Package org.apache.pdfbox.io

Class ScratchFile

java.lang.Object
org.apache.pdfbox.io.ScratchFile
All Implemented Interfaces:
Closeable, AutoCloseable, RandomAccessStreamCache
public class ScratchFile extends Object implements RandomAccessStreamCache
Implements a memory page handling mechanism as base for creating (multiple) RandomAccess buffers each having its set of pages (implemented by ScratchFileBuffer). A buffer is created calling createBuffer().

Pages can be stored in main memory or in a temporary file. A mixed mode is supported storing a certain amount of pages in memory and only the additional ones in temporary file (defined by maximum main memory to be used).

Pages can be marked as 'free' in order to re-use them. For in-memory pages this will release the used memory while for pages in temporary file this simply marks the area as free to re-use.

If a temporary file was created (done with the first page to be stored in temporary file) it is deleted when close() is called.

Using this class for RandomAccess buffers allows for a direct control on the maximum memory usage and allows processing large files for which we otherwise would get an OutOfMemoryError in case of using RandomAccessReadBuffer.

This base class for providing pages is thread safe (the buffer implementations are not).

  • Constructor Details

    • ScratchFile

      public ScratchFile(File scratchFileDirectory) throws IOException
      Initializes page handler. If a scratchFileDirectory is supplied, then the scratch file will be created in that directory.

      All pages will be stored in the scratch file.

      Parameters:
      scratchFileDirectory - The directory in which to create the scratch file or null to created it in the default temporary directory.
      Throws:
      IOException - If scratch file directory was given but don't exist.

    • ScratchFile

      public ScratchFile(MemoryUsageSetting memUsageSetting) throws IOException
      Initializes page handler. If a scratchFileDirectory is supplied, then the scratch file will be created in that directory.

      Depending on the size of allowed memory usage a number of pages (memorySize/PAGE_SIZE) will be stored in-memory and only additional pages will be written to/read from scratch file.

      Parameters:
      memUsageSetting - set how memory/temporary files are used for buffering streams etc.
      Throws:
      IOException - If scratch file directory was given but don't exist.

  • Method Details

    • getMainMemoryOnlyInstance

      public static ScratchFile getMainMemoryOnlyInstance()
      Getter for an instance using only unrestricted main memory for buffering (same as new ScratchFile(MemoryUsageSetting.setupMainMemoryOnly())).
      Returns:
      instance configured to only use main memory with no size restriction

    • getMainMemoryOnlyInstance

      public static ScratchFile getMainMemoryOnlyInstance(long maxMainMemoryBytes)
      Getter for an instance to only use main-memory with the defined maximum.
      Parameters:
      maxMainMemoryBytes - maximum number of main-memory to be used; -1 for no restriction; 0 will also be interpreted here as no restriction
      Returns:
      instance configured to only use main memory with no size restriction or null if cannot create scratch file

    • createBuffer

      public RandomAccess createBuffer() throws IOException
      Creates a new buffer using this page handler.
      Specified by:
      createBuffer in interface RandomAccessStreamCache
      Returns:
      A new buffer.
      Throws:
      IOException - If an error occurred.

    • close

      public void close() throws IOException
      Closes and deletes the temporary file. No further interaction with the scratch file or associated buffers can happen after this method is called. It also releases in-memory pages.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException - If there was a problem closing or deleting the temporary file.