| /* |
| * 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(); |
| } |
| } |