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/*
* Copyright 2016 The Netty Project
*
* The Netty Project 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:
*
* https://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 io.netty.channel;
import static io.netty.util.internal.ObjectUtil.checkPositiveOrZero;
/**
* WriteBufferWaterMark is used to set low water mark and high water mark for the write buffer.
*
* If the number of bytes queued in the write buffer exceeds the
* {@linkplain #high high water mark}, {@link Channel#isWritable()}
* will start to return {@code false}.
*
* If the number of bytes queued in the write buffer exceeds the
* {@linkplain #high high water mark} and then
* dropped down below the {@linkplain #low low water mark},
* {@link Channel#isWritable()} will start to return
* {@code true} again.
*
* Note that messages needs to be handled by the {@link MessageSizeEstimator}
* used by the channel for {@link Channel#isWritable()} to provide accurate back-pressure.
*/
public final class WriteBufferWaterMark {
private static final int DEFAULT_LOW_WATER_MARK = 32 * 1024;
private static final int DEFAULT_HIGH_WATER_MARK = 64 * 1024;
public static final WriteBufferWaterMark DEFAULT =
new WriteBufferWaterMark(DEFAULT_LOW_WATER_MARK, DEFAULT_HIGH_WATER_MARK, false);
private final int low;
private final int high;
/**
* Create a new instance.
*
* @param low low water mark for write buffer.
* @param high high water mark for write buffer
*/
public WriteBufferWaterMark(int low, int high) {
this(low, high, true);
}
/**
* This constructor is needed to keep backward-compatibility.
*/
WriteBufferWaterMark(int low, int high, boolean validate) {
if (validate) {
checkPositiveOrZero(low, "low");
if (high < low) {
throw new IllegalArgumentException(
"write buffer's high water mark cannot be less than " +
" low water mark (" + low + "): " +
high);
}
}
this.low = low;
this.high = high;
}
/**
* Returns the low water mark for the write buffer.
*/
public int low() {
return low;
}
/**
* Returns the high water mark for the write buffer.
*/
public int high() {
return high;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder(55)
.append("WriteBufferWaterMark(low: ")
.append(low)
.append(", high: ")
.append(high)
.append(")");
return builder.toString();
}
}