org.apache.hadoop.fs.StreamCapabilities Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.hadoop.fs;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* Interface to query streams for supported capabilities.
*
* Capability strings must be in lower case.
*
* Constant strings are chosen over enums in order to allow other file systems
* to define their own capabilities.
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface StreamCapabilities {
/**
* Stream hflush capability implemented by {@link Syncable#hflush()}.
*
* Use the {@link #HSYNC} probe to check for the support of Syncable;
* it's that presence of {@code hsync()} which matters.
*/
@Deprecated
String HFLUSH = "hflush";
/**
* Stream hsync capability implemented by {@link Syncable#hsync()}.
*/
String HSYNC = "hsync";
/**
* Stream setReadahead capability implemented by
* {@link CanSetReadahead#setReadahead(Long)}.
*/
String READAHEAD = "in:readahead";
/**
* Stream setDropBehind capability implemented by
* {@link CanSetDropBehind#setDropBehind(Boolean)}.
*/
String DROPBEHIND = "dropbehind";
/**
* Stream unbuffer capability implemented by {@link CanUnbuffer#unbuffer()}.
*/
String UNBUFFER = "in:unbuffer";
/**
* Stream read(ByteBuffer) capability implemented by
* {@link ByteBufferReadable#read(java.nio.ByteBuffer)}.
*/
String READBYTEBUFFER = "in:readbytebuffer";
/**
* Stream read(long, ByteBuffer) capability implemented by
* {@link ByteBufferPositionedReadable#read(long, java.nio.ByteBuffer)}.
*/
String PREADBYTEBUFFER = "in:preadbytebuffer";
/**
* IOStatisticsSource API.
*/
String IOSTATISTICS = "iostatistics";
/**
* Stream abort() capability implemented by {@link Abortable#abort()}.
* This matches the Path Capability
* {@link CommonPathCapabilities#ABORTABLE_STREAM}.
*/
String ABORTABLE_STREAM = CommonPathCapabilities.ABORTABLE_STREAM;
/**
* Capabilities that a stream can support and be queried for.
*/
@Deprecated
enum StreamCapability {
HFLUSH(StreamCapabilities.HFLUSH),
HSYNC(StreamCapabilities.HSYNC);
private final String capability;
StreamCapability(String value) {
this.capability = value;
}
public final String getValue() {
return capability;
}
}
/**
* Query the stream for a specific capability.
*
* @param capability string to query the stream support for.
* @return True if the stream supports capability.
*/
boolean hasCapability(String capability);
}