org.apache.jackrabbit.oak.spi.blob

Class AbstractBlobStore

java.lang.Object

org.apache.jackrabbit.oak.spi.blob.AbstractBlobStore

All Implemented Interfaces:

Cache.Backend<AbstractBlobStore.BlockId,AbstractBlobStore.Data>, BlobStore, GarbageCollectableBlobStore

Direct Known Subclasses:

FileBlobStore, MemoryBlobStore

public abstract class AbstractBlobStore
extends Object
implements GarbageCollectableBlobStore, Cache.Backend<AbstractBlobStore.BlockId,AbstractBlobStore.Data>

An abstract data store that splits the binaries in relatively small blocks, so that each block fits in memory.

Each data store id is a list of zero or more entries. Each entry is either

• data (a number of bytes), or
• the hash code of the content of a number of bytes, or
• the hash code of the content of a data store id (indirect hash)

Thanks to the indirection, blocks can be kept relatively small, so that caching is simpler, and so that the storage backend doesn't need to support arbitrary size blobs (some storage backends buffer blobs in memory) and fast seeks (some storage backends re-read the whole blob when seeking).

The format of a 'data' entry is: type (one byte; 0 for data), length (variable size int), data (bytes).

The format of a 'hash of content' entry is: type (one byte; 1 for hash), level (variable size int, 0 meaning not nested), size (variable size long), hash code length (variable size int), hash code.

The format of a 'hash of data store id' entry is: type (one byte; 1 for hash), level (variable size int, nesting level), total size (variable size long), size of data store id (variable size long), hash code length (variable size int), hash code.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbstractBlobStore.BlockId A block id.
static class	AbstractBlobStore.Data The data for a block.

Constructor Summary

Constructors

Constructor and Description
AbstractBlobStore()

Method Summary

Methods

Modifier and Type	Method and Description
void	clearInUse() Clear all objects marked as "transiently in use".
String	getBlobId(String reference) Returns the blobId that referred by the given binary reference.
long	getBlobLength(String blobId) Get the length of the blob.
int	getBlockSize()
long	getBlockSizeMin() Get the minimum block size (if there is any).
InputStream	getInputStream(String blobId) Returns a new stream for given blobId.
String	getReference(String blobId) Returns a secure reference to blob referred by blobid, or null if no such reference is available.
AbstractBlobStore.Data	load(AbstractBlobStore.BlockId id) Load the object.
int	readBlob(String blobId, long pos, byte[] buff, int off, int length) Read a number of bytes from a blob.
Iterator<String>	resolveChunks(String blobId) Resolve chunks from the given Id.
void	setBlockSize(int x) Set the block size used by this blob store, if the blob store splits binaries into blocks.
void	setBlockSizeMin(int x)
void	setReferenceKey(byte[] referenceKey)
void	setReferenceKeyEncoded(String encodedKey) Set the referenceKey from Base64 encoded byte array
void	setReferenceKeyPlainText(String textKey) Set the referenceKey from plain text.
abstract void	startMark() Start the mark phase.
abstract int	sweep() Remove all unused blocks.
String	writeBlob(InputStream in) Write a blob from an input stream.
String	writeBlob(String tempFilePath) Write a blob from a temporary file.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.jackrabbit.oak.spi.blob.GarbageCollectableBlobStore

clearCache, deleteChunks, getAllChunkIds

Constructor Detail

AbstractBlobStore

public AbstractBlobStore()

Method Detail

setBlockSizeMin

public void setBlockSizeMin(int x)

getBlockSizeMin

public long getBlockSizeMin()

Description copied from interface: GarbageCollectableBlobStore

Get the minimum block size (if there is any).

Specified by:

getBlockSizeMin in interface GarbageCollectableBlobStore

Returns:

the block size

setBlockSize

public void setBlockSize(int x)

Description copied from interface: GarbageCollectableBlobStore

Set the block size used by this blob store, if the blob store splits binaries into blocks. If not, this setting is ignored.

Specified by:

setBlockSize in interface GarbageCollectableBlobStore

Parameters:

x - the block size in bytes.

getBlockSize

public int getBlockSize()

writeBlob

public String writeBlob(String tempFilePath)
                 throws IOException

Description copied from interface: GarbageCollectableBlobStore

Write a blob from a temporary file. The temporary file is removed afterwards. A file based blob stores might simply rename the file, so that no additional writes are necessary.

Specified by:

writeBlob in interface GarbageCollectableBlobStore

Parameters:

tempFilePath - the temporary file name

Returns:

the blob id

Throws:

IOException

writeBlob

public String writeBlob(InputStream in)
                 throws IOException

Description copied from interface: BlobStore

Write a blob from an input stream. This method closes the input stream.

Specified by:

writeBlob in interface BlobStore

Parameters:

in - the input stream

Returns:

the blob id

Throws:

IOException

getInputStream

public InputStream getInputStream(String blobId)
                           throws IOException

Description copied from interface: BlobStore

Returns a new stream for given blobId. The streams returned from multiple calls to this method are byte wise equals. That is, subsequent calls to read return the same sequence of bytes as long as neither call throws an exception.

Specified by:

getInputStream in interface BlobStore

Parameters:

blobId - the blob id

Returns:

a new stream for given blobId

Throws:

IOException

getReference

public String getReference(String blobId)

Description copied from interface: BlobStore

Returns a secure reference to blob referred by blobid, or null if no such reference is available.

Specified by:

getReference in interface BlobStore

Parameters:

blobId - blobId referring the blob for which reference is required

Returns:

binary reference, or null

getBlobId

public String getBlobId(String reference)

Description copied from interface: BlobStore

Returns the blobId that referred by the given binary reference. Returns null if the reference is invalid, for example if it points to a blob that does not exist.

Specified by:

getBlobId in interface BlobStore

Parameters:

reference - binary reference

Returns:

matching blobId, or null

setReferenceKey

public void setReferenceKey(byte[] referenceKey)

setReferenceKeyEncoded

public void setReferenceKeyEncoded(String encodedKey)

Set the referenceKey from Base64 encoded byte array

Parameters:

encodedKey - base64 encoded key

setReferenceKeyPlainText

public void setReferenceKeyPlainText(String textKey)

Set the referenceKey from plain text. Key content would be UTF-8 encoding of the string.

This is useful when setting key via generic bean property manipulation from string properties. User can specify the key in plain text and that would be passed on this object via PropertiesUtil.populate(Object, java.util.Map, boolean)

Parameters:

textKey - base64 encoded key

See Also:

PropertiesUtil.populate(Object, java.util.Map, boolean)

clearInUse

public void clearInUse()

Description copied from interface: GarbageCollectableBlobStore

Clear all objects marked as "transiently in use".

Specified by:

clearInUse in interface GarbageCollectableBlobStore

startMark

public abstract void startMark()
                        throws IOException

Description copied from interface: GarbageCollectableBlobStore

Start the mark phase.

Specified by:

startMark in interface GarbageCollectableBlobStore

Throws:

IOException

sweep

public abstract int sweep()
                   throws IOException

Description copied from interface: GarbageCollectableBlobStore

Remove all unused blocks.

Specified by:

sweep in interface GarbageCollectableBlobStore

Returns:

the number of removed blocks

Throws:

IOException

readBlob

public int readBlob(String blobId,
           long pos,
           byte[] buff,
           int off,
           int length)
             throws IOException

Description copied from interface: BlobStore

Read a number of bytes from a blob.

Specified by:

readBlob in interface BlobStore

Parameters:

blobId - the blob id

pos - the position within the blob

buff - the target byte array

off - the offset within the target array

length - the number of bytes to read

Returns:

the number of bytes read

Throws:

IOException

load

public AbstractBlobStore.Data load(AbstractBlobStore.BlockId id)

Description copied from interface: Cache.Backend

Load the object. The method does not need to be synchronized (it is synchronized in the cache)

Specified by:

load in interface Cache.Backend<AbstractBlobStore.BlockId,AbstractBlobStore.Data>

Parameters:

id - the key

Returns:

the value

getBlobLength

public long getBlobLength(String blobId)
                   throws IOException

Description copied from interface: BlobStore

Get the length of the blob.

Specified by:

getBlobLength in interface BlobStore

Parameters:

blobId - the blob id

Returns:

the length

Throws:

IOException

resolveChunks

public Iterator<String> resolveChunks(String blobId)
                               throws IOException

Description copied from interface: GarbageCollectableBlobStore

Resolve chunks from the given Id.

Specified by:

resolveChunks in interface GarbageCollectableBlobStore

Parameters:

blobId - the blob id

Returns:

the iterator

Throws:

IOException - Signals that an I/O exception has occurred.