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/*
* Copyright 2015 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.cloud;
import java.io.Closeable;
import java.io.IOException;
import java.nio.channels.ReadableByteChannel;
/**
* 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 {@link Restorable} to allow saving the reader's state to continue reading
* afterwards.
*/
public interface ReadChannel extends ReadableByteChannel, Closeable, Restorable {
/**
* Overridden to remove IOException.
*
* @see java.nio.channels.Channel#close()
*/
@Override
void close();
/** Set the offset to read from. */
void seek(long position) throws IOException;
/**
* Sets the minimum size that will be read by a single RPC. Read data will be locally buffered
* until consumed.
*/
void setChunkSize(int chunkSize);
/**
* Captures the read channel state so that it can be saved and restored afterwards.
*
* @return a {@link RestorableState} object that contains the read channel state and can restore
* it afterwards.
*/
@Override
RestorableState capture();
/**
* 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 {@link #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 {@code limit} will define a left-closed,
* right-open interval along with either {@code 0} or any value provided to {@link
* #seek(long)}, i.e. {@code [}{@link #seek(long)}{@code , }{@link #limit(long)}{@code )}.
*
*
An example to help illustrate the relationship
*
* Imagine some data {@code [A, B, C, D, E, F, G, H, I, J]}, 10 bytes total.
*
*
* - {@code limit(5)} would produce {@code [A, B, C, D, E]}
*
- {@code seek(8)} would produce {@code [I, J]}
*
- {@code seek(2)} {@code limit(5)} would produce {@code [C, D, E]}
*
- {@code seek(3)} {@code limit(3)} would produce {@code []}
*
*
* 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 {@code this}.
*
* @param limit the maximum number of bytes to limit this channel to
* @return The instance of channel which will respect the limit.
* @throws UnsupportedOperationException If the {@code this} instances does not support limiting
* @since 2.4.0
*/
default ReadChannel limit(long limit) {
return this;
}
/**
* The currently defined limit for this channel. Initial value is {@link Long#MAX_VALUE}
*
* @return the current limit for this channel
* @throws UnsupportedOperationException If the {@code this} instances does not support limiting
* @since 2.4.0
*/
default long limit() {
return Long.MAX_VALUE;
}
}