1 files changed, 92 insertions, 0 deletions

diff --git a/src/main/java/org/gnunet/construct/parsers/IntegerUtil.java b/src/main/java/org/gnunet/construct/parsers/IntegerUtil.java
new file mode 100644
index 0000000..83391de
--- /dev/null
+++ b/src/main/java/org/gnunet/construct/parsers/IntegerUtil.java
@@ -0,0 +1,92 @@
+/*
+ This file is part of GNUnet.
+ (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., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, 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 sign 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 sign
+            byte sign = (byte) ((val >>> (7*8)) & 0x80);
+            // remove the sign 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");
+    }
+}