Package org.apache.myfaces.util.lang

Class StreamCharBuffer

  • All Implemented Interfaces:
    Externalizable, Serializable, CharSequence
    public class StreamCharBuffer
extends Object
implements 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. See 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 ( CharBufferChunk), String chunks (StringChunk) and other StreamCharBuffers as sub chunks (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.

    See org.codehaus.groovy.grails.web.util.StreamCharBuffer file licensed under ASL v2.0 Copyright 2009 the original author or authors. Author Lari Hotari, Sagire Software Oy
    See Also:
    Serialized Form

    • 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 final void reset()

      • reset

        public final void reset​(boolean resetChunkSize)
        resets the state of this buffer (empties it)
        Parameters:
        resetChunkSize -

      • clear

        public final void clear()
        Clears the buffer and notifies the parents of this buffer of the change

      • connectTo

        public final void connectTo​(Writer w)
        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:
        w -

      • connectTo

        public final void connectTo​(Writer w,
                            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:
        the Writer

      • getReader

        public Reader getReader()
        Creates a new 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:
        the Reader

      • 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:
        the Reader

      • 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
        flushTarget - calls target.flush() before finishing
        emptyAfter - empties the buffer if true
        Throws:
        IOException

      • readAsCharArray

        public char[] readAsCharArray()
        Reads the buffer to a char[].
        Returns:
        the chars

      • readAsString

        public String readAsString()
        Reads the buffer to a String.
        Returns:
        the String

      • 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()
        Uses String's hashCode to support compatibility with String instances in maps, sets, etc.
        Overrides:
        hashCode in class Object
        See Also:
        Object.hashCode()

      • toCharArray

        public char[] toCharArray()
        Reads the buffer to a char[]. Caches the result if there aren't any readers.
        Returns:
        the chars

      • size

        public int size()

      • isEmpty

        public boolean isEmpty()

      • 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

      • asBoolean

        public boolean asBoolean()