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Class ncsa.horizon.util.MessageBuffer

java.lang.Object
  |
  +--java.io.Writer
        |
        +--ncsa.horizon.util.MessageBuffer

public class MessageBuffer

extends java.io.Writer

implements java.lang.Cloneable, java.io.Serializable

a buffer holding text that grows as necessary but can be optionally limited to a certain maximum size.

The limit of the buffer is set when the buffer is constructed. This limit can be set either as a number of characters/bytes (default) or a number of lines (as delimited by \n characters). Clients write messages to this writer which are appended to the end of the buffer. If the size of the buffer plus the size of the new message (either in number of lines or characters) exceeds the buffer limit, text at the beginning of the buffer will be trimmed off.

How much text gets automatically trimmed depends on the property accessed via is/setTrimmedByLines(). If isTrimmedByLines() returns true (which is the default), whole lines will be trimmed from the beginning of the buffer as necessary to keep the buffer size below its limit.

This class also supports listeners who are notified whenever the buffer is flushed or cleared. (Flushing does not cause any data to be thrown away.) This allows such clients as gui components (like a TextArea) to update their displays, especially when new messages are sent. In this case, it is convenient to wrap the buffer with a PrintWriter or MultiPrintWriter with auto-flushing; this will cause listeners to be alerted automatically after every complete line (ending in a newline character).

See Also:

MultiPrintWriter, MessageCenter, Serialized Form

Inner Class Summary

	MessageBuffer.Enum
static	MessageBuffer.Listener an interface for objects that wish to listen for changes to this buffer

Field Summary

int	capacity the maximum capacity.
boolean	capIsByLines true if capacity refers to a number of lines
boolean	trimByLines true if the buffer should be automatically trimmed at line boundaries

Fields inherited from class java.io.Writer

lock

Constructor Summary

MessageBuffer(int maxcap, boolean byLines, java.lang.String str)
create a MessageBuffer with a given maximum capacity and given contents

MessageBuffer(int maxcap, boolean byLines)
create a MessageBuffer with a given maximum capacity

MessageBuffer(int maxchar)
create a MessageBuffer with a given maximum character capacity

MessageBuffer()
create a MessageBuffer with unlimited capacity

Method Summary

void	addListener(MessageBuffer.Listener l) add a listener of this buffer
boolean	capacityIsByLines() return true if the capacity of the buffer has been set by the number of lines
void	clear() clear contents of buffer
java.lang.Object	clone()
void	close() close this writer.
static int	countLines(char[] str, int offset, int count) count the number of lines in a given string
void	flush() flush this writer.
int	getLineCount() return the number of lines in the buffer
boolean	isTrimmedByLines() return true if this buffer will be trimmed by whole lines.
int	length() return length of contents
MessageBuffer.Enum	lines() get an enumerator of the lines in the buffer
static void	main(java.lang.String[] argv)
int	maxCapacity() return the maximum this buffer can hold.
void	removeListener(MessageBuffer.Listener l) remove a listener of this buffer
void	setTrimmedByLines(boolean yes) set whether this buffer will be trimmed by whole lines.
java.lang.String	toString() convert contents to a String
void	trimChars(int nchars) trim characters from the beginning of the buffer
void	trimLines(int nlines) trim whole lines from the beginning of the buffer
void	write(char[] str, int offset, int count) append a message to the buffer

Methods inherited from class java.io.Writer

close, flush, write, write, write, write, write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notifyAll, notify, toString, wait, wait, wait

Field Detail

trimByLines

protected boolean trimByLines

true if the buffer should be automatically trimmed at line boundaries

capacity

protected int capacity

the maximum capacity. A value of zero or less means no limit.

capIsByLines

protected boolean capIsByLines

true if capacity refers to a number of lines

Constructor Detail

MessageBuffer

public MessageBuffer(int maxcap,
                     boolean byLines,
                     java.lang.String str)

create a MessageBuffer with a given maximum capacity and given contents

Parameters:

maxcap - the maximum size of the buffer; there is no maximum limit if maxcap <= 0

byLines - if true, the maxcap refers to the number of lines; otherwise, it is the number of characters.

str - string to initialize buffer with (ignored if null)

MessageBuffer

public MessageBuffer(int maxcap,
                     boolean byLines)

create a MessageBuffer with a given maximum capacity

Parameters:

maxcap - the maximum size of the buffer; there is no maximum limit if maxcap <= 0

byLines - if true, the maxcap refers to the number of lines; otherwise, it is the number of characters.

MessageBuffer

public MessageBuffer(int maxchar)

create a MessageBuffer with a given maximum character capacity

Parameters:

maxchar - the maximum number of characters in the buffer; there is no maximum limit if maxcap <= 0

MessageBuffer

public MessageBuffer()

create a MessageBuffer with unlimited capacity

Method Detail

isTrimmedByLines

public boolean isTrimmedByLines()

return true if this buffer will be trimmed by whole lines. Lines delimited by newline characters

setTrimmedByLines

public void setTrimmedByLines(boolean yes)

set whether this buffer will be trimmed by whole lines. Lines delimited by newline characters

write

public void write(char[] str,
                  int offset,
                  int count)

append a message to the buffer

Overrides:

write in class java.io.Writer

trimChars

public void trimChars(int nchars)

trim characters from the beginning of the buffer

Parameters:

nchars - the number of characters to trim from beginning of buffer.

trimLines

public void trimLines(int nlines)

trim whole lines from the beginning of the buffer

countLines

public static int countLines(char[] str,
                             int offset,
                             int count)

count the number of lines in a given string

capacityIsByLines

public boolean capacityIsByLines()

return true if the capacity of the buffer has been set by the number of lines

maxCapacity

public int maxCapacity()

return the maximum this buffer can hold. If capacityIsByLines() is true, then the return value is the maximum number of lines; otherwise, it is the maximum number of characters.

toString

public java.lang.String toString()

convert contents to a String

Overrides:

toString in class java.lang.Object

length

public int length()

return length of contents

getLineCount

public int getLineCount()

return the number of lines in the buffer

clear

public void clear()

clear contents of buffer

lines

public MessageBuffer.Enum lines()

get an enumerator of the lines in the buffer

flush

public void flush()

flush this writer. This implementation does nothing.

Overrides:

flush in class java.io.Writer

close

public void close()

close this writer. This implementation does nothing.

Overrides:

close in class java.io.Writer

addListener

public void addListener(MessageBuffer.Listener l)

add a listener of this buffer

removeListener

public void removeListener(MessageBuffer.Listener l)

remove a listener of this buffer

clone

public java.lang.Object clone()

Overrides:

clone in class java.lang.Object

main

public static void main(java.lang.String[] argv)