org.spearce.jgit/src/org/spearce/jgit/util/NB.java

   1 /*
   2  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
   3  *
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or
   7  * without modification, are permitted provided that the following
   8  * conditions are met:
   9  *
  10  * - Redistributions of source code must retain the above copyright
  11  *   notice, this list of conditions and the following disclaimer.
  12  *
  13  * - Redistributions in binary form must reproduce the above
  14  *   copyright notice, this list of conditions and the following
  15  *   disclaimer in the documentation and/or other materials provided
  16  *   with the distribution.
  17  *
  18  * - Neither the name of the Git Development Community nor the
  19  *   names of its contributors may be used to endorse or promote
  20  *   products derived from this software without specific prior
  21  *   written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  24  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  25  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  26  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  28  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  31  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  32  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  33  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  35  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 package org.spearce.jgit.util;
  39
  40 import java.io.EOFException;
  41 import java.io.IOException;
  42 import java.io.InputStream;
  43
  44 /** Conversion utilities for network byte order handling. */
  45 public final class NB {
  46         /**
  47          * Read the entire byte array into memory, or throw an exception.
  48          *
  49          * @param fd
  50          *            input stream to read the data from.
  51          * @param dst
  52          *            buffer that must be fully populated, [off, off+len).
  53          * @param off
  54          *            position within the buffer to start writing to.
  55          * @param len
  56          *            number of bytes that must be read.
  57          * @throws EOFException
  58          *             the stream ended before dst was fully populated.
  59          * @throws IOException
  60          *             there was an error reading from the stream.
  61          */
  62         public static void readFully(final InputStream fd, final byte[] dst,
  63                         int off, int len) throws IOException {
  64                 while (len > 0) {
  65                         final int r = fd.read(dst, off, len);
  66                         if (r <= 0)
  67                                 throw new EOFException("Short read of block.");
  68                         off += r;
  69                         len -= r;
  70                 }
  71         }
  72
  73         /**
  74          * Compare a 32 bit unsigned integer stored in a 32 bit signed integer.
  75          * <p>
  76          * This function performs an unsigned compare operation, even though Java
  77          * does not natively support unsigned integer values. Negative numbers are
  78          * treated as larger than positive ones.
  79          *
  80          * @param a
  81          *            the first value to compare.
  82          * @param b
  83          *            the second value to compare.
  84          * @return < 0 if a < b; 0 if a == b; > 0 if a > b.
  85          */
  86         public static int compareUInt32(final int a, final int b) {
  87                 final int cmp = (a >>> 1) - (b >>> 1);
  88                 if (cmp != 0)
  89                         return cmp;
  90                 return (a & 1) - (b & 1);
  91         }
  92
  93         /**
  94          * Convert sequence of 2 bytes (network byte order) into unsigned value.
  95          *
  96          * @param intbuf
  97          *            buffer to acquire the 2 bytes of data from.
  98          * @param offset
  99          *            position within the buffer to begin reading from. This
 100          *            position and the next byte after it (for a total of 2 bytes)
 101          *            will be read.
 102          * @return unsigned integer value that matches the 16 bits read.
 103          */
 104         public static int decodeUInt16(final byte[] intbuf, final int offset) {
 105                 int r = (intbuf[offset] & 0xff) << 8;
 106                 return r | (intbuf[offset + 1] & 0xff);
 107         }
 108
 109         /**
 110          * Convert sequence of 4 bytes (network byte order) into signed value.
 111          *
 112          * @param intbuf
 113          *            buffer to acquire the 4 bytes of data from.
 114          * @param offset
 115          *            position within the buffer to begin reading from. This
 116          *            position and the next 3 bytes after it (for a total of 4
 117          *            bytes) will be read.
 118          * @return signed integer value that matches the 32 bits read.
 119          */
 120         public static int decodeInt32(final byte[] intbuf, final int offset) {
 121                 int r = intbuf[offset] << 8;
 122
 123                 r |= intbuf[offset + 1] & 0xff;
 124                 r <<= 8;
 125
 126                 r |= intbuf[offset + 2] & 0xff;
 127                 return (r << 8) | (intbuf[offset + 3] & 0xff);
 128         }
 129
 130         /**
 131          * Convert sequence of 4 bytes (network byte order) into unsigned value.
 132          *
 133          * @param intbuf
 134          *            buffer to acquire the 4 bytes of data from.
 135          * @param offset
 136          *            position within the buffer to begin reading from. This
 137          *            position and the next 3 bytes after it (for a total of 4
 138          *            bytes) will be read.
 139          * @return unsigned integer value that matches the 32 bits read.
 140          */
 141         public static long decodeUInt32(final byte[] intbuf, final int offset) {
 142                 int low = (intbuf[offset + 1] & 0xff) << 8;
 143                 low |= (intbuf[offset + 2] & 0xff);
 144                 low <<= 8;
 145
 146                 low |= (intbuf[offset + 3] & 0xff);
 147                 return ((long) (intbuf[offset] & 0xff)) << 24 | low;
 148         }
 149
 150         /**
 151          * Convert sequence of 8 bytes (network byte order) into unsigned value.
 152          *
 153          * @param intbuf
 154          *            buffer to acquire the 8 bytes of data from.
 155          * @param offset
 156          *            position within the buffer to begin reading from. This
 157          *            position and the next 7 bytes after it (for a total of 8
 158          *            bytes) will be read.
 159          * @return unsigned integer value that matches the 64 bits read.
 160          */
 161         public static long decodeUInt64(final byte[] intbuf, final int offset) {
 162                 return (decodeUInt32(intbuf, offset) << 32)
 163                                 | decodeUInt32(intbuf, offset + 4);
 164         }
 165
 166         /**
 167          * Write a 16 bit integer as a sequence of 2 bytes (network byte order).
 168          *
 169          * @param intbuf
 170          *            buffer to write the 2 bytes of data into.
 171          * @param offset
 172          *            position within the buffer to begin writing to. This position
 173          *            and the next byte after it (for a total of 2 bytes) will be
 174          *            replaced.
 175          * @param v
 176          *            the value to write.
 177          */
 178         public static void encodeInt16(final byte[] intbuf, final int offset, int v) {
 179                 intbuf[offset + 1] = (byte) v;
 180                 v >>>= 8;
 181
 182                 intbuf[offset] = (byte) v;
 183         }
 184
 185         /**
 186          * Write a 32 bit integer as a sequence of 4 bytes (network byte order).
 187          *
 188          * @param intbuf
 189          *            buffer to write the 4 bytes of data into.
 190          * @param offset
 191          *            position within the buffer to begin writing to. This position
 192          *            and the next 3 bytes after it (for a total of 4 bytes) will be
 193          *            replaced.
 194          * @param v
 195          *            the value to write.
 196          */
 197         public static void encodeInt32(final byte[] intbuf, final int offset, int v) {
 198                 intbuf[offset + 3] = (byte) v;
 199                 v >>>= 8;
 200
 201                 intbuf[offset + 2] = (byte) v;
 202                 v >>>= 8;
 203
 204                 intbuf[offset + 1] = (byte) v;
 205                 v >>>= 8;
 206
 207                 intbuf[offset] = (byte) v;
 208         }
 209
 210         /**
 211          * Write a 64 bit integer as a sequence of 8 bytes (network byte order).
 212          *
 213          * @param intbuf
 214          *            buffer to write the 48bytes of data into.
 215          * @param offset
 216          *            position within the buffer to begin writing to. This position
 217          *            and the next 7 bytes after it (for a total of 8 bytes) will be
 218          *            replaced.
 219          * @param v
 220          *            the value to write.
 221          */
 222         public static void encodeInt64(final byte[] intbuf, final int offset, long v) {
 223                 intbuf[offset + 7] = (byte) v;
 224                 v >>>= 8;
 225
 226                 intbuf[offset + 6] = (byte) v;
 227                 v >>>= 8;
 228
 229                 intbuf[offset + 5] = (byte) v;
 230                 v >>>= 8;
 231
 232                 intbuf[offset + 4] = (byte) v;
 233                 v >>>= 8;
 234
 235                 intbuf[offset + 3] = (byte) v;
 236                 v >>>= 8;
 237
 238                 intbuf[offset + 2] = (byte) v;
 239                 v >>>= 8;
 240
 241                 intbuf[offset + 1] = (byte) v;
 242                 v >>>= 8;
 243
 244                 intbuf[offset] = (byte) v;
 245         }
 246
 247         private NB() {
 248                 // Don't create instances of a static only utility.
 249         }
 250 }