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/*
* 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);
}
}
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