text: /*
   * Copyright (c) 2003 Fabrice Bellard
   *
   * 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
   */
  
  /**
   * @file
   * ID3v2 header parser
   *
   * Specifications available at:
   * http://id3.org/Developer_Information
   */
  
  #include "config.h"
  
  #if CONFIG_ZLIB
  #include <zlib.h>
  #endif
  
  #include "libavutil/avstring.h"
  #include "libavutil/dict.h"
  #include "libavutil/intreadwrite.h"
  #include "avio_internal.h"
  #include "internal.h"
  #include "id3v1.h"
  #include "id3v2.h"
  
  const AVMetadataConv ff_id3v2_34_metadata_conv[] = {
      { "TALB", "album"        },
      { "TCOM", "composer"     },
      { "TCON", "genre"        },
      { "TCOP", "copyright"    },
      { "TENC", "encoded_by"   },
      { "TIT2", "title"        },
      { "TLAN", "language"     },
      { "TPE1", "artist"       },
      { "TPE2", "album_artist" },
      { "TPE3", "performer"    },
      { "TPOS", "disc"         },
      { "TPUB", "publisher"    },
      { "TRCK", "track"        },
      { "TSSE", "encoder"      },
      { "USLT", "lyrics"       },
      { 0 }
  };
  
  const AVMetadataConv ff_id3v2_4_metadata_conv[] = {
      { "TCMP", "compilation"   },
      { "TDRC", "date"          },
      { "TDRL", "date"          },
      { "TDEN", "creation_time" },
      { "TSOA", "album-sort"    },
      { "TSOP", "artist-sort"   },
      { "TSOT", "title-sort"    },
      { 0 }
  };
  
  static const AVMetadataConv id3v2_2_metadata_conv[] = {
      { "TAL", "album"        },
      { "TCO", "genre"        },
      { "TCP", "compilation"  },
      { "TT2", "title"        },
      { "TEN", "encoded_by"   },
      { "TP1", "artist"       },
      { "TP2", "album_artist" },
      { "TP3", "performer"    },
      { "TRK", "track"        },
      { 0 }
  };
  
  const char ff_id3v2_tags[][4] = {
      "TALB", "TBPM", "TCOM", "TCON", "TCOP", "TDLY", "TENC", "TEXT",
      "TFLT", "TIT1", "TIT2", "TIT3", "TKEY", "TLAN", "TLEN", "TMED",
      "TOAL", "TOFN", "TOLY", "TOPE", "TOWN", "TPE1", "TPE2", "TPE3",
      "TPE4", "TPOS", "TPUB", "TRCK", "TRSN", "TRSO", "TSRC", "TSSE",
      { 0 },
  };
  
  const char ff_id3v2_4_tags[][4] = {
      "TDEN", "TDOR", "TDRC", "TDRL", "TDTG", "TIPL", "TMCL", "TMOO",
      "TPRO", "TSOA", "TSOP", "TSOT", "TSST",
      { 0 },
  };
  
  const char ff_id3v2_3_tags[][4] = {
      "TDAT", "TIME", "TORY", "TRDA", "TSIZ", "TYER",
      { 0 },
  };
  
  const char *ff_id3v2_picture_types[21] = {
      "Other",
      "32x32 pixels 'file icon'",
      "Other file icon",
      "Cover (front)",
      "Cover (back)",
      "Leaflet page",
      "Media (e.g. label side of CD)",
      "Lead artist/lead performer/soloist",
      "Artist/performer",
      "Conductor",
      "Band/Orchestra",
      "Composer",
      "Lyricist/text writer",
      "Recording Location",
      "During recording",
      "During performance",
      "Movie/video screen capture",
      "A bright coloured fish",
      "Illustration",
      "Band/artist logotype",
      "Publisher/Studio logotype",
  };
  
  const CodecMime ff_id3v2_mime_tags[] = {
      { "image/gif",  AV_CODEC_ID_GIF   },
      { "image/jpeg", AV_CODEC_ID_MJPEG },
      { "image/jpg",  AV_CODEC_ID_MJPEG },
      { "image/png",  AV_CODEC_ID_PNG   },
      { "image/tiff", AV_CODEC_ID_TIFF  },
      { "image/bmp",  AV_CODEC_ID_BMP   },
      { "JPG",        AV_CODEC_ID_MJPEG }, /* ID3v2.2  */
      { "PNG",        AV_CODEC_ID_PNG   }, /* ID3v2.2  */
      { "",           AV_CODEC_ID_NONE  },
  };
  
  int ff_id3v2_match(const uint8_t *buf, const char *magic)
  {
      return  buf[0]         == magic[0] &&
              buf[1]         == magic[1] &&
              buf[2]         == magic[2] &&
              buf[3]         != 0xff     &&
              buf[4]         != 0xff     &&
             (buf[6] & 0x80) == 0        &&
             (buf[7] & 0x80) == 0        &&
             (buf[8] & 0x80) == 0        &&
             (buf[9] & 0x80) == 0;
  }
  
  int ff_id3v2_tag_len(const uint8_t *buf)
  {
      int len = ((buf[6] & 0x7f) << 21) +
                ((buf[7] & 0x7f) << 14) +
                ((buf[8] & 0x7f) << 7) +
                (buf[9] & 0x7f) +
                ID3v2_HEADER_SIZE;
      if (buf[5] & 0x10)
          len += ID3v2_HEADER_SIZE;
      return len;
  }
  
  static unsigned int get_size(AVIOContext *s, int len)
  {
      int v = 0;
      while (len--)
          v = (v << 7) + (avio_r8(s) & 0x7F);
      return v;
  }
  
  static unsigned int size_to_syncsafe(unsigned int size)
  {
      return (((size) & (0x7f <<  0)) >> 0) +
             (((size) & (0x7f <<  8)) >> 1) +
             (((size) & (0x7f << 16)) >> 2) +
             (((size) & (0x7f << 24)) >> 3);
  }
  
  /* No real verification, only check that the tag consists of
   * a combination of capital alpha-numerical characters */
  static int is_tag(const char *buf, unsigned int len)
  {
      if (!len)
          return 0;
  
      while (len--)
          if ((buf[len] < 'A' ||
               buf[len] > 'Z') &&
              (buf[len] < '0' ||
               buf[len] > '9'))
              return 0;
  
      return 1;
  }
  
  /**
   * Return 1 if the tag of length len at the given offset is valid, 0 if not, -1 on error
   */
  static int check_tag(AVIOContext *s, int offset, unsigned int len)
  {
      char tag[4];
  
      if (len > 4 ||
          avio_seek(s, offset, SEEK_SET) < 0 ||
          avio_read(s, tag, len) < len)
          return -1;
      else if (!AV_RB32(tag) || is_tag(tag, len))
          return 1;
  
      return 0;
  }
  
  /**
   * Free GEOB type extra metadata.
   */
  static void free_geobtag(void *obj)
  {
      ID3v2ExtraMetaGEOB *geob = obj;
      av_freep(&geob->mime_type);
      av_freep(&geob->file_name);
      av_freep(&geob->description);
      av_freep(&geob->data);
      av_free(geob);
  }
  
  /**
   * Decode characters to UTF-8 according to encoding type. The decoded buffer is
   * always null terminated. Stop reading when either *maxread bytes are read from
   * pb or U+0000 character is found.
   *
   * @param dst Pointer where the address of the buffer with the decoded bytes is
   * stored. Buffer must be freed by caller.
   * @param maxread Pointer to maximum number of characters to read from the
   * AVIOContext. After execution the value is decremented by the number of bytes
   * actually read.
   * @returns 0 if no error occurred, dst is uninitialized on error
   */
  static int decode_str(AVFormatContext *s, AVIOContext *pb, int encoding,
                        uint8_t **dst, int *maxread)
  {
      int ret;
      uint8_t tmp;
      uint32_t ch = 1;
      int left = *maxread;
      unsigned int (*get)(AVIOContext*) = avio_rb16;
      AVIOContext *dynbuf;
  
      if ((ret = avio_open_dyn_buf(&dynbuf)) < 0) {
          av_log(s, AV_LOG_ERROR, "Error opening memory stream\n");
          return ret;
      }
  
      switch (encoding) {
      case ID3v2_ENCODING_ISO8859:
          while (left && ch) {
              ch = avio_r8(pb);
              PUT_UTF8(ch, tmp, avio_w8(dynbuf, tmp);)
              left--;
          }
          break;
  
      case ID3v2_ENCODING_UTF16BOM:
          if ((left -= 2) < 0) {
              av_log(s, AV_LOG_ERROR, "Cannot read BOM value, input too short\n");
              ffio_free_dyn_buf(&dynbuf);
              *dst = NULL;
              return AVERROR_INVALIDDATA;
          }
          switch (avio_rb16(pb)) {
          case 0xfffe:
              get = avio_rl16;
          case 0xfeff:
              break;
          default:
              av_log(s, AV_LOG_ERROR, "Incorrect BOM value\n");
              ffio_free_dyn_buf(&dynbuf);
              *dst = NULL;
              *maxread = left;
              return AVERROR_INVALIDDATA;
          }
          // fall-through
  
      case ID3v2_ENCODING_UTF16BE:
          while ((left > 1) && ch) {
              GET_UTF16(ch, ((left -= 2) >= 0 ? get(pb) : 0), break;)
              PUT_UTF8(ch, tmp, avio_w8(dynbuf, tmp);)
          }
          if (left < 0)
              left += 2;  /* did not read last char from pb */
          break;
  
      case ID3v2_ENCODING_UTF8:
          while (left && ch) {
              ch = avio_r8(pb);
              avio_w8(dynbuf, ch);
              left--;
          }
          break;
      default:
          av_log(s, AV_LOG_WARNING, "Unknown encoding\n");
      }
  
      if (ch)
          avio_w8(dynbuf, 0);
  
      avio_close_dyn_buf(dynbuf, dst);
      *maxread = left;
  
      return 0;
  }
  
  /**
   * Parse a text tag.
   */
  static void read_ttag(AVFormatContext *s, AVIOContext *pb, int taglen,
                        AVDictionary **metadata, const char *key)
  {
      uint8_t *dst;
      int encoding, dict_flags = AV_DICT_DONT_OVERWRITE | AV_DICT_DONT_STRDUP_VAL;
      unsigned genre;
  
      if (taglen < 1)
          return;
  
      encoding = avio_r8(pb);
      taglen--; /* account for encoding type byte */
  
      if (decode_str(s, pb, encoding, &dst, &taglen) < 0) {
          av_log(s, AV_LOG_ERROR, "Error reading frame %s, skipped\n", key);
          return;
      }
  
      if (!(strcmp(key, "TCON") && strcmp(key, "TCO"))                         &&
          (sscanf(dst, "(%d)", &genre) == 1 || sscanf(dst, "%d", &genre) == 1) &&
          genre <= ID3v1_GENRE_MAX) {
          av_freep(&dst);
          dst = av_strdup(ff_id3v1_genre_str[genre]);
      } else if (!(strcmp(key, "TXXX") && strcmp(key, "TXX"))) {
          /* dst now contains the key, need to get value */
          key = dst;
          if (decode_str(s, pb, encoding, &dst, &taglen) < 0) {
              av_log(s, AV_LOG_ERROR, "Error reading frame %s, skipped\n", key);
              av_freep(&key);
              return;
          }
          dict_flags |= AV_DICT_DONT_STRDUP_KEY;
      } else if (!*dst)
          av_freep(&dst);
  
      if (dst)
          av_dict_set(metadata, key, dst, dict_flags);
  }
  
  static void read_uslt(AVFormatContext *s, AVIOContext *pb, int taglen,
                        AVDictionary **metadata)
  {
      uint8_t lang[4];
      uint8_t *descriptor = NULL; // 'Content descriptor'
      uint8_t *text = NULL;
      char *key = NULL;
      int encoding;
      int ok = 0;
  
      if (taglen < 1)
          goto error;
  
      encoding = avio_r8(pb);
      taglen--;
  
      if (avio_read(pb, lang, 3) < 3)
          goto error;
      lang[3] = '\0';
      taglen -= 3;
  
      if (decode_str(s, pb, encoding, &descriptor, &taglen) < 0)
          goto error;
  
      if (decode_str(s, pb, encoding, &text, &taglen) < 0)
          goto error;
  
      // FFmpeg does not support hierarchical metadata, so concatenate the keys.
      key = av_asprintf("lyrics-%s%s%s", descriptor[0] ? (char *)descriptor : "",
                                         descriptor[0] ? "-" : "",
                                         lang);
      if (!key)
          goto error;
  
      av_dict_set(metadata, key, text, 0);
  
      ok = 1;
  error:
      if (!ok)
          av_log(s, AV_LOG_ERROR, "Error reading lyrics, skipped\n");
      av_free(descriptor);
      av_free(text);
      av_free(key);
  }
  
  /**
   * Parse GEOB tag into a ID3v2ExtraMetaGEOB struct.
   */
  static void read_geobtag(AVFormatContext *s, AVIOContext *pb, int taglen,
                           const char *tag, ID3v2ExtraMeta **extra_meta,
                           int isv34)
  {
      ID3v2ExtraMetaGEOB *geob_data = NULL;
      ID3v2ExtraMeta *new_extra     = NULL;
      char encoding;
      unsigned int len;
  
      if (taglen < 1)
          return;
  
      geob_data = av_mallocz(sizeof(ID3v2ExtraMetaGEOB));
      if (!geob_data) {
          av_log(s, AV_LOG_ERROR, "Failed to alloc %"SIZE_SPECIFIER" bytes\n",
                 sizeof(ID3v2ExtraMetaGEOB));
          return;
      }
  
      new_extra = av_mallocz(sizeof(ID3v2ExtraMeta));
      if (!new_extra) {
          av_log(s, AV_LOG_ERROR, "Failed to alloc %"SIZE_SPECIFIER" bytes\n",
                 sizeof(ID3v2ExtraMeta));
          goto fail;
      }
  
      /* read encoding type byte */
      encoding = avio_r8(pb);
      taglen--;
  
      /* read MIME type (always ISO-8859) */
      if (decode_str(s, pb, ID3v2_ENCODING_ISO8859, &geob_data->mime_type,
                     &taglen) < 0 ||
          taglen <= 0)
          goto fail;
  
      /* read file name */
      if (decode_str(s, pb, encoding, &geob_data->file_name, &taglen) < 0 ||
          taglen <= 0)
          goto fail;
  
      /* read content description */
      if (decode_str(s, pb, encoding, &geob_data->description, &taglen) < 0 ||
          taglen < 0)
          goto fail;
  
      if (taglen) {
          /* save encapsulated binary data */
          geob_data->data = av_malloc(taglen);
          if (!geob_data->data) {
              av_log(s, AV_LOG_ERROR, "Failed to alloc %d bytes\n", taglen);
              goto fail;
          }
          if ((len = avio_read(pb, geob_data->data, taglen)) < taglen)
              av_log(s, AV_LOG_WARNING,
                     "Error reading GEOB frame, data truncated.\n");
          geob_data->datasize = len;
      } else {
          geob_data->data     = NULL;
          geob_data->datasize = 0;
      }
  
      /* add data to the list */
      new_extra->tag  = "GEOB";
      new_extra->data = geob_data;
      new_extra->next = *extra_meta;
      *extra_meta     = new_extra;
  
      return;
  
  fail:
      av_log(s, AV_LOG_ERROR, "Error reading frame %s, skipped\n", tag);
      free_geobtag(geob_data);
      av_free(new_extra);
      return;
  }
  
  static int is_number(const char *str)
  {
      while (*str >= '0' && *str <= '9')
          str++;
      return !*str;
  }
  
  static AVDictionaryEntry *get_date_tag(AVDictionary *m, const char *tag)
  {
      AVDictionaryEntry *t;
      if ((t = av_dict_get(m, tag, NULL, AV_DICT_MATCH_CASE)) &&
          strlen(t->value) == 4 && is_number(t->value))
          return t;
      return NULL;
  }
  
  static void merge_date(AVDictionary **m)
  {
      AVDictionaryEntry *t;
      char date[17] = { 0 };      // YYYY-MM-DD hh:mm
  
      if (!(t = get_date_tag(*m, "TYER")) &&
          !(t = get_date_tag(*m, "TYE")))
          return;
      av_strlcpy(date, t->value, 5);
      av_dict_set(m, "TYER", NULL, 0);
      av_dict_set(m, "TYE", NULL, 0);
  
      if (!(t = get_date_tag(*m, "TDAT")) &&
          !(t = get_date_tag(*m, "TDA")))
          goto finish;
      snprintf(date + 4, sizeof(date) - 4, "-%.2s-%.2s", t->value + 2, t->value);
      av_dict_set(m, "TDAT", NULL, 0);
      av_dict_set(m, "TDA", NULL, 0);
  
      if (!(t = get_date_tag(*m, "TIME")) &&
          !(t = get_date_tag(*m, "TIM")))
          goto finish;
      snprintf(date + 10, sizeof(date) - 10,
               " %.2s:%.2s", t->value, t->value + 2);
      av_dict_set(m, "TIME", NULL, 0);
      av_dict_set(m, "TIM", NULL, 0);
  
  finish:
      if (date[0])
          av_dict_set(m, "date", date, 0);
  }
  
  static void free_apic(void *obj)
  {
      ID3v2ExtraMetaAPIC *apic = obj;
      av_buffer_unref(&apic->buf);
      av_freep(&apic->description);
      av_freep(&apic);
  }
  
  static void read_apic(AVFormatContext *s, AVIOContext *pb, int taglen,
                        const char *tag, ID3v2ExtraMeta **extra_meta,
                        int isv34)
  {
      int enc, pic_type;
      char mimetype[64];
      const CodecMime *mime     = ff_id3v2_mime_tags;
      enum AVCodecID id         = AV_CODEC_ID_NONE;
      ID3v2ExtraMetaAPIC *apic  = NULL;
      ID3v2ExtraMeta *new_extra = NULL;
      int64_t end               = avio_tell(pb) + taglen;
  
      if (taglen <= 4 || (!isv34 && taglen <= 6))
          goto fail;
  
      new_extra = av_mallocz(sizeof(*new_extra));
      apic      = av_mallocz(sizeof(*apic));
      if (!new_extra || !apic)
          goto fail;
  
      enc = avio_r8(pb);
      taglen--;
  
      /* mimetype */
      if (isv34) {
          taglen -= avio_get_str(pb, taglen, mimetype, sizeof(mimetype));
      } else {
          avio_read(pb, mimetype, 3);
          mimetype[3] = 0;
          taglen    -= 3;
      }
  
      while (mime->id != AV_CODEC_ID_NONE) {
          if (!av_strncasecmp(mime->str, mimetype, sizeof(mimetype))) {
              id = mime->id;
              break;
          }
          mime++;
      }
      if (id == AV_CODEC_ID_NONE) {
          av_log(s, AV_LOG_WARNING,
                 "Unknown attached picture mimetype: %s, skipping.\n", mimetype);
          goto fail;
      }
      apic->id = id;
  
      /* picture type */
      pic_type = avio_r8(pb);
      taglen--;
      if (pic_type < 0 || pic_type >= FF_ARRAY_ELEMS(ff_id3v2_picture_types)) {
          av_log(s, AV_LOG_WARNING, "Unknown attached picture type %d.\n",
                 pic_type);
          pic_type = 0;
      }
      apic->type = ff_id3v2_picture_types[pic_type];
  
      /* description and picture data */
      if (decode_str(s, pb, enc, &apic->description, &taglen) < 0) {
          av_log(s, AV_LOG_ERROR,
                 "Error decoding attached picture description.\n");
          goto fail;
      }
  
      apic->buf = av_buffer_alloc(taglen + FF_INPUT_BUFFER_PADDING_SIZE);
      if (!apic->buf || !taglen || avio_read(pb, apic->buf->data, taglen) != taglen)
          goto fail;
      memset(apic->buf->data + taglen, 0, FF_INPUT_BUFFER_PADDING_SIZE);
  
      new_extra->tag  = "APIC";
      new_extra->data = apic;
      new_extra->next = *extra_meta;
      *extra_meta     = new_extra;
  
      return;
  
  fail:
      if (apic)
          free_apic(apic);
      av_freep(&new_extra);
      avio_seek(pb, end, SEEK_SET);
  }
  
  static void read_chapter(AVFormatContext *s, AVIOContext *pb, int len, const char *ttag, ID3v2ExtraMeta **extra_meta, int isv34)
  {
      AVRational time_base = {1, 1000};
      uint32_t start, end;
      AVChapter *chapter;
      uint8_t *dst = NULL;
      int taglen;
      char tag[5];
  
      if (!s) {
          /* We should probably just put the chapter data to extra_meta here
           * and do the AVFormatContext-needing part in a separate
           * ff_id3v2_parse_apic()-like function. */
          av_log(NULL, AV_LOG_DEBUG, "No AVFormatContext, skipped ID3 chapter data\n");
          return;
      }
  
      if (decode_str(s, pb, 0, &dst, &len) < 0)
          return;
      if (len < 16)
          return;
  
      start = avio_rb32(pb);
      end   = avio_rb32(pb);
      avio_skip(pb, 8);
  
      chapter = avpriv_new_chapter(s, s->nb_chapters + 1, time_base, start, end, dst);
      if (!chapter) {
          av_free(dst);
          return;
      }
  
      len -= 16;
      while (len > 10) {
          if (avio_read(pb, tag, 4) < 4)
              goto end;
          tag[4] = 0;
          taglen = avio_rb32(pb);
          avio_skip(pb, 2);
          len -= 10;
          if (taglen < 0 || taglen > len)
              goto end;
          if (tag[0] == 'T')
              read_ttag(s, pb, taglen, &chapter->metadata, tag);
          else
              avio_skip(pb, taglen);
          len -= taglen;
      }
  
      ff_metadata_conv(&chapter->metadata, NULL, ff_id3v2_34_metadata_conv);
      ff_metadata_conv(&chapter->metadata, NULL, ff_id3v2_4_metadata_conv);
  end:
      av_free(dst);
  }
  
  static void free_priv(void *obj)
  {
      ID3v2ExtraMetaPRIV *priv = obj;
      av_freep(&priv->owner);
      av_freep(&priv->data);
      av_freep(&priv);
  }
  
  static void read_priv(AVFormatContext *s, AVIOContext *pb, int taglen,
                        const char *tag, ID3v2ExtraMeta **extra_meta, int isv34)
  {
      ID3v2ExtraMeta *meta;
      ID3v2ExtraMetaPRIV *priv;
  
      meta = av_mallocz(sizeof(*meta));
      priv = av_mallocz(sizeof(*priv));
  
      if (!meta || !priv)
          goto fail;
  
      if (decode_str(s, pb, ID3v2_ENCODING_ISO8859, &priv->owner, &taglen) < 0)
          goto fail;
  
      priv->data = av_malloc(taglen);
      if (!priv->data)
          goto fail;
  
      priv->datasize = taglen;
  
      if (avio_read(pb, priv->data, priv->datasize) != priv->datasize)
          goto fail;
  
      meta->tag   = "PRIV";
      meta->data  = priv;
      meta->next  = *extra_meta;
      *extra_meta = meta;
  
      return;
  
  fail:
      if (priv)
          free_priv(priv);
      av_freep(&meta);
  }
  
  typedef struct ID3v2EMFunc {
      const char *tag3;
      const char *tag4;
      void (*read)(AVFormatContext *s, AVIOContext *pb, int taglen,
                   const char *tag, ID3v2ExtraMeta **extra_meta,
                   int isv34);
      void (*free)(void *obj);
  } ID3v2EMFunc;
  
  static const ID3v2EMFunc id3v2_extra_meta_funcs[] = {
      { "GEO", "GEOB", read_geobtag, free_geobtag },
      { "PIC", "APIC", read_apic,    free_apic    },
      { "CHAP","CHAP", read_chapter, NULL         },
      { "PRIV","PRIV", read_priv,    free_priv    },
      { NULL }
  };
  
  /**
   * Get the corresponding ID3v2EMFunc struct for a tag.
   * @param isv34 Determines if v2.2 or v2.3/4 strings are used
   * @return A pointer to the ID3v2EMFunc struct if found, NULL otherwise.
   */
  static const ID3v2EMFunc *get_extra_meta_func(const char *tag, int isv34)
  {
      int i = 0;
      while (id3v2_extra_meta_funcs[i].tag3) {
          if (tag && !memcmp(tag,
                      (isv34 ? id3v2_extra_meta_funcs[i].tag4 :
                               id3v2_extra_meta_funcs[i].tag3),
                      (isv34 ? 4 : 3)))
              return &id3v2_extra_meta_funcs[i];
          i++;
      }
      return NULL;
  }
  
  static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
                          AVFormatContext *s, int len, uint8_t version,
                          uint8_t flags, ID3v2ExtraMeta **extra_meta)
  {
      int isv34, unsync;
      unsigned tlen;
      char tag[5];
      int64_t next, end = avio_tell(pb) + len;
      int taghdrlen;
      const char *reason = NULL;
      AVIOContext pb_local;
      AVIOContext *pbx;
      unsigned char *buffer = NULL;
      int buffer_size       = 0;
      const ID3v2EMFunc *extra_func = NULL;
      unsigned char *uncompressed_buffer = NULL;
      av_unused int uncompressed_buffer_size = 0;
  
      av_log(s, AV_LOG_DEBUG, "id3v2 ver:%d flags:%02X len:%d\n", version, flags, len);
  
      switch (version) {
      case 2:
          if (flags & 0x40) {
              reason = "compression";
              goto error;
          }
          isv34     = 0;
          taghdrlen = 6;
          break;
  
      case 3:
      case 4:
          isv34     = 1;
          taghdrlen = 10;
          break;
  
      default:
          reason = "version";
          goto error;
      }
  
      unsync = flags & 0x80;
  
      if (isv34 && flags & 0x40) { /* Extended header present, just skip over it */
          int extlen = get_size(pb, 4);
          if (version == 4)
              /* In v2.4 the length includes the length field we just read. */
              extlen -= 4;
  
          if (extlen < 0) {
              reason = "invalid extended header length";
              goto error;
          }
          avio_skip(pb, extlen);
          len -= extlen + 4;
          if (len < 0) {
              reason = "extended header too long.";
              goto error;
          }
      }
  
      while (len >= taghdrlen) {
          unsigned int tflags = 0;
          int tunsync         = 0;
          int tcomp           = 0;
          int tencr           = 0;
          unsigned long av_unused dlen;
  
          if (isv34) {
              if (avio_read(pb, tag, 4) < 4)
                  break;
              tag[4] = 0;
              if (version == 3) {
                  tlen = avio_rb32(pb);
              } else {
                  /* some encoders incorrectly uses v3 sizes instead of syncsafe ones
                   * so check the next tag to see which one to use */
                  tlen = avio_rb32(pb);
                  if (tlen > 0x7f) {
                      if (tlen < len) {
                          int64_t cur = avio_tell(pb);
  
                          if (ffio_ensure_seekback(pb, 2 /* tflags */ + tlen + 4 /* next tag */))
                              break;
  
                          if (check_tag(pb, cur + 2 + size_to_syncsafe(tlen), 4) == 1)
                              tlen = size_to_syncsafe(tlen);
                          else if (check_tag(pb, cur + 2 + tlen, 4) != 1)
                              break;
                          avio_seek(pb, cur, SEEK_SET);
                      } else
                          tlen = size_to_syncsafe(tlen);
                  }
              }
              tflags  = avio_rb16(pb);
              tunsync = tflags & ID3v2_FLAG_UNSYNCH;
          } else {
              if (avio_read(pb, tag, 3) < 3)
                  break;
              tag[3] = 0;
              tlen   = avio_rb24(pb);
          }
          if (tlen > (1<<28))
              break;
          len -= taghdrlen + tlen;
  
          if (len < 0)
              break;
  
          next = avio_tell(pb) + tlen;
  
          if (!tlen) {
              if (tag[0])
                  av_log(s, AV_LOG_DEBUG, "Invalid empty frame %s, skipping.\n",
                         tag);
              continue;
          }
  
          if (tflags & ID3v2_FLAG_DATALEN) {
              if (tlen < 4)
                  break;
              dlen = avio_rb32(pb);
              tlen -= 4;
          } else
              dlen = tlen;
  
          tcomp = tflags & ID3v2_FLAG_COMPRESSION;
          tencr = tflags & ID3v2_FLAG_ENCRYPTION;
  
          /* skip encrypted tags and, if no zlib, compressed tags */
          if (tencr || (!CONFIG_ZLIB && tcomp)) {
              const char *type;
              if (!tcomp)
                  type = "encrypted";
              else if (!tencr)
                  type = "compressed";
              else
                  type = "encrypted and compressed";
  
              av_log(s, AV_LOG_WARNING, "Skipping %s ID3v2 frame %s.\n", type, tag);
              avio_skip(pb, tlen);
          /* check for text tag or supported special meta tag */
          } else if (tag[0] == 'T' ||
                     !memcmp(tag, "USLT", 4) ||
                     (extra_meta &&
                      (extra_func = get_extra_meta_func(tag, isv34)))) {
              pbx = pb;
  
              if (unsync || tunsync || tcomp) {
                  av_fast_malloc(&buffer, &buffer_size, tlen);
                  if (!buffer) {
                      av_log(s, AV_LOG_ERROR, "Failed to alloc %d bytes\n", tlen);
                      goto seek;
                  }
              }
              if (unsync || tunsync) {
                  int64_t end = avio_tell(pb) + tlen;
                  uint8_t *b;
  
                  b = buffer;
                  while (avio_tell(pb) < end && b - buffer < tlen && !pb->eof_reached) {
                      *b++ = avio_r8(pb);
                      if (*(b - 1) == 0xff && avio_tell(pb) < end - 1 &&
                          b - buffer < tlen &&
                          !pb->eof_reached ) {
                          uint8_t val = avio_r8(pb);
                          *b++ = val ? val : avio_r8(pb);
                      }
                  }
                  ffio_init_context(&pb_local, buffer, b - buffer, 0, NULL, NULL, NULL,
                                    NULL);
                  tlen = b - buffer;
                  pbx  = &pb_local; // read from sync buffer
              }
  
  #if CONFIG_ZLIB
                  if (tcomp) {
                      int err;
  
                      av_log(s, AV_LOG_DEBUG, "Compresssed frame %s tlen=%d dlen=%ld\n", tag, tlen, dlen);
  
                      av_fast_malloc(&uncompressed_buffer, &uncompressed_buffer_size, dlen);
                      if (!uncompressed_buffer) {
                          av_log(s, AV_LOG_ERROR, "Failed to alloc %ld bytes\n", dlen);
                          goto seek;
                      }
  
                      if (!(unsync || tunsync)) {
                          err = avio_read(pb, buffer, tlen);
                          if (err < 0) {
                              av_log(s, AV_LOG_ERROR, "Failed to read compressed tag\n");
                              goto seek;
                          }
                          tlen = err;
                      }
  
                      err = uncompress(uncompressed_buffer, &dlen, buffer, tlen);
                      if (err != Z_OK) {
                          av_log(s, AV_LOG_ERROR, "Failed to uncompress tag: %d\n", err);
                          goto seek;
                      }
                      ffio_init_context(&pb_local, uncompressed_buffer, dlen, 0, NULL, NULL, NULL, NULL);
                      tlen = dlen;
                      pbx = &pb_local; // read from sync buffer
                  }
  #endif
              if (tag[0] == 'T')
                  /* parse text tag */
                  read_ttag(s, pbx, tlen, metadata, tag);
              else if (!memcmp(tag, "USLT", 4))
                  read_uslt(s, pbx, tlen, metadata);
              else
                  /* parse special meta tag */
                  extra_func->read(s, pbx, tlen, tag, extra_meta, isv34);
          } else if (!tag[0]) {
              if (tag[1])
                  av_log(s, AV_LOG_WARNING, "invalid frame id, assuming padding\n");
              avio_skip(pb, tlen);
              break;
          }
          /* Skip to end of tag */
  seek:
          avio_seek(pb, next, SEEK_SET);
      }
  
      /* Footer preset, always 10 bytes, skip over it */
      if (version == 4 && flags & 0x10)
          end += 10;
  
  error:
      if (reason)
          av_log(s, AV_LOG_INFO, "ID3v2.%d tag skipped, cannot handle %s\n",
                 version, reason);
      avio_seek(pb, end, SEEK_SET);
      av_free(buffer);
      av_free(uncompressed_buffer);
      return;
  }
  
  static void id3v2_read_internal(AVIOContext *pb, AVDictionary **metadata,
                                  AVFormatContext *s, const char *magic,
                                  ID3v2ExtraMeta **extra_meta, int64_t max_search_size)
  {
      int len, ret;
      uint8_t buf[ID3v2_HEADER_SIZE];
      int found_header;
      int64_t start, off;
  
      if (max_search_size && max_search_size < ID3v2_HEADER_SIZE)
          return;
  
      start = avio_tell(pb);
      do {
          /* save the current offset in case there's nothing to read/skip */
          off = avio_tell(pb);
          if (max_search_size && off - start >= max_search_size - ID3v2_HEADER_SIZE) {
              avio_seek(pb, off, SEEK_SET);
              break;
          }
  
          ret = avio_read(pb, buf, ID3v2_HEADER_SIZE);
          if (ret != ID3v2_HEADER_SIZE) {
              avio_seek(pb, off, SEEK_SET);
              break;
          }
          found_header = ff_id3v2_match(buf, magic);
          if (found_header) {
              /* parse ID3v2 header */
              len = ((buf[6] & 0x7f) << 21) |
                    ((buf[7] & 0x7f) << 14) |
                    ((buf[8] & 0x7f) << 7) |
                     (buf[9] & 0x7f);
              id3v2_parse(pb, metadata, s, len, buf[3], buf[5], extra_meta);
          } else {
              avio_seek(pb, off, SEEK_SET);
          }
      } while (found_header);
      ff_metadata_conv(metadata, NULL, ff_id3v2_34_metadata_conv);
      ff_metadata_conv(metadata, NULL, id3v2_2_metadata_conv);
      ff_metadata_conv(metadata, NULL, ff_id3v2_4_metadata_conv);
      merge_date(metadata);
  }
  
  void ff_id3v2_read_dict(AVIOContext *pb, AVDictionary **metadata,
                          const char *magic, ID3v2ExtraMeta **extra_meta)
  {
      id3v2_read_internal(pb, metadata, NULL, magic, extra_meta, 0);
  }
  
  void ff_id3v2_read(AVFormatContext *s, const char *magic,
                     ID3v2ExtraMeta **extra_meta, unsigned int max_search_size)
  {
      id3v2_read_internal(s->pb, &s->metadata, s, magic, extra_meta, max_search_size);
  }
  
  void ff_id3v2_free_extra_meta(ID3v2ExtraMeta **extra_meta)
  {
      ID3v2ExtraMeta *current = *extra_meta, *next;
      const ID3v2EMFunc *extra_func;
  
      while (current) {
          if ((extra_func = get_extra_meta_func(current->tag, 1)))
              extra_func->free(current->data);
          next = current->next;
          av_freep(&current);
          current = next;
      }
  
      *extra_meta = NULL;
  }
  
  int ff_id3v2_parse_apic(AVFormatContext *s, ID3v2ExtraMeta **extra_meta)
  {
      ID3v2ExtraMeta *cur;
  
      for (cur = *extra_meta; cur; cur = cur->next) {
          ID3v2ExtraMetaAPIC *apic;
          AVStream *st;
  
          if (strcmp(cur->tag, "APIC"))
              continue;
          apic = cur->data;
  
          if (!(st = avformat_new_stream(s, NULL)))
              return AVERROR(ENOMEM);
  
          st->disposition      |= AV_DISPOSITION_ATTACHED_PIC;
          st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
          st->codec->codec_id   = apic->id;
          av_dict_set(&st->metadata, "title",   apic->description, 0);
          av_dict_set(&st->metadata, "comment", apic->type, 0);
  
          av_init_packet(&st->attached_pic);
          st->attached_pic.buf          = apic->buf;
          st->attached_pic.data         = apic->buf->data;
          st->attached_pic.size         = apic->buf->size - FF_INPUT_BUFFER_PADDING_SIZE;
          st->attached_pic.stream_index = st->index;
          st->attached_pic.flags       |= AV_PKT_FLAG_KEY;
  
          apic->buf = NULL;
      }
  
      return 0;
  }
  