| /* |
| * Copyright 2016-present Open Networking Laboratory |
| * |
| * 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 org.onosproject.bmv2.api.utils; |
| |
| import com.google.common.annotations.Beta; |
| import org.onlab.util.HexString; |
| import org.onlab.util.ImmutableByteSequence; |
| |
| import java.util.Arrays; |
| |
| import static com.google.common.base.Preconditions.checkArgument; |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| /** |
| * Collection of utility methods to deal with flow rule translation. |
| */ |
| @Beta |
| public final class Bmv2TranslatorUtils { |
| |
| private Bmv2TranslatorUtils() { |
| // Ban constructor. |
| } |
| |
| /** |
| * Returns the number of bytes necessary to contain the given bit-width. |
| * |
| * @param bitWidth an integer value |
| * @return an integer value |
| */ |
| public static int roundToBytes(int bitWidth) { |
| return (int) Math.ceil((double) bitWidth / 8); |
| } |
| |
| /** |
| * Trims or expands the given byte sequence so to fit a given bit-width. |
| * |
| * @param original a byte sequence |
| * @param bitWidth an integer value |
| * @return a new byte sequence |
| * @throws ByteSequenceFitException if the byte sequence cannot be fitted in the given bit-width |
| */ |
| public static ImmutableByteSequence fitByteSequence(ImmutableByteSequence original, int bitWidth) |
| throws ByteSequenceFitException { |
| |
| checkNotNull(original, "byte sequence cannot be null"); |
| checkArgument(bitWidth > 0, "byte width must a non-zero positive integer"); |
| |
| int newByteWidth = roundToBytes(bitWidth); |
| |
| if (original.size() == newByteWidth) { |
| // nothing to do |
| return original; |
| } |
| |
| byte[] originalBytes = original.asArray(); |
| |
| if (newByteWidth > original.size()) { |
| // pad missing bytes with zeros |
| return ImmutableByteSequence.copyFrom(Arrays.copyOf(originalBytes, newByteWidth)); |
| } |
| |
| byte[] newBytes = new byte[newByteWidth]; |
| // ImmutableByteSequence is always big-endian, hence check the array in reverse order |
| int diff = originalBytes.length - newByteWidth; |
| for (int i = originalBytes.length - 1; i > 0; i--) { |
| byte ob = originalBytes[i]; // original byte |
| byte nb; // new byte |
| if (i > diff) { |
| // no need to truncate, copy as is |
| nb = ob; |
| } else if (i == diff) { |
| // truncate this byte, check if we're loosing something |
| byte mask = (byte) ((1 >> ((bitWidth % 8) + 1)) - 1); |
| if ((ob & ~mask) != 0) { |
| throw new ByteSequenceFitException(originalBytes, bitWidth); |
| } else { |
| nb = (byte) (ob & mask); |
| } |
| } else { |
| // drop this byte, check if we're loosing something |
| if (originalBytes[i] != 0) { |
| throw new ByteSequenceFitException(originalBytes, bitWidth); |
| } else { |
| continue; |
| } |
| } |
| newBytes[i - diff] = nb; |
| } |
| |
| return ImmutableByteSequence.copyFrom(newBytes); |
| } |
| |
| /** |
| * A byte sequence fit exception. |
| */ |
| public static class ByteSequenceFitException extends Exception { |
| public ByteSequenceFitException(byte[] bytes, int bitWidth) { |
| super("cannot fit " + HexString.toHexString(bytes) + " into a " + bitWidth + " bits value"); |
| } |
| } |
| } |