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/*
This file is part of GNUnet.
Copyright (C) 2011, 2012 Christian Grothoff (and other contributing authors)
GNUnet is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 3, or (at your
option) any later version.
GNUnet is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/
package org.gnunet.construct.parsers;
import java.math.BigInteger;
import java.nio.ByteBuffer;
public class IntegerUtil {
public static long readLong(ByteBuffer srcBuf, boolean isSigned, int byteSize) {
long val = 0;
final int first = srcBuf.position();
final int last = first + byteSize - 1;
// read all bytes except the last
while (srcBuf.position() != last) {
byte b = srcBuf.get();
// byte b may be signed, if so interpret it as unsigned byte; store it in an int
int s = b >= 0 ? b : (256 + b);
val |= s;
val <<= 8;
}
// read the last byte, we don't have to shift val after that
byte b = srcBuf.get();
int s = b >= 0 ? b : (256 + b);
val |= s;
if (isSigned) {
// explicitly OR signRaw bit to the right place if the source buffer is
// too large
long sign = (srcBuf.get(first) & 0x80);
val |= (sign << 7);
}
return val;
}
public static void writeLong(final long val, final ByteBuffer dstBuf, boolean isSigned, int byteSize) {
long myval = val;
// position of the last byte we are responsible to write
int last = dstBuf.position() + byteSize - 1;
while (last >= dstBuf.position()) {
dstBuf.put(last, (byte) (myval & 0xFF));
myval >>>= 8;
last -= 1;
}
if (isSigned) {
// a long has 8 bytes, shift by 7 bytes (non-arithmetically) to get the signRaw
byte sign = (byte) ((val >>> (7*8)) & 0x80);
// remove the signRaw bit from the buffer
dstBuf.put(dstBuf.position() + byteSize - 1, (byte) (dstBuf.get(dstBuf.position() + byteSize - 1) & ~sign));
// ... and put it in the right place (lowest byte)
dstBuf.put(dstBuf.position(), (byte) (dstBuf.get(dstBuf.position()) | sign));
}
dstBuf.position(dstBuf.position() + byteSize);
}
public static void writeBitInteger(BigInteger big, ByteBuffer dstBuf, boolean isSigned, int byteSize) {
throw new UnsupportedOperationException("not yet implemented");
}
public static BigInteger readBigInteger(final ByteBuffer srcBuf, boolean isSigned, int byteSize) {
throw new UnsupportedOperationException("not yet implemented");
}
}
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