## org.codehaus.groovy.grails.web.util
Class StreamCharBuffer

    java.lang.Object
      org.codehaus.groovy.grails.web.util.StreamCharBuffer

All Implemented Interfaces:
  groovy.lang.Writable, Externalizable, Serializable, CharSequence

    public class StreamCharBuffer

extends Object
implements groovy.lang.Writable, CharSequence, Externalizable

StreamCharBuffer is a multipurpose in-memory buffer that can replace JDK in-memory buffers (StringBuffer, StringBuilder, StringWriter).

Grails GSP rendering uses this class as a buffer that is optimized for performance.

StreamCharBuffer keeps the buffer in a linked list of "chunks". The main difference compared to JDK in-memory buffers (StringBuffer, StringBuilder & StringWriter) is that the buffer can be held in several smaller buffers ("chunks" here). In JDK in-memory buffers, the buffer has to be expanded whenever it gets filled up. The old buffer's data is copied to the new one and the old one is discarded. In StreamCharBuffer, there are several ways to prevent unnecessary allocation & copy operations. The StreamCharBuffer contains a linked list of different type of chunks: char arrays, java.lang.String chunks and other StreamCharBuffers as sub chunks. A StringChunk is appended to the linked list whenever a java.lang.String of a length that exceeds the "stringChunkMinSize" value is written to the buffer.

Grails tag libraries also use a StreamCharBuffer to "capture" the output of the taglib and return it to the caller. The buffer can be appended to it's parent buffer directly without extra object generation (like converting to java.lang.String in between). for example this line of code in a taglib would just append the buffer returned from the body closure evaluation to the buffer of the taglib:
`out << body()`
other example:
`out << g.render(template: '/some/template', model:[somebean: somebean])`
There's no extra java.lang.String generation overhead.

There's a java.io.Writer interface for appending character data to the buffer and a java.io.Reader interface for reading data.

Each `getReader()` call will create a new reader instance that keeps it own state.
There is a alternative method `getReader(boolean)` for creating the reader. When reader is created by calling getReader(true), the reader will remove already read characters from the buffer. In this mode only a single reader instance is supported.

There's also several other options for reading data:
`readAsCharArray()` reads the buffer to a char[] array
`readAsString()` reads the buffer and wraps the char[] data as a String
`writeTo(Writer)` writes the buffer to a java.io.Writer
`toCharArray()` returns the buffer as a char[] array, caches the return value internally so that this method can be called several times.
`toString()` returns the buffer as a String, caches the return value internally

By using the "connectTo" method, one can connect the buffer directly to a target java.io.Writer. The internal buffer gets flushed automaticly to the target whenever the buffer gets filled up. `connectTo(Writer)`

This class is not thread-safe. Object instances of this class are intended to be used by a single Thread. The Reader and Writer interfaces can be open simultaneous and the same Thread can write and read several times.

Main operation principle:

StreamCharBuffer keeps the buffer in a linked link of "chunks".
The main difference compared to JDK in-memory buffers (StringBuffer, StringBuilder & StringWriter) is that the buffer can be held in several smaller buffers ("chunks" here).
In JDK in-memory buffers, the buffer has to be expanded whenever it gets filled up. The old buffer's data is copied to the new one and the old one is discarded.
In StreamCharBuffer, there are several ways to prevent unnecessary allocation & copy operations.

There can be several different type of chunks: char arrays ( `StreamCharBuffer.CharBufferChunk`), String chunks (`StreamCharBuffer.StringChunk`) and other StreamCharBuffers as sub chunks (`StreamCharBuffer.StreamCharBufferSubChunk`).

Child StreamCharBuffers can be changed after adding to parent buffer. The flush() method must be called on the child buffer's Writer to notify the parent that the child buffer's content has been changed (used for calculating total size).

A StringChunk is appended to the linked list whenever a java.lang.String of a length that exceeds the "stringChunkMinSize" value is written to the buffer.

If the buffer is in "connectTo" mode, any String or char[] that's length is over writeDirectlyToConnectedMinSize gets written directly to the target. The buffer content will get fully flushed to the target before writing the String or char[].

There can be several targets "listening" the buffer in "connectTo" mode. The same content will be written to all targets.

Growable chunksize: By default, a newly allocated chunk's size will grow based on the total size of all written chunks.
The default growProcent value is 100. If the total size is currently 1024, the newly created chunk will have a internal buffer that's size is 1024.
Growable chunksize can be turned off by setting the growProcent to 0.
There's a default maximum chunksize of 1MB by default. The minimum size is the initial chunksize size.

System properties to change default configuration parameters:

System Property name | Description | Default value
--- | --- | ---
streamcharbuffer.chunksize | default chunk size - the size the first allocated buffer | 512
streamcharbuffer.maxchunksize | maximum chunk size - the maximum size of the allocated buffer | 1048576
streamcharbuffer.growprocent | growing buffer percentage - the newly allocated buffer is defined by total_size * (growpercent/100) | 100
streamcharbuffer.subbufferchunkminsize | minimum size of child StreamCharBuffer chunk - if the size is smaller, the content is copied to the parent buffer | 512
streamcharbuffer.substringchunkminsize | minimum size of String chunks - if the size is smaller, the content is copied to the buffer | 512
streamcharbuffer.chunkminsize | minimum size of chunk that gets written directly to the target in connected mode. | 256

Configuration values can also be changed for each instance of StreamCharBuffer individually. Default values are defined with System Properties.

Author:
  Lari Hotari, Sagire Software Oy
See Also:
  Serialized Form

Nested Class Summary
`(package private) class` `StreamCharBuffer.AbstractChunk`
`(package private) class` `StreamCharBuffer.AbstractChunkReader`
`(package private) class` `StreamCharBuffer.AllocatedBuffer`
`(package private) class` `StreamCharBuffer.AllocatedBufferReader`
`(package private) class` `StreamCharBuffer.CharBufferChunk` The data in the buffer is stored in a linked list of StreamCharBufferChunks.
`(package private) class` `StreamCharBuffer.CharBufferChunkReader`
`(package private) static class` `StreamCharBuffer.ChunkReader`
`(package private) static class` `StreamCharBuffer.ConnectedWriter` Simple holder class for the connected writer
`static interface` `StreamCharBuffer.LazyInitializingWriter` Interface for a Writer that gets initialized if it is used Can be used for passing in to "connectTo" method of StreamCharBuffer
`(package private) static class` `StreamCharBuffer.MultiOutputWriter` delegates to several writers, used in "connectTo" mode.
`(package private) static class` `StreamCharBuffer.SingleOutputWriter`
`class` `StreamCharBuffer.StreamCharBufferReader` This is the java.io.Reader implementation for StreamCharBuffer
`(package private) class` `StreamCharBuffer.StreamCharBufferSubChunk`
`(package private) class` `StreamCharBuffer.StreamCharBufferSubChunkReader`
`class` `StreamCharBuffer.StreamCharBufferWriter` This is the java.io.Writer implementation for StreamCharBuffer
`(package private) class` `StreamCharBuffer.StringChunk` StringChunk is a wrapper for java.lang.String.
`(package private) class` `StreamCharBuffer.StringChunkReader`

Field Summary
`(package private) int` `allocatedBufferIdSequence`
`(package private) boolean` `hasReaders`
`(package private) boolean` `preferSubChunkWhenWritingToOtherBuffer`
`(package private) int` `readerCount`

Constructor Summary
`StreamCharBuffer()`
`StreamCharBuffer(int chunkSize)`
`StreamCharBuffer(int chunkSize, int growProcent)`
`StreamCharBuffer(int chunkSize, int growProcent, int maxChunkSize)`

Method Summary
`(package private) void` `addChunk(StreamCharBuffer.AbstractChunk newChunk)`
`(package private) void` `addParentBuffer(StreamCharBuffer parent)`
`protected int` `allocateSpace()`
`void` `appendStreamCharBufferChunk(StreamCharBuffer subBuffer)`
`(package private) void` `appendStringChunk(String str, int off, int len)`
`protected static void` `arrayCopy(char[] src, int srcPos, char[] dest, int destPos, int length)`
`(package private) boolean` `bufferChanged(StreamCharBuffer buffer)`
`char` `charAt(int index)`
`void` `connectTo(StreamCharBuffer.LazyInitializingWriter writer)`
`void` `connectTo(StreamCharBuffer.LazyInitializingWriter writer, boolean autoFlush)`
`void` `connectTo(Writer writer)` Connect this buffer to a target Writer.
`void` `connectTo(Writer writer, boolean autoFlush)`
`boolean` `equals(Object o)` equals uses String.equals to check for equality to support compatibility with String instances in maps, sets, etc.
`int` `getChunkMinSize()`
`Reader` `getReader()` Creates a new java.io.Reader instance for reading/consuming data from the buffer.
`Reader` `getReader(boolean removeAfterReading)` Like getReader(), but when removeAfterReading is true, the read data will be removed from the buffer.
`int` `getSubBufferChunkMinSize()`
`int` `getSubStringChunkMinSize()`
`int` `getWriteDirectlyToConnectedMinSize()`
`Writer` `getWriter()` Writer interface for adding/writing data to the buffer.
`int` `hashCode()` hashCode() uses String's hashCode to support compatibility with String instances in maps, sets, etc.
`protected boolean` `isChunkSizeResizeable()`
`boolean` `isConnectedMode()`
`boolean` `isPreferSubChunkWhenWritingToOtherBuffer()`
`int` `length()`
`(package private) void` `notifyBufferChange()`
`String` `plus(Object value)`
`String` `plus(String value)`
`char[]` `readAsCharArray()` reads the buffer to a char[]
`String` `readAsString()` reads the buffer to a String
`void` `readExternal(ObjectInput in)`
`void` `removeConnections()`
`void` `reset()`
`void` `reset(boolean resetChunkSize)` resets the state of this buffer (empties it)
`protected void` `resizeChunkSizeAsProcentageOfTotalSize()`
`void` `setChunkMinSize(int chunkMinSize)`
`void` `setPreferSubChunkWhenWritingToOtherBuffer(boolean preferSubChunkWhenWritingToOtherBuffer)`
`void` `setSubBufferChunkMinSize(int subBufferChunkMinSize)`
`void` `setSubStringChunkMinSize(int stringChunkMinSize)` Minimum size for a String to be added as a StringChunk instead of copying content to the char[] buffer of the current StreamCharBufferChunk
`void` `setWriteDirectlyToConnectedMinSize(int writeDirectlyToConnectedMinSize)` Minimum size for a String or char[] to get written directly to connected writer (in "connectTo" mode).
`int` `size()`
`CharSequence` `subSequence(int start, int end)`
`char[]` `toCharArray()` reads the buffer to a char[] caches the result if there aren't any readers
`String` `toString()` reads (and empties) the buffer to a String, but caches the return value for subsequent calls.
`void` `writeExternal(ObjectOutput out)`
`Writer` `writeTo(Writer target)` Writes the buffer content to a target java.io.Writer
`void` `writeTo(Writer target, boolean flushTarget, boolean emptyAfter)` Writes the buffer content to a target java.io.Writer

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### preferSubChunkWhenWritingToOtherBuffer

    boolean preferSubChunkWhenWritingToOtherBuffer

### allocatedBufferIdSequence

    int allocatedBufferIdSequence

### readerCount

    int readerCount

### hasReaders

    boolean hasReaders

Constructor Detail

### StreamCharBuffer

    public StreamCharBuffer()

### StreamCharBuffer

    public StreamCharBuffer(int chunkSize)

### StreamCharBuffer

    public StreamCharBuffer(int chunkSize,
                            int growProcent)

### StreamCharBuffer

    public StreamCharBuffer(int chunkSize,
                            int growProcent,
                            int maxChunkSize)

Method Detail

### isPreferSubChunkWhenWritingToOtherBuffer

    public boolean isPreferSubChunkWhenWritingToOtherBuffer()

### setPreferSubChunkWhenWritingToOtherBuffer

    public void setPreferSubChunkWhenWritingToOtherBuffer(boolean preferSubChunkWhenWritingToOtherBuffer)

### reset

    public void reset()

### reset

    public void reset(boolean resetChunkSize)

  resets the state of this buffer (empties it)

  Parameters:
    `resetChunkSize` -

### connectTo

    public final void connectTo(Writer writer)

  Connect this buffer to a target Writer. When the buffer (a chunk) get filled up, it will automaticly write it's content to the Writer

  Parameters:
    `writer` -

### connectTo

    public final void connectTo(Writer writer,
                                boolean autoFlush)

### connectTo

    public final void connectTo(StreamCharBuffer.LazyInitializingWriter writer)

### connectTo

    public final void connectTo(StreamCharBuffer.LazyInitializingWriter writer,
                                boolean autoFlush)

### removeConnections

    public final void removeConnections()

### getSubStringChunkMinSize

    public int getSubStringChunkMinSize()

### setSubStringChunkMinSize

    public void setSubStringChunkMinSize(int stringChunkMinSize)

  Minimum size for a String to be added as a StringChunk instead of copying content to the char[] buffer of the current StreamCharBufferChunk

  Parameters:
    `stringChunkMinSize` -

### getSubBufferChunkMinSize

    public int getSubBufferChunkMinSize()

### setSubBufferChunkMinSize

    public void setSubBufferChunkMinSize(int subBufferChunkMinSize)

### getWriteDirectlyToConnectedMinSize

    public int getWriteDirectlyToConnectedMinSize()

### setWriteDirectlyToConnectedMinSize

    public void setWriteDirectlyToConnectedMinSize(int writeDirectlyToConnectedMinSize)

  Minimum size for a String or char[] to get written directly to connected writer (in "connectTo" mode).

  Parameters:
    `writeDirectlyToConnectedMinSize` -

### getChunkMinSize

    public int getChunkMinSize()

### setChunkMinSize

    public void setChunkMinSize(int chunkMinSize)

### getWriter

    public Writer getWriter()

  Writer interface for adding/writing data to the buffer.

  Returns:

### getReader

    public Reader getReader()

  Creates a new java.io.Reader instance for reading/consuming data from the buffer. Each call creates a new instance that will keep it's reading state. There can be several readers on the buffer. (single thread only supported)

  Returns:

### getReader

    public Reader getReader(boolean removeAfterReading)

  Like getReader(), but when removeAfterReading is true, the read data will be removed from the buffer.

  Parameters:
    `removeAfterReading` -
  Returns:

### writeTo

    public Writer writeTo(Writer target)
                   throws IOException

  Writes the buffer content to a target java.io.Writer

  Specified by:
    `writeTo` in interface `groovy.lang.Writable`
  Parameters:
    `target` -
  Throws:
    `IOException`

### writeTo

    public void writeTo(Writer target,
                        boolean flushTarget,
                        boolean emptyAfter)
                 throws IOException

  Writes the buffer content to a target java.io.Writer

  Parameters:
    `target` - Writer
    `flushAll` - flush all content in buffer (if this is false, only filled chunks will be written)
    `flushTarget` - calls target.flush() before finishing
  Throws:
    `IOException`

### readAsCharArray

    public char[] readAsCharArray()

  reads the buffer to a char[]

  Returns:

### readAsString

    public String readAsString()

  reads the buffer to a String

  Returns:

### toString

    public String toString()

  reads (and empties) the buffer to a String, but caches the return value for subsequent calls. if more content has been added between 2 calls, the returned value will be joined from the previously cached value and the data read from the buffer.

  Specified by:
    `toString` in interface `CharSequence`
  Overrides:
    `toString` in class `Object`
  See Also:
    `Object.toString()`

### hashCode

    public int hashCode()

  hashCode() uses String's hashCode to support compatibility with String instances in maps, sets, etc.

  Overrides:
    `hashCode` in class `Object`
  See Also:
    `Object.hashCode()`

### equals

    public boolean equals(Object o)

  equals uses String.equals to check for equality to support compatibility with String instances in maps, sets, etc.

  Overrides:
    `equals` in class `Object`
  See Also:
    `Object.equals(java.lang.Object)`

### plus

    public String plus(String value)

### plus

    public String plus(Object value)

### toCharArray

    public char[] toCharArray()

  reads the buffer to a char[] caches the result if there aren't any readers

  Returns:

### size

    public int size()

### allocateSpace

    protected int allocateSpace()
                         throws IOException

  Throws:
    `IOException`

### appendStringChunk

    void appendStringChunk(String str,
                           int off,
                           int len)
                     throws IOException

  Throws:
    `IOException`

### appendStreamCharBufferChunk

    public void appendStreamCharBufferChunk(StreamCharBuffer subBuffer)
                                     throws IOException

  Throws:
    `IOException`

### addChunk

    void addChunk(StreamCharBuffer.AbstractChunk newChunk)

### isConnectedMode

    public boolean isConnectedMode()

### isChunkSizeResizeable

    protected boolean isChunkSizeResizeable()

### resizeChunkSizeAsProcentageOfTotalSize

    protected void resizeChunkSizeAsProcentageOfTotalSize()

### arrayCopy

    protected static final void arrayCopy(char[] src,
                                          int srcPos,
                                          char[] dest,
                                          int destPos,
                                          int length)

### charAt

    public char charAt(int index)

  Specified by:
    `charAt` in interface `CharSequence`

### length

    public int length()

  Specified by:
    `length` in interface `CharSequence`

### subSequence

    public CharSequence subSequence(int start,
                                    int end)

  Specified by:
    `subSequence` in interface `CharSequence`

### addParentBuffer

    void addParentBuffer(StreamCharBuffer parent)

### bufferChanged

    boolean bufferChanged(StreamCharBuffer buffer)

### notifyBufferChange

    void notifyBufferChange()

### readExternal

    public void readExternal(ObjectInput in)
                      throws IOException,
                             ClassNotFoundException

  Specified by:
    `readExternal` in interface `Externalizable`
  Throws:
    `IOException`
    `ClassNotFoundException`
  See Also:
    `Externalizable.readExternal(java.io.ObjectInput)`

### writeExternal

    public void writeExternal(ObjectOutput out)
                       throws IOException

  Specified by:
    `writeExternal` in interface `Externalizable`
  Throws:
    `IOException`
  See Also:
    `Externalizable.writeExternal(java.io.ObjectOutput)`

Copyright (c) 2005-2009 The Grails project