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• How to save variables at start of script for use later if script needs to be re-run due to errors or bad user input

  28 novembre 2023, par slyfox1186

  I have a script that uses GitHub's API to get the latest version number of the repositories that I am trying to download and then compile.

  


  Due to the fact that without using a specialized token from GitHub you are only allowed 50 API calls a day vs the 5000 a day with the API user token.

  


  I want to be able to parse all of the repositories and grab the version numbers that my script will then import into the code up front so in case someone who accidentally cancels the build in the middle of it (for who knows what reasons) wont have to eat up their 50 day API call allowance.

  


  Essentially, store each repo's version number, if the user then needs to rerun the script and version numbers that have been saved so far will be skipped (thus eliminating an API call) and any numbers that are still needing to be sourced will be called and then stored for used in the script.

  


  I am kinda of lost for a method on how to go about this.

  


  Maybe some sort of external file can be generated ?

  


  So what my script does is it builds FFmpeg from source code and all of the external libraries that you can link to it are also built from their latest source code.

  


  The code calls the function git_ver_fn and passes arguments to it which are parsed inside the function and directed to another functions git_1_fn or git_2_fn which passed those parsed arguments that have been passed on to the CURL command which changes the URL based on the arguments passed. It uses the jq command to capture the GitHub version number and download link for the tar.gz file.

  


  It is the version number I am and trying to figure out the best way to store in case the script fails and has to be rerun, which will eat up all of the 50 APT limit that GitHub imposes without a token. I can't post my token in the script because GitHub deactivates it and thus the users will be SOL if they need to run the script more than once.

  


  curl_timeout='5'

git_1_fn()
{
    # SCRAPE GITHUB WEBSITE FOR LATEST REPO VERSION
    github_repo="$1"
    github_url="$2"

    if curl_cmd="$(curl -m "$curl_timeout" -sSL "https://api.github.com/repos/$github_repo/$github_url")"; then
        g_ver="$(echo "$curl_cmd" | jq -r '.[0].name')"
        g_ver="${g_ver#v}"
        g_ssl="$(echo "$curl_cmd" | jq -r '.[0].name')"
        g_ssl="${g_ssl#OpenSSL }"
        g_pkg="$(echo "$curl_cmd" | jq -r '.[0].name')"
        g_pkg="${g_pkg#pkg-config-}"
        g_url="$(echo "$curl_cmd" | jq -r '.[0].tarball_url')"
    fi
}

git_2_fn()
{
    videolan_repo="$1"
    videolan_url="$2"
    if curl_cmd="$(curl -m "$curl_timeout" -sSL "https://code.videolan.org/api/v4/projects/$videolan_repo/repository/$videolan_url")"; then
        g_ver="$(echo "$curl_cmd" | jq -r '.[0].commit.id')"
        g_sver="$(echo "$curl_cmd" | jq -r '.[0].commit.short_id')"
        g_ver1="$(echo "$curl_cmd" | jq -r '.[0].name')"
        g_ver1="${g_ver1#v}"
    fi
}

git_ver_fn()
{
    local v_flag v_tag url_tag

    v_url="$1"
    v_tag="$2"

    if [ -n "$3" ]; then v_flag="$3"; fi

    if [ "$v_flag" = 'B' ] && [  "$v_tag" = '2' ]; then
        url_tag='git_2_fn' gv_url='branches'
    fi

    if [ "$v_flag" = 'X' ] && [  "$v_tag" = '5' ]; then
        url_tag='git_5_fn'
    fi

    if [ "$v_flag" = 'T' ] && [  "$v_tag" = '1' ]; then
        url_tag='git_1_fn' gv_url='tags'
    elif [ "$v_flag" = 'T' ] && [  "$v_tag" = '2' ]; then
        url_tag='git_2_fn' gv_url='tags'
    fi

    if [ "$v_flag" = 'R' ] && [  "$v_tag" = '1' ]; then
        url_tag='git_1_fn'; gv_url='releases'
    elif [ "$v_flag" = 'R' ] && [  "$v_tag" = '2' ]; then
        url_tag='git_2_fn'; gv_url='releases'
    fi

    case "$v_tag" in
        2)          url_tag='git_2_fn';;
    esac

    "$url_tag" "$v_url" "$gv_url" 2>/dev/null
}

# begin source code building
git_ver_fn 'freedesktop/pkg-config' '1' 'T'
if build 'pkg-config' "$g_pkg"; then
    download "https://pkgconfig.freedesktop.org/releases/$g_ver.tar.gz" "$g_ver.tar.gz"
    execute ./configure --silent --prefix="$workspace" --with-pc-path="$workspace"/lib/pkgconfig/ --with-internal-glib
    execute make -j "$cpu_threads"
    execute make install
    build_done 'pkg-config' "$g_pkg"
fi

git_ver_fn 'yasm/yasm' '1' 'T'
if build 'yasm' "$g_ver"; then
    download "https://github.com/yasm/yasm/releases/download/v$g_ver/yasm-$g_ver.tar.gz" "yasm-$g_ver.tar.gz"
    execute ./configure --prefix="$workspace"
    execute make -j "$cpu_threads"
    execute make install
    build_done 'yasm' "$g_ver"
fi


  


• Decompressing time-To-Sample table (STTS) in an MP4 file

  30 mai 2016, par man-r

  i have an mp4 video byte array and i need to generate a thumbnail for it using its middle frame (e.g. if the video length is 10 seconds then i need to get the picture from 5th second).

  i managed to parse through the file and extract its boxes (atom). i have also managed to get the video length from the mvhd box. also i managed to extract
  1. the time-To-Sample table from stts box,
  2. the sample-To-Chunk table from stcs box,
  3. the chunk-Offset table from stco box,
  4. the sample Size table from stsz box,
  5. the Sync Sample table from stss box

  i know that all the actual media are available in the mdat box and that i need to correlate the above table to find the exact frame offset in the file but my question is how ? the tables data seems to be compressed (specially the time-To-Sample table) but i don’t know how decompress them.

  any help is appreciated.

  below are code samples

  code to convert byte to hex

  public static char[] bytesToHex(byte[] bytes) {
  
      char[] hexChars = new char[bytes.length * 2];
  
      for ( int j = 0; j < bytes.length; j++ ) {
  
          int v = bytes[j] & 0xFF;
  
  
  
          hexChars[j * 2] = hexArray[v >>> 4];
  
          hexChars[j * 2 + 1] = hexArray[v & 0x0F];            
  
      }
  
      return hexChars;
  
  }

  code for getting the box offset

  final static String MOOV                          = "6D6F6F76";
  
  final static String MOOV_MVHD                     = "6D766864";
  
  final static String MOOV_TRAK                     = "7472616B";
  
  final static String MOOV_TRAK_MDIA                = "6D646961";
  
  final static String MOOV_TRAK_MDIA_MINF           = "6D696E66";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL      = "7374626C";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSD = "73747364";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STTS = "73747473";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSS = "73747373";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSC = "73747363";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STCO = "7374636F";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSZ = "7374737A";
  
  
  
  static int getBox(char[] s, int offset, String type) {
  
      int typeOffset = -1;
  
      for (int i = offset*2; i-1) {
  
                  break;
  
              } 
  
          }
  
          i+=(size*2);
  
      }
  
  
  
      return typeOffset;
  
  }

  code for getting the duration and timescale

  static int[] getDuration(char[] s) {
  
      int mvhdOffset = getBox(s, 0, MOOV_MVHD);
  
      int timeScaleStart = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4)*2;
  
      int timeScaleEnd   = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4 + 4)*2;
  
  
  
      int durationStart  = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4 + 4)*2;
  
      int durationEnd    = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4 + 4 + 4)*2;
  
  
  
      String timeScaleHex = new String(Arrays.copyOfRange(s, timeScaleStart, timeScaleEnd));
  
      String durationHex = new String(Arrays.copyOfRange(s, durationStart, durationEnd));
  
  
  
      int timeScale = Integer.parseInt(timeScaleHex, 16);
  
      int duration = Integer.parseInt(durationHex, 16);
  
  
  
      int[] result = {duration, timeScale};
  
      return result;
  
  }

  code to get the time-To-Sample table

  static int[][] getTimeToSampleTable(char[] s, int trakOffset) {
  
      int offset = getBox(s, trakOffset, MOOV_TRAK_MDIA_MINF_STBL_STTS);
  
      int sizeStart = offset*2;
  
      int sizeEnd   = offset*2 + (4)*2;
  
  
  
      int typeStart = offset*2 + (4)*2;
  
      int typeEnd   = offset*2 + (4 + 4)*2;
  
  
  
      int noOfEntriesStart = offset*2 + (4 + 4 + 1 + 3)*2;
  
      int noOfEntriesEnd   = offset*2 + (4 + 4 + 1 + 3 + 4)*2;
  
  
  
      String sizeHex = new String(Arrays.copyOfRange(s, sizeStart, sizeEnd));
  
      String typeHex = new String(Arrays.copyOfRange(s, typeStart, typeEnd));
  
      String noOfEntriesHex = new String(Arrays.copyOfRange(s, noOfEntriesStart, noOfEntriesEnd));
  
  
  
      int size = Integer.parseInt(sizeHex, 16);
  
      int noOfEntries = Integer.parseInt(noOfEntriesHex, 16);
  
  
  
      int[][] timeToSampleTable = new int[noOfEntries][2];
  
  
  
      for (int i = 0; icode>

• MP4 file data structure

  16 décembre 2015, par man-r

  i have an mp4 video byte array and i need to generate a thumbnail for it using its middle frame (e.g. if the video length is 10 seconds then i need to get the picture from 5th second).

  i managed to parse through the file and extract its boxes (atom). i have also managed to get the video length from the mvhd box. also i managed to extract
  1. the time-To-Sample table from stts box,
  2. the sample-To-Chunk table from stcs box,
  3. the chunk-Offset table from stco box,
  4. the sample Size table from stsz box,
  5. the Sync Sample table from stss box

  i know that all the actual media are available in the mdat box and that i need to correlate the above table to find the exact frame offset in the file but my question is how ? the tables data seems to be compressed (specially the time-To-Sample table) but i don’t know how decompress them.

  any help is appreciated.

  below are code samples

  code to convert byte to hex

  public static char[] bytesToHex(byte[] bytes) {
  
      char[] hexChars = new char[bytes.length * 2];
  
      for ( int j = 0; j < bytes.length; j++ ) {
  
          int v = bytes[j] & 0xFF;
  
  
  
          hexChars[j * 2] = hexArray[v >>> 4];
  
          hexChars[j * 2 + 1] = hexArray[v & 0x0F];            
  
      }
  
      return hexChars;
  
  }

  code for getting the box offset

  final static String MOOV                          = "6D6F6F76";
  
  final static String MOOV_MVHD                     = "6D766864";
  
  final static String MOOV_TRAK                     = "7472616B";
  
  final static String MOOV_TRAK_MDIA                = "6D646961";
  
  final static String MOOV_TRAK_MDIA_MINF           = "6D696E66";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL      = "7374626C";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSD = "73747364";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STTS = "73747473";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSS = "73747373";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSC = "73747363";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STCO = "7374636F";
  
  final static String MOOV_TRAK_MDIA_MINF_STBL_STSZ = "7374737A";
  
  
  
  static int getBox(char[] s, int offset, String type) {
  
      int typeOffset = -1;
  
      for (int i = offset*2; i-1) {
  
                  break;
  
              } 
  
          }
  
          i+=(size*2);
  
      }
  
  
  
      return typeOffset;
  
  }

  code for getting the duration and timescale

  static int[] getDuration(char[] s) {
  
      int mvhdOffset = getBox(s, 0, MOOV_MVHD);
  
      int timeScaleStart = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4)*2;
  
      int timeScaleEnd   = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4 + 4)*2;
  
  
  
      int durationStart  = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4 + 4)*2;
  
      int durationEnd    = (mvhdOffset*2) + (4 + 4 + 1 + 3 + 4 + 4 + 4 + 4)*2;
  
  
  
      String timeScaleHex = new String(Arrays.copyOfRange(s, timeScaleStart, timeScaleEnd));
  
      String durationHex = new String(Arrays.copyOfRange(s, durationStart, durationEnd));
  
  
  
      int timeScale = Integer.parseInt(timeScaleHex, 16);
  
      int duration = Integer.parseInt(durationHex, 16);
  
  
  
      int[] result = {duration, timeScale};
  
      return result;
  
  }

  code to get the time-To-Sample table

  static int[][] getTimeToSampleTable(char[] s, int trakOffset) {
  
      int offset = getBox(s, trakOffset, MOOV_TRAK_MDIA_MINF_STBL_STTS);
  
      int sizeStart = offset*2;
  
      int sizeEnd   = offset*2 + (4)*2;
  
  
  
      int typeStart = offset*2 + (4)*2;
  
      int typeEnd   = offset*2 + (4 + 4)*2;
  
  
  
      int noOfEntriesStart = offset*2 + (4 + 4 + 1 + 3)*2;
  
      int noOfEntriesEnd   = offset*2 + (4 + 4 + 1 + 3 + 4)*2;
  
  
  
      String sizeHex = new String(Arrays.copyOfRange(s, sizeStart, sizeEnd));
  
      String typeHex = new String(Arrays.copyOfRange(s, typeStart, typeEnd));
  
      String noOfEntriesHex = new String(Arrays.copyOfRange(s, noOfEntriesStart, noOfEntriesEnd));
  
  
  
      int size = Integer.parseInt(sizeHex, 16);
  
      int noOfEntries = Integer.parseInt(noOfEntriesHex, 16);
  
  
  
      int[][] timeToSampleTable = new int[noOfEntries][2];
  
  
  
      for (int i = 0; icode>