JGit 7.2.0.202503040940-r · org.eclipse.jgit.internal.storage.dfs.ReadableChannel

Method Summary

Modifier and Type	Method and Description
public int	Returns: recommended alignment size for randomly positioned reads. Does not need to be a power of 2. blockSize() Get the recommended alignment for reads.
public long	Returns: r current offset. position() Get the current position of the channel.
public void	position(long position to move the channel to. The next read will start from here. This should be a multiple of the `blockSize()`. newPosition) Seek the current position of the channel to a new offset.
public void	setReadAheadBytes(int requested size of the read ahead buffer, in bytes. bufferSize) Recommend the channel maintain a read-ahead buffer.
public long	Returns: r total size of the channel; -1 if not yet available. size() Get the total size of the channel.

Inherited from java.nio.channels.ReadableByteChannel:: read

Method Detail

blockSize back to summary

blockSize	back to summary
public int blockSize() Get the recommended alignment for reads. Starting a read at multiples of the blockSize is more efficient than starting a read at any other position. If 0 or -1 the channel does not have any specific block size recommendation. Channels should not recommend large block sizes. Sizes up to 1-4 MiB may be reasonable, but sizes above that may be horribly inefficient. The `org.eclipse.jgit.internal.storage.dfs.DfsBlockCache` favors the alignment suggested by the channel rather than the configured size under the assumption that reads are very expensive and the channel knows what size is best to access it with. Returns:int recommended alignment size for randomly positioned reads. Does not need to be a power of 2.

public int blockSize()

Get the recommended alignment for reads.

Starting a read at multiples of the blockSize is more efficient than starting a read at any other position. If 0 or -1 the channel does not have any specific block size recommendation.

Channels should not recommend large block sizes. Sizes up to 1-4 MiB may be reasonable, but sizes above that may be horribly inefficient. The org.eclipse.jgit.internal.storage.dfs.DfsBlockCache favors the alignment suggested by the channel rather than the configured size under the assumption that reads are very expensive and the channel knows what size is best to access it with.

Returns:int: recommended alignment size for randomly positioned reads. Does not need to be a power of 2.

position	back to summary
public long position() throws IOException Get the current position of the channel. Returns:long r current offset. Exceptions IOException: the channel's current position cannot be obtained.

position

back to summary

public long position() throws IOException

Get the current position of the channel.

Returns:long

r current offset.

Exceptions

IOException:: the channel's current position cannot be obtained.

position back to summary

position	back to summary
public void position(long newPosition) throws IOException Seek the current position of the channel to a new offset. Parameters newPosition:long position to move the channel to. The next read will start from here. This should be a multiple of the `blockSize()`. Exceptions IOException: the position cannot be updated. This may be because the channel only supports block aligned IO and the current position is not block aligned.

public void position(long newPosition) throws IOException

Seek the current position of the channel to a new offset.

Parameters

newPosition:long: position to move the channel to. The next read will start from here. This should be a multiple of the blockSize().

Exceptions

IOException:: the position cannot be updated. This may be because the channel only supports block aligned IO and the current position is not block aligned.

setReadAheadBytes back to summary

setReadAheadBytes	back to summary
public void setReadAheadBytes(int bufferSize) throws IOException Recommend the channel maintain a read-ahead buffer. A read-ahead buffer of approximately `bufferSize` in bytes may be allocated and used by the channel to smooth out latency for read. Callers can continue to read in smaller than `bufferSize` chunks. With read-ahead buffering enabled read latency may fluctuate in a pattern of one slower read followed by `(bufferSize / readSize) - 1` fast reads satisfied by the read-ahead buffer. When summed up overall time to read the same contiguous range should be lower than if read-ahead was not enabled, as the implementation can combine reads to increase throughput. To avoid unnecessary IO callers should only enable read-ahead if the majority of the channel will be accessed in order. Implementations may chose to read-ahead using asynchronous APIs or background threads, or may simply aggregate reads using a buffer. This read ahead stays in effect until the channel is closed or the buffer size is set to 0. Parameters bufferSize:int requested size of the read ahead buffer, in bytes. Exceptions IOException: if the read ahead cannot be adjusted.

public void setReadAheadBytes(int bufferSize) throws IOException

Recommend the channel maintain a read-ahead buffer.

A read-ahead buffer of approximately bufferSize in bytes may be allocated and used by the channel to smooth out latency for read.

Callers can continue to read in smaller than bufferSize chunks. With read-ahead buffering enabled read latency may fluctuate in a pattern of one slower read followed by (bufferSize / readSize) - 1 fast reads satisfied by the read-ahead buffer. When summed up overall time to read the same contiguous range should be lower than if read-ahead was not enabled, as the implementation can combine reads to increase throughput.

To avoid unnecessary IO callers should only enable read-ahead if the majority of the channel will be accessed in order.

Implementations may chose to read-ahead using asynchronous APIs or background threads, or may simply aggregate reads using a buffer.

This read ahead stays in effect until the channel is closed or the buffer size is set to 0.

Parameters

bufferSize:int: requested size of the read ahead buffer, in bytes.

Exceptions

IOException:: if the read ahead cannot be adjusted.

size	back to summary
public long size() throws IOException Get the total size of the channel. Prior to reading from a channel the size might not yet be known. Implementors may return -1 until after the first read method call. Once a read has been completed, the underlying file size should be available. Returns:long r total size of the channel; -1 if not yet available. Exceptions IOException: the size cannot be determined.

size

back to summary

public long size() throws IOException

Get the total size of the channel.

Prior to reading from a channel the size might not yet be known. Implementors may return -1 until after the first read method call. Once a read has been completed, the underlying file size should be available.

Returns:long

r total size of the channel; -1 if not yet available.

Exceptions

IOException:: the size cannot be determined.

public Interface ReadableChannel

Method Summary

Method Detail