com.cryptape.cita.rlp.RlpEncoder Maven / Gradle / Ivy
package com.cryptape.cita.rlp;
import java.util.Arrays;
import java.util.List;
/**
* Recursive Length Prefix (RLP) encoder.
*
* For the specification, refer to p16 of the
* yellow paper and here.
*/
public class RlpEncoder {
private static final int STRING_OFFSET = 0x80;
private static final int LIST_OFFSET = 0xc0;
public static byte[] encode(RlpType value) {
if (value instanceof RlpString) {
return encodeString((RlpString) value);
} else {
return encodeList((RlpList) value);
}
}
private static byte[] encode(byte[] bytesValue, int offset) {
if (bytesValue.length == 1
&& offset == STRING_OFFSET
&& bytesValue[0] >= (byte) 0x00
&& bytesValue[0] <= (byte) 0x7f) {
return bytesValue;
} else if (bytesValue.length < 55) {
byte[] result = new byte[bytesValue.length + 1];
result[0] = (byte) (offset + bytesValue.length);
System.arraycopy(bytesValue, 0, result, 1, bytesValue.length);
return result;
} else {
byte[] encodedStringLength = toMinimalByteArray(bytesValue.length);
byte[] result = new byte[bytesValue.length + encodedStringLength.length + 1];
result[0] = (byte) ((offset + 0x37) + encodedStringLength.length);
System.arraycopy(encodedStringLength, 0, result, 1, encodedStringLength.length);
System.arraycopy(
bytesValue, 0, result, encodedStringLength.length + 1, bytesValue.length);
return result;
}
}
static byte[] encodeString(RlpString value) {
return encode(value.getBytes(), STRING_OFFSET);
}
private static byte[] toMinimalByteArray(int value) {
byte[] encoded = toByteArray(value);
for (int i = 0; i < encoded.length; i++) {
if (encoded[i] != 0) {
return Arrays.copyOfRange(encoded, i, encoded.length);
}
}
return new byte[]{ };
}
private static byte[] toByteArray(int value) {
return new byte[] {
(byte) ((value >> 24) & 0xff),
(byte) ((value >> 16) & 0xff),
(byte) ((value >> 8) & 0xff),
(byte) (value & 0xff)
};
}
static byte[] encodeList(RlpList value) {
List values = value.getValues();
if (values.isEmpty()) {
return encode(new byte[]{ }, LIST_OFFSET);
} else {
byte[] result = new byte[0];
for (RlpType entry:values) {
result = concat(result, encode(entry));
}
return encode(result, LIST_OFFSET);
}
}
private static byte[] concat(byte[] b1, byte[] b2) {
byte[] result = Arrays.copyOf(b1, b1.length + b2.length);
System.arraycopy(b2, 0, result, b1.length, b2.length);
return result;
}
}