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package model.asn1;
import model.asn1.exceptions.ParseException;
import model.asn1.parsing.BytesReader;
import model.pki.cert.TbsCertificate;
import ui.Utils;
import java.math.BigInteger;
import java.util.Arrays;
/**
* An ASN.1 INTEGER type. By spec, it can be arbitrarily long. But just like it's impossible to have an
* endless tape in a turing machine, this implementation uses fixed length internally to represent ints.
*/
public class Int extends ASN1Object {
/**
* The X.680 universal class tag assignment.
*/
public static final Tag TAG = new Tag(TagClass.UNIVERSAL, false, 0x2);
private final BigInteger value;
/**
* EFFECTS: Initiate the INTEGER object with the given tag and an optional context-specific tag number for explicit
* encoding. For more information, consult {@link ASN1Object}.
* REQUIRES: Consult {@link ASN1Object}.
*/
public Int(Tag tag, Tag parentTag, BigInteger value) {
super(tag, parentTag);
this.value = value;
}
/**
* EFFECTS: Initiate the INTEGER object with the given tag and an optional context-specific tag number for explicit
* encoding. For more information, consult {@link ASN1Object}.
* REQUIRES: Consult {@link ASN1Object}.
*/
public Int(Tag tag, Tag parentTag, long value) {
this(tag, parentTag, BigInteger.valueOf(value));
}
/**
* EFFECTS: Parse input and get the int value. Tags are parsed in {@link ASN1Object}.
* Throws {@link ParseException} if encoded value are invalid:
* - Early EOF (not enough bytes)
* - Zero bytes length
* - Other issues denoted in {@link ASN1Object}
* MODIFIES: this, encoded
*/
public Int(BytesReader encoded, boolean hasParentTag) throws ParseException {
super(encoded, hasParentTag);
if (getLength() == 0) {
throw new ParseException("Integer with zero length");
}
this.value = new BigInteger(Utils.byteToByte(encoded.require(getLength(), true)));
}
/**
* EFFECTS: Produce the big-endian two's complement encoding of the value, in the shortest possible way (i.e., no
* leading 0x0 bytes, and no leading 0xFF bytes if negative). Notes, if a positive number is desired (or mandated
* like {@link TbsCertificate#getSerialNumber()}, append 0x0 to the MSB manually. This method always results in a
* signed integer. For simplicity, the first 0x0 is always removed except when the number itself is 0, and others
* are kept.
*/
@Override
public Byte[] encodeValueDER() {
Byte[] bytes = Utils.byteToByte(value.toByteArray());
if (bytes.length == 1) {
return bytes;
}
if (bytes[0] == 0x0) {
return Arrays.stream(bytes)
.skip(1)
.toArray(Byte[]::new);
}
return bytes;
}
/**
* EFFECTS: Get the value in long.
* Throws {@link ArithmeticException} if the value is too large for long.
*/
public long getLong() throws ArithmeticException {
return value.longValueExact();
}
public BigInteger getValue() {
return value;
}
}
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