERTISE
  
  #define NGX_HTTP_V2_STATE_BUFFER_SIZE    16
  
  #define NGX_HTTP_V2_MAX_FRAME_SIZE       ((1 << 24) - 1)
  
  #define NGX_HTTP_V2_INT_OCTETS           4
  #define NGX_HTTP_V2_MAX_FIELD                                                 \
      (127 + (1 << (NGX_HTTP_V2_INT_OCTETS - 1) * 7) - 1)
  
  #define NGX_HTTP_V2_FRAME_HEADER_SIZE    9
  
  /* frame types */
  #define NGX_HTTP_V2_DATA_FRAME           0x0
  #define NGX_HTTP_V2_HEADERS_FRAME        0x1
  #define NGX_HTTP_V2_PRIORITY_FRAME       0x2
  #define NGX_HTTP_V2_RST_STREAM_FRAME     0x3
  #define NGX_HTTP_V2_SETTINGS_FRAME       0x4
  #define NGX_HTTP_V2_PUSH_PROMISE_FRAME   0x5
  #define NGX_HTTP_V2_PING_FRAME           0x6
  #define NGX_HTTP_V2_GOAWAY_FRAME         0x7
  #define NGX_HTTP_V2_WINDOW_UPDATE_FRAME  0x8
  #define NGX_HTTP_V2_CONTINUATION_FRAME   0x9
  
  /* frame flags */
  #define NGX_HTTP_V2_NO_FLAG              0x00
  #define NGX_HTTP_V2_ACK_FLAG             0x01
  #define NGX_HTTP_V2_END_STREAM_FLAG      0x01
  #define NGX_HTTP_V2_END_HEADERS_FLAG     0x04
  #define NGX_HTTP_V2_PADDED_FLAG          0x08
  #define NGX_HTTP_V2_PRIORITY_FLAG        0x20
  
  #define NGX_HTTP_V2_MAX_WINDOW           ((1U << 31) - 1)
  #define NGX_HTTP_V2_DEFAULT_WINDOW       65535
  
  
  typedef struct ngx_http_v2_connection_s   ngx_http_v2_connection_t;
  typedef struct ngx_http_v2_node_s         ngx_http_v2_node_t;
  typedef struct ngx_http_v2_out_frame_s    ngx_http_v2_out_frame_t;
  
  
  typedef u_char *(*ngx_http_v2_handler_pt) (ngx_http_v2_connection_t *h2c,
      u_char *pos, u_char *end);
  
  
  typedef struct {
      ngx_str_t                        name;
      ngx_str_t                        value;
  } ngx_http_v2_header_t;
  
  
  typedef struct {
      ngx_uint_t                       sid;
      size_t                           length;
      size_t                           padding;
      unsigned                         flags:8;
  
      unsigned                         incomplete:1;
      unsigned                         keep_pool:1;
  
      /* HPACK */
      unsigned                         parse_name:1;
      unsigned                         parse_value:1;
      unsigned                         index:1;
      ngx_http_v2_header_t             header;
      size_t                           header_limit;
      u_char                           field_state;
      u_char                          *field_start;
      u_char                          *field_end;
      size_t                           field_rest;
      ngx_pool_t                      *pool;
  
      ngx_http_v2_stream_t            *stream;
  
      u_char                           buffer[NGX_HTTP_V2_STATE_BUFFER_SIZE];
      size_t                           buffer_used;
      ngx_http_v2_handler_pt           handler;
  } ngx_http_v2_state_t;
  
  
  
  typedef struct {
      ngx_http_v2_header_t           **entries;
  
      ngx_uint_t                       added;
      ngx_uint_t                       deleted;
      ngx_uint_t                       reused;
      ngx_uint_t                       allocated;
  
      size_t                           size;
      size_t                           free;
      u_char                          *storage;
      u_char                          *pos;
  } ngx_http_v2_hpack_t;
  
  
  struct ngx_http_v2_connection_s {
      ngx_connection_t                *connection;
      ngx_http_connection_t           *http_connection;
  
      ngx_uint_t                       processing;
  
      size_t                           send_window;
      size_t                           recv_window;
      size_t                           init_window;
  
      size_t                           frame_size;
  
      ngx_queue_t                      waiting;
  
      ngx_http_v2_state_t              state;
  
      ngx_http_v2_hpack_t              hpack;
  
      ngx_pool_t                      *pool;
  
      ngx_http_v2_out_frame_t         *free_frames;
      ngx_connection_t                *free_fake_connections;
  
      ngx_http_v2_node_t             **streams_index;
  
      ngx_http_v2_out_frame_t         *last_out;
  
      ngx_queue_t                      dependencies;
      ngx_queue_t                      closed;
  
      ngx_uint_t                       last_sid;
  
      unsigned                         closed_nodes:8;
      unsigned                         settings_ack:1;
      unsigned                         blocked:1;
      unsigned                         goaway:1;
  };
  
  
  struct ngx_http_v2_node_s {
      ngx_uint_t                       id;
      ngx_http_v2_node_t              *index;
      ngx_http_v2_node_t              *parent;
      ngx_queue_t                      queue;
      ngx_queue_t                      children;
      ngx_queue_t                      reuse;
      ngx_uint_t                       rank;
      ngx_uint_t                       weight;
      double                           rel_weight;
      ngx_http_v2_stream_t            *stream;
  };
  
  
  struct ngx_http_v2_stream_s {
      ngx_http_request_t              *request;
      ngx_http_v2_connection_t        *connection;
      ngx_http_v2_node_t              *node;
  
      ngx_uint_t                       queued;
  
      /*
       * A change to SETTINGS_INITIAL_WINDOW_SIZE could cause the
       * send_window to become negative, hence it's signed.
       */
      ssize_t                          send_window;
      size_t                           recv_window;
  
      ngx_buf_t                       *preread;
  
      ngx_http_v2_out_frame_t         *free_frames;
      ngx_chain_t                     *free_frame_headers;
      ngx_chain_t                     *free_bufs;
  
      ngx_queue_t                      queue;
  
      ngx_array_t                     *cookies;
  
      size_t                           header_limit;
  
      ngx_pool_t                      *pool;
  
      unsigned                         waiting:1;
      unsigned                         blocked:1;
      unsigned                         exhausted:1;
      unsigned                         in_closed:1;
      unsigned                         out_closed:1;
      unsigned                         rst_sent:1;
      unsigned                         no_flow_control:1;
      unsigned                         skip_data:1;
  };
  
  
  struct ngx_http_v2_out_frame_s {
      ngx_http_v2_out_frame_t         *next;
      ngx_chain_t                     *first;
      ngx_chain_t                     *last;
      ngx_int_t                      (*handler)(ngx_http_v2_connection_t *h2c,
                                          ngx_http_v2_out_frame_t *frame);
  
      ngx_http_v2_stream_t            *stream;
      size_t                           length;
  
      unsigned                         blocked:1;
      unsigned                         fin:1;
  };
  
  
  static ngx_inline void
  ngx_http_v2_queue_frame(ngx_http_v2_connection_t *h2c,
      ngx_http_v2_out_frame_t *frame)
  {
      ngx_http_v2_out_frame_t  **out;
  
      for (out = &h2c->last_out; *out; out = &(*out)->next) {
  
          if ((*out)->blocked || (*out)->stream == NULL) {
              break;
          }
  
          if ((*out)->stream->node->rank < frame->stream->node->rank
              || ((*out)->stream->node->rank == frame->stream->node->rank
                  && (*out)->stream->node->rel_weight
                     >= frame->stream->node->rel_weight))
          {
              break;
          }
      }
  
      frame->next = *out;
      *out = frame;
  }
  
  
  static ngx_inline void
  ngx_http_v2_queue_blocked_frame(ngx_http_v2_connection_t *h2c,
      ngx_http_v2_out_frame_t *frame)
  {
      ngx_http_v2_out_frame_t  **out;
  
      for (out = &h2c->last_out; *out; out = &(*out)->next)
      {
          if ((*out)->blocked || (*out)->stream == NULL) {
              break;
          }
      }
  
      frame->next = *out;
      *out = frame;
  }
  
  
  void ngx_http_v2_init(ngx_event_t *rev);
  void ngx_http_v2_request_headers_init(void);
  
  ngx_int_t ngx_http_v2_read_request_body(ngx_http_request_t *r,
      ngx_http_client_body_handler_pt post_handler);
  ngx_int_t ngx_http_v2_read_unbuffered_request_body(ngx_http_request_t *r);
  
  void ngx_http_v2_close_stream(ngx_http_v2_stream_t *stream, ngx_int_t rc);
  
  ngx_int_t ngx_http_v2_send_output_queue(ngx_http_v2_connection_t *h2c);
  
  
  ngx_int_t ngx_http_v2_get_indexed_header(ngx_http_v2_connection_t *h2c,
      ngx_uint_t index, ngx_uint_t name_only);
  ngx_int_t ngx_http_v2_add_header(ngx_http_v2_connection_t *h2c,
      ngx_http_v2_header_t *header);
  ngx_int_t ngx_http_v2_table_size(ngx_http_v2_connection_t *h2c, size_t size);
  
  
  ngx_int_t ngx_http_v2_huff_decode(u_char *state, u_char *src, size_t len,
      u_char **dst, ngx_uint_t last, ngx_log_t *log);
  size_t ngx_http_v2_huff_encode(u_char *src, size_t len, u_char *dst,
      ngx_uint_t lower);
  
  
  #define ngx_http_v2_prefix(bits)  ((1 << (bits)) - 1)
  
  
  #if (NGX_HAVE_NONALIGNED)
  
  #define ngx_http_v2_parse_uint16(p)  ntohs(*(uint16_t *) (p))
  #define ngx_http_v2_parse_uint32(p)  ntohl(*(uint32_t *) (p))
  
  #else
  
  #define ngx_http_v2_parse_uint16(p)  ((p)[0] << 8 | (p)[1])
  #define ngx_http_v2_parse_uint32(p)                                           \
      ((uint32_t) (p)[0] << 24 | (p)[1] << 16 | (p)[2] << 8 | (p)[3])
  
  #endif
  
  #define ngx_http_v2_parse_length(p)  ((p) >> 8)
  #define ngx_http_v2_parse_type(p)    ((p) & 0xff)
  #define ngx_http_v2_parse_sid(p)     (ngx_http_v2_parse_uint32(p) & 0x7fffffff)
  #define ngx_http_v2_parse_window(p)  (ngx_http_v2_parse_uint32(p) & 0x7fffffff)
  
  
  #define ngx_http_v2_write_uint16_aligned(p, s)                                \
      (*(uint16_t *) (p) = htons((uint16_t) (s)), (p) + sizeof(uint16_t))
  #define ngx_http_v2_write_uint32_aligned(p, s)                                \
      (*(uint32_t *) (p) = htonl((uint32_t) (s)), (p) + sizeof(uint32_t))
  
  #if (NGX_HAVE_NONALIGNED)
  
  #define ngx_http_v2_write_uint16  ngx_http_v2_write_uint16_aligned
  #define ngx_http_v2_write_uint32  ngx_http_v2_write_uint32_aligned
  
  #else
  
  #define ngx_http_v2_write_uint16(p, s)                                        \
      ((p)[0] = (u_char) ((s) >> 8),                                            \
       (p)[1] = (u_char)  (s),                                                  \
       (p) + sizeof(uint16_t))
  
  #define ngx_http_v2_write_uint32(p, s)                                        \
      ((p)[0] = (u_char) ((s) >> 24),                                           \
       (p)[1] = (u_char) ((s) >> 16),                                           \
       (p)[2] = (u_char) ((s) >> 8),                                            \
       (p)[3] = (u_char)  (s),                                                  \
       (p) + sizeof(uint32_t))
  
  #endif
  
  #define ngx_http_v2_write_len_and_type(p, l, t)                               \
      ngx_http_v2_write_uint32_aligned(p, (l) << 8 | (t))
  
  #define ngx_http_v2_write_sid  ngx_http_v2_write_uint32
  
  #endif /* _NGX_HTTP_V2_H_INCLUDED_ */
  