local ZPOS64_T zip64local_SearchCentralDir64()

in zlib/contrib/minizip/zip.c [745:840]
69 lines of code
26 McCabe index (conditional complexity)

local ZPOS64_T zip64local_SearchCentralDir64(const zlib_filefunc64_32_def* pzlib_filefunc_def, voidpf filestream) {
  unsigned char* buf;
  ZPOS64_T uSizeFile;
  ZPOS64_T uBackRead;
  ZPOS64_T uMaxBack=0xffff; /* maximum size of global comment */
  ZPOS64_T uPosFound=0;
  uLong uL;
  ZPOS64_T relativeOffset;

  if (ZSEEK64(*pzlib_filefunc_def,filestream,0,ZLIB_FILEFUNC_SEEK_END) != 0)
    return 0;

  uSizeFile = ZTELL64(*pzlib_filefunc_def,filestream);

  if (uMaxBack>uSizeFile)
    uMaxBack = uSizeFile;

  buf = (unsigned char*)ALLOC(BUFREADCOMMENT+4);
  if (buf==NULL)
    return 0;

  uBackRead = 4;
  while (uBackRead<uMaxBack)
  {
    uLong uReadSize;
    ZPOS64_T uReadPos;
    int i;
    if (uBackRead+BUFREADCOMMENT>uMaxBack)
      uBackRead = uMaxBack;
    else
      uBackRead+=BUFREADCOMMENT;
    uReadPos = uSizeFile-uBackRead ;

    uReadSize = ((BUFREADCOMMENT+4) < (uSizeFile-uReadPos)) ?
      (BUFREADCOMMENT+4) : (uLong)(uSizeFile-uReadPos);
    if (ZSEEK64(*pzlib_filefunc_def,filestream,uReadPos,ZLIB_FILEFUNC_SEEK_SET)!=0)
      break;

    if (ZREAD64(*pzlib_filefunc_def,filestream,buf,uReadSize)!=uReadSize)
      break;

    for (i=(int)uReadSize-3; (i--)>0;)
    {
      // Signature "0x07064b50" Zip64 end of central directory locator
      if (((*(buf+i))==0x50) && ((*(buf+i+1))==0x4b) && ((*(buf+i+2))==0x06) && ((*(buf+i+3))==0x07))
      {
        uPosFound = uReadPos+(unsigned)i;
        break;
      }
    }

      if (uPosFound!=0)
        break;
  }

  free(buf);
  if (uPosFound == 0)
    return 0;

  /* Zip64 end of central directory locator */
  if (ZSEEK64(*pzlib_filefunc_def,filestream, uPosFound,ZLIB_FILEFUNC_SEEK_SET)!=0)
    return 0;

  /* the signature, already checked */
  if (zip64local_getLong(pzlib_filefunc_def,filestream,&uL)!=ZIP_OK)
    return 0;

  /* number of the disk with the start of the zip64 end of central directory */
  if (zip64local_getLong(pzlib_filefunc_def,filestream,&uL)!=ZIP_OK)
    return 0;
  if (uL != 0)
    return 0;

  /* relative offset of the zip64 end of central directory record */
  if (zip64local_getLong64(pzlib_filefunc_def,filestream,&relativeOffset)!=ZIP_OK)
    return 0;

  /* total number of disks */
  if (zip64local_getLong(pzlib_filefunc_def,filestream,&uL)!=ZIP_OK)
    return 0;
  if (uL != 1)
    return 0;

  /* Goto Zip64 end of central directory record */
  if (ZSEEK64(*pzlib_filefunc_def,filestream, relativeOffset,ZLIB_FILEFUNC_SEEK_SET)!=0)
    return 0;

  /* the signature */
  if (zip64local_getLong(pzlib_filefunc_def,filestream,&uL)!=ZIP_OK)
    return 0;

  if (uL != 0x06064b50) // signature of 'Zip64 end of central directory'
    return 0;

  return relativeOffset;
}