138 lines
4.2 KiB
Java
138 lines
4.2 KiB
Java
/*
|
|
* Copyright (C) 2008 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.internal.util;
|
|
|
|
import android.compat.annotation.UnsupportedAppUsage;
|
|
|
|
/**
|
|
* An object that provides bitwise incremental write access to a byte array.
|
|
*
|
|
* This is useful, for example, when writing a series of fields that
|
|
* may not be aligned on byte boundaries.
|
|
*
|
|
* NOTE -- This class is not threadsafe.
|
|
*/
|
|
@android.ravenwood.annotation.RavenwoodKeepWholeClass
|
|
public class BitwiseOutputStream {
|
|
|
|
// The byte array being written to, which will be grown as needed.
|
|
private byte[] mBuf;
|
|
|
|
// The current position offset, in bits, from the msb in byte 0.
|
|
private int mPos;
|
|
|
|
// The last bit offset, given the current buf length.
|
|
private int mEnd;
|
|
|
|
/**
|
|
* An exception to report access problems.
|
|
*/
|
|
public static class AccessException extends Exception {
|
|
public AccessException(String s) {
|
|
super("BitwiseOutputStream access failed: " + s);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Create object from hint at desired size.
|
|
*
|
|
* @param startingLength initial internal byte array length in bytes
|
|
*/
|
|
@UnsupportedAppUsage
|
|
public BitwiseOutputStream(int startingLength) {
|
|
mBuf = new byte[startingLength];
|
|
mEnd = startingLength << 3;
|
|
mPos = 0;
|
|
}
|
|
|
|
/**
|
|
* Return byte array containing accumulated data, sized to just fit.
|
|
*
|
|
* @return newly allocated byte array
|
|
*/
|
|
@UnsupportedAppUsage
|
|
public byte[] toByteArray() {
|
|
int len = (mPos >>> 3) + ((mPos & 0x07) > 0 ? 1 : 0); // &7==%8
|
|
byte[] newBuf = new byte[len];
|
|
System.arraycopy(mBuf, 0, newBuf, 0, len);
|
|
return newBuf;
|
|
}
|
|
|
|
/**
|
|
* Allocate a new internal buffer, if needed.
|
|
*
|
|
* @param bits additional bits to be accommodated
|
|
*/
|
|
private void possExpand(int bits) {
|
|
if ((mPos + bits) < mEnd) return;
|
|
byte[] newBuf = new byte[(mPos + bits) >>> 2];
|
|
System.arraycopy(mBuf, 0, newBuf, 0, mEnd >>> 3);
|
|
mBuf = newBuf;
|
|
mEnd = newBuf.length << 3;
|
|
}
|
|
|
|
/**
|
|
* Write some data and increment the current position.
|
|
*
|
|
* The 8-bit limit on access to bitwise streams is intentional to
|
|
* avoid endianness issues.
|
|
*
|
|
* @param bits the amount of data to write (gte 0, lte 8)
|
|
* @param data to write, will be masked to expose only bits param from lsb
|
|
*/
|
|
@UnsupportedAppUsage
|
|
public void write(int bits, int data) throws AccessException {
|
|
if ((bits < 0) || (bits > 8)) {
|
|
throw new AccessException("illegal write (" + bits + " bits)");
|
|
}
|
|
possExpand(bits);
|
|
data &= (-1 >>> (32 - bits));
|
|
int index = mPos >>> 3;
|
|
int offset = 16 - (mPos & 0x07) - bits; // &7==%8
|
|
data <<= offset;
|
|
mPos += bits;
|
|
mBuf[index] |= data >>> 8;
|
|
if (offset < 8) mBuf[index + 1] |= data & 0xFF;
|
|
}
|
|
|
|
/**
|
|
* Write data in bulk from a byte array and increment the current position.
|
|
*
|
|
* @param bits the amount of data to write
|
|
* @param arr the byte array containing data to be written
|
|
*/
|
|
@UnsupportedAppUsage
|
|
public void writeByteArray(int bits, byte[] arr) throws AccessException {
|
|
for (int i = 0; i < arr.length; i++) {
|
|
int increment = Math.min(8, bits - (i << 3));
|
|
if (increment > 0) {
|
|
write(increment, (byte)(arr[i] >>> (8 - increment)));
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Increment the current position, implicitly writing zeros.
|
|
*
|
|
* @param bits the amount by which to increment the position
|
|
*/
|
|
public void skip(int bits) {
|
|
possExpand(bits);
|
|
mPos += bits;
|
|
}
|
|
}
|