Overview

The FreeHEP IO package extends the Java IO package with a number of input and output streams.

The FreeHEP IO package lives in org.freehep.util.io and is included in freehep-base.jar.

The FreeHEP IO streams are in use by the FreeHEP VectorGraphics package and the PostScript viewer. Of course all these classes are usable elsewhere.

A special part of the streams are the "Tagged" in and output streams which allow for tagged blocks to be read and written.

Below follows a description of the different streams available:

General Streams

FinishableOutputStream

This interface allows you to call finish() on a stream, which will write any end-of-stream marker.

NoCloseInputStream

This class (which is buffered by itself) allows you to call a non-active close(). If you have a stream from which you suddenly need to read in a different encoding (ASCII85, ...), wrap the stream in a NoCloseInputStream, then wrap that one in the encoding, read until the end-of-stream marker, then close that stream and keep reading from the underlying stream.

BitIn- / OutputStream

Reads or writes in bit format of any length bit streams.

ByteOrderInput- / OutputStream

Reads or writes lo- of hi-endian byte streams.

ByteCountInput- / OutputStream

Reads or writes a stream while keeping track the number of bytes read or written. Also keeps track of sub-counts if necessary.

UniquePrintStream

Keeps track of the strings one is printing and prints them only on the first occasion. Allows you to filter error messages for instance.

Standard Encoding Streams

ASCII85In- / OutputStream

Reads or writes ASCII85 encoding, used in e-mail for instance.

ASCIIHexIn- / OutputStream

Reads or writes ASCIIHex encoding.

DCTIn- / OutputStream

Reads or writes Discrete Cosine Transform encoding, used in JPEG image for instance.

RunLengthIn- / OutputStream

Reads or writes Run Length encoding, used in PostScript sometimes.

EExecEn- / Decryption

Reads or writes EExec encoding, used in Type1 fonts.

Tagged Streams

TaggedInput- / OutputStream, Tag, UndefinedTag, TagSet, Action, Action.Unknown and ActionSet

Reads or writes tags. Tags are blocks identified by some tag-id and a tag-length. A specific TagSet can be used to handle the tags as they are read or written. UndefinedTags can be skipped automatically. For writing the tag-length is automatically calculated. Total stream length can also be calculated. Actions are handled as a special set of "Tags".

Conditional Streams

ConditionalInputStream

Reads a stream and filters parts depending on properties set and statements in the stream. Works like the conditional compilation part of a C pre-processor.

RoutedInputStream and RouteListener

Routes a stream to a listener, who can keep reading from the stream, for a certain delimited part of the stream.

PromptInputStream and PromptListener

Reads a stream until the prompt and signals the listener.

Miscellaneous Classes

StandardFileFilter

Implements a filter with the default file filter scheme used in most Operating Systems. You can specify "*" for 0 or more "any" characters, and "?" for a single "any" character.