Field Detail

• CACHE_DIRNAME

  public static final java.lang.String CACHE_DIRNAME

  See Also:

  Constant Field Values

• README_NAME

  public static final java.lang.String README_NAME

  See Also:

  Constant Field Values

Constructor Detail

• DiskCache

  public DiskCache​(java.io.File dir,
                   long limit)

  Constructor.

  Parameters:

  dir - directory into which cache files will be written

  limit - cache size indicator; if positive, it's the maximum cache size in bytes; if negative, it's the amount of space on the disk that cache usage tries to keep free; if zero, it's something adaptive

Method Detail

• getDir

  public java.io.File getDir()

  Returns the directory associated with this cache.

  Returns:

  cache directory

• fileAdded

  public void fileAdded​(java.io.File f)

  Records that a file has been added to the cache. This record is used to report persistently added files at shutdown. No check is made that the file in question actually was added.

  Parameters:

  f - file added

• ready

  public void ready()
             throws java.io.IOException

  Ensures that this cache's directory is ready for use. Should be called before the cache is used.

  Throws:

  java.io.IOException

• log

  public void log​(java.lang.String txt)

  Logging utility function. This just passes a message to the logging system, using the logging level associated with this instance.

  Parameters:

  txt - message to log

• tidy

  public void tidy()

  Removes files from this cache's directory if it contains more data than the configured cache limit.

• getWriteSummary

  public java.lang.String getWriteSummary()

  Returns a string summarising total cache files written to date.

  Returns:

  summary text

• touch

  public void touch​(java.io.File file)

  Updates the lastModified timestamp for a given file.

  Parameters:

  file - file to touch

• hashText

  public static java.lang.String hashText​(java.lang.String txt)

  Returns a default-length hash string corresponding to a given string. This doesn't have to be cryptographically secure, but accidental collisions are to be avoided.

  Parameters:

  txt - text to hash

  Returns:

  fixed-length hash string

• hashText

  public static java.lang.String hashText​(java.lang.String txt,
                                          int nchar)

  Returns a configurable-length hash string corresponding to a given string. This doesn't have to be cryptographically secure, but accidental collisions are to be avoided.

  Parameters:

  txt - text to hash

  nchar - number of characters in output (currently up to 32)

  Returns:

  hash string

• toWorkFilename

  public static java.io.File toWorkFilename​(java.io.File file)

  Produces a working filename to be used as temporary workspace when assembling a given destination filename.

  We could just use one of the File.createTempFile methods, but attempt to come up with a name that is (a) likely to be unique and (b) bears some resemlance to the requested destination file, for ease of debugging etc.

  Parameters:

  file - destination file

  Returns:

  workspace file

• formatByteSize

  public static java.lang.String formatByteSize​(long nbyte)

  Formats a string representing a number of bytes for human consumption.

  Parameters:

  nbyte - byte count

  Returns:

  storage size string

• getSystemTmpDir

  public static java.io.File getSystemTmpDir()

  Returns the default system scratch directory. This is supplied from the java.io.tmpdir system property.

  Returns:

  scratch directory

• toCacheDir

  public static java.io.File toCacheDir​(java.io.File baseDir,
                                        java.lang.String label)

  Constructs a cache directory path given a base directory and a purpose-specific label.

  Parameters:

  baseDir - base directory; if null, java.io.tmpdir is used

  label - purpose-specific label (used for subdirectory name)

  Returns:

  directory to which cache files can be written

• mkdirs

  public static boolean mkdirs​(java.io.File dir,
                               boolean ownerOnly)

  Creates a scratch directory and any missing parents, assigning write privileges for all or owner-only. This is like File.mkdirs(), but it allows the option of assigning global write privileges to any created directories.

  Parameters:

  dir - target directory

  ownerOnly - true to make created directories writable by ownwer only, false to make them writable by all

  Returns:

  true if creation succeeded

• getDefaultCacheLimit

  public static long getDefaultCacheLimit​(java.io.File dir)

  Returns a cacheLimit value that is suitable for general usage. The return value is negative, meaning that it corresponds to requiring a certain number of bytes free on the filesystem.

  Parameters:

  dir - cache directory