MINA源码分析---学习mina中整数和网络字节的转换处理
主要学习网络字节和计算机上表示的整数之间相互转换以及和小端字节序的转换
package org.apache.mina.proxy.utils;
import java.io.UnsupportedEncodingException;
/**
* ByteUtilities.java - Byte manipulation functions.
* @since MINA 2.0.0-M3
*/
public class ByteUtilities {
/**
* Returns the integer represented by up to 4 bytes in network byte order.
* 把网络字节序的4字节转换成整数
* @param buf the buffer to read the bytes from
* @param start
* @param count
* @return
*/
public static int networkByteOrderToInt(byte[] buf, int start, int count) {
if (count > 4) {
throw new IllegalArgumentException(
"Cannot handle more than 4 bytes");
}
int result = 0;
//(这里面是考虑32位机器)采用与低8位字节做或操作,然后左移8位,把4个字节变成一个整数的32位
for (int i = 0; i < count; i++) {
result <<= 8;
result |= (buf[start + i] & 0xff);
}
return result;
}
/**
* Encodes an integer into up to 4 bytes in network byte order.
* 把一个整数编码成4个网络字节序的字节
* @param num the int to convert to a byte array
* @param count the number of reserved bytes for the write operation
* @return the resulting byte array
*/
public static byte[] intToNetworkByteOrder(int num, int count) {
byte[] buf = new byte[count];
intToNetworkByteOrder(num, buf, 0, count);
return buf;
}
/**
* Encodes an integer into up to 4 bytes in network byte order in the
* supplied buffer starting at start offset and writing
* count bytes.
*
* @param num the int to convert to a byte array
* @param buf the buffer to write the bytes to
* @param start the offset from beginning for the write operation
* @param count the number of reserved bytes for the write operation
*/
public static void intToNetworkByteOrder(int num, byte[] buf, int start,
int count) {
if (count > 4) {
throw new IllegalArgumentException(
"Cannot handle more than 4 bytes");
}
//网络字节序:先传输的是高位字节,后面的是低位字节
for (int i = count - 1; i >= 0; i--) {
buf[start + i] = (byte) (num & 0xff);
num >>>= 8; //无符号右移
}
}
/**
* Write a 16 bit short as LITTLE_ENDIAN.
*
* @param v the short to write
*/
public final static byte[] writeShort(short v) {
return writeShort(v, new byte[2], 0);
}
/**
* Write a 16 bit short as LITTLE_ENDIAN to
* the given array b at offset offset.
*
* @param v the short to write
* @param b the byte array to write to
* @param offset the offset at which to start writing in the array
*/
public final static byte[] writeShort(short v, byte[] b, int offset) {
b[offset] = (byte) v;
b[offset + 1] = (byte) (v >> 8);
return b;
}
/**
* Write a 32 bit int as LITTLE_ENDIAN.
*
* @param v the int to write
*/
public final static byte[] writeInt(int v) {
return writeInt(v, new byte[4], 0);
}
/**
* Write a 32 bit int as LITTLE_ENDIAN to
* the given array b at offset offset.
* 写一个32位整数 用 小端序 存放在字节数组中
* @param v the int to write
* @param b the byte array to write to
* @param offset the offset at which to start writing in the array
*/
public final static byte[] writeInt(int v, byte[] b, int offset) {
b[offset] = (byte) v;//先存放低位字节,这就是小端字节序
b[offset + 1] = (byte) (v >> 8);//有符号右移
b[offset + 2] = (byte) (v >> 16);
b[offset + 3] = (byte) (v >> 24);
return b;
}
/**
* Invert the endianness of words (4 bytes) in the given byte array
* starting at the given offset and repeating length/4 times.
* eg: b0b1b2b3 -> b3b2b1b0
* 反转4个字节的顺序
* @param b the byte array
* @param offset the offset at which to change word start
* @param length the number of bytes on which to operate
* (should be a multiple of 4)
*/
public final static void changeWordEndianess(byte[] b, int offset,
int length) {
byte tmp;
for (int i = offset; i < offset + length; i += 4) {
tmp = b[i];
b[i] = b[i + 3];
b[i + 3] = tmp;
tmp = b[i + 1];
b[i + 1] = b[i + 2];
b[i + 2] = tmp;
}
}
/**
* Invert two bytes in the given byte array starting at the given
* offset and repeating the inversion length/2 times.
* eg: b0b1 -> b1b0
* 反转两个字节的顺序
* @param b the byte array
* @param offset the offset at which to change word start
* @param length the number of bytes on which to operate
* (should be a multiple of 2)
*/
public final static void changeByteEndianess(byte[] b, int offset,
int length) {
byte tmp;
for (int i = offset; i < offset + length; i += 2) {
tmp = b[i];
b[i] = b[i + 1];
b[i + 1] = tmp;
}
}
/**
* Converts an OEM string as defined in NTLM protocol (eg ASCII charset)
* to a byte array.
*
* @param s the string to convert
* @return the result byte array
* @throws UnsupportedEncodingException if the string is not an OEM string
*/
public final static byte[] getOEMStringAsByteArray(String s)
throws UnsupportedEncodingException {
return s.getBytes("ASCII");
}
/**
* Converts an UTF-16LE string as defined in NTLM protocol to a byte array.
*
* @param s the string to convert
* @return the result byte array
* @throws UnsupportedEncodingException if the string is not an UTF-16LE string
*/
public final static byte[] getUTFStringAsByteArray(String s)
throws UnsupportedEncodingException {
return s.getBytes("UTF-16LE");
}
/**
* Encodes the string to a byte array using UTF-16LE or the ASCII charset
* in function of the useUnicode argument.
*
* @param s the string to encode
* @param useUnicode if true then string is encoded to UTF-16LE
* otherwise to ASCII
* @return the encoded string as a byte array
* @throws UnsupportedEncodingException if encoding fails
*/
public final static byte[] encodeString(String s, boolean useUnicode)
throws UnsupportedEncodingException {
if (useUnicode) {
return getUTFStringAsByteArray(s);
}
return getOEMStringAsByteArray(s);
}
/**
* Returns a hexadecimal representation of the given byte array.
*
* @param bytes the array to output to an hex string
* @return the hex representation as a string
*/
public static String asHex(byte[] bytes) {
return asHex(bytes, null);
}
/**
* Returns a hexadecimal representation of the given byte array.
* 把字节数组转换成16进制字符表示
* @param bytes the array to output to an hex string
* @param separator the separator to use between each byte in the output
* string. If null no char is inserted between each byte value.
* @return the hex representation as a string
*/
public static String asHex(byte[] bytes, String separator) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < bytes.length; i++) {
//8位字节转换成 16进制
String code = Integer.toHexString(bytes[i] & 0xFF);
if ((bytes[i] & 0xFF) < 16) {
sb.append('0');
}
sb.append(code);
if (separator != null && i < bytes.length - 1) {
sb.append(separator);
}
}
return sb.toString();
}
/**
* Converts a hex string representation to a byte array.
*
* @param hex the string holding the hex values
* @return the resulting byte array
*/
public static byte[] asByteArray(String hex) {
byte[] bts = new byte[hex.length() / 2];
for (int i = 0; i < bts.length; i++) {
bts[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2),
16);
}
return bts;
}
/**
* Reads an int from 4 bytes of the given array at offset 0.
*
* @param b the byte array to read
* @param offset the offset at which to start
* @return the int value
*/
public static final int makeIntFromByte4(byte[] b) {
return makeIntFromByte4(b, 0);
}
/**
* Reads an int from 4 bytes of the given array at the given offset.
*
* @param b the byte array to read
* @param offset the offset at which to start
* @return the int value
*/
public static final int makeIntFromByte4(byte[] b, int offset) {
return b[offset] << 24 | (b[offset + 1] & 0xff) << 16
| (b[offset + 2] & 0xff) << 8 | (b[offset + 3] & 0xff);
}
/**
* Reads an int from 2 bytes of the given array at offset 0.
*
* @param b the byte array to read
* @return the int value
*/
public static final int makeIntFromByte2(byte[] b) {
return makeIntFromByte2(b, 0);
}
/**
* Reads an int from 2 bytes of the given array at the given offset.
*
* @param b the byte array to read
* @param offset the offset at which to start
* @return the int value
*/
public static final int makeIntFromByte2(byte[] b, int offset) {
return (b[offset] & 0xff) << 8 | (b[offset + 1] & 0xff);
}
/**
* Returns true if the flag testFlag is set in the
* flags flagset.
*
* @param flagset the flagset to test
* @param testFlag the flag we search the presence of
* @return true if testFlag is present in the flagset, false otherwise.
*/
public final static boolean isFlagSet(int flagSet, int testFlag) {
return (flagSet & testFlag) > 0;
}
}