| /* |
| * Copyright (C) 2016 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.Wifi |
| */ |
| |
| package com.android.server.wifi; |
| |
| import com.android.internal.annotations.VisibleForTesting; |
| |
| import java.nio.BufferUnderflowException; |
| import java.nio.ByteBuffer; |
| import java.nio.ByteOrder; |
| import java.nio.charset.Charset; |
| |
| /** |
| * Utility class for reading generic data (e.g. various length integer, string) from ByteBuffer. |
| */ |
| public class ByteBufferReader { |
| @VisibleForTesting |
| public static final int MINIMUM_INTEGER_SIZE = Byte.BYTES; |
| |
| @VisibleForTesting |
| public static final int MAXIMUM_INTEGER_SIZE = Long.BYTES; |
| |
| /** |
| * Read an integer value from a buffer. |
| * |
| * @param payload The buffer to read from |
| * @param byteOrder Byte order of the buffer |
| * @param size The number of bytes to read from the buffer |
| * @return The integer value |
| * @throws BufferUnderflowException |
| * @throws IllegalArgumentException |
| */ |
| public static long readInteger(ByteBuffer payload, ByteOrder byteOrder, int size) { |
| if (size < MINIMUM_INTEGER_SIZE || size > MAXIMUM_INTEGER_SIZE) { |
| throw new IllegalArgumentException("Invalid size " + size); |
| } |
| |
| // Read the necessary bytes. |
| byte[] octets = new byte[size]; |
| payload.get(octets); |
| |
| // Format the value based on byte order. |
| long value = 0; |
| if (byteOrder == ByteOrder.LITTLE_ENDIAN) { |
| for (int n = octets.length - 1; n >= 0; n--) { |
| value = (value << Byte.SIZE) | (octets[n] & 0xFF); |
| } |
| } else { |
| for (byte octet : octets) { |
| value = (value << Byte.SIZE) | (octet & 0xFF); |
| } |
| } |
| return value; |
| } |
| |
| /** |
| * Read a string from a buffer. An empty String will be returned for a String with 0 length. |
| * |
| * @param payload The buffer to read from |
| * @param length Number of bytes to read from the buffer |
| * @param charset The character set of the string |
| * @return {@link String} |
| * @throws BufferUnderflowException |
| * @throws NegativeArraySizeException |
| */ |
| public static String readString(ByteBuffer payload, int length, Charset charset) { |
| byte[] octets = new byte[length]; |
| payload.get(octets); |
| return new String(octets, charset); |
| } |
| |
| /** |
| * Read a string from a buffer where the string value is preceded by the length of the string |
| * (1 byte) in the buffer. |
| * |
| * @param payload The buffer to read from |
| * @param charset The character set of the string |
| * @return {@link String} |
| * @throws BufferUnderflowException |
| */ |
| public static String readStringWithByteLength(ByteBuffer payload, Charset charset) { |
| int length = payload.get() & 0xFF; |
| return readString(payload, length, charset); |
| } |
| } |