Buffer (org.openidentityplatform.commons.parent 2.2.3 Documentation)

java.lang.Object
- com.persistit.Buffer

```
public class Buffer
extends Object
```
Memory structure that holds and manipulates the state of a fixed-length page of a Volume. Persistit manipulates the content of a page by copying it into a Buffer, reading and/or modifying modifying the Buffer, and then writing the Buffer's content back into the page. There are several types of pages within the BTree structure - e.g., index pages and data pages. A Buffer can hold and manipulate any kind of page.

Multiple Buffers are managed by a BufferPool that provides methods to locate, load and store the contents of the Buffer.

Buffer provides the low-level methods that organize keys and values into byte arrays to be stored in database files.

Version:

1.0

Field Summary

Fields
Modifier and Type	Field and Description
`protected Persistit`	`_persistit`
`static long`	`DEFAULT_MAX_WAIT_TIME` Default maximum time to wait for access to this resource.
`static int`	`HEADER_SIZE` Size of standard header portion of each page type
`static int`	`MAX_BUFFER_SIZE` Architectural upper bound on buffer size
`static int`	`MAX_KEY_RATIO`
`static int`	`MIN_BUFFER_SIZE` Architectural lower bound on buffer size
`static int`	`PAGE_TYPE_DATA` Page type code for a data page.
`static int`	`PAGE_TYPE_GARBAGE` Page type code for a page that has been converted to hold a list of garbage chains.
`static int`	`PAGE_TYPE_HEAD`
`static int`	`PAGE_TYPE_INDEX_MAX` Maximum page type code for an index page.
`static int`	`PAGE_TYPE_INDEX_MIN` Minimum page type code for an index page.
`static int`	`PAGE_TYPE_LONG_RECORD` Page type code for pages used to store continuation bytes for long records
`static int`	`PAGE_TYPE_MAX` Largest value page type code.
`static int`	`PAGE_TYPE_UNALLOCATED` Page type code for an unallocated page.
`static String[]`	`TYPE_NAMES`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`getAlloc()`
`int`	`getAvailableSize()`
`int`	`getBufferSize()`
`ByteBuffer`	`getByteBuffer()`
`long`	`getGeneration()`
`int`	`getIndex()` Gets the index of this Buffer within the buffer pool
`int`	`getKeyCount()`
`long`	`getPageAddress()`
`int`	`getPageType()` Gets the page type
`String`	`getPageTypeName()`
`static String`	`getPageTypeName(long page, int type)`
`Management.RecordInfo[]`	`getRecords()`
`long`	`getRightSibling()` Get the page address of the right sibling page
`String`	`getStatusCode()`
`static String`	`getStatusCode(int state)`
`String`	`getStatusDisplayString()`
`long`	`getTimestamp()`
`Volume`	`getVolume()`
`Thread`	`getWriterThread()`
`boolean`	`isAvailable(boolean writer)`
`boolean`	`isDataPage()`
`boolean`	`isGarbagePage()`
`boolean`	`isHeadPage()`
`boolean`	`isIndexPage()`
`boolean`	`isLongRecordPage()`
`boolean`	`isTemporary()`
`boolean`	`isUnallocatedPage()`
`boolean`	`isValid()`
`void`	`setPageAddressAndVolume(long pageAddress, Volume volume)`
`String`	`summarize()`
`String`	`toString()`
`String`	`toStringDetail()`

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

- Field Detail
  - MIN_BUFFER_SIZE
```
public static final int MIN_BUFFER_SIZE
```
    Architectural lower bound on buffer size
    
    See Also:
    
    Constant Field Values
  - MAX_BUFFER_SIZE
```
public static final int MAX_BUFFER_SIZE
```
    Architectural upper bound on buffer size
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_UNALLOCATED
```
public static final int PAGE_TYPE_UNALLOCATED
```
    Page type code for an unallocated page.
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_DATA
```
public static final int PAGE_TYPE_DATA
```
    Page type code for a data page. Data pages are the leaf pages of the BTree.
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_INDEX_MIN
```
public static final int PAGE_TYPE_INDEX_MIN
```
    Minimum page type code for an index page. Index pages are the non-leaf pages of the BTree.
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_INDEX_MAX
```
public static final int PAGE_TYPE_INDEX_MAX
```
    Maximum page type code for an index page. Index pages are the non-leaf pages of the BTree.
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_GARBAGE
```
public static final int PAGE_TYPE_GARBAGE
```
    Page type code for a page that has been converted to hold a list of garbage chains. Pages deallocated as a result of (@link Exchange#remove) operations are added organized into Garbage pages.
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_LONG_RECORD
```
public static final int PAGE_TYPE_LONG_RECORD
```
    Page type code for pages used to store continuation bytes for long records
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_MAX
```
public static final int PAGE_TYPE_MAX
```
    Largest value page type code.
    
    See Also:
    
    Constant Field Values
  - PAGE_TYPE_HEAD
```
public static final int PAGE_TYPE_HEAD
```
    See Also:
    
    Constant Field Values
  - TYPE_NAMES
```
public static final String[] TYPE_NAMES
```
  - HEADER_SIZE
```
public static final int HEADER_SIZE
```
    Size of standard header portion of each page type
    
    See Also:
    
    Constant Field Values
  - MAX_KEY_RATIO
```
public static final int MAX_KEY_RATIO
```
    See Also:
    
    Constant Field Values
  - DEFAULT_MAX_WAIT_TIME
```
public static final long DEFAULT_MAX_WAIT_TIME
```
    Default maximum time to wait for access to this resource. Methods throw an InUseException when this time is exceeded.
    
    See Also:
    
    Constant Field Values
  - _persistit
```
protected final Persistit _persistit
```
- Method Detail
  - getVolume
```
public Volume getVolume()
```
    Returns:
    
    The Volume to which the page currently occupying this Buffer belongs
  - getByteBuffer
```
public ByteBuffer getByteBuffer()
```
    Returns:
    
    The ByteBuffer facade for this Buffer.
  - getPageAddress
```
public long getPageAddress()
```
    Returns:
    
    The page address of the current page.
  - getBufferSize
```
public int getBufferSize()
```
    Returns:
    
    The size of the buffer, in bytes
  - getTimestamp
```
public long getTimestamp()
```
    Returns:
    
    Timestamp at which page held by this buffer was last changed
  - getAvailableSize
```
public int getAvailableSize()
```
    Returns:
    
    Number of remaining bytes available for allocation
  - getKeyCount
```
public int getKeyCount()
```
    Returns:
    
    Number of key-value pairs currently stored in this page.
  - getAlloc
```
public int getAlloc()
```
    Returns:
    
    Offset to next available allocation block within the page.
  - getPageType
```
public int getPageType()
```
    Gets the page type
    
    Returns:
    
    the type as an integer
  - getPageTypeName
```
public String getPageTypeName()
```
    Returns:
    
    A displayable String version of the page type.
  - getPageTypeName
```
public static String getPageTypeName(long page,
                                     int type)
```
  - getIndex
```
public int getIndex()
```
    Gets the index of this Buffer within the buffer pool
    
    Returns:
    
    The index
  - getRightSibling
```
public long getRightSibling()
```
    Get the page address of the right sibling page
    
    Returns:
    
    the sibling's address
  - setPageAddressAndVolume
```
public void setPageAddressAndVolume(long pageAddress,
                                    Volume volume)
```
  - isUnallocatedPage
```
public boolean isUnallocatedPage()
```
    Returns:
    
    true if the current page is unallocated
  - isDataPage
```
public boolean isDataPage()
```
    Returns:
    
    true if the current page is a data page
  - isIndexPage
```
public boolean isIndexPage()
```
    Returns:
    
    true if the current page is an index page
  - isGarbagePage
```
public boolean isGarbagePage()
```
    Returns:
    
    true if the current page is a garbage page
  - isHeadPage
```
public boolean isHeadPage()
```
    Returns:
    
    true if the current page is the head page of a Volume
  - isLongRecordPage
```
public boolean isLongRecordPage()
```
    Returns:
    
    true if the current page is a long record page
  - summarize
```
public String summarize()
```
    Returns:
    
    A displayable summary of information about the page contained in this Buffer.
  - toString
```
public String toString()
```
  - toStringDetail
```
public String toStringDetail()
```
    Returns:
    
    a human-readable inventory of the contents of this buffer
  - getRecords
```
public Management.RecordInfo[] getRecords()
```
    Returns:
    
    an array of Records extracted from this buffer.
  - isAvailable
```
public boolean isAvailable(boolean writer)
```
  - isValid
```
public boolean isValid()
```
  - isTemporary
```
public boolean isTemporary()
```
  - getGeneration
```
public long getGeneration()
```
  - getStatusCode
```
public String getStatusCode()
```
  - getStatusDisplayString
```
public String getStatusDisplayString()
```
  - getStatusCode
```
public static String getStatusCode(int state)
```
  - getWriterThread
```
public Thread getWriterThread()
```

Class Buffer

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MIN_BUFFER_SIZE

MAX_BUFFER_SIZE

PAGE_TYPE_UNALLOCATED

PAGE_TYPE_DATA

PAGE_TYPE_INDEX_MIN

PAGE_TYPE_INDEX_MAX

PAGE_TYPE_GARBAGE

PAGE_TYPE_LONG_RECORD

PAGE_TYPE_MAX

PAGE_TYPE_HEAD

TYPE_NAMES

HEADER_SIZE

MAX_KEY_RATIO

DEFAULT_MAX_WAIT_TIME

_persistit

Method Detail

getVolume

getByteBuffer

getPageAddress

getBufferSize

getTimestamp

getAvailableSize

getKeyCount

getAlloc

getPageType

getPageTypeName

getPageTypeName

getIndex

getRightSibling

setPageAddressAndVolume

isUnallocatedPage

isDataPage

isIndexPage

isGarbagePage

isHeadPage

isLongRecordPage

summarize

toString

toStringDetail

getRecords

isAvailable

isValid

isTemporary

getGeneration

getStatusCode

getStatusDisplayString

getStatusCode

getWriterThread