com.google.cloud

Interface ReadChannel

All Superinterfaces:

AutoCloseable, Channel, Closeable, ReadableByteChannel, Restorable<ReadChannel>

public interface ReadChannel
extends ReadableByteChannel, Closeable, Restorable<ReadChannel>

A channel for reading data from a Google Cloud object.

Implementations of this class may buffer data internally to reduce remote calls. This interface implements Restorable to allow saving the reader's state to continue reading afterwards.

Method Summary

Modifier and Type	Method and Description
RestorableState<ReadChannel>	capture() Captures the read channel state so that it can be saved and restored afterwards.
void	close() Overridden to remove IOException.
default long	limit() The currently defined limit for this channel.
default ReadChannel	limit(long limit) Limit the maximum number of bytes to be read from the objects content, counting from the beginning of the object, which will be available to read from this channel.
void	seek(long position) Set the offset to read from.
void	setChunkSize(int chunkSize) Sets the minimum size that will be read by a single RPC.

Methods inherited from interface java.nio.channels.ReadableByteChannel

read

Methods inherited from interface java.nio.channels.Channel

isOpen

Method Detail

close

void close()

Overridden to remove IOException.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Channel

Specified by:

close in interface Closeable

See Also:

Channel.close()

seek

void seek(long position)
   throws IOException

Set the offset to read from.

Throws:

IOException

setChunkSize

void setChunkSize(int chunkSize)

Sets the minimum size that will be read by a single RPC. Read data will be locally buffered until consumed.

capture

RestorableState<ReadChannel> capture()

Captures the read channel state so that it can be saved and restored afterwards.

Specified by:

capture in interface Restorable<ReadChannel>

Returns:

a RestorableState object that contains the read channel state and can restore it afterwards.

limit

default ReadChannel limit(long limit)

Limit the maximum number of bytes to be read from the objects content, counting from the beginning of the object, which will be available to read from this channel. If the limit is larger than the actual size of the content this will have no material impact.

If used in conjunction with seek(long) the total number of returned bytes from this channel will be reduced by the number of bytes specified to seek.

The value provided as limit will define a left-closed, right-open interval along with either 0 or any value provided to seek(long), i.e. [seek(long), limit(long)).

An example to help illustrate the relationship

Imagine some data [A, B, C, D, E, F, G, H, I, J], 10 bytes total.

1. limit(5) would produce [A, B, C, D, E]
2. seek(8) would produce [I, J]
3. seek(2) limit(5) would produce [C, D, E]
4. seek(3) limit(3) would produce []

NOTE:Implementers are not required to return a new instance from this method, however they are allowed to. Users of this method should always use the instance returned from this method.

Default Implementation:By default, this method will simply return this.

Parameters:

limit - the maximum number of bytes to limit this channel to

Returns:

The instance of channel which will respect the limit.

Throws:

UnsupportedOperationException - If the this instances does not support limiting

Since:

2.4.0

limit

default long limit()

The currently defined limit for this channel. Initial value is Long.MAX_VALUE

Returns:

the current limit for this channel

Throws:

UnsupportedOperationException - If the this instances does not support limiting

Since:

2.4.0