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/*
* Copyright (C) 2022 The Android Open Source Project
*
* 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.android.net.module.util.async;
import java.util.Arrays;
/**
* Implements a circular read-write byte buffer.
*
* @hide
*/
public final class CircularByteBuffer implements ReadableByteBuffer {
private final byte[] mBuffer;
private final int mCapacity;
private int mReadPos;
private int mWritePos;
private int mSize;
public CircularByteBuffer(int capacity) {
mCapacity = capacity;
mBuffer = new byte[mCapacity];
}
@Override
public void clear() {
mReadPos = 0;
mWritePos = 0;
mSize = 0;
Arrays.fill(mBuffer, (byte) 0);
}
@Override
public int capacity() {
return mCapacity;
}
@Override
public int size() {
return mSize;
}
/** Returns the amount of remaining writeable space in this buffer. */
public int freeSize() {
return mCapacity - mSize;
}
@Override
public byte peek(int offset) {
if (offset < 0 || offset >= size()) {
throw new IllegalArgumentException("Invalid offset=" + offset + ", size=" + size());
}
return mBuffer[(mReadPos + offset) % mCapacity];
}
@Override
public void readBytes(byte[] dst, int dstPos, int dstLen) {
if (dst != null) {
Assertions.throwsIfOutOfBounds(dst, dstPos, dstLen);
}
if (dstLen > size()) {
throw new IllegalArgumentException("Invalid len=" + dstLen + ", size=" + size());
}
while (dstLen > 0) {
final int copyLen = getCopyLen(mReadPos, mWritePos, dstLen);
if (dst != null) {
System.arraycopy(mBuffer, mReadPos, dst, dstPos, copyLen);
}
dstPos += copyLen;
dstLen -= copyLen;
mSize -= copyLen;
mReadPos = (mReadPos + copyLen) % mCapacity;
}
if (mSize == 0) {
// Reset to the beginning for better contiguous access.
mReadPos = 0;
mWritePos = 0;
}
}
@Override
public void peekBytes(int offset, byte[] dst, int dstPos, int dstLen) {
Assertions.throwsIfOutOfBounds(dst, dstPos, dstLen);
if (offset + dstLen > size()) {
throw new IllegalArgumentException("Invalid len=" + dstLen
+ ", offset=" + offset + ", size=" + size());
}
int tmpReadPos = (mReadPos + offset) % mCapacity;
while (dstLen > 0) {
final int copyLen = getCopyLen(tmpReadPos, mWritePos, dstLen);
System.arraycopy(mBuffer, tmpReadPos, dst, dstPos, copyLen);
dstPos += copyLen;
dstLen -= copyLen;
tmpReadPos = (tmpReadPos + copyLen) % mCapacity;
}
}
@Override
public int getDirectReadSize() {
if (size() == 0) {
return 0;
}
return (mReadPos < mWritePos ? (mWritePos - mReadPos) : (mCapacity - mReadPos));
}
@Override
public int getDirectReadPos() {
return mReadPos;
}
@Override
public byte[] getDirectReadBuffer() {
return mBuffer;
}
@Override
public void accountForDirectRead(int len) {
if (len < 0 || len > size()) {
throw new IllegalArgumentException("Invalid len=" + len + ", size=" + size());
}
mSize -= len;
mReadPos = (mReadPos + len) % mCapacity;
}
/** Copies given data to the end of the buffer. */
public void writeBytes(byte[] buffer, int pos, int len) {
Assertions.throwsIfOutOfBounds(buffer, pos, len);
if (len > freeSize()) {
throw new IllegalArgumentException("Invalid len=" + len + ", size=" + freeSize());
}
while (len > 0) {
final int copyLen = getCopyLen(mWritePos, mReadPos,len);
System.arraycopy(buffer, pos, mBuffer, mWritePos, copyLen);
pos += copyLen;
len -= copyLen;
mSize += copyLen;
mWritePos = (mWritePos + copyLen) % mCapacity;
}
}
private int getCopyLen(int startPos, int endPos, int len) {
if (startPos < endPos) {
return Math.min(len, endPos - startPos);
} else {
return Math.min(len, mCapacity - startPos);
}
}
/** Returns the amount of contiguous writeable space. */
public int getDirectWriteSize() {
if (freeSize() == 0) {
return 0; // Return zero in case buffer is full.
}
return (mWritePos < mReadPos ? (mReadPos - mWritePos) : (mCapacity - mWritePos));
}
/** Returns the position of contiguous writeable space. */
public int getDirectWritePos() {
return mWritePos;
}
/** Returns the buffer reference for direct write operation. */
public byte[] getDirectWriteBuffer() {
return mBuffer;
}
/** Must be called after performing a direct write using getDirectWriteBuffer(). */
public void accountForDirectWrite(int len) {
if (len < 0 || len > freeSize()) {
throw new IllegalArgumentException("Invalid len=" + len + ", size=" + freeSize());
}
mSize += len;
mWritePos = (mWritePos + len) % mCapacity;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("CircularByteBuffer{c=");
sb.append(mCapacity);
sb.append(",s=");
sb.append(mSize);
sb.append(",r=");
sb.append(mReadPos);
sb.append(",w=");
sb.append(mWritePos);
sb.append('}');
return sb.toString();
}
}
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