* NOTE: This class may eventually disappear, to
* be supplanted by big-endian byte arrays which hold both signed
* and unsigned arbitrary-precision integers.
*
* @version 1.23
* @author David Brownell
*/
public final class BigInt {
// Big endian -- MSB first.
private byte[] places;
/**
* Constructs a "Big" integer from a set of (big-endian) bytes.
* Leading zeroes should be stripped off.
*
* @param data a sequence of bytes, most significant bytes/digits
* first. CONSUMED.
*/
public BigInt(byte[] data) {
places = data.clone();
}
/**
* Constructs a "Big" integer from a "BigInteger", which must be
* positive (or zero) in value.
*/
public BigInt(BigInteger i) {
byte[] temp = i.toByteArray();
if ((temp[0] & 0x80) != 0)
throw new IllegalArgumentException("negative BigInteger");
// XXX we assume exactly _one_ sign byte is used...
if (temp[0] != 0)
places = temp;
else {
// Note that if i = new BigInteger("0"),
// i.toByteArray() contains only 1 zero.
if (temp.length == 1) {
places = new byte[1];
places[0] = (byte) 0;
} else {
places = new byte[temp.length - 1];
for (int j = 1; j < temp.length; j++)
places[j - 1] = temp[j];
}
}
}
/**
* Constructs a "Big" integer from a normal Java integer.
*
* @param i the java primitive integer
*/
public BigInt(int i) {
if (i < (1 << 8)) {
places = new byte[1];
places[0] = (byte) i;
} else if (i < (1 << 16)) {
places = new byte[2];
places[0] = (byte) (i >> 8);
places[1] = (byte) i;
} else if (i < (1 << 24)) {
places = new byte[3];
places[0] = (byte) (i >> 16);
places[1] = (byte) (i >> 8);
places[2] = (byte) i;
} else {
places = new byte[4];
places[0] = (byte) (i >> 24);
places[1] = (byte) (i >> 16);
places[2] = (byte) (i >> 8);
places[3] = (byte) i;
}
}
/**
* Converts the "big" integer to a java primitive integer.
*
* @exception NumberFormatException if 32 bits is insufficient.
*/
public int toInt() {
if (places.length > 4)
throw new NumberFormatException("BigInt.toInt, too big");
int retval = 0, i = 0;
for (; i < places.length; i++)
retval = (retval << 8) + (places[i] & 0xff);
return retval;
}
/**
* Returns a hexadecimal printed representation. The value is
* formatted to fit on lines of at least 75 characters, with
* embedded newlines. Words are separated for readability,
* with eight words (32 bytes) per line.
*/
public String toString() {
return hexify();
}
/**
* Returns a BigInteger value which supports many arithmetic
* operations. Assumes negative values will never occur.
*/
public BigInteger toBigInteger() {
return new BigInteger(1, places);
}
/**
* Returns the length of the data as a byte array.
*/
public int byteLength() {
return places.length;
}
/**
* Returns the data as a byte array. The most significant bit
* of the array is bit zero (as in java.math.BigInteger).
*/
public byte[] toByteArray() {
if (places.length == 0) {
byte zero[] = new byte[1];
zero[0] = (byte) 0;
return zero;
} else {
return places.clone();
}
}
private static final String digits = "0123456789abcdef";
private String hexify() {
if (places.length == 0)
return " 0 ";
StringBuffer buf = new StringBuffer(places.length * 2);
buf.append(" "); // four spaces
for (int i = 0; i < places.length; i++) {
buf.append(digits.charAt((places[i] >> 4) & 0x0f));
buf.append(digits.charAt(places[i] & 0x0f));
if (((i + 1) % 32) == 0) {
if ((i + 1) != places.length)
buf.append("\n "); // line after four words
} else if (((i + 1) % 4) == 0)
buf.append(' '); // space between words
}
return buf.toString();
}
/**
* Returns true iff the parameter is a numerically equivalent
* BigInt.
*
* @param other the object being compared with this one.
*/
public boolean equals(Object other) {
if (other instanceof BigInt)
return equals((BigInt) other);
return false;
}
/**
* Returns true iff the parameter is numerically equivalent.
*
* @param other the BigInt being compared with this one.
*/
public boolean equals(BigInt other) {
if (this == other)
return true;
byte[] otherPlaces = other.toByteArray();
if (places.length != otherPlaces.length)
return false;
for (int i = 0; i < places.length; i++)
if (places[i] != otherPlaces[i])
return false;
return true;
}
}