Mega Code Archive
Number in hexadecimal format are used throughout Freenet
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//package freenet.support;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.util.BitSet;
/**
* Number in hexadecimal format are used throughout Freenet.
*
* <p>Unless otherwise stated, the conventions follow the rules outlined in the
* Java Language Specification.</p>
*
* @author syoung
*/
public class HexUtil {
/**
* Converts a byte array into a string of lower case hex chars.
*
* @param bs
* A byte array
* @param off
* The index of the first byte to read
* @param length
* The number of bytes to read.
* @return the string of hex chars.
*/
public static final String bytesToHex(byte[] bs, int off, int length) {
if (bs.length <= off || bs.length < off+length)
throw new IllegalArgumentException();
StringBuilder sb = new StringBuilder(length * 2);
bytesToHexAppend(bs, off, length, sb);
return sb.toString();
}
public static final void bytesToHexAppend(
byte[] bs,
int off,
int length,
StringBuilder sb) {
if (bs.length <= off || bs.length < off+length)
throw new IllegalArgumentException();
sb.ensureCapacity(sb.length() + length * 2);
for (int i = off; i < (off + length); i++) {
sb.append(Character.forDigit((bs[i] >>> 4) & 0xf, 16));
sb.append(Character.forDigit(bs[i] & 0xf, 16));
}
}
public static final String bytesToHex(byte[] bs) {
return bytesToHex(bs, 0, bs.length);
}
public static final byte[] hexToBytes(String s) {
return hexToBytes(s, 0);
}
public static final byte[] hexToBytes(String s, int off) {
byte[] bs = new byte[off + (1 + s.length()) / 2];
hexToBytes(s, bs, off);
return bs;
}
/**
* Converts a String of hex characters into an array of bytes.
*
* @param s
* A string of hex characters (upper case or lower) of even
* length.
* @param out
* A byte array of length at least s.length()/2 + off
* @param off
* The first byte to write of the array
*/
public static final void hexToBytes(String s, byte[] out, int off)
throws NumberFormatException, IndexOutOfBoundsException {
int slen = s.length();
if ((slen % 2) != 0) {
s = '0' + s;
}
if (out.length < off + slen / 2) {
throw new IndexOutOfBoundsException(
"Output buffer too small for input ("
+ out.length
+ '<'
+ off
+ slen / 2
+ ')');
}
// Safe to assume the string is even length
byte b1, b2;
for (int i = 0; i < slen; i += 2) {
b1 = (byte) Character.digit(s.charAt(i), 16);
b2 = (byte) Character.digit(s.charAt(i + 1), 16);
if ((b1 < 0) || (b2 < 0)) {
throw new NumberFormatException();
}
out[off + i / 2] = (byte) (b1 << 4 | b2);
}
}
/**
* Pack the bits in ba into a byte[].
*
* @param ba : the BitSet
* @param size : How many bits shall be taken into account starting from the LSB?
*/
public final static byte[] bitsToBytes(BitSet ba, int size) {
int bytesAlloc = countBytesForBits(size);
byte[] b = new byte[bytesAlloc];
StringBuilder sb =null;
for(int i=0;i<b.length;i++) {
short s = 0;
for(int j=0;j<8;j++) {
int idx = i*8+j;
boolean val =
idx > size - 1 ? false :
ba.get(idx);
s |= val ? (1<<j) : 0;
}
if(s > 255) throw new IllegalStateException("WTF? s = "+s);
b[i] = (byte)s;
}
return b;
}
/**
* Pack the bits in ba into a byte[] then convert that
* to a hex string and return it.
*/
public final static String bitsToHexString(BitSet ba, int size) {
return bytesToHex(bitsToBytes(ba, size));
}
/**
* @return the number of bytes required to represent the
* bitset
*/
public static int countBytesForBits(int size) {
// Brackets matter here! == takes precedence over the rest
return (size/8) + ((size % 8) == 0 ? 0:1);
}
/**
* Read bits from a byte array into a bitset
* @param b the byte[] to read from
* @param ba the bitset to write to
*/
public static void bytesToBits(byte[] b, BitSet ba, int maxSize) {
int x = 0;
for(int i=0;i<b.length;i++) {
for(int j=0;j<8;j++) {
if(x > maxSize) break;
int mask = 1 << j;
boolean value = (mask & b[i]) != 0;
ba.set(x, value);
x++;
}
}
}
/**
* Read a hex string of bits and write it into a bitset
* @param s hex string of the stored bits
* @param ba the bitset to store the bits in
* @param length the maximum number of bits to store
*/
public static void hexToBits(String s, BitSet ba, int length) {
byte[] b = hexToBytes(s);
bytesToBits(b, ba, length);
}
/**
* Write a (reasonably short) BigInteger to a stream.
* @param integer the BigInteger to write
* @param out the stream to write it to
*/
public static void writeBigInteger(BigInteger integer, DataOutputStream out) throws IOException {
if(integer.signum() == -1) {
//dump("Negative BigInteger", Logger.ERROR, true);
throw new IllegalStateException("Negative BigInteger!");
}
byte[] buf = integer.toByteArray();
if(buf.length > Short.MAX_VALUE)
throw new IllegalStateException("Too long: "+buf.length);
out.writeShort((short)buf.length);
out.write(buf);
}
/**
* Read a (reasonably short) BigInteger from a DataInputStream
* @param dis the stream to read from
* @return a BigInteger
*/
public static BigInteger readBigInteger(DataInputStream dis) throws IOException {
short i = dis.readShort();
if(i < 0) throw new IOException("Invalid BigInteger length: "+i);
byte[] buf = new byte[i];
dis.readFully(buf);
return new BigInteger(1,buf);
}
/**
* Turn a BigInteger into a hex string.
* BigInteger.toString(16) NPEs on Sun JDK 1.4.2_05. :<
* The bugs in their Big* are getting seriously irritating...
*/
public static String biToHex(BigInteger bi) {
return bytesToHex(bi.toByteArray());
}
}
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