99 lines
3.3 KiB
Java
99 lines
3.3 KiB
Java
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/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.Wifi
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*/
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package com.android.server.wifi;
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import com.android.internal.annotations.VisibleForTesting;
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import java.nio.BufferUnderflowException;
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import java.nio.ByteBuffer;
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import java.nio.ByteOrder;
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import java.nio.charset.Charset;
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/**
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* Utility class for reading generic data (e.g. various length integer, string) from ByteBuffer.
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*/
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public class ByteBufferReader {
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@VisibleForTesting
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public static final int MINIMUM_INTEGER_SIZE = Byte.BYTES;
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@VisibleForTesting
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public static final int MAXIMUM_INTEGER_SIZE = Long.BYTES;
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/**
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* Read an integer value from a buffer.
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*
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* @param payload The buffer to read from
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* @param byteOrder Byte order of the buffer
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* @param size The number of bytes to read from the buffer
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* @return The integer value
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* @throws BufferUnderflowException
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* @throws IllegalArgumentException
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*/
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public static long readInteger(ByteBuffer payload, ByteOrder byteOrder, int size) {
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if (size < MINIMUM_INTEGER_SIZE || size > MAXIMUM_INTEGER_SIZE) {
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throw new IllegalArgumentException("Invalid size " + size);
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}
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// Read the necessary bytes.
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byte[] octets = new byte[size];
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payload.get(octets);
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// Format the value based on byte order.
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long value = 0;
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if (byteOrder == ByteOrder.LITTLE_ENDIAN) {
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for (int n = octets.length - 1; n >= 0; n--) {
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value = (value << Byte.SIZE) | (octets[n] & 0xFF);
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}
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} else {
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for (byte octet : octets) {
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value = (value << Byte.SIZE) | (octet & 0xFF);
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}
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}
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return value;
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}
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/**
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* Read a string from a buffer. An empty String will be returned for a String with 0 length.
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*
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* @param payload The buffer to read from
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* @param length Number of bytes to read from the buffer
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* @param charset The character set of the string
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* @return {@link String}
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* @throws BufferUnderflowException
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* @throws NegativeArraySizeException
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*/
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public static String readString(ByteBuffer payload, int length, Charset charset) {
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byte[] octets = new byte[length];
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payload.get(octets);
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return new String(octets, charset);
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}
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/**
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* Read a string from a buffer where the string value is preceded by the length of the string
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* (1 byte) in the buffer.
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*
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* @param payload The buffer to read from
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* @param charset The character set of the string
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* @return {@link String}
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* @throws BufferUnderflowException
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*/
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public static String readStringWithByteLength(ByteBuffer payload, Charset charset) {
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int length = payload.get() & 0xFF;
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return readString(payload, length, charset);
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}
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}
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