epan/nghttp2_hd_huffman.h

   1 /* @file
   2  * nghttp2 - HTTP/2 C Library
   3  *
   4  * Copyright (c) 2013 Tatsuhiro Tsujikawa
   5  *
   6  * SPDX-License-Identifier: MIT
   7  */
   8 #ifndef NGHTTP2_HD_HUFFMAN_H
   9 #define NGHTTP2_HD_HUFFMAN_H
  10
  11 #include <config.h>
  12
  13 #include <stdlib.h>
  14 #include <stdint.h>
  15
  16 typedef enum {
  17   /* FSA accepts this state as the end of huffman encoding
  18      sequence. */
  19   NGHTTP2_HUFF_ACCEPTED = 1 << 14,
  20   /* This state emits symbol */
  21   NGHTTP2_HUFF_SYM = 1 << 15,
  22 } nghttp2_huff_decode_flag;
  23
  24 typedef struct {
  25   /* fstate is the current huffman decoding state, which is actually
  26      the node ID of internal huffman tree with
  27      nghttp2_huff_decode_flag OR-ed.  We have 257 leaf nodes, but they
  28      are identical to root node other than emitting a symbol, so we
  29      have 256 internal nodes [1..255], inclusive.  The node ID 256 is
  30      a special node and it is a terminal state that means decoding
  31      failed. */
  32   uint16_t fstate;
  33   /* symbol if NGHTTP2_HUFF_SYM flag set */
  34   uint8_t sym;
  35 } nghttp2_huff_decode;
  36
  37 typedef nghttp2_huff_decode huff_decode_table_type[16];
  38
  39 typedef struct {
  40   /* fstate is the current huffman decoding state. */
  41   uint16_t fstate;
  42 } nghttp2_hd_huff_decode_context;
  43
  44 typedef struct {
  45   /* The number of bits in this code */
  46   uint32_t nbits;
  47   /* Huffman code aligned to LSB */
  48   uint32_t code;
  49 } nghttp2_huff_sym;
  50
  51 extern const nghttp2_huff_sym huff_sym_table[];
  52 extern const nghttp2_huff_decode huff_decode_table[][16];
  53
  54 #endif /* NGHTTP2_HD_HUFFMAN_H */