/*
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <libavutil/avassert.h>
#include <libavutil/opt.h>
#include <libavutil/pixfmt.h>

#include "cbs/cbs.h"
#include "cbs/cbs_av1.h"

#include "cbs_internal.h"


static int cbs_av1_read_uvlc(CodedBitstreamContext *ctx, GetBitContext *gbc,
  const char *name, uint32_t *write_to,
  uint32_t range_min, uint32_t range_max) {
  uint32_t zeroes, bits_value, value;
  int position;

  if(ctx->trace_enable)
    position = get_bits_count(gbc);

  zeroes = 0;
  while(1) {
    if(get_bits_left(gbc) < 1) {
      av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
                                         "%s: bitstream ended.\n",
        name);
      return AVERROR_INVALIDDATA;
    }

    if(get_bits1(gbc))
      break;
    ++zeroes;
  }

  if(zeroes >= 32) {
    value = MAX_UINT_BITS(32);
  }
  else {
    if(get_bits_left(gbc) < zeroes) {
      av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
                                         "%s: bitstream ended.\n",
        name);
      return AVERROR_INVALIDDATA;
    }

    bits_value = get_bits_long(gbc, zeroes);
    value      = bits_value + (UINT32_C(1) << zeroes) - 1;
  }

  if(ctx->trace_enable) {
    char bits[65];
    int i, j, k;

    if(zeroes >= 32) {
      while(zeroes > 32) {
        k = FFMIN(zeroes - 32, 32);
        for(i = 0; i < k; i++)
          bits[i] = '0';
        bits[i] = 0;
        ff_cbs_trace_syntax_element(ctx, position, name,
          NULL, bits, 0);
        zeroes -= k;
        position += k;
      }
    }

    for(i = 0; i < zeroes; i++)
      bits[i] = '0';
    bits[i++] = '1';

    if(zeroes < 32) {
      for(j = 0; j < zeroes; j++)
        bits[i++] = (bits_value >> (zeroes - j - 1) & 1) ? '1' : '0';
    }

    bits[i] = 0;
    ff_cbs_trace_syntax_element(ctx, position, name,
      NULL, bits, value);
  }

  if(value < range_min || value > range_max) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
                                       "%" PRIu32 ", but must be in [%" PRIu32 ",%" PRIu32 "].\n",
      name, value, range_min, range_max);
    return AVERROR_INVALIDDATA;
  }

  *write_to = value;
  return 0;
}

static int cbs_av1_write_uvlc(CodedBitstreamContext *ctx, PutBitContext *pbc,
  const char *name, uint32_t value,
  uint32_t range_min, uint32_t range_max) {
  uint32_t v;
  int position, zeroes;

  if(value < range_min || value > range_max) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
                                       "%" PRIu32 ", but must be in [%" PRIu32 ",%" PRIu32 "].\n",
      name, value, range_min, range_max);
    return AVERROR_INVALIDDATA;
  }

  if(ctx->trace_enable)
    position = put_bits_count(pbc);

  zeroes = av_log2(value + 1);
  v      = value - (1U << zeroes) + 1;
  put_bits(pbc, zeroes, 0);
  put_bits(pbc, 1, 1);
  put_bits(pbc, zeroes, v);

  if(ctx->trace_enable) {
    char bits[65];
    int i, j;
    i = 0;
    for(j = 0; j < zeroes; j++)
      bits[i++] = '0';
    bits[i++] = '1';
    for(j = 0; j < zeroes; j++)
      bits[i++] = (v >> (zeroes - j - 1) & 1) ? '1' : '0';
    bits[i++] = 0;
    ff_cbs_trace_syntax_element(ctx, position, name, NULL,
      bits, value);
  }

  return 0;
}

static int cbs_av1_read_leb128(CodedBitstreamContext *ctx, GetBitContext *gbc,
  const char *name, uint64_t *write_to) {
  uint64_t value;
  int position, err, i;

  if(ctx->trace_enable)
    position = get_bits_count(gbc);

  value = 0;
  for(i = 0; i < 8; i++) {
    int subscript[2] = { 1, i };
    uint32_t byte;
    err = ff_cbs_read_unsigned(ctx, gbc, 8, "leb128_byte[i]", subscript,
      &byte, 0x00, 0xff);
    if(err < 0)
      return err;

    value |= (uint64_t)(byte & 0x7f) << (i * 7);
    if(!(byte & 0x80))
      break;
  }

  if(value > UINT32_MAX)
    return AVERROR_INVALIDDATA;

  if(ctx->trace_enable)
    ff_cbs_trace_syntax_element(ctx, position, name, NULL, "", value);

  *write_to = value;
  return 0;
}

static int cbs_av1_write_leb128(CodedBitstreamContext *ctx, PutBitContext *pbc,
  const char *name, uint64_t value) {
  int position, err, len, i;
  uint8_t byte;

  len = (av_log2(value) + 7) / 7;

  if(ctx->trace_enable)
    position = put_bits_count(pbc);

  for(i = 0; i < len; i++) {
    int subscript[2] = { 1, i };

    byte = value >> (7 * i) & 0x7f;
    if(i < len - 1)
      byte |= 0x80;

    err = ff_cbs_write_unsigned(ctx, pbc, 8, "leb128_byte[i]", subscript,
      byte, 0x00, 0xff);
    if(err < 0)
      return err;
  }

  if(ctx->trace_enable)
    ff_cbs_trace_syntax_element(ctx, position, name, NULL, "", value);

  return 0;
}

static int cbs_av1_read_ns(CodedBitstreamContext *ctx, GetBitContext *gbc,
  uint32_t n, const char *name,
  const int *subscripts, uint32_t *write_to) {
  uint32_t m, v, extra_bit, value;
  int position, w;

  av_assert0(n > 0);

  if(ctx->trace_enable)
    position = get_bits_count(gbc);

  w = av_log2(n) + 1;
  m = (1 << w) - n;

  if(get_bits_left(gbc) < w) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid non-symmetric value at "
                                       "%s: bitstream ended.\n",
      name);
    return AVERROR_INVALIDDATA;
  }

  if(w - 1 > 0)
    v = get_bits(gbc, w - 1);
  else
    v = 0;

  if(v < m) {
    value = v;
  }
  else {
    extra_bit = get_bits1(gbc);
    value     = (v << 1) - m + extra_bit;
  }

  if(ctx->trace_enable) {
    char bits[33];
    int i;
    for(i = 0; i < w - 1; i++)
      bits[i] = (v >> i & 1) ? '1' : '0';
    if(v >= m)
      bits[i++] = extra_bit ? '1' : '0';
    bits[i] = 0;

    ff_cbs_trace_syntax_element(ctx, position,
      name, subscripts, bits, value);
  }

  *write_to = value;
  return 0;
}

static int cbs_av1_write_ns(CodedBitstreamContext *ctx, PutBitContext *pbc,
  uint32_t n, const char *name,
  const int *subscripts, uint32_t value) {
  uint32_t w, m, v, extra_bit;
  int position;

  if(value > n) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
                                       "%" PRIu32 ", but must be in [0,%" PRIu32 "].\n",
      name, value, n);
    return AVERROR_INVALIDDATA;
  }

  if(ctx->trace_enable)
    position = put_bits_count(pbc);

  w = av_log2(n) + 1;
  m = (1 << w) - n;

  if(put_bits_left(pbc) < w)
    return AVERROR(ENOSPC);

  if(value < m) {
    v = value;
    put_bits(pbc, w - 1, v);
  }
  else {
    v         = m + ((value - m) >> 1);
    extra_bit = (value - m) & 1;
    put_bits(pbc, w - 1, v);
    put_bits(pbc, 1, extra_bit);
  }

  if(ctx->trace_enable) {
    char bits[33];
    int i;
    for(i = 0; i < w - 1; i++)
      bits[i] = (v >> i & 1) ? '1' : '0';
    if(value >= m)
      bits[i++] = extra_bit ? '1' : '0';
    bits[i] = 0;

    ff_cbs_trace_syntax_element(ctx, position,
      name, subscripts, bits, value);
  }

  return 0;
}

static int cbs_av1_read_increment(CodedBitstreamContext *ctx, GetBitContext *gbc,
  uint32_t range_min, uint32_t range_max,
  const char *name, uint32_t *write_to) {
  uint32_t value;
  int position, i;
  char bits[33];

  av_assert0(range_min <= range_max && range_max - range_min < sizeof(bits) - 1);
  if(ctx->trace_enable)
    position = get_bits_count(gbc);

  for(i = 0, value = range_min; value < range_max;) {
    if(get_bits_left(gbc) < 1) {
      av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid increment value at "
                                         "%s: bitstream ended.\n",
        name);
      return AVERROR_INVALIDDATA;
    }
    if(get_bits1(gbc)) {
      bits[i++] = '1';
      ++value;
    }
    else {
      bits[i++] = '0';
      break;
    }
  }

  if(ctx->trace_enable) {
    bits[i] = 0;
    ff_cbs_trace_syntax_element(ctx, position,
      name, NULL, bits, value);
  }

  *write_to = value;
  return 0;
}

static int cbs_av1_write_increment(CodedBitstreamContext *ctx, PutBitContext *pbc,
  uint32_t range_min, uint32_t range_max,
  const char *name, uint32_t value) {
  int len;

  av_assert0(range_min <= range_max && range_max - range_min < 32);
  if(value < range_min || value > range_max) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
                                       "%" PRIu32 ", but must be in [%" PRIu32 ",%" PRIu32 "].\n",
      name, value, range_min, range_max);
    return AVERROR_INVALIDDATA;
  }

  if(value == range_max)
    len = range_max - range_min;
  else
    len = value - range_min + 1;
  if(put_bits_left(pbc) < len)
    return AVERROR(ENOSPC);

  if(ctx->trace_enable) {
    char bits[33];
    int i;
    for(i = 0; i < len; i++) {
      if(range_min + i == value)
        bits[i] = '0';
      else
        bits[i] = '1';
    }
    bits[i] = 0;
    ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc),
      name, NULL, bits, value);
  }

  if(len > 0)
    put_bits(pbc, len, (1 << len) - 1 - (value != range_max));

  return 0;
}

static int cbs_av1_read_subexp(CodedBitstreamContext *ctx, GetBitContext *gbc,
  uint32_t range_max, const char *name,
  const int *subscripts, uint32_t *write_to) {
  uint32_t value;
  int position, err;
  uint32_t max_len, len, range_offset, range_bits;

  if(ctx->trace_enable)
    position = get_bits_count(gbc);

  av_assert0(range_max > 0);
  max_len = av_log2(range_max - 1) - 3;

  err = cbs_av1_read_increment(ctx, gbc, 0, max_len,
    "subexp_more_bits", &len);
  if(err < 0)
    return err;

  if(len) {
    range_bits   = 2 + len;
    range_offset = 1 << range_bits;
  }
  else {
    range_bits   = 3;
    range_offset = 0;
  }

  if(len < max_len) {
    err = ff_cbs_read_unsigned(ctx, gbc, range_bits,
      "subexp_bits", NULL, &value,
      0, MAX_UINT_BITS(range_bits));
    if(err < 0)
      return err;
  }
  else {
    err = cbs_av1_read_ns(ctx, gbc, range_max - range_offset,
      "subexp_final_bits", NULL, &value);
    if(err < 0)
      return err;
  }
  value += range_offset;

  if(ctx->trace_enable)
    ff_cbs_trace_syntax_element(ctx, position,
      name, subscripts, "", value);

  *write_to = value;
  return err;
}

static int cbs_av1_write_subexp(CodedBitstreamContext *ctx, PutBitContext *pbc,
  uint32_t range_max, const char *name,
  const int *subscripts, uint32_t value) {
  int position, err;
  uint32_t max_len, len, range_offset, range_bits;

  if(value > range_max) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
                                       "%" PRIu32 ", but must be in [0,%" PRIu32 "].\n",
      name, value, range_max);
    return AVERROR_INVALIDDATA;
  }

  if(ctx->trace_enable)
    position = put_bits_count(pbc);

  av_assert0(range_max > 0);
  max_len = av_log2(range_max - 1) - 3;

  if(value < 8) {
    range_bits   = 3;
    range_offset = 0;
    len          = 0;
  }
  else {
    range_bits = av_log2(value);
    len        = range_bits - 2;
    if(len > max_len) {
      // The top bin is combined with the one below it.
      av_assert0(len == max_len + 1);
      --range_bits;
      len = max_len;
    }
    range_offset = 1 << range_bits;
  }

  err = cbs_av1_write_increment(ctx, pbc, 0, max_len,
    "subexp_more_bits", len);
  if(err < 0)
    return err;

  if(len < max_len) {
    err = ff_cbs_write_unsigned(ctx, pbc, range_bits,
      "subexp_bits", NULL,
      value - range_offset,
      0, MAX_UINT_BITS(range_bits));
    if(err < 0)
      return err;
  }
  else {
    err = cbs_av1_write_ns(ctx, pbc, range_max - range_offset,
      "subexp_final_bits", NULL,
      value - range_offset);
    if(err < 0)
      return err;
  }

  if(ctx->trace_enable)
    ff_cbs_trace_syntax_element(ctx, position,
      name, subscripts, "", value);

  return err;
}


static int cbs_av1_tile_log2(int blksize, int target) {
  int k;
  for(k = 0; (blksize << k) < target; k++)
    ;
  return k;
}

static int cbs_av1_get_relative_dist(const AV1RawSequenceHeader *seq,
  unsigned int a, unsigned int b) {
  unsigned int diff, m;
  if(!seq->enable_order_hint)
    return 0;
  diff = a - b;
  m    = 1 << seq->order_hint_bits_minus_1;
  diff = (diff & (m - 1)) - (diff & m);
  return diff;
}

static size_t cbs_av1_get_payload_bytes_left(GetBitContext *gbc) {
  GetBitContext tmp = *gbc;
  size_t size       = 0;
  for(int i = 0; get_bits_left(&tmp) >= 8; i++) {
    if(get_bits(&tmp, 8))
      size = i;
  }
  return size;
}


#define HEADER(name)                \
  do {                              \
    ff_cbs_trace_header(ctx, name); \
  } while(0)

#define CHECK(call) \
  do {              \
    err = (call);   \
    if(err < 0)     \
      return err;   \
  } while(0)

#define FUNC_NAME(rw, codec, name) cbs_##codec##_##rw##_##name
#define FUNC_AV1(rw, name) FUNC_NAME(rw, av1, name)
#define FUNC(name) FUNC_AV1(READWRITE, name)

#define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]) { subs, __VA_ARGS__ }) : NULL)

#define fb(width, name) \
  xf(width, name, current->name, 0, MAX_UINT_BITS(width), 0, )
#define fc(width, name, range_min, range_max) \
  xf(width, name, current->name, range_min, range_max, 0, )
#define flag(name) fb(1, name)
#define su(width, name) \
  xsu(width, name, current->name, 0, )

#define fbs(width, name, subs, ...) \
  xf(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define fcs(width, name, range_min, range_max, subs, ...) \
  xf(width, name, current->name, range_min, range_max, subs, __VA_ARGS__)
#define flags(name, subs, ...) \
  xf(1, name, current->name, 0, 1, subs, __VA_ARGS__)
#define sus(width, name, subs, ...) \
  xsu(width, name, current->name, subs, __VA_ARGS__)

#define fixed(width, name, value)                    \
  do {                                               \
    av_unused uint32_t fixed_value = value;          \
    xf(width, name, fixed_value, value, value, 0, ); \
  } while(0)


#define READ
#define READWRITE read
#define RWContext GetBitContext

#define xf(width, name, var, range_min, range_max, subs, ...) \
  do {                                                        \
    uint32_t value;                                           \
    CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name,         \
      SUBSCRIPTS(subs, __VA_ARGS__),                          \
      &value, range_min, range_max));                         \
    var = value;                                              \
  } while(0)

#define xsu(width, name, var, subs, ...)            \
  do {                                              \
    int32_t value;                                  \
    CHECK(ff_cbs_read_signed(ctx, rw, width, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__), &value,        \
      MIN_INT_BITS(width),                          \
      MAX_INT_BITS(width)));                        \
    var = value;                                    \
  } while(0)

#define uvlc(name, range_min, range_max)    \
  do {                                      \
    uint32_t value;                         \
    CHECK(cbs_av1_read_uvlc(ctx, rw, #name, \
      &value, range_min, range_max));       \
    current->name = value;                  \
  } while(0)

#define ns(max_value, name, subs, ...)               \
  do {                                               \
    uint32_t value;                                  \
    CHECK(cbs_av1_read_ns(ctx, rw, max_value, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__), &value));       \
    current->name = value;                           \
  } while(0)

#define increment(name, min, max)                                    \
  do {                                                               \
    uint32_t value;                                                  \
    CHECK(cbs_av1_read_increment(ctx, rw, min, max, #name, &value)); \
    current->name = value;                                           \
  } while(0)

#define subexp(name, max, subs, ...)               \
  do {                                             \
    uint32_t value;                                \
    CHECK(cbs_av1_read_subexp(ctx, rw, max, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__), &value));     \
    current->name = value;                         \
  } while(0)

#define delta_q(name)                                \
  do {                                               \
    uint8_t delta_coded;                             \
    int8_t delta_q;                                  \
    xf(1, name.delta_coded, delta_coded, 0, 1, 0, ); \
    if(delta_coded)                                  \
      xsu(1 + 6, name.delta_q, delta_q, 0, );        \
    else                                             \
      delta_q = 0;                                   \
    current->name = delta_q;                         \
  } while(0)

#define leb128(name)                                    \
  do {                                                  \
    uint64_t value;                                     \
    CHECK(cbs_av1_read_leb128(ctx, rw, #name, &value)); \
    current->name = value;                              \
  } while(0)

#define infer(name, value) \
  do {                     \
    current->name = value; \
  } while(0)

#define byte_alignment(rw) (get_bits_count(rw) % 8)

#include "cbs_av1_syntax_template.c"

#undef READ
#undef READWRITE
#undef RWContext
#undef xf
#undef xsu
#undef uvlc
#undef ns
#undef increment
#undef subexp
#undef delta_q
#undef leb128
#undef infer
#undef byte_alignment


#define WRITE
#define READWRITE write
#define RWContext PutBitContext

#define xf(width, name, var, range_min, range_max, subs, ...) \
  do {                                                        \
    CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name,        \
      SUBSCRIPTS(subs, __VA_ARGS__),                          \
      var, range_min, range_max));                            \
  } while(0)

#define xsu(width, name, var, subs, ...)             \
  do {                                               \
    CHECK(ff_cbs_write_signed(ctx, rw, width, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__), var,            \
      MIN_INT_BITS(width),                           \
      MAX_INT_BITS(width)));                         \
  } while(0)

#define uvlc(name, range_min, range_max)                    \
  do {                                                      \
    CHECK(cbs_av1_write_uvlc(ctx, rw, #name, current->name, \
      range_min, range_max));                               \
  } while(0)

#define ns(max_value, name, subs, ...)                \
  do {                                                \
    CHECK(cbs_av1_write_ns(ctx, rw, max_value, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__),                  \
      current->name));                                \
  } while(0)

#define increment(name, min, max)                           \
  do {                                                      \
    CHECK(cbs_av1_write_increment(ctx, rw, min, max, #name, \
      current->name));                                      \
  } while(0)

#define subexp(name, max, subs, ...)                \
  do {                                              \
    CHECK(cbs_av1_write_subexp(ctx, rw, max, #name, \
      SUBSCRIPTS(subs, __VA_ARGS__),                \
      current->name));                              \
  } while(0)

#define delta_q(name)                                       \
  do {                                                      \
    xf(1, name.delta_coded, current->name != 0, 0, 1, 0, ); \
    if(current->name)                                       \
      xsu(1 + 6, name.delta_q, current->name, 0, );         \
  } while(0)

#define leb128(name)                                            \
  do {                                                          \
    CHECK(cbs_av1_write_leb128(ctx, rw, #name, current->name)); \
  } while(0)

#define infer(name, value)                                \
  do {                                                    \
    if(current->name != (value)) {                        \
      av_log(ctx->log_ctx, AV_LOG_ERROR,                  \
        "%s does not match inferred value: "              \
        "%" PRId64 ", but should be %" PRId64 ".\n",      \
        #name, (int64_t)current->name, (int64_t)(value)); \
      return AVERROR_INVALIDDATA;                         \
    }                                                     \
  } while(0)

#define byte_alignment(rw) (put_bits_count(rw) % 8)

#include "cbs_av1_syntax_template.c"

#undef WRITE
#undef READWRITE
#undef RWContext
#undef xf
#undef xsu
#undef uvlc
#undef ns
#undef increment
#undef subexp
#undef delta_q
#undef leb128
#undef infer
#undef byte_alignment


static int cbs_av1_split_fragment(CodedBitstreamContext *ctx,
  CodedBitstreamFragment *frag,
  int header) {
  GetBitContext gbc;
  uint8_t *data;
  size_t size;
  uint64_t obu_length;
  int pos, err, trace;

  // Don't include this parsing in trace output.
  trace             = ctx->trace_enable;
  ctx->trace_enable = 0;

  data = frag->data;
  size = frag->data_size;

  if(INT_MAX / 8 < size) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid fragment: "
                                       "too large (%zu bytes).\n",
      size);
    err = AVERROR_INVALIDDATA;
    goto fail;
  }

  if(header && size && data[0] & 0x80) {
    // first bit is nonzero, the extradata does not consist purely of
    // OBUs. Expect MP4/Matroska AV1CodecConfigurationRecord
    int config_record_version = data[0] & 0x7f;

    if(config_record_version != 1) {
      av_log(ctx->log_ctx, AV_LOG_ERROR,
        "Unknown version %d of AV1CodecConfigurationRecord "
        "found!\n",
        config_record_version);
      err = AVERROR_INVALIDDATA;
      goto fail;
    }

    if(size <= 4) {
      if(size < 4) {
        av_log(ctx->log_ctx, AV_LOG_WARNING,
          "Undersized AV1CodecConfigurationRecord v%d found!\n",
          config_record_version);
        err = AVERROR_INVALIDDATA;
        goto fail;
      }

      goto success;
    }

    // In AV1CodecConfigurationRecord v1, actual OBUs start after
    // four bytes. Thus set the offset as required for properly
    // parsing them.
    data += 4;
    size -= 4;
  }

  while(size > 0) {
    AV1RawOBUHeader header;
    uint64_t obu_size;

    init_get_bits(&gbc, data, 8 * size);

    err = cbs_av1_read_obu_header(ctx, &gbc, &header);
    if(err < 0)
      goto fail;

    if(header.obu_has_size_field) {
      if(get_bits_left(&gbc) < 8) {
        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU: fragment "
                                           "too short (%zu bytes).\n",
          size);
        err = AVERROR_INVALIDDATA;
        goto fail;
      }
      err = cbs_av1_read_leb128(ctx, &gbc, "obu_size", &obu_size);
      if(err < 0)
        goto fail;
    }
    else
      obu_size = size - 1 - header.obu_extension_flag;

    pos = get_bits_count(&gbc);
    av_assert0(pos % 8 == 0 && pos / 8 <= size);

    obu_length = pos / 8 + obu_size;

    if(size < obu_length) {
      av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU length: "
                                         "%" PRIu64 ", but only %zu bytes remaining in fragment.\n",
        obu_length, size);
      err = AVERROR_INVALIDDATA;
      goto fail;
    }

    err = ff_cbs_insert_unit_data(frag, -1, header.obu_type,
      data, obu_length, frag->data_ref);
    if(err < 0)
      goto fail;

    data += obu_length;
    size -= obu_length;
  }

success:
  err = 0;
fail:
  ctx->trace_enable = trace;
  return err;
}

static int cbs_av1_ref_tile_data(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit,
  GetBitContext *gbc,
  AV1RawTileData *td) {
  int pos;

  pos = get_bits_count(gbc);
  if(pos >= 8 * unit->data_size) {
    av_log(ctx->log_ctx, AV_LOG_ERROR, "Bitstream ended before "
                                       "any data in tile group (%d bits read).\n",
      pos);
    return AVERROR_INVALIDDATA;
  }
  // Must be byte-aligned at this point.
  av_assert0(pos % 8 == 0);

  td->data_ref = av_buffer_ref(unit->data_ref);
  if(!td->data_ref)
    return AVERROR(ENOMEM);

  td->data      = unit->data + pos / 8;
  td->data_size = unit->data_size - pos / 8;

  return 0;
}

static int cbs_av1_read_unit(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit) {
  CodedBitstreamAV1Context *priv = ctx->priv_data;
  AV1RawOBU *obu;
  GetBitContext gbc;
  int err, start_pos, end_pos;

  err = ff_cbs_alloc_unit_content2(ctx, unit);
  if(err < 0)
    return err;
  obu = unit->content;

  err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
  if(err < 0)
    return err;

  err = cbs_av1_read_obu_header(ctx, &gbc, &obu->header);
  if(err < 0)
    return err;
  av_assert0(obu->header.obu_type == unit->type);

  if(obu->header.obu_has_size_field) {
    uint64_t obu_size;
    err = cbs_av1_read_leb128(ctx, &gbc, "obu_size", &obu_size);
    if(err < 0)
      return err;
    obu->obu_size = obu_size;
  }
  else {
    if(unit->data_size < 1 + obu->header.obu_extension_flag) {
      av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU length: "
                                         "unit too short (%zu).\n",
        unit->data_size);
      return AVERROR_INVALIDDATA;
    }
    obu->obu_size = unit->data_size - 1 - obu->header.obu_extension_flag;
  }

  start_pos = get_bits_count(&gbc);

  if(obu->header.obu_extension_flag) {
    if(obu->header.obu_type != AV1_OBU_SEQUENCE_HEADER &&
       obu->header.obu_type != AV1_OBU_TEMPORAL_DELIMITER &&
       priv->operating_point_idc) {
      int in_temporal_layer =
        (priv->operating_point_idc >> priv->temporal_id) & 1;
      int in_spatial_layer =
        (priv->operating_point_idc >> (priv->spatial_id + 8)) & 1;
      if(!in_temporal_layer || !in_spatial_layer) {
        return AVERROR(EAGAIN); // drop_obu()
      }
    }
  }

  switch(obu->header.obu_type) {
  case AV1_OBU_SEQUENCE_HEADER: {
    err = cbs_av1_read_sequence_header_obu(ctx, &gbc,
      &obu->obu.sequence_header);
    if(err < 0)
      return err;

    if(priv->operating_point >= 0) {
      AV1RawSequenceHeader *sequence_header = &obu->obu.sequence_header;

      if(priv->operating_point > sequence_header->operating_points_cnt_minus_1) {
        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid Operating Point %d requested. "
                                           "Must not be higher than %u.\n",
          priv->operating_point, sequence_header->operating_points_cnt_minus_1);
        return AVERROR(EINVAL);
      }
      priv->operating_point_idc = sequence_header->operating_point_idc[priv->operating_point];
    }

    av_buffer_unref(&priv->sequence_header_ref);
    priv->sequence_header = NULL;

    priv->sequence_header_ref = av_buffer_ref(unit->content_ref);
    if(!priv->sequence_header_ref)
      return AVERROR(ENOMEM);
    priv->sequence_header = &obu->obu.sequence_header;
  } break;
  case AV1_OBU_TEMPORAL_DELIMITER: {
    err = cbs_av1_read_temporal_delimiter_obu(ctx, &gbc);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_FRAME_HEADER:
  case AV1_OBU_REDUNDANT_FRAME_HEADER: {
    err = cbs_av1_read_frame_header_obu(ctx, &gbc,
      &obu->obu.frame_header,
      obu->header.obu_type ==
        AV1_OBU_REDUNDANT_FRAME_HEADER,
      unit->data_ref);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_TILE_GROUP: {
    err = cbs_av1_read_tile_group_obu(ctx, &gbc,
      &obu->obu.tile_group);
    if(err < 0)
      return err;

    err = cbs_av1_ref_tile_data(ctx, unit, &gbc,
      &obu->obu.tile_group.tile_data);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_FRAME: {
    err = cbs_av1_read_frame_obu(ctx, &gbc, &obu->obu.frame,
      unit->data_ref);
    if(err < 0)
      return err;

    err = cbs_av1_ref_tile_data(ctx, unit, &gbc,
      &obu->obu.frame.tile_group.tile_data);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_TILE_LIST: {
    err = cbs_av1_read_tile_list_obu(ctx, &gbc,
      &obu->obu.tile_list);
    if(err < 0)
      return err;

    err = cbs_av1_ref_tile_data(ctx, unit, &gbc,
      &obu->obu.tile_list.tile_data);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_METADATA: {
    err = cbs_av1_read_metadata_obu(ctx, &gbc, &obu->obu.metadata);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_PADDING: {
    err = cbs_av1_read_padding_obu(ctx, &gbc, &obu->obu.padding);
    if(err < 0)
      return err;
  } break;
  default:
    return AVERROR(ENOSYS);
  }

  end_pos = get_bits_count(&gbc);
  av_assert0(end_pos <= unit->data_size * 8);

  if(obu->obu_size > 0 &&
     obu->header.obu_type != AV1_OBU_TILE_GROUP &&
     obu->header.obu_type != AV1_OBU_TILE_LIST &&
     obu->header.obu_type != AV1_OBU_FRAME) {
    int nb_bits = obu->obu_size * 8 + start_pos - end_pos;

    if(nb_bits <= 0)
      return AVERROR_INVALIDDATA;

    err = cbs_av1_read_trailing_bits(ctx, &gbc, nb_bits);
    if(err < 0)
      return err;
  }

  return 0;
}

static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
  CodedBitstreamUnit *unit,
  PutBitContext *pbc) {
  CodedBitstreamAV1Context *priv = ctx->priv_data;
  AV1RawOBU *obu                 = unit->content;
  PutBitContext pbc_tmp;
  AV1RawTileData *td;
  size_t header_size;
  int err, start_pos, end_pos, data_pos;

  // OBUs in the normal bitstream format must contain a size field
  // in every OBU (in annex B it is optional, but we don't support
  // writing that).
  obu->header.obu_has_size_field = 1;

  err = cbs_av1_write_obu_header(ctx, pbc, &obu->header);
  if(err < 0)
    return err;

  if(obu->header.obu_has_size_field) {
    pbc_tmp = *pbc;
    // Add space for the size field to fill later.
    put_bits32(pbc, 0);
    put_bits32(pbc, 0);
  }

  td        = NULL;
  start_pos = put_bits_count(pbc);

  switch(obu->header.obu_type) {
  case AV1_OBU_SEQUENCE_HEADER: {
    err = cbs_av1_write_sequence_header_obu(ctx, pbc,
      &obu->obu.sequence_header);
    if(err < 0)
      return err;

    av_buffer_unref(&priv->sequence_header_ref);
    priv->sequence_header = NULL;

    err = ff_cbs_make_unit_refcounted(ctx, unit);
    if(err < 0)
      return err;

    priv->sequence_header_ref = av_buffer_ref(unit->content_ref);
    if(!priv->sequence_header_ref)
      return AVERROR(ENOMEM);
    priv->sequence_header = &obu->obu.sequence_header;
  } break;
  case AV1_OBU_TEMPORAL_DELIMITER: {
    err = cbs_av1_write_temporal_delimiter_obu(ctx, pbc);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_FRAME_HEADER:
  case AV1_OBU_REDUNDANT_FRAME_HEADER: {
    err = cbs_av1_write_frame_header_obu(ctx, pbc,
      &obu->obu.frame_header,
      obu->header.obu_type ==
        AV1_OBU_REDUNDANT_FRAME_HEADER,
      NULL);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_TILE_GROUP: {
    err = cbs_av1_write_tile_group_obu(ctx, pbc,
      &obu->obu.tile_group);
    if(err < 0)
      return err;

    td = &obu->obu.tile_group.tile_data;
  } break;
  case AV1_OBU_FRAME: {
    err = cbs_av1_write_frame_obu(ctx, pbc, &obu->obu.frame, NULL);
    if(err < 0)
      return err;

    td = &obu->obu.frame.tile_group.tile_data;
  } break;
  case AV1_OBU_TILE_LIST: {
    err = cbs_av1_write_tile_list_obu(ctx, pbc, &obu->obu.tile_list);
    if(err < 0)
      return err;

    td = &obu->obu.tile_list.tile_data;
  } break;
  case AV1_OBU_METADATA: {
    err = cbs_av1_write_metadata_obu(ctx, pbc, &obu->obu.metadata);
    if(err < 0)
      return err;
  } break;
  case AV1_OBU_PADDING: {
    err = cbs_av1_write_padding_obu(ctx, pbc, &obu->obu.padding);
    if(err < 0)
      return err;
  } break;
  default:
    return AVERROR(ENOSYS);
  }

  end_pos     = put_bits_count(pbc);
  header_size = (end_pos - start_pos + 7) / 8;
  if(td) {
    obu->obu_size = header_size + td->data_size;
  }
  else if(header_size > 0) {
    // Add trailing bits and recalculate.
    err = cbs_av1_write_trailing_bits(ctx, pbc, 8 - end_pos % 8);
    if(err < 0)
      return err;
    end_pos       = put_bits_count(pbc);
    obu->obu_size = header_size = (end_pos - start_pos + 7) / 8;
  }
  else {
    // Empty OBU.
    obu->obu_size = 0;
  }

  end_pos = put_bits_count(pbc);
  // Must now be byte-aligned.
  av_assert0(end_pos % 8 == 0);
  flush_put_bits(pbc);
  start_pos /= 8;
  end_pos /= 8;

  *pbc = pbc_tmp;
  err  = cbs_av1_write_leb128(ctx, pbc, "obu_size", obu->obu_size);
  if(err < 0)
    return err;

  data_pos = put_bits_count(pbc) / 8;
  flush_put_bits(pbc);
  av_assert0(data_pos <= start_pos);

  if(8 * obu->obu_size > put_bits_left(pbc))
    return AVERROR(ENOSPC);

  if(obu->obu_size > 0) {
    memmove(pbc->buf + data_pos,
      pbc->buf + start_pos, header_size);
    skip_put_bytes(pbc, header_size);

    if(td) {
      memcpy(pbc->buf + data_pos + header_size,
        td->data, td->data_size);
      skip_put_bytes(pbc, td->data_size);
    }
  }

  // OBU data must be byte-aligned.
  av_assert0(put_bits_count(pbc) % 8 == 0);

  return 0;
}

static int cbs_av1_assemble_fragment(CodedBitstreamContext *ctx,
  CodedBitstreamFragment *frag) {
  size_t size, pos;
  int i;

  size = 0;
  for(i = 0; i < frag->nb_units; i++)
    size += frag->units[i].data_size;

  frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
  if(!frag->data_ref)
    return AVERROR(ENOMEM);
  frag->data = frag->data_ref->data;
  memset(frag->data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);

  pos = 0;
  for(i = 0; i < frag->nb_units; i++) {
    memcpy(frag->data + pos, frag->units[i].data,
      frag->units[i].data_size);
    pos += frag->units[i].data_size;
  }
  av_assert0(pos == size);
  frag->data_size = size;

  return 0;
}

static void cbs_av1_flush(CodedBitstreamContext *ctx) {
  CodedBitstreamAV1Context *priv = ctx->priv_data;

  av_buffer_unref(&priv->frame_header_ref);
  priv->sequence_header = NULL;
  priv->frame_header    = NULL;

  memset(priv->ref, 0, sizeof(priv->ref));
  priv->operating_point_idc = 0;
  priv->seen_frame_header   = 0;
  priv->tile_num            = 0;
}

static void cbs_av1_close(CodedBitstreamContext *ctx) {
  CodedBitstreamAV1Context *priv = ctx->priv_data;

  av_buffer_unref(&priv->sequence_header_ref);
  av_buffer_unref(&priv->frame_header_ref);
}

static void cbs_av1_free_metadata(void *unit, uint8_t *content) {
  AV1RawOBU *obu = (AV1RawOBU *)content;
  AV1RawMetadata *md;

  av_assert0(obu->header.obu_type == AV1_OBU_METADATA);
  md = &obu->obu.metadata;

  switch(md->metadata_type) {
  case AV1_METADATA_TYPE_ITUT_T35:
    av_buffer_unref(&md->metadata.itut_t35.payload_ref);
    break;
  }
  av_free(content);
}

static const CodedBitstreamUnitTypeDescriptor cbs_av1_unit_types[] = {
  CBS_UNIT_TYPE_POD(AV1_OBU_SEQUENCE_HEADER, AV1RawOBU),
  CBS_UNIT_TYPE_POD(AV1_OBU_TEMPORAL_DELIMITER, AV1RawOBU),
  CBS_UNIT_TYPE_POD(AV1_OBU_FRAME_HEADER, AV1RawOBU),
  CBS_UNIT_TYPE_POD(AV1_OBU_REDUNDANT_FRAME_HEADER, AV1RawOBU),

  CBS_UNIT_TYPE_INTERNAL_REF(AV1_OBU_TILE_GROUP, AV1RawOBU,
    obu.tile_group.tile_data.data),
  CBS_UNIT_TYPE_INTERNAL_REF(AV1_OBU_FRAME, AV1RawOBU,
    obu.frame.tile_group.tile_data.data),
  CBS_UNIT_TYPE_INTERNAL_REF(AV1_OBU_TILE_LIST, AV1RawOBU,
    obu.tile_list.tile_data.data),
  CBS_UNIT_TYPE_INTERNAL_REF(AV1_OBU_PADDING, AV1RawOBU,
    obu.padding.payload),

  CBS_UNIT_TYPE_COMPLEX(AV1_OBU_METADATA, AV1RawOBU,
    &cbs_av1_free_metadata),

  CBS_UNIT_TYPE_END_OF_LIST
};

#define OFFSET(x) offsetof(CodedBitstreamAV1Context, x)
static const AVOption cbs_av1_options[] = {
  { "operating_point", "Set operating point to select layers to parse from a scalable bitstream",
    OFFSET(operating_point), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, AV1_MAX_OPERATING_POINTS - 1, 0 },
  { NULL }
};

static const AVClass cbs_av1_class = {
  .class_name = "cbs_av1",
  .item_name  = av_default_item_name,
  .option     = cbs_av1_options,
  .version    = LIBAVUTIL_VERSION_INT,
};

const CodedBitstreamType ff_cbs_type_av1 = {
  .codec_id = AV_CODEC_ID_AV1,

  .priv_class     = &cbs_av1_class,
  .priv_data_size = sizeof(CodedBitstreamAV1Context),

  .unit_types = cbs_av1_unit_types,

  .split_fragment    = &cbs_av1_split_fragment,
  .read_unit         = &cbs_av1_read_unit,
  .write_unit        = &cbs_av1_write_obu,
  .assemble_fragment = &cbs_av1_assemble_fragment,

  .flush = &cbs_av1_flush,
  .close = &cbs_av1_close,
};