/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include <grpc/support/port_platform.h>

#include "src/core/ext/transport/chttp2/transport/hpack_parser.h"
#include "src/core/ext/transport/chttp2/transport/internal.h"

#include <assert.h>
#include <stddef.h>
#include <string.h>

#include "absl/strings/str_cat.h"
#include "absl/strings/str_format.h"

#include <grpc/support/alloc.h>
#include <grpc/support/log.h>

#include "src/core/ext/transport/chttp2/transport/bin_encoder.h"
#include "src/core/lib/debug/stats.h"
#include "src/core/lib/gpr/string.h"
#include "src/core/lib/profiling/timers.h"
#include "src/core/lib/slice/slice_internal.h"
#include "src/core/lib/slice/slice_string_helpers.h"
#include "src/core/lib/surface/validate_metadata.h"
#include "src/core/lib/transport/http2_errors.h"

grpc_core::DebugOnlyTraceFlag grpc_trace_chttp2_hpack_parser(
    false, "chttp2_hpack_parser");

typedef enum {
  NOT_BINARY,
  BINARY_BEGIN,
  B64_BYTE0,
  B64_BYTE1,
  B64_BYTE2,
  B64_BYTE3
} binary_state;

/* How parsing works:

   The parser object keeps track of a function pointer which represents the
   current parse state.

   Each time new bytes are presented, we call into the current state, which
   recursively parses until all bytes in the given chunk are exhausted.

   The parse state that terminates then saves its function pointer to be the
   current state so that it can resume when more bytes are available.

   It's expected that most optimizing compilers will turn this code into
   a set of indirect jumps, and so not waste stack space. */

/* forward declarations for parsing states */
static grpc_error* parse_begin(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                               const uint8_t* end);
static grpc_error* parse_error(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                               const uint8_t* end, grpc_error* error);
static grpc_error* still_parse_error(grpc_chttp2_hpack_parser* p,
                                     const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_illegal_op(grpc_chttp2_hpack_parser* p,
                                    const uint8_t* cur, const uint8_t* end);

static grpc_error* parse_string_prefix(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_key_string(grpc_chttp2_hpack_parser* p,
                                    const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_value_string_with_indexed_key(
    grpc_chttp2_hpack_parser* p, const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_value_string_with_literal_key(
    grpc_chttp2_hpack_parser* p, const uint8_t* cur, const uint8_t* end);

static grpc_error* parse_value0(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end);
static grpc_error* parse_value1(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end);
static grpc_error* parse_value2(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end);
static grpc_error* parse_value3(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end);
static grpc_error* parse_value4(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end);
static grpc_error* parse_value5up(grpc_chttp2_hpack_parser* p,
                                  const uint8_t* cur, const uint8_t* end);

static grpc_error* parse_indexed_field(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_indexed_field_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_lithdr_incidx(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_lithdr_incidx_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_lithdr_incidx_v(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_lithdr_notidx(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_lithdr_notidx_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_lithdr_notidx_v(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_lithdr_nvridx(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_lithdr_nvridx_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_lithdr_nvridx_v(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end);
static grpc_error* parse_max_tbl_size(grpc_chttp2_hpack_parser* p,
                                      const uint8_t* cur, const uint8_t* end);
static grpc_error* parse_max_tbl_size_x(grpc_chttp2_hpack_parser* p,
                                        const uint8_t* cur, const uint8_t* end);

/* we translate the first byte of a hpack field into one of these decoding
   cases, then use a lookup table to jump directly to the appropriate parser.

   _X => the integer index is all ones, meaning we need to do varint decoding
   _V => the integer index is all zeros, meaning we need to decode an additional
         string value */
typedef enum {
  INDEXED_FIELD,
  INDEXED_FIELD_X,
  LITHDR_INCIDX,
  LITHDR_INCIDX_X,
  LITHDR_INCIDX_V,
  LITHDR_NOTIDX,
  LITHDR_NOTIDX_X,
  LITHDR_NOTIDX_V,
  LITHDR_NVRIDX,
  LITHDR_NVRIDX_X,
  LITHDR_NVRIDX_V,
  MAX_TBL_SIZE,
  MAX_TBL_SIZE_X,
  ILLEGAL
} first_byte_type;

/* jump table of parse state functions -- order must match first_byte_type
   above */
static const grpc_chttp2_hpack_parser_state first_byte_action[] = {
    parse_indexed_field,   parse_indexed_field_x, parse_lithdr_incidx,
    parse_lithdr_incidx_x, parse_lithdr_incidx_v, parse_lithdr_notidx,
    parse_lithdr_notidx_x, parse_lithdr_notidx_v, parse_lithdr_nvridx,
    parse_lithdr_nvridx_x, parse_lithdr_nvridx_v, parse_max_tbl_size,
    parse_max_tbl_size_x,  parse_illegal_op};

/* indexes the first byte to a parse state function - generated by
   gen_hpack_tables.c */
static const uint8_t first_byte_lut[256] = {
    LITHDR_NOTIDX_V, LITHDR_NOTIDX, LITHDR_NOTIDX, LITHDR_NOTIDX,
    LITHDR_NOTIDX,   LITHDR_NOTIDX, LITHDR_NOTIDX, LITHDR_NOTIDX,
    LITHDR_NOTIDX,   LITHDR_NOTIDX, LITHDR_NOTIDX, LITHDR_NOTIDX,
    LITHDR_NOTIDX,   LITHDR_NOTIDX, LITHDR_NOTIDX, LITHDR_NOTIDX_X,
    LITHDR_NVRIDX_V, LITHDR_NVRIDX, LITHDR_NVRIDX, LITHDR_NVRIDX,
    LITHDR_NVRIDX,   LITHDR_NVRIDX, LITHDR_NVRIDX, LITHDR_NVRIDX,
    LITHDR_NVRIDX,   LITHDR_NVRIDX, LITHDR_NVRIDX, LITHDR_NVRIDX,
    LITHDR_NVRIDX,   LITHDR_NVRIDX, LITHDR_NVRIDX, LITHDR_NVRIDX_X,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE,
    MAX_TBL_SIZE,    MAX_TBL_SIZE,  MAX_TBL_SIZE,  MAX_TBL_SIZE_X,
    LITHDR_INCIDX_V, LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX,
    LITHDR_INCIDX,   LITHDR_INCIDX, LITHDR_INCIDX, LITHDR_INCIDX_X,
    ILLEGAL,         INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD,
    INDEXED_FIELD,   INDEXED_FIELD, INDEXED_FIELD, INDEXED_FIELD_X,
};

/* state table for huffman decoding: given a state, gives an index/16 into
   next_sub_tbl. Taking that index and adding the value of the nibble being
   considered returns the next state.

   generated by gen_hpack_tables.c */
static const uint8_t next_tbl[256] = {
    0,  1,  2,  3,  4,  1,  2, 5,  6,  1, 7,  8,  1,  3,  3,  9,  10, 11, 1,  1,
    1,  12, 1,  2,  13, 1,  1, 1,  1,  1, 1,  1,  1,  1,  1,  1,  1,  1,  1,  2,
    14, 1,  15, 16, 1,  17, 1, 15, 2,  7, 3,  18, 19, 1,  1,  1,  1,  20, 1,  1,
    1,  1,  1,  1,  1,  1,  1, 1,  15, 2, 2,  7,  21, 1,  22, 1,  1,  1,  1,  1,
    1,  1,  1,  15, 2,  2,  2, 2,  2,  2, 23, 24, 25, 1,  1,  1,  1,  2,  2,  2,
    26, 3,  3,  27, 10, 28, 1, 1,  1,  1, 1,  1,  2,  3,  29, 10, 30, 1,  1,  1,
    1,  1,  1,  1,  1,  1,  1, 1,  1,  1, 1,  31, 1,  1,  1,  1,  1,  1,  1,  2,
    2,  2,  2,  2,  2,  2,  2, 32, 1,  1, 15, 33, 1,  34, 35, 9,  36, 1,  1,  1,
    1,  1,  1,  1,  37, 1,  1, 1,  1,  1, 1,  2,  2,  2,  2,  2,  2,  2,  26, 9,
    38, 1,  1,  1,  1,  1,  1, 1,  15, 2, 2,  2,  2,  26, 3,  3,  39, 1,  1,  1,
    1,  1,  1,  1,  1,  1,  1, 1,  2,  2, 2,  2,  2,  2,  7,  3,  3,  3,  40, 2,
    41, 1,  1,  1,  42, 43, 1, 1,  44, 1, 1,  1,  1,  15, 2,  2,  2,  2,  2,  2,
    3,  3,  3,  45, 46, 1,  1, 2,  2,  2, 35, 3,  3,  18, 47, 2,
};

/* next state, based upon current state and the current nibble: see above.
   generated by gen_hpack_tables.c */
static const int16_t next_sub_tbl[48 * 16] = {
    1,   204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217,
    218, 2,   6,   10,  13,  14,  15,  16,  17,  2,   6,   10,  13,  14,  15,
    16,  17,  3,   7,   11,  24,  3,   7,   11,  24,  3,   7,   11,  24,  3,
    7,   11,  24,  4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,
    4,   8,   4,   8,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   5,
    199, 200, 201, 202, 203, 4,   8,   4,   8,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   9,   133, 134, 135, 136, 137, 138, 139, 140,
    141, 142, 143, 144, 145, 146, 147, 3,   7,   11,  24,  3,   7,   11,  24,
    4,   8,   4,   8,   4,   8,   4,   8,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   0,   12,  132, 4,   8,   4,   8,   4,   8,
    4,   8,   4,   8,   4,   8,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   0,   0,   18,  19,  20,  21,  4,   8,   4,
    8,   4,   8,   4,   8,   4,   8,   0,   0,   0,   22,  23,  91,  25,  26,
    27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  37,  38,  39,  40,  3,
    7,   11,  24,  3,   7,   11,  24,  0,   0,   0,   0,   0,   41,  42,  43,
    2,   6,   10,  13,  14,  15,  16,  17,  3,   7,   11,  24,  3,   7,   11,
    24,  4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   0,   0,
    44,  45,  2,   6,   10,  13,  14,  15,  16,  17,  46,  47,  48,  49,  50,
    51,  52,  57,  4,   8,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   53,  54,  55,  56,  58,  59,  60,  61,  62,  63,  64,  65,  66,  67,
    68,  69,  70,  71,  72,  74,  0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   73,  75,  76,  77,  78,  79,  80,  81,  82,
    83,  84,  85,  86,  87,  88,  89,  90,  3,   7,   11,  24,  3,   7,   11,
    24,  3,   7,   11,  24,  0,   0,   0,   0,   3,   7,   11,  24,  3,   7,
    11,  24,  4,   8,   4,   8,   0,   0,   0,   92,  0,   0,   0,   93,  94,
    95,  96,  97,  98,  99,  100, 101, 102, 103, 104, 105, 3,   7,   11,  24,
    4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,
    8,   4,   8,   4,   8,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   0,   106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 4,
    8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   0,   0,
    0,   117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130,
    131, 2,   6,   10,  13,  14,  15,  16,  17,  4,   8,   4,   8,   4,   8,
    4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   148,
    149, 150, 151, 3,   7,   11,  24,  4,   8,   4,   8,   0,   0,   0,   0,
    0,   0,   152, 153, 3,   7,   11,  24,  3,   7,   11,  24,  3,   7,   11,
    24,  154, 155, 156, 164, 3,   7,   11,  24,  3,   7,   11,  24,  3,   7,
    11,  24,  4,   8,   4,   8,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    157, 158, 159, 160, 161, 162, 163, 165, 166, 167, 168, 169, 170, 171, 172,
    173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187,
    188, 189, 190, 191, 192, 193, 194, 195, 196, 4,   8,   4,   8,   4,   8,
    4,   8,   4,   8,   4,   8,   4,   8,   197, 198, 4,   8,   4,   8,   4,
    8,   4,   8,   0,   0,   0,   0,   0,   0,   219, 220, 3,   7,   11,  24,
    4,   8,   4,   8,   4,   8,   0,   0,   221, 222, 223, 224, 3,   7,   11,
    24,  3,   7,   11,  24,  4,   8,   4,   8,   4,   8,   225, 228, 4,   8,
    4,   8,   4,   8,   0,   0,   0,   0,   0,   0,   0,   0,   226, 227, 229,
    230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244,
    4,   8,   4,   8,   4,   8,   4,   8,   4,   8,   0,   0,   0,   0,   0,
    0,   0,   0,   0,   0,   0,   0,   245, 246, 247, 248, 249, 250, 251, 252,
    253, 254, 0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
    0,   0,   255,
};

/* emission table: indexed like next_tbl, ultimately gives the byte to be
   emitted, or -1 for no byte, or 256 for end of stream

   generated by gen_hpack_tables.c */
static const uint16_t emit_tbl[256] = {
    0,   1,   2,   3,   4,   5,   6,   7,   0,   8,   9,   10,  11,  12,  13,
    14,  15,  16,  17,  18,  19,  20,  21,  22,  0,   23,  24,  25,  26,  27,
    28,  29,  30,  31,  32,  33,  34,  35,  36,  37,  38,  39,  40,  41,  42,
    43,  44,  45,  46,  47,  48,  49,  50,  51,  52,  53,  54,  0,   55,  56,
    57,  58,  59,  60,  61,  62,  63,  64,  65,  66,  67,  68,  69,  70,  0,
    71,  72,  73,  74,  75,  76,  77,  78,  79,  80,  81,  82,  83,  84,  85,
    86,  87,  88,  89,  90,  91,  92,  93,  94,  95,  96,  97,  98,  99,  100,
    101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115,
    116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130,
    131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145,
    146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 0,
    160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174,
    0,   175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188,
    189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203,
    204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218,
    219, 220, 221, 0,   222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232,
    233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247,
    248,
};

/* generated by gen_hpack_tables.c */
static const int16_t emit_sub_tbl[249 * 16] = {
    -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,
    -1,  48,  48,  48,  48,  48,  48,  48,  48,  49,  49,  49,  49,  49,  49,
    49,  49,  48,  48,  48,  48,  49,  49,  49,  49,  50,  50,  50,  50,  97,
    97,  97,  97,  48,  48,  49,  49,  50,  50,  97,  97,  99,  99,  101, 101,
    105, 105, 111, 111, 48,  49,  50,  97,  99,  101, 105, 111, 115, 116, -1,
    -1,  -1,  -1,  -1,  -1,  32,  32,  32,  32,  32,  32,  32,  32,  37,  37,
    37,  37,  37,  37,  37,  37,  99,  99,  99,  99,  101, 101, 101, 101, 105,
    105, 105, 105, 111, 111, 111, 111, 115, 115, 116, 116, 32,  37,  45,  46,
    47,  51,  52,  53,  54,  55,  56,  57,  61,  61,  61,  61,  61,  61,  61,
    61,  65,  65,  65,  65,  65,  65,  65,  65,  115, 115, 115, 115, 116, 116,
    116, 116, 32,  32,  37,  37,  45,  45,  46,  46,  61,  65,  95,  98,  100,
    102, 103, 104, 108, 109, 110, 112, 114, 117, -1,  -1,  58,  58,  58,  58,
    58,  58,  58,  58,  66,  66,  66,  66,  66,  66,  66,  66,  47,  47,  51,
    51,  52,  52,  53,  53,  54,  54,  55,  55,  56,  56,  57,  57,  61,  61,
    65,  65,  95,  95,  98,  98,  100, 100, 102, 102, 103, 103, 104, 104, 108,
    108, 109, 109, 110, 110, 112, 112, 114, 114, 117, 117, 58,  66,  67,  68,
    69,  70,  71,  72,  73,  74,  75,  76,  77,  78,  79,  80,  81,  82,  83,
    84,  85,  86,  87,  89,  106, 107, 113, 118, 119, 120, 121, 122, -1,  -1,
    -1,  -1,  38,  38,  38,  38,  38,  38,  38,  38,  42,  42,  42,  42,  42,
    42,  42,  42,  44,  44,  44,  44,  44,  44,  44,  44,  59,  59,  59,  59,
    59,  59,  59,  59,  88,  88,  88,  88,  88,  88,  88,  88,  90,  90,  90,
    90,  90,  90,  90,  90,  33,  33,  34,  34,  40,  40,  41,  41,  63,  63,
    39,  43,  124, -1,  -1,  -1,  35,  35,  35,  35,  35,  35,  35,  35,  62,
    62,  62,  62,  62,  62,  62,  62,  0,   0,   0,   0,   36,  36,  36,  36,
    64,  64,  64,  64,  91,  91,  91,  91,  69,  69,  69,  69,  69,  69,  69,
    69,  70,  70,  70,  70,  70,  70,  70,  70,  71,  71,  71,  71,  71,  71,
    71,  71,  72,  72,  72,  72,  72,  72,  72,  72,  73,  73,  73,  73,  73,
    73,  73,  73,  74,  74,  74,  74,  74,  74,  74,  74,  75,  75,  75,  75,
    75,  75,  75,  75,  76,  76,  76,  76,  76,  76,  76,  76,  77,  77,  77,
    77,  77,  77,  77,  77,  78,  78,  78,  78,  78,  78,  78,  78,  79,  79,
    79,  79,  79,  79,  79,  79,  80,  80,  80,  80,  80,  80,  80,  80,  81,
    81,  81,  81,  81,  81,  81,  81,  82,  82,  82,  82,  82,  82,  82,  82,
    83,  83,  83,  83,  83,  83,  83,  83,  84,  84,  84,  84,  84,  84,  84,
    84,  85,  85,  85,  85,  85,  85,  85,  85,  86,  86,  86,  86,  86,  86,
    86,  86,  87,  87,  87,  87,  87,  87,  87,  87,  89,  89,  89,  89,  89,
    89,  89,  89,  106, 106, 106, 106, 106, 106, 106, 106, 107, 107, 107, 107,
    107, 107, 107, 107, 113, 113, 113, 113, 113, 113, 113, 113, 118, 118, 118,
    118, 118, 118, 118, 118, 119, 119, 119, 119, 119, 119, 119, 119, 120, 120,
    120, 120, 120, 120, 120, 120, 121, 121, 121, 121, 121, 121, 121, 121, 122,
    122, 122, 122, 122, 122, 122, 122, 38,  38,  38,  38,  42,  42,  42,  42,
    44,  44,  44,  44,  59,  59,  59,  59,  88,  88,  88,  88,  90,  90,  90,
    90,  33,  34,  40,  41,  63,  -1,  -1,  -1,  39,  39,  39,  39,  39,  39,
    39,  39,  43,  43,  43,  43,  43,  43,  43,  43,  124, 124, 124, 124, 124,
    124, 124, 124, 35,  35,  35,  35,  62,  62,  62,  62,  0,   0,   36,  36,
    64,  64,  91,  91,  93,  93,  126, 126, 94,  125, -1,  -1,  60,  60,  60,
    60,  60,  60,  60,  60,  96,  96,  96,  96,  96,  96,  96,  96,  123, 123,
    123, 123, 123, 123, 123, 123, -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  92,
    92,  92,  92,  92,  92,  92,  92,  195, 195, 195, 195, 195, 195, 195, 195,
    208, 208, 208, 208, 208, 208, 208, 208, 128, 128, 128, 128, 130, 130, 130,
    130, 131, 131, 131, 131, 162, 162, 162, 162, 184, 184, 184, 184, 194, 194,
    194, 194, 224, 224, 224, 224, 226, 226, 226, 226, 153, 153, 161, 161, 167,
    167, 172, 172, 176, 176, 177, 177, 179, 179, 209, 209, 216, 216, 217, 217,
    227, 227, 229, 229, 230, 230, 129, 132, 133, 134, 136, 146, 154, 156, 160,
    163, 164, 169, 170, 173, 178, 181, 185, 186, 187, 189, 190, 196, 198, 228,
    232, 233, -1,  -1,  -1,  -1,  1,   1,   1,   1,   1,   1,   1,   1,   135,
    135, 135, 135, 135, 135, 135, 135, 137, 137, 137, 137, 137, 137, 137, 137,
    138, 138, 138, 138, 138, 138, 138, 138, 139, 139, 139, 139, 139, 139, 139,
    139, 140, 140, 140, 140, 140, 140, 140, 140, 141, 141, 141, 141, 141, 141,
    141, 141, 143, 143, 143, 143, 143, 143, 143, 143, 147, 147, 147, 147, 147,
    147, 147, 147, 149, 149, 149, 149, 149, 149, 149, 149, 150, 150, 150, 150,
    150, 150, 150, 150, 151, 151, 151, 151, 151, 151, 151, 151, 152, 152, 152,
    152, 152, 152, 152, 152, 155, 155, 155, 155, 155, 155, 155, 155, 157, 157,
    157, 157, 157, 157, 157, 157, 158, 158, 158, 158, 158, 158, 158, 158, 165,
    165, 165, 165, 165, 165, 165, 165, 166, 166, 166, 166, 166, 166, 166, 166,
    168, 168, 168, 168, 168, 168, 168, 168, 174, 174, 174, 174, 174, 174, 174,
    174, 175, 175, 175, 175, 175, 175, 175, 175, 180, 180, 180, 180, 180, 180,
    180, 180, 182, 182, 182, 182, 182, 182, 182, 182, 183, 183, 183, 183, 183,
    183, 183, 183, 188, 188, 188, 188, 188, 188, 188, 188, 191, 191, 191, 191,
    191, 191, 191, 191, 197, 197, 197, 197, 197, 197, 197, 197, 231, 231, 231,
    231, 231, 231, 231, 231, 239, 239, 239, 239, 239, 239, 239, 239, 9,   9,
    9,   9,   142, 142, 142, 142, 144, 144, 144, 144, 145, 145, 145, 145, 148,
    148, 148, 148, 159, 159, 159, 159, 171, 171, 171, 171, 206, 206, 206, 206,
    215, 215, 215, 215, 225, 225, 225, 225, 236, 236, 236, 236, 237, 237, 237,
    237, 199, 199, 207, 207, 234, 234, 235, 235, 192, 193, 200, 201, 202, 205,
    210, 213, 218, 219, 238, 240, 242, 243, 255, -1,  203, 203, 203, 203, 203,
    203, 203, 203, 204, 204, 204, 204, 204, 204, 204, 204, 211, 211, 211, 211,
    211, 211, 211, 211, 212, 212, 212, 212, 212, 212, 212, 212, 214, 214, 214,
    214, 214, 214, 214, 214, 221, 221, 221, 221, 221, 221, 221, 221, 222, 222,
    222, 222, 222, 222, 222, 222, 223, 223, 223, 223, 223, 223, 223, 223, 241,
    241, 241, 241, 241, 241, 241, 241, 244, 244, 244, 244, 244, 244, 244, 244,
    245, 245, 245, 245, 245, 245, 245, 245, 246, 246, 246, 246, 246, 246, 246,
    246, 247, 247, 247, 247, 247, 247, 247, 247, 248, 248, 248, 248, 248, 248,
    248, 248, 250, 250, 250, 250, 250, 250, 250, 250, 251, 251, 251, 251, 251,
    251, 251, 251, 252, 252, 252, 252, 252, 252, 252, 252, 253, 253, 253, 253,
    253, 253, 253, 253, 254, 254, 254, 254, 254, 254, 254, 254, 2,   2,   2,
    2,   3,   3,   3,   3,   4,   4,   4,   4,   5,   5,   5,   5,   6,   6,
    6,   6,   7,   7,   7,   7,   8,   8,   8,   8,   11,  11,  11,  11,  12,
    12,  12,  12,  14,  14,  14,  14,  15,  15,  15,  15,  16,  16,  16,  16,
    17,  17,  17,  17,  18,  18,  18,  18,  19,  19,  19,  19,  20,  20,  20,
    20,  21,  21,  21,  21,  23,  23,  23,  23,  24,  24,  24,  24,  25,  25,
    25,  25,  26,  26,  26,  26,  27,  27,  27,  27,  28,  28,  28,  28,  29,
    29,  29,  29,  30,  30,  30,  30,  31,  31,  31,  31,  127, 127, 127, 127,
    220, 220, 220, 220, 249, 249, 249, 249, 10,  13,  22,  256, 93,  93,  93,
    93,  126, 126, 126, 126, 94,  94,  125, 125, 60,  96,  123, -1,  92,  195,
    208, -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  128,
    128, 128, 128, 128, 128, 128, 128, 130, 130, 130, 130, 130, 130, 130, 130,
    131, 131, 131, 131, 131, 131, 131, 131, 162, 162, 162, 162, 162, 162, 162,
    162, 184, 184, 184, 184, 184, 184, 184, 184, 194, 194, 194, 194, 194, 194,
    194, 194, 224, 224, 224, 224, 224, 224, 224, 224, 226, 226, 226, 226, 226,
    226, 226, 226, 153, 153, 153, 153, 161, 161, 161, 161, 167, 167, 167, 167,
    172, 172, 172, 172, 176, 176, 176, 176, 177, 177, 177, 177, 179, 179, 179,
    179, 209, 209, 209, 209, 216, 216, 216, 216, 217, 217, 217, 217, 227, 227,
    227, 227, 229, 229, 229, 229, 230, 230, 230, 230, 129, 129, 132, 132, 133,
    133, 134, 134, 136, 136, 146, 146, 154, 154, 156, 156, 160, 160, 163, 163,
    164, 164, 169, 169, 170, 170, 173, 173, 178, 178, 181, 181, 185, 185, 186,
    186, 187, 187, 189, 189, 190, 190, 196, 196, 198, 198, 228, 228, 232, 232,
    233, 233, 1,   135, 137, 138, 139, 140, 141, 143, 147, 149, 150, 151, 152,
    155, 157, 158, 165, 166, 168, 174, 175, 180, 182, 183, 188, 191, 197, 231,
    239, -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  9,   9,   9,
    9,   9,   9,   9,   9,   142, 142, 142, 142, 142, 142, 142, 142, 144, 144,
    144, 144, 144, 144, 144, 144, 145, 145, 145, 145, 145, 145, 145, 145, 148,
    148, 148, 148, 148, 148, 148, 148, 159, 159, 159, 159, 159, 159, 159, 159,
    171, 171, 171, 171, 171, 171, 171, 171, 206, 206, 206, 206, 206, 206, 206,
    206, 215, 215, 215, 215, 215, 215, 215, 215, 225, 225, 225, 225, 225, 225,
    225, 225, 236, 236, 236, 236, 236, 236, 236, 236, 237, 237, 237, 237, 237,
    237, 237, 237, 199, 199, 199, 199, 207, 207, 207, 207, 234, 234, 234, 234,
    235, 235, 235, 235, 192, 192, 193, 193, 200, 200, 201, 201, 202, 202, 205,
    205, 210, 210, 213, 213, 218, 218, 219, 219, 238, 238, 240, 240, 242, 242,
    243, 243, 255, 255, 203, 204, 211, 212, 214, 221, 222, 223, 241, 244, 245,
    246, 247, 248, 250, 251, 252, 253, 254, -1,  -1,  -1,  -1,  -1,  -1,  -1,
    -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  2,   2,   2,   2,   2,   2,   2,
    2,   3,   3,   3,   3,   3,   3,   3,   3,   4,   4,   4,   4,   4,   4,
    4,   4,   5,   5,   5,   5,   5,   5,   5,   5,   6,   6,   6,   6,   6,
    6,   6,   6,   7,   7,   7,   7,   7,   7,   7,   7,   8,   8,   8,   8,
    8,   8,   8,   8,   11,  11,  11,  11,  11,  11,  11,  11,  12,  12,  12,
    12,  12,  12,  12,  12,  14,  14,  14,  14,  14,  14,  14,  14,  15,  15,
    15,  15,  15,  15,  15,  15,  16,  16,  16,  16,  16,  16,  16,  16,  17,
    17,  17,  17,  17,  17,  17,  17,  18,  18,  18,  18,  18,  18,  18,  18,
    19,  19,  19,  19,  19,  19,  19,  19,  20,  20,  20,  20,  20,  20,  20,
    20,  21,  21,  21,  21,  21,  21,  21,  21,  23,  23,  23,  23,  23,  23,
    23,  23,  24,  24,  24,  24,  24,  24,  24,  24,  25,  25,  25,  25,  25,
    25,  25,  25,  26,  26,  26,  26,  26,  26,  26,  26,  27,  27,  27,  27,
    27,  27,  27,  27,  28,  28,  28,  28,  28,  28,  28,  28,  29,  29,  29,
    29,  29,  29,  29,  29,  30,  30,  30,  30,  30,  30,  30,  30,  31,  31,
    31,  31,  31,  31,  31,  31,  127, 127, 127, 127, 127, 127, 127, 127, 220,
    220, 220, 220, 220, 220, 220, 220, 249, 249, 249, 249, 249, 249, 249, 249,
    10,  10,  13,  13,  22,  22,  256, 256, 67,  67,  67,  67,  67,  67,  67,
    67,  68,  68,  68,  68,  68,  68,  68,  68,  95,  95,  95,  95,  95,  95,
    95,  95,  98,  98,  98,  98,  98,  98,  98,  98,  100, 100, 100, 100, 100,
    100, 100, 100, 102, 102, 102, 102, 102, 102, 102, 102, 103, 103, 103, 103,
    103, 103, 103, 103, 104, 104, 104, 104, 104, 104, 104, 104, 108, 108, 108,
    108, 108, 108, 108, 108, 109, 109, 109, 109, 109, 109, 109, 109, 110, 110,
    110, 110, 110, 110, 110, 110, 112, 112, 112, 112, 112, 112, 112, 112, 114,
    114, 114, 114, 114, 114, 114, 114, 117, 117, 117, 117, 117, 117, 117, 117,
    58,  58,  58,  58,  66,  66,  66,  66,  67,  67,  67,  67,  68,  68,  68,
    68,  69,  69,  69,  69,  70,  70,  70,  70,  71,  71,  71,  71,  72,  72,
    72,  72,  73,  73,  73,  73,  74,  74,  74,  74,  75,  75,  75,  75,  76,
    76,  76,  76,  77,  77,  77,  77,  78,  78,  78,  78,  79,  79,  79,  79,
    80,  80,  80,  80,  81,  81,  81,  81,  82,  82,  82,  82,  83,  83,  83,
    83,  84,  84,  84,  84,  85,  85,  85,  85,  86,  86,  86,  86,  87,  87,
    87,  87,  89,  89,  89,  89,  106, 106, 106, 106, 107, 107, 107, 107, 113,
    113, 113, 113, 118, 118, 118, 118, 119, 119, 119, 119, 120, 120, 120, 120,
    121, 121, 121, 121, 122, 122, 122, 122, 38,  38,  42,  42,  44,  44,  59,
    59,  88,  88,  90,  90,  -1,  -1,  -1,  -1,  33,  33,  33,  33,  33,  33,
    33,  33,  34,  34,  34,  34,  34,  34,  34,  34,  40,  40,  40,  40,  40,
    40,  40,  40,  41,  41,  41,  41,  41,  41,  41,  41,  63,  63,  63,  63,
    63,  63,  63,  63,  39,  39,  39,  39,  43,  43,  43,  43,  124, 124, 124,
    124, 35,  35,  62,  62,  0,   36,  64,  91,  93,  126, -1,  -1,  94,  94,
    94,  94,  94,  94,  94,  94,  125, 125, 125, 125, 125, 125, 125, 125, 60,
    60,  60,  60,  96,  96,  96,  96,  123, 123, 123, 123, -1,  -1,  -1,  -1,
    92,  92,  92,  92,  195, 195, 195, 195, 208, 208, 208, 208, 128, 128, 130,
    130, 131, 131, 162, 162, 184, 184, 194, 194, 224, 224, 226, 226, 153, 161,
    167, 172, 176, 177, 179, 209, 216, 217, 227, 229, 230, -1,  -1,  -1,  -1,
    -1,  -1,  -1,  129, 129, 129, 129, 129, 129, 129, 129, 132, 132, 132, 132,
    132, 132, 132, 132, 133, 133, 133, 133, 133, 133, 133, 133, 134, 134, 134,
    134, 134, 134, 134, 134, 136, 136, 136, 136, 136, 136, 136, 136, 146, 146,
    146, 146, 146, 146, 146, 146, 154, 154, 154, 154, 154, 154, 154, 154, 156,
    156, 156, 156, 156, 156, 156, 156, 160, 160, 160, 160, 160, 160, 160, 160,
    163, 163, 163, 163, 163, 163, 163, 163, 164, 164, 164, 164, 164, 164, 164,
    164, 169, 169, 169, 169, 169, 169, 169, 169, 170, 170, 170, 170, 170, 170,
    170, 170, 173, 173, 173, 173, 173, 173, 173, 173, 178, 178, 178, 178, 178,
    178, 178, 178, 181, 181, 181, 181, 181, 181, 181, 181, 185, 185, 185, 185,
    185, 185, 185, 185, 186, 186, 186, 186, 186, 186, 186, 186, 187, 187, 187,
    187, 187, 187, 187, 187, 189, 189, 189, 189, 189, 189, 189, 189, 190, 190,
    190, 190, 190, 190, 190, 190, 196, 196, 196, 196, 196, 196, 196, 196, 198,
    198, 198, 198, 198, 198, 198, 198, 228, 228, 228, 228, 228, 228, 228, 228,
    232, 232, 232, 232, 232, 232, 232, 232, 233, 233, 233, 233, 233, 233, 233,
    233, 1,   1,   1,   1,   135, 135, 135, 135, 137, 137, 137, 137, 138, 138,
    138, 138, 139, 139, 139, 139, 140, 140, 140, 140, 141, 141, 141, 141, 143,
    143, 143, 143, 147, 147, 147, 147, 149, 149, 149, 149, 150, 150, 150, 150,
    151, 151, 151, 151, 152, 152, 152, 152, 155, 155, 155, 155, 157, 157, 157,
    157, 158, 158, 158, 158, 165, 165, 165, 165, 166, 166, 166, 166, 168, 168,
    168, 168, 174, 174, 174, 174, 175, 175, 175, 175, 180, 180, 180, 180, 182,
    182, 182, 182, 183, 183, 183, 183, 188, 188, 188, 188, 191, 191, 191, 191,
    197, 197, 197, 197, 231, 231, 231, 231, 239, 239, 239, 239, 9,   9,   142,
    142, 144, 144, 145, 145, 148, 148, 159, 159, 171, 171, 206, 206, 215, 215,
    225, 225, 236, 236, 237, 237, 199, 207, 234, 235, 192, 192, 192, 192, 192,
    192, 192, 192, 193, 193, 193, 193, 193, 193, 193, 193, 200, 200, 200, 200,
    200, 200, 200, 200, 201, 201, 201, 201, 201, 201, 201, 201, 202, 202, 202,
    202, 202, 202, 202, 202, 205, 205, 205, 205, 205, 205, 205, 205, 210, 210,
    210, 210, 210, 210, 210, 210, 213, 213, 213, 213, 213, 213, 213, 213, 218,
    218, 218, 218, 218, 218, 218, 218, 219, 219, 219, 219, 219, 219, 219, 219,
    238, 238, 238, 238, 238, 238, 238, 238, 240, 240, 240, 240, 240, 240, 240,
    240, 242, 242, 242, 242, 242, 242, 242, 242, 243, 243, 243, 243, 243, 243,
    243, 243, 255, 255, 255, 255, 255, 255, 255, 255, 203, 203, 203, 203, 204,
    204, 204, 204, 211, 211, 211, 211, 212, 212, 212, 212, 214, 214, 214, 214,
    221, 221, 221, 221, 222, 222, 222, 222, 223, 223, 223, 223, 241, 241, 241,
    241, 244, 244, 244, 244, 245, 245, 245, 245, 246, 246, 246, 246, 247, 247,
    247, 247, 248, 248, 248, 248, 250, 250, 250, 250, 251, 251, 251, 251, 252,
    252, 252, 252, 253, 253, 253, 253, 254, 254, 254, 254, 2,   2,   3,   3,
    4,   4,   5,   5,   6,   6,   7,   7,   8,   8,   11,  11,  12,  12,  14,
    14,  15,  15,  16,  16,  17,  17,  18,  18,  19,  19,  20,  20,  21,  21,
    23,  23,  24,  24,  25,  25,  26,  26,  27,  27,  28,  28,  29,  29,  30,
    30,  31,  31,  127, 127, 220, 220, 249, 249, -1,  -1,  10,  10,  10,  10,
    10,  10,  10,  10,  13,  13,  13,  13,  13,  13,  13,  13,  22,  22,  22,
    22,  22,  22,  22,  22,  256, 256, 256, 256, 256, 256, 256, 256, 45,  45,
    45,  45,  45,  45,  45,  45,  46,  46,  46,  46,  46,  46,  46,  46,  47,
    47,  47,  47,  47,  47,  47,  47,  51,  51,  51,  51,  51,  51,  51,  51,
    52,  52,  52,  52,  52,  52,  52,  52,  53,  53,  53,  53,  53,  53,  53,
    53,  54,  54,  54,  54,  54,  54,  54,  54,  55,  55,  55,  55,  55,  55,
    55,  55,  56,  56,  56,  56,  56,  56,  56,  56,  57,  57,  57,  57,  57,
    57,  57,  57,  50,  50,  50,  50,  50,  50,  50,  50,  97,  97,  97,  97,
    97,  97,  97,  97,  99,  99,  99,  99,  99,  99,  99,  99,  101, 101, 101,
    101, 101, 101, 101, 101, 105, 105, 105, 105, 105, 105, 105, 105, 111, 111,
    111, 111, 111, 111, 111, 111, 115, 115, 115, 115, 115, 115, 115, 115, 116,
    116, 116, 116, 116, 116, 116, 116, 32,  32,  32,  32,  37,  37,  37,  37,
    45,  45,  45,  45,  46,  46,  46,  46,  47,  47,  47,  47,  51,  51,  51,
    51,  52,  52,  52,  52,  53,  53,  53,  53,  54,  54,  54,  54,  55,  55,
    55,  55,  56,  56,  56,  56,  57,  57,  57,  57,  61,  61,  61,  61,  65,
    65,  65,  65,  95,  95,  95,  95,  98,  98,  98,  98,  100, 100, 100, 100,
    102, 102, 102, 102, 103, 103, 103, 103, 104, 104, 104, 104, 108, 108, 108,
    108, 109, 109, 109, 109, 110, 110, 110, 110, 112, 112, 112, 112, 114, 114,
    114, 114, 117, 117, 117, 117, 58,  58,  66,  66,  67,  67,  68,  68,  69,
    69,  70,  70,  71,  71,  72,  72,  73,  73,  74,  74,  75,  75,  76,  76,
    77,  77,  78,  78,  79,  79,  80,  80,  81,  81,  82,  82,  83,  83,  84,
    84,  85,  85,  86,  86,  87,  87,  89,  89,  106, 106, 107, 107, 113, 113,
    118, 118, 119, 119, 120, 120, 121, 121, 122, 122, 38,  42,  44,  59,  88,
    90,  -1,  -1,  33,  33,  33,  33,  34,  34,  34,  34,  40,  40,  40,  40,
    41,  41,  41,  41,  63,  63,  63,  63,  39,  39,  43,  43,  124, 124, 35,
    62,  -1,  -1,  -1,  -1,  0,   0,   0,   0,   0,   0,   0,   0,   36,  36,
    36,  36,  36,  36,  36,  36,  64,  64,  64,  64,  64,  64,  64,  64,  91,
    91,  91,  91,  91,  91,  91,  91,  93,  93,  93,  93,  93,  93,  93,  93,
    126, 126, 126, 126, 126, 126, 126, 126, 94,  94,  94,  94,  125, 125, 125,
    125, 60,  60,  96,  96,  123, 123, -1,  -1,  92,  92,  195, 195, 208, 208,
    128, 130, 131, 162, 184, 194, 224, 226, -1,  -1,  153, 153, 153, 153, 153,
    153, 153, 153, 161, 161, 161, 161, 161, 161, 161, 161, 167, 167, 167, 167,
    167, 167, 167, 167, 172, 172, 172, 172, 172, 172, 172, 172, 176, 176, 176,
    176, 176, 176, 176, 176, 177, 177, 177, 177, 177, 177, 177, 177, 179, 179,
    179, 179, 179, 179, 179, 179, 209, 209, 209, 209, 209, 209, 209, 209, 216,
    216, 216, 216, 216, 216, 216, 216, 217, 217, 217, 217, 217, 217, 217, 217,
    227, 227, 227, 227, 227, 227, 227, 227, 229, 229, 229, 229, 229, 229, 229,
    229, 230, 230, 230, 230, 230, 230, 230, 230, 129, 129, 129, 129, 132, 132,
    132, 132, 133, 133, 133, 133, 134, 134, 134, 134, 136, 136, 136, 136, 146,
    146, 146, 146, 154, 154, 154, 154, 156, 156, 156, 156, 160, 160, 160, 160,
    163, 163, 163, 163, 164, 164, 164, 164, 169, 169, 169, 169, 170, 170, 170,
    170, 173, 173, 173, 173, 178, 178, 178, 178, 181, 181, 181, 181, 185, 185,
    185, 185, 186, 186, 186, 186, 187, 187, 187, 187, 189, 189, 189, 189, 190,
    190, 190, 190, 196, 196, 196, 196, 198, 198, 198, 198, 228, 228, 228, 228,
    232, 232, 232, 232, 233, 233, 233, 233, 1,   1,   135, 135, 137, 137, 138,
    138, 139, 139, 140, 140, 141, 141, 143, 143, 147, 147, 149, 149, 150, 150,
    151, 151, 152, 152, 155, 155, 157, 157, 158, 158, 165, 165, 166, 166, 168,
    168, 174, 174, 175, 175, 180, 180, 182, 182, 183, 183, 188, 188, 191, 191,
    197, 197, 231, 231, 239, 239, 9,   142, 144, 145, 148, 159, 171, 206, 215,
    225, 236, 237, -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  -1,  199, 199,
    199, 199, 199, 199, 199, 199, 207, 207, 207, 207, 207, 207, 207, 207, 234,
    234, 234, 234, 234, 234, 234, 234, 235, 235, 235, 235, 235, 235, 235, 235,
    192, 192, 192, 192, 193, 193, 193, 193, 200, 200, 200, 200, 201, 201, 201,
    201, 202, 202, 202, 202, 205, 205, 205, 205, 210, 210, 210, 210, 213, 213,
    213, 213, 218, 218, 218, 218, 219, 219, 219, 219, 238, 238, 238, 238, 240,
    240, 240, 240, 242, 242, 242, 242, 243, 243, 243, 243, 255, 255, 255, 255,
    203, 203, 204, 204, 211, 211, 212, 212, 214, 214, 221, 221, 222, 222, 223,
    223, 241, 241, 244, 244, 245, 245, 246, 246, 247, 247, 248, 248, 250, 250,
    251, 251, 252, 252, 253, 253, 254, 254, 2,   3,   4,   5,   6,   7,   8,
    11,  12,  14,  15,  16,  17,  18,  19,  20,  21,  23,  24,  25,  26,  27,
    28,  29,  30,  31,  127, 220, 249, -1,  10,  10,  10,  10,  13,  13,  13,
    13,  22,  22,  22,  22,  256, 256, 256, 256,
};

static const uint8_t inverse_base64[256] = {
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 62,  255,
    255, 255, 63,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,  255, 255,
    255, 64,  255, 255, 255, 0,   1,   2,   3,   4,   5,   6,   7,   8,   9,
    10,  11,  12,  13,  14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,
    25,  255, 255, 255, 255, 255, 255, 26,  27,  28,  29,  30,  31,  32,  33,
    34,  35,  36,  37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
    49,  50,  51,  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    255,
};

static void GPR_ATTRIBUTE_NOINLINE on_hdr_log(grpc_mdelem md) {
  char* k = grpc_slice_to_c_string(GRPC_MDKEY(md));
  char* v = nullptr;
  if (grpc_is_binary_header_internal(GRPC_MDKEY(md))) {
    v = grpc_dump_slice(GRPC_MDVALUE(md), GPR_DUMP_HEX);
  } else {
    v = grpc_slice_to_c_string(GRPC_MDVALUE(md));
  }
  gpr_log(
      GPR_INFO,
      "Decode: '%s: %s', elem_interned=%d [%d], k_interned=%d, v_interned=%d",
      k, v, GRPC_MDELEM_IS_INTERNED(md), GRPC_MDELEM_STORAGE(md),
      grpc_slice_is_interned(GRPC_MDKEY(md)),
      grpc_slice_is_interned(GRPC_MDVALUE(md)));
  gpr_free(k);
  gpr_free(v);
}

/* emission helpers */
template <bool do_add>
static grpc_error* on_hdr(grpc_chttp2_hpack_parser* p, grpc_mdelem md) {
  if (GRPC_TRACE_FLAG_ENABLED(grpc_trace_chttp2_hpack_parser)) {
    on_hdr_log(md);
  }
  if (do_add) {
    GPR_DEBUG_ASSERT(GRPC_MDELEM_STORAGE(md) == GRPC_MDELEM_STORAGE_INTERNED ||
                     GRPC_MDELEM_STORAGE(md) == GRPC_MDELEM_STORAGE_STATIC);
    grpc_error* err = grpc_chttp2_hptbl_add(&p->table, md);
    if (GPR_UNLIKELY(err != GRPC_ERROR_NONE)) return err;
  }
  return p->on_header(p->on_header_user_data, md);
}

static grpc_core::UnmanagedMemorySlice take_string_extern(
    grpc_chttp2_hpack_parser* /*p*/, grpc_chttp2_hpack_parser_string* str) {
  grpc_core::UnmanagedMemorySlice s;
  if (!str->copied) {
    GPR_DEBUG_ASSERT(!grpc_slice_is_interned(str->data.referenced));
    s = static_cast<grpc_core::UnmanagedMemorySlice&>(str->data.referenced);
    str->copied = true;
    str->data.referenced = grpc_core::UnmanagedMemorySlice();
  } else {
    s = grpc_core::UnmanagedMemorySlice(str->data.copied.str,
                                        str->data.copied.length);
  }
  str->data.copied.length = 0;
  return s;
}

static grpc_core::ManagedMemorySlice take_string_intern(
    grpc_chttp2_hpack_parser* /*p*/, grpc_chttp2_hpack_parser_string* str) {
  grpc_core::ManagedMemorySlice s;
  if (!str->copied) {
    s = grpc_core::ManagedMemorySlice(&str->data.referenced);
    grpc_slice_unref_internal(str->data.referenced);
    str->copied = true;
    str->data.referenced = grpc_empty_slice();
  } else {
    s = grpc_core::ManagedMemorySlice(str->data.copied.str,
                                      str->data.copied.length);
  }
  str->data.copied.length = 0;
  return s;
}

/* jump to the next state */
static grpc_error* parse_next(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                              const uint8_t* end) {
  p->state = *p->next_state++;
  return p->state(p, cur, end);
}

/* begin parsing a header: all functionality is encoded into lookup tables
   above */
static grpc_error* parse_begin(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                               const uint8_t* end) {
  if (cur == end) {
    p->state = parse_begin;
    return GRPC_ERROR_NONE;
  }

  return first_byte_action[first_byte_lut[*cur]](p, cur, end);
}

/* stream dependency and prioritization data: we just skip it */
static grpc_error* parse_stream_weight(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  if (cur == end) {
    p->state = parse_stream_weight;
    return GRPC_ERROR_NONE;
  }

  return p->after_prioritization(p, cur + 1, end);
}

static grpc_error* parse_stream_dep3(grpc_chttp2_hpack_parser* p,
                                     const uint8_t* cur, const uint8_t* end) {
  if (cur == end) {
    p->state = parse_stream_dep3;
    return GRPC_ERROR_NONE;
  }

  return parse_stream_weight(p, cur + 1, end);
}

static grpc_error* parse_stream_dep2(grpc_chttp2_hpack_parser* p,
                                     const uint8_t* cur, const uint8_t* end) {
  if (cur == end) {
    p->state = parse_stream_dep2;
    return GRPC_ERROR_NONE;
  }

  return parse_stream_dep3(p, cur + 1, end);
}

static grpc_error* parse_stream_dep1(grpc_chttp2_hpack_parser* p,
                                     const uint8_t* cur, const uint8_t* end) {
  if (cur == end) {
    p->state = parse_stream_dep1;
    return GRPC_ERROR_NONE;
  }

  return parse_stream_dep2(p, cur + 1, end);
}

static grpc_error* parse_stream_dep0(grpc_chttp2_hpack_parser* p,
                                     const uint8_t* cur, const uint8_t* end) {
  if (cur == end) {
    p->state = parse_stream_dep0;
    return GRPC_ERROR_NONE;
  }

  return parse_stream_dep1(p, cur + 1, end);
}

static grpc_error* GPR_ATTRIBUTE_NOINLINE
on_invalid_hpack_idx(grpc_chttp2_hpack_parser* p) {
  return grpc_error_set_int(
      grpc_error_set_int(
          GRPC_ERROR_CREATE_FROM_STATIC_STRING("Invalid HPACK index received"),
          GRPC_ERROR_INT_INDEX, static_cast<intptr_t>(p->index)),
      GRPC_ERROR_INT_SIZE, static_cast<intptr_t>(p->table.num_ents));
}

/* emit an indexed field; jumps to begin the next field on completion */
static grpc_error* finish_indexed_field(grpc_chttp2_hpack_parser* p,
                                        const uint8_t* cur,
                                        const uint8_t* end) {
  grpc_mdelem md = grpc_chttp2_hptbl_lookup<true>(&p->table, p->index);
  if (GPR_UNLIKELY(GRPC_MDISNULL(md))) {
    return on_invalid_hpack_idx(p);
  }
  GRPC_STATS_INC_HPACK_RECV_INDEXED();
  grpc_error* err = on_hdr<false>(p, md);
  if (GPR_UNLIKELY(err != GRPC_ERROR_NONE)) return err;
  return parse_begin(p, cur, end);
}

/* parse an indexed field with index < 127 */
static grpc_error* parse_indexed_field(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  p->dynamic_table_update_allowed = 0;
  p->index = (*cur) & 0x7f;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  return finish_indexed_field(p, cur + 1, end);
}

/* parse an indexed field with index >= 127 */
static grpc_error* parse_indexed_field_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      finish_indexed_field};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = 0x7f;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  p->parsing.value = &p->index;
  return parse_value0(p, cur + 1, end);
}

/* When finishing with a header, get the cached md element for this index.
   This is set in parse_value_string(). We ensure (in debug mode) that the
   cached metadata corresponds with the index we are examining. */
static grpc_mdelem get_precomputed_md_for_idx(grpc_chttp2_hpack_parser* p) {
  GPR_DEBUG_ASSERT(p->md_for_index.payload != 0);
  GPR_DEBUG_ASSERT(static_cast<int64_t>(p->index) == p->precomputed_md_index);
  grpc_mdelem md = p->md_for_index;
  GPR_DEBUG_ASSERT(!GRPC_MDISNULL(md)); /* handled in string parsing */
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
#ifndef NDEBUG
  p->precomputed_md_index = -1;
#endif
  return md;
}

static const grpc_core::ManagedMemorySlice& get_indexed_key(grpc_mdelem md) {
  GPR_DEBUG_ASSERT(GRPC_MDELEM_IS_INTERNED(md));
  return static_cast<const grpc_core::ManagedMemorySlice&>(
      grpc_slice_ref_internal(GRPC_MDKEY(md)));
}

/* finish a literal header with incremental indexing */
static grpc_error* finish_lithdr_incidx(grpc_chttp2_hpack_parser* p,
                                        const uint8_t* cur,
                                        const uint8_t* end) {
  GRPC_STATS_INC_HPACK_RECV_LITHDR_INCIDX();
  grpc_mdelem md = get_precomputed_md_for_idx(p);
  grpc_error* err = on_hdr<true>(
      p, grpc_mdelem_from_slices(get_indexed_key(md),
                                 take_string_intern(p, &p->value)));
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* finish a literal header with incremental indexing with no index */
static grpc_error* finish_lithdr_incidx_v(grpc_chttp2_hpack_parser* p,
                                          const uint8_t* cur,
                                          const uint8_t* end) {
  GRPC_STATS_INC_HPACK_RECV_LITHDR_INCIDX_V();
  grpc_error* err = on_hdr<true>(
      p, grpc_mdelem_from_slices(take_string_intern(p, &p->key),
                                 take_string_intern(p, &p->value)));
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* parse a literal header with incremental indexing; index < 63 */
static grpc_error* parse_lithdr_incidx(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_value_string_with_indexed_key, finish_lithdr_incidx};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = (*cur) & 0x3f;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  return parse_string_prefix(p, cur + 1, end);
}

/* parse a literal header with incremental indexing; index >= 63 */
static grpc_error* parse_lithdr_incidx_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_string_prefix, parse_value_string_with_indexed_key,
      finish_lithdr_incidx};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = 0x3f;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  p->parsing.value = &p->index;
  return parse_value0(p, cur + 1, end);
}

/* parse a literal header with incremental indexing; index = 0 */
static grpc_error* parse_lithdr_incidx_v(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_key_string, parse_string_prefix,
      parse_value_string_with_literal_key, finish_lithdr_incidx_v};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  return parse_string_prefix(p, cur + 1, end);
}

/* finish a literal header without incremental indexing */
static grpc_error* finish_lithdr_notidx(grpc_chttp2_hpack_parser* p,
                                        const uint8_t* cur,
                                        const uint8_t* end) {
  GRPC_STATS_INC_HPACK_RECV_LITHDR_NOTIDX();
  grpc_mdelem md = get_precomputed_md_for_idx(p);
  grpc_error* err = on_hdr<false>(
      p, grpc_mdelem_from_slices(get_indexed_key(md),
                                 take_string_extern(p, &p->value)));
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* finish a literal header without incremental indexing with index = 0 */
static grpc_error* finish_lithdr_notidx_v(grpc_chttp2_hpack_parser* p,
                                          const uint8_t* cur,
                                          const uint8_t* end) {
  GRPC_STATS_INC_HPACK_RECV_LITHDR_NOTIDX_V();
  grpc_error* err = on_hdr<false>(
      p, grpc_mdelem_from_slices(take_string_intern(p, &p->key),
                                 take_string_extern(p, &p->value)));
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* parse a literal header without incremental indexing; index < 15 */
static grpc_error* parse_lithdr_notidx(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_value_string_with_indexed_key, finish_lithdr_notidx};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = (*cur) & 0xf;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  return parse_string_prefix(p, cur + 1, end);
}

/* parse a literal header without incremental indexing; index >= 15 */
static grpc_error* parse_lithdr_notidx_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_string_prefix, parse_value_string_with_indexed_key,
      finish_lithdr_notidx};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = 0xf;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  p->parsing.value = &p->index;
  return parse_value0(p, cur + 1, end);
}

/* parse a literal header without incremental indexing; index == 0 */
static grpc_error* parse_lithdr_notidx_v(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_key_string, parse_string_prefix,
      parse_value_string_with_literal_key, finish_lithdr_notidx_v};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  return parse_string_prefix(p, cur + 1, end);
}

/* finish a literal header that is never indexed */
static grpc_error* finish_lithdr_nvridx(grpc_chttp2_hpack_parser* p,
                                        const uint8_t* cur,
                                        const uint8_t* end) {
  GRPC_STATS_INC_HPACK_RECV_LITHDR_NVRIDX();
  grpc_mdelem md = get_precomputed_md_for_idx(p);
  grpc_error* err = on_hdr<false>(
      p, grpc_mdelem_from_slices(get_indexed_key(md),
                                 take_string_extern(p, &p->value)));
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* finish a literal header that is never indexed with an extra value */
static grpc_error* finish_lithdr_nvridx_v(grpc_chttp2_hpack_parser* p,
                                          const uint8_t* cur,
                                          const uint8_t* end) {
  GRPC_STATS_INC_HPACK_RECV_LITHDR_NVRIDX_V();
  grpc_error* err = on_hdr<false>(
      p, grpc_mdelem_from_slices(take_string_intern(p, &p->key),
                                 take_string_extern(p, &p->value)));
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* parse a literal header that is never indexed; index < 15 */
static grpc_error* parse_lithdr_nvridx(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_value_string_with_indexed_key, finish_lithdr_nvridx};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = (*cur) & 0xf;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  return parse_string_prefix(p, cur + 1, end);
}

/* parse a literal header that is never indexed; index >= 15 */
static grpc_error* parse_lithdr_nvridx_x(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_string_prefix, parse_value_string_with_indexed_key,
      finish_lithdr_nvridx};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  p->index = 0xf;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  p->parsing.value = &p->index;
  return parse_value0(p, cur + 1, end);
}

/* parse a literal header that is never indexed; index == 0 */
static grpc_error* parse_lithdr_nvridx_v(grpc_chttp2_hpack_parser* p,
                                         const uint8_t* cur,
                                         const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      parse_key_string, parse_string_prefix,
      parse_value_string_with_literal_key, finish_lithdr_nvridx_v};
  p->dynamic_table_update_allowed = 0;
  p->next_state = and_then;
  return parse_string_prefix(p, cur + 1, end);
}

/* finish parsing a max table size change */
static grpc_error* finish_max_tbl_size(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  if (GRPC_TRACE_FLAG_ENABLED(grpc_trace_chttp2_hpack_parser)) {
    gpr_log(GPR_INFO, "MAX TABLE SIZE: %d", p->index);
  }
  grpc_error* err =
      grpc_chttp2_hptbl_set_current_table_size(&p->table, p->index);
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_begin(p, cur, end);
}

/* parse a max table size change, max size < 15 */
static grpc_error* parse_max_tbl_size(grpc_chttp2_hpack_parser* p,
                                      const uint8_t* cur, const uint8_t* end) {
  if (p->dynamic_table_update_allowed == 0) {
    return parse_error(
        p, cur, end,
        GRPC_ERROR_CREATE_FROM_STATIC_STRING(
            "More than two max table size changes in a single frame"));
  }
  p->dynamic_table_update_allowed--;
  p->index = (*cur) & 0x1f;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  return finish_max_tbl_size(p, cur + 1, end);
}

/* parse a max table size change, max size >= 15 */
static grpc_error* parse_max_tbl_size_x(grpc_chttp2_hpack_parser* p,
                                        const uint8_t* cur,
                                        const uint8_t* end) {
  static const grpc_chttp2_hpack_parser_state and_then[] = {
      finish_max_tbl_size};
  if (p->dynamic_table_update_allowed == 0) {
    return parse_error(
        p, cur, end,
        GRPC_ERROR_CREATE_FROM_STATIC_STRING(
            "More than two max table size changes in a single frame"));
  }
  p->dynamic_table_update_allowed--;
  p->next_state = and_then;
  p->index = 0x1f;
  p->md_for_index.payload = 0; /* Invalidate cached md when index changes. */
  p->parsing.value = &p->index;
  return parse_value0(p, cur + 1, end);
}

/* a parse error: jam the parse state into parse_error, and return error */
static grpc_error* parse_error(grpc_chttp2_hpack_parser* p,
                               const uint8_t* /*cur*/, const uint8_t* /*end*/,
                               grpc_error* err) {
  GPR_ASSERT(err != GRPC_ERROR_NONE);
  if (p->last_error == GRPC_ERROR_NONE) {
    p->last_error = GRPC_ERROR_REF(err);
  }
  p->state = still_parse_error;
  return err;
}

static grpc_error* still_parse_error(grpc_chttp2_hpack_parser* p,
                                     const uint8_t* /*cur*/,
                                     const uint8_t* /*end*/) {
  return GRPC_ERROR_REF(p->last_error);
}

static grpc_error* parse_illegal_op(grpc_chttp2_hpack_parser* p,
                                    const uint8_t* cur, const uint8_t* end) {
  GPR_ASSERT(cur != end);
  grpc_error* err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(
      absl::StrCat("Illegal hpack op code ", *cur).c_str());
  return parse_error(p, cur, end, err);
}

/* parse the 1st byte of a varint into p->parsing.value
   no overflow is possible */
static grpc_error* parse_value0(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end) {
  if (cur == end) {
    p->state = parse_value0;
    return GRPC_ERROR_NONE;
  }

  *p->parsing.value += (*cur) & 0x7f;

  if ((*cur) & 0x80) {
    return parse_value1(p, cur + 1, end);
  } else {
    return parse_next(p, cur + 1, end);
  }
}

/* parse the 2nd byte of a varint into p->parsing.value
   no overflow is possible */
static grpc_error* parse_value1(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end) {
  if (cur == end) {
    p->state = parse_value1;
    return GRPC_ERROR_NONE;
  }

  *p->parsing.value += ((static_cast<uint32_t>(*cur)) & 0x7f) << 7;

  if ((*cur) & 0x80) {
    return parse_value2(p, cur + 1, end);
  } else {
    return parse_next(p, cur + 1, end);
  }
}

/* parse the 3rd byte of a varint into p->parsing.value
   no overflow is possible */
static grpc_error* parse_value2(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end) {
  if (cur == end) {
    p->state = parse_value2;
    return GRPC_ERROR_NONE;
  }

  *p->parsing.value += ((static_cast<uint32_t>(*cur)) & 0x7f) << 14;

  if ((*cur) & 0x80) {
    return parse_value3(p, cur + 1, end);
  } else {
    return parse_next(p, cur + 1, end);
  }
}

/* parse the 4th byte of a varint into p->parsing.value
   no overflow is possible */
static grpc_error* parse_value3(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end) {
  if (cur == end) {
    p->state = parse_value3;
    return GRPC_ERROR_NONE;
  }

  *p->parsing.value += ((static_cast<uint32_t>(*cur)) & 0x7f) << 21;

  if ((*cur) & 0x80) {
    return parse_value4(p, cur + 1, end);
  } else {
    return parse_next(p, cur + 1, end);
  }
}

/* parse the 5th byte of a varint into p->parsing.value
   depending on the byte, we may overflow, and care must be taken */
static grpc_error* parse_value4(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end) {
  uint8_t c;
  uint32_t cur_value;
  uint32_t add_value;

  if (cur == end) {
    p->state = parse_value4;
    return GRPC_ERROR_NONE;
  }

  c = (*cur) & 0x7f;
  if (c > 0xf) {
    goto error;
  }

  cur_value = *p->parsing.value;
  add_value = (static_cast<uint32_t>(c)) << 28;
  if (add_value > 0xffffffffu - cur_value) {
    goto error;
  }

  *p->parsing.value = cur_value + add_value;

  if ((*cur) & 0x80) {
    return parse_value5up(p, cur + 1, end);
  } else {
    return parse_next(p, cur + 1, end);
  }

error:
  grpc_error* err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(
      absl::StrFormat(
          "integer overflow in hpack integer decoding: have 0x%08x, "
          "got byte 0x%02x on byte 5",
          *p->parsing.value, *cur)
          .c_str());
  return parse_error(p, cur, end, err);
}

/* parse any trailing bytes in a varint: it's possible to append an arbitrary
   number of 0x80's and not affect the value - a zero will terminate - and
   anything else will overflow */
static grpc_error* parse_value5up(grpc_chttp2_hpack_parser* p,
                                  const uint8_t* cur, const uint8_t* end) {
  while (cur != end && *cur == 0x80) {
    ++cur;
  }

  if (cur == end) {
    p->state = parse_value5up;
    return GRPC_ERROR_NONE;
  }

  if (*cur == 0) {
    return parse_next(p, cur + 1, end);
  }

  grpc_error* err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(
      absl::StrFormat(
          "integer overflow in hpack integer decoding: have 0x%08x, "
          "got byte 0x%02x sometime after byte 5",
          *p->parsing.value, *cur)
          .c_str());
  return parse_error(p, cur, end, err);
}

/* parse a string prefix */
static grpc_error* parse_string_prefix(grpc_chttp2_hpack_parser* p,
                                       const uint8_t* cur, const uint8_t* end) {
  if (cur == end) {
    p->state = parse_string_prefix;
    return GRPC_ERROR_NONE;
  }

  p->strlen = (*cur) & 0x7f;
  p->huff = (*cur) >> 7;
  if (p->strlen == 0x7f) {
    p->parsing.value = &p->strlen;
    return parse_value0(p, cur + 1, end);
  } else {
    return parse_next(p, cur + 1, end);
  }
}

/* append some bytes to a string */
static void append_bytes(grpc_chttp2_hpack_parser_string* str,
                         const uint8_t* data, size_t length) {
  if (length == 0) return;
  if (length + str->data.copied.length > str->data.copied.capacity) {
    GPR_ASSERT(str->data.copied.length + length <= UINT32_MAX);
    str->data.copied.capacity =
        static_cast<uint32_t>(str->data.copied.length + length);
    str->data.copied.str = static_cast<char*>(
        gpr_realloc(str->data.copied.str, str->data.copied.capacity));
  }
  memcpy(str->data.copied.str + str->data.copied.length, data, length);
  GPR_ASSERT(length <= UINT32_MAX - str->data.copied.length);
  str->data.copied.length += static_cast<uint32_t>(length);
}

static grpc_error* append_string(grpc_chttp2_hpack_parser* p,
                                 const uint8_t* cur, const uint8_t* end) {
  grpc_chttp2_hpack_parser_string* str = p->parsing.str;
  uint32_t bits;
  uint8_t decoded[3];
  switch (static_cast<binary_state>(p->binary)) {
    case NOT_BINARY:
      append_bytes(str, cur, static_cast<size_t>(end - cur));
      return GRPC_ERROR_NONE;
    case BINARY_BEGIN:
      if (cur == end) {
        p->binary = BINARY_BEGIN;
        return GRPC_ERROR_NONE;
      }
      if (*cur == 0) {
        /* 'true-binary' case */
        ++cur;
        p->binary = NOT_BINARY;
        GRPC_STATS_INC_HPACK_RECV_BINARY();
        append_bytes(str, cur, static_cast<size_t>(end - cur));
        return GRPC_ERROR_NONE;
      }
      GRPC_STATS_INC_HPACK_RECV_BINARY_BASE64();
    /* fallthrough */
    b64_byte0:
    case B64_BYTE0:
      if (cur == end) {
        p->binary = B64_BYTE0;
        return GRPC_ERROR_NONE;
      }
      bits = inverse_base64[*cur];
      ++cur;
      if (bits == 255)
        return parse_error(
            p, cur, end,
            GRPC_ERROR_CREATE_FROM_STATIC_STRING("Illegal base64 character"));
      else if (bits == 64)
        goto b64_byte0;
      p->base64_buffer = bits << 18;
    /* fallthrough */
    b64_byte1:
    case B64_BYTE1:
      if (cur == end) {
        p->binary = B64_BYTE1;
        return GRPC_ERROR_NONE;
      }
      bits = inverse_base64[*cur];
      ++cur;
      if (bits == 255)
        return parse_error(
            p, cur, end,
            GRPC_ERROR_CREATE_FROM_STATIC_STRING("Illegal base64 character"));
      else if (bits == 64)
        goto b64_byte1;
      p->base64_buffer |= bits << 12;
    /* fallthrough */
    b64_byte2:
    case B64_BYTE2:
      if (cur == end) {
        p->binary = B64_BYTE2;
        return GRPC_ERROR_NONE;
      }
      bits = inverse_base64[*cur];
      ++cur;
      if (bits == 255)
        return parse_error(
            p, cur, end,
            GRPC_ERROR_CREATE_FROM_STATIC_STRING("Illegal base64 character"));
      else if (bits == 64)
        goto b64_byte2;
      p->base64_buffer |= bits << 6;
    /* fallthrough */
    b64_byte3:
    case B64_BYTE3:
      if (cur == end) {
        p->binary = B64_BYTE3;
        return GRPC_ERROR_NONE;
      }
      bits = inverse_base64[*cur];
      ++cur;
      if (bits == 255)
        return parse_error(
            p, cur, end,
            GRPC_ERROR_CREATE_FROM_STATIC_STRING("Illegal base64 character"));
      else if (bits == 64)
        goto b64_byte3;
      p->base64_buffer |= bits;
      bits = p->base64_buffer;
      decoded[0] = static_cast<uint8_t>(bits >> 16);
      decoded[1] = static_cast<uint8_t>(bits >> 8);
      decoded[2] = static_cast<uint8_t>(bits);
      append_bytes(str, decoded, 3);
      goto b64_byte0;
  }
  GPR_UNREACHABLE_CODE(return parse_error(
      p, cur, end,
      GRPC_ERROR_CREATE_FROM_STATIC_STRING("Should never reach here")));
}

static grpc_error* finish_str(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                              const uint8_t* end) {
  uint8_t decoded[2];
  uint32_t bits;
  grpc_chttp2_hpack_parser_string* str = p->parsing.str;
  switch (static_cast<binary_state>(p->binary)) {
    case NOT_BINARY:
      break;
    case BINARY_BEGIN:
      break;
    case B64_BYTE0:
      break;
    case B64_BYTE1:
      return parse_error(p, cur, end,
                         GRPC_ERROR_CREATE_FROM_STATIC_STRING(
                             "illegal base64 encoding")); /* illegal encoding */
    case B64_BYTE2:
      bits = p->base64_buffer;
      if (bits & 0xffff) {
        grpc_error* err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(
            absl::StrFormat("trailing bits in base64 encoding: 0x%04x",
                            bits & 0xffff)
                .c_str());
        return parse_error(p, cur, end, err);
      }
      decoded[0] = static_cast<uint8_t>(bits >> 16);
      append_bytes(str, decoded, 1);
      break;
    case B64_BYTE3:
      bits = p->base64_buffer;
      if (bits & 0xff) {
        grpc_error* err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(
            absl::StrFormat("trailing bits in base64 encoding: 0x%02x",
                            bits & 0xff)
                .c_str());
        return parse_error(p, cur, end, err);
      }
      decoded[0] = static_cast<uint8_t>(bits >> 16);
      decoded[1] = static_cast<uint8_t>(bits >> 8);
      append_bytes(str, decoded, 2);
      break;
  }
  return GRPC_ERROR_NONE;
}

/* decode a nibble from a huffman encoded stream */
static grpc_error* huff_nibble(grpc_chttp2_hpack_parser* p, uint8_t nibble) {
  int16_t emit = emit_sub_tbl[16 * emit_tbl[p->huff_state] + nibble];
  int16_t next = next_sub_tbl[16 * next_tbl[p->huff_state] + nibble];
  if (emit != -1) {
    if (emit >= 0 && emit < 256) {
      uint8_t c = static_cast<uint8_t>(emit);
      grpc_error* err = append_string(p, &c, (&c) + 1);
      if (err != GRPC_ERROR_NONE) return err;
    } else {
      assert(emit == 256);
    }
  }
  p->huff_state = next;
  return GRPC_ERROR_NONE;
}

/* decode full bytes from a huffman encoded stream */
static grpc_error* add_huff_bytes(grpc_chttp2_hpack_parser* p,
                                  const uint8_t* cur, const uint8_t* end) {
  for (; cur != end; ++cur) {
    grpc_error* err = huff_nibble(p, *cur >> 4);
    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
    err = huff_nibble(p, *cur & 0xf);
    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  }
  return GRPC_ERROR_NONE;
}

/* decode some string bytes based on the current decoding mode
   (huffman or not) */
static grpc_error* add_str_bytes(grpc_chttp2_hpack_parser* p,
                                 const uint8_t* cur, const uint8_t* end) {
  if (p->huff) {
    return add_huff_bytes(p, cur, end);
  } else {
    return append_string(p, cur, end);
  }
}

/* parse a string - tries to do large chunks at a time */
static grpc_error* parse_string(grpc_chttp2_hpack_parser* p, const uint8_t* cur,
                                const uint8_t* end) {
  size_t remaining = p->strlen - p->strgot;
  size_t given = static_cast<size_t>(end - cur);
  if (remaining <= given) {
    grpc_error* err = add_str_bytes(p, cur, cur + remaining);
    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
    err = finish_str(p, cur + remaining, end);
    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
    return parse_next(p, cur + remaining, end);
  } else {
    grpc_error* err = add_str_bytes(p, cur, cur + given);
    if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
    GPR_ASSERT(given <= UINT32_MAX - p->strgot);
    p->strgot += static_cast<uint32_t>(given);
    p->state = parse_string;
    return GRPC_ERROR_NONE;
  }
}

/* begin parsing a string - performs setup, calls parse_string */
static grpc_error* begin_parse_string(grpc_chttp2_hpack_parser* p,
                                      const uint8_t* cur, const uint8_t* end,
                                      uint8_t binary,
                                      grpc_chttp2_hpack_parser_string* str) {
  if (!p->huff && binary == NOT_BINARY &&
      static_cast<uint32_t>(end - cur) >= p->strlen &&
      p->current_slice_refcount != nullptr) {
    GRPC_STATS_INC_HPACK_RECV_UNCOMPRESSED();
    str->copied = false;
    str->data.referenced.refcount = p->current_slice_refcount;
    str->data.referenced.data.refcounted.bytes = const_cast<uint8_t*>(cur);
    str->data.referenced.data.refcounted.length = p->strlen;
    grpc_slice_ref_internal(str->data.referenced);
    return parse_next(p, cur + p->strlen, end);
  }
  p->strgot = 0;
  str->copied = true;
  str->data.copied.length = 0;
  p->parsing.str = str;
  p->huff_state = 0;
  p->binary = binary;
  switch (p->binary) {
    case NOT_BINARY:
      if (p->huff) {
        GRPC_STATS_INC_HPACK_RECV_HUFFMAN();
      } else {
        GRPC_STATS_INC_HPACK_RECV_UNCOMPRESSED();
      }
      break;
    case BINARY_BEGIN:
      /* stats incremented later: don't know true binary or not */
      break;
    default:
      abort();
  }
  return parse_string(p, cur, end);
}

/* parse the key string */
static grpc_error* parse_key_string(grpc_chttp2_hpack_parser* p,
                                    const uint8_t* cur, const uint8_t* end) {
  return begin_parse_string(p, cur, end, NOT_BINARY, &p->key);
}

/* check if a key represents a binary header or not */

static bool is_binary_literal_header(grpc_chttp2_hpack_parser* p) {
  /* We know that either argument here is a reference counter slice.
   * 1. If it is a grpc_core::StaticSlice, the refcount is set to kNoopRefcount.
   * 2. If it's p->key.data.referenced, then p->key.copied was set to false,
   *    which occurs in begin_parse_string() - where the refcount is set to
   *    p->current_slice_refcount, which is not null. */
  return grpc_is_refcounted_slice_binary_header(
      p->key.copied ? grpc_core::ExternallyManagedSlice(
                          p->key.data.copied.str, p->key.data.copied.length)
                    : p->key.data.referenced);
}

/* Cache the metadata for the given index during initial parsing. This avoids a
   pointless recomputation of the metadata when finishing a header. We read the
   cached value in get_precomputed_md_for_idx(). */
static void set_precomputed_md_idx(grpc_chttp2_hpack_parser* p,
                                   grpc_mdelem md) {
  GPR_DEBUG_ASSERT(p->md_for_index.payload == 0);
  GPR_DEBUG_ASSERT(p->precomputed_md_index == -1);
  p->md_for_index = md;
#ifndef NDEBUG
  p->precomputed_md_index = p->index;
#endif
}

/* Determines if a metadata element key associated with the current parser index
   is a binary indexed header during string parsing. We'll need to revisit this
   metadata when we're done parsing, so we cache the metadata for this index
   here using set_precomputed_md_idx(). */
static grpc_error* is_binary_indexed_header(grpc_chttp2_hpack_parser* p,
                                            bool* is) {
  grpc_mdelem elem = grpc_chttp2_hptbl_lookup(&p->table, p->index);
  if (GPR_UNLIKELY(GRPC_MDISNULL(elem))) {
    return on_invalid_hpack_idx(p);
  }
  /* We know that GRPC_MDKEY(elem) points to a reference counted slice since:
   * 1. elem was a result of grpc_chttp2_hptbl_lookup
   * 2. An item in this table is either static (see entries with
   *    index < GRPC_CHTTP2_LAST_STATIC_ENTRY or added via
   *    grpc_chttp2_hptbl_add).
   * 3. If added via grpc_chttp2_hptbl_add, the entry is either static or
   *    interned.
   * 4. Both static and interned element slices have non-null refcounts. */
  *is = grpc_is_refcounted_slice_binary_header(GRPC_MDKEY(elem));
  set_precomputed_md_idx(p, elem);
  return GRPC_ERROR_NONE;
}

/* parse the value string */
static grpc_error* parse_value_string(grpc_chttp2_hpack_parser* p,
                                      const uint8_t* cur, const uint8_t* end,
                                      bool is_binary) {
  return begin_parse_string(p, cur, end, is_binary ? BINARY_BEGIN : NOT_BINARY,
                            &p->value);
}

static grpc_error* parse_value_string_with_indexed_key(
    grpc_chttp2_hpack_parser* p, const uint8_t* cur, const uint8_t* end) {
  bool is_binary = false;
  grpc_error* err = is_binary_indexed_header(p, &is_binary);
  if (err != GRPC_ERROR_NONE) return parse_error(p, cur, end, err);
  return parse_value_string(p, cur, end, is_binary);
}

static grpc_error* parse_value_string_with_literal_key(
    grpc_chttp2_hpack_parser* p, const uint8_t* cur, const uint8_t* end) {
  return parse_value_string(p, cur, end, is_binary_literal_header(p));
}

/* "Uninitialized" header parser to save us a branch in on_hdr().  */
static grpc_error* on_header_uninitialized(void* /*user_data*/,
                                           grpc_mdelem md) {
  GRPC_MDELEM_UNREF(md);
  return GRPC_ERROR_CREATE_FROM_STATIC_STRING("on_header callback not set");
}

/* PUBLIC INTERFACE */

void grpc_chttp2_hpack_parser_init(grpc_chttp2_hpack_parser* p) {
  p->on_header = on_header_uninitialized;
  p->on_header_user_data = nullptr;
  p->state = parse_begin;
  p->key.data.referenced = grpc_empty_slice();
  p->key.data.copied.str = nullptr;
  p->key.data.copied.capacity = 0;
  p->key.data.copied.length = 0;
  p->value.data.referenced = grpc_empty_slice();
  p->value.data.copied.str = nullptr;
  p->value.data.copied.capacity = 0;
  p->value.data.copied.length = 0;
  /* Cached metadata for the current index the parser is handling. This is set
     to 0 initially, invalidated when the index changes, and invalidated when it
     is read (by get_precomputed_md_for_idx()). It is set during string parsing,
     by set_precomputed_md_idx() - which is called by parse_value_string().
     The goal here is to avoid recomputing the metadata for the index when
     finishing with a header as well as the initial parse. */
  p->md_for_index.payload = 0;
#ifndef NDEBUG
  /* In debug mode, this ensures that the cached metadata we're reading is in
   * fact correct for the index we are examining. */
  p->precomputed_md_index = -1;
#endif
  p->dynamic_table_update_allowed = 2;
  p->last_error = GRPC_ERROR_NONE;
}

void grpc_chttp2_hpack_parser_set_has_priority(grpc_chttp2_hpack_parser* p) {
  p->after_prioritization = p->state;
  p->state = parse_stream_dep0;
}

void grpc_chttp2_hpack_parser_destroy(grpc_chttp2_hpack_parser* p) {
  grpc_chttp2_hptbl_destroy(&p->table);
  GRPC_ERROR_UNREF(p->last_error);
  grpc_slice_unref_internal(p->key.data.referenced);
  grpc_slice_unref_internal(p->value.data.referenced);
  gpr_free(p->key.data.copied.str);
  gpr_free(p->value.data.copied.str);
}

grpc_error* grpc_chttp2_hpack_parser_parse(grpc_chttp2_hpack_parser* p,
                                           const grpc_slice& slice) {
/* max number of bytes to parse at a time... limits call stack depth on
 * compilers without TCO */
#define MAX_PARSE_LENGTH 1024
  p->current_slice_refcount = slice.refcount;
  const uint8_t* start = GRPC_SLICE_START_PTR(slice);
  const uint8_t* end = GRPC_SLICE_END_PTR(slice);
  grpc_error* error = GRPC_ERROR_NONE;
  while (start != end && error == GRPC_ERROR_NONE) {
    const uint8_t* target = start + GPR_MIN(MAX_PARSE_LENGTH, end - start);
    error = p->state(p, start, target);
    start = target;
  }
  p->current_slice_refcount = nullptr;
  return error;
}

typedef void (*maybe_complete_func_type)(grpc_chttp2_transport* t,
                                         grpc_chttp2_stream* s);
static const maybe_complete_func_type maybe_complete_funcs[] = {
    grpc_chttp2_maybe_complete_recv_initial_metadata,
    grpc_chttp2_maybe_complete_recv_trailing_metadata};

static void force_client_rst_stream(void* sp, grpc_error* /*error*/) {
  grpc_chttp2_stream* s = static_cast<grpc_chttp2_stream*>(sp);
  grpc_chttp2_transport* t = s->t;
  if (!s->write_closed) {
    grpc_chttp2_add_rst_stream_to_next_write(t, s->id, GRPC_HTTP2_NO_ERROR,
                                             &s->stats.outgoing);
    grpc_chttp2_initiate_write(t, GRPC_CHTTP2_INITIATE_WRITE_FORCE_RST_STREAM);
    grpc_chttp2_mark_stream_closed(t, s, true, true, GRPC_ERROR_NONE);
  }
  GRPC_CHTTP2_STREAM_UNREF(s, "final_rst");
}

static void parse_stream_compression_md(grpc_chttp2_transport* /*t*/,
                                        grpc_chttp2_stream* s,
                                        grpc_metadata_batch* initial_metadata) {
  if (initial_metadata->idx.named.content_encoding == nullptr ||
      grpc_stream_compression_method_parse(
          GRPC_MDVALUE(initial_metadata->idx.named.content_encoding->md), false,
          &s->stream_decompression_method) == 0) {
    s->stream_decompression_method =
        GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS;
  }

  if (s->stream_decompression_method !=
      GRPC_STREAM_COMPRESSION_IDENTITY_DECOMPRESS) {
    s->stream_decompression_ctx = nullptr;
    grpc_slice_buffer_init(&s->decompressed_data_buffer);
  }
}

grpc_error* grpc_chttp2_header_parser_parse(void* hpack_parser,
                                            grpc_chttp2_transport* t,
                                            grpc_chttp2_stream* s,
                                            const grpc_slice& slice,
                                            int is_last) {
  GPR_TIMER_SCOPE("grpc_chttp2_header_parser_parse", 0);
  grpc_chttp2_hpack_parser* parser =
      static_cast<grpc_chttp2_hpack_parser*>(hpack_parser);
  if (s != nullptr) {
    s->stats.incoming.header_bytes += GRPC_SLICE_LENGTH(slice);
  }
  grpc_error* error = grpc_chttp2_hpack_parser_parse(parser, slice);
  if (error != GRPC_ERROR_NONE) {
    return error;
  }
  if (is_last) {
    if (parser->is_boundary && parser->state != parse_begin) {
      return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
          "end of header frame not aligned with a hpack record boundary");
    }
    /* need to check for null stream: this can occur if we receive an invalid
       stream id on a header */
    if (s != nullptr) {
      if (parser->is_boundary) {
        if (s->header_frames_received == GPR_ARRAY_SIZE(s->metadata_buffer)) {
          return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
              "Too many trailer frames");
        }
        /* Process stream compression md element if it exists */
        if (s->header_frames_received ==
            0) { /* Only acts on initial metadata */
          parse_stream_compression_md(t, s, &s->metadata_buffer[0].batch);
        }
        s->published_metadata[s->header_frames_received] =
            GRPC_METADATA_PUBLISHED_FROM_WIRE;
        maybe_complete_funcs[s->header_frames_received](t, s);
        s->header_frames_received++;
      }
      if (parser->is_eof) {
        if (t->is_client && !s->write_closed) {
          /* server eof ==> complete closure; we may need to forcefully close
             the stream. Wait until the combiner lock is ready to be released
             however -- it might be that we receive a RST_STREAM following this
             and can avoid the extra write */
          GRPC_CHTTP2_STREAM_REF(s, "final_rst");
          t->combiner->FinallyRun(
              GRPC_CLOSURE_CREATE(force_client_rst_stream, s, nullptr),
              GRPC_ERROR_NONE);
        }
        grpc_chttp2_mark_stream_closed(t, s, true, false, GRPC_ERROR_NONE);
      }
    }
    parser->on_header = on_header_uninitialized;
    parser->on_header_user_data = nullptr;
    parser->is_boundary = 0xde;
    parser->is_eof = 0xde;
    parser->dynamic_table_update_allowed = 2;
  }
  return GRPC_ERROR_NONE;
}
