| /* |
| * Copyright (C) 2019 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.server.integrity.model; |
| |
| import java.io.IOException; |
| import java.io.InputStream; |
| |
| /** A wrapper class for reading a stream of bits. */ |
| public class BitInputStream { |
| |
| private long mBitPointer; |
| private boolean mReadFromStream; |
| |
| private byte[] mRuleBytes; |
| private InputStream mRuleInputStream; |
| |
| private byte mCurrentRuleByte; |
| |
| public BitInputStream(byte[] ruleBytes) { |
| this.mRuleBytes = ruleBytes; |
| this.mBitPointer = 0; |
| this.mReadFromStream = false; |
| } |
| |
| public BitInputStream(InputStream ruleInputStream) { |
| this.mRuleInputStream = ruleInputStream; |
| this.mReadFromStream = true; |
| } |
| |
| /** |
| * Read the next number of bits from the stream. |
| * |
| * @param numOfBits The number of bits to read. |
| * @return The value read from the stream. |
| */ |
| public int getNext(int numOfBits) throws IOException { |
| int component = 0; |
| int count = 0; |
| |
| while (count++ < numOfBits) { |
| if (mBitPointer % 8 == 0) { |
| mCurrentRuleByte = getNextByte(); |
| } |
| int offset = 7 - (int) (mBitPointer % 8); |
| |
| component <<= 1; |
| component |= (mCurrentRuleByte >>> offset) & 1; |
| |
| mBitPointer++; |
| } |
| |
| return component; |
| } |
| |
| /** Check if there are bits left in the stream. */ |
| public boolean hasNext() throws IOException { |
| if (mReadFromStream) { |
| return mRuleInputStream.available() > 0; |
| } else { |
| return mBitPointer / 8 < mRuleBytes.length; |
| } |
| } |
| |
| private byte getNextByte() throws IOException { |
| if (mReadFromStream) { |
| return (byte) mRuleInputStream.read(); |
| } else { |
| int idx = (int) (mBitPointer / 8); |
| if (idx >= mRuleBytes.length) { |
| throw new IllegalArgumentException(String.format("Invalid byte index: %d", idx)); |
| } |
| return mRuleBytes[idx]; |
| } |
| } |
| } |