org.spearce.jgit/src/org/spearce/jgit/lib/ObjectId.java

   1 /*
   2  *  Copyright (C) 2006  Shawn Pearce <spearce@spearce.org>
   3  *
   4  *  This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU General Public
   6  *  License, version 2, as published by the Free Software Foundation.
   7  *
   8  *  This library is distributed in the hope that it will be useful,
   9  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  *  General Public License for more details.
  12  *
  13  *  You should have received a copy of the GNU General Public
  14  *  License along with this library; if not, write to the Free Software
  15  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
  16  */
  17 package org.spearce.jgit.lib;
  18
  19 import java.io.UnsupportedEncodingException;
  20
  21 import org.spearce.jgit.util.NB;
  22
  23 /**
  24  * A SHA-1 abstraction.
  25  */
  26 public class ObjectId extends AnyObjectId {
  27         private static final ObjectId ZEROID;
  28
  29         private static final String ZEROID_STR;
  30
  31         static {
  32                 ZEROID = new ObjectId(0, 0, 0, 0, 0);
  33                 ZEROID_STR = ZEROID.toString();
  34         }
  35
  36         /**
  37          * Get the special all-null ObjectId.
  38          *
  39          * @return the all-null ObjectId, often used to stand-in for no object.
  40          */
  41         public static final ObjectId zeroId() {
  42                 return ZEROID;
  43         }
  44
  45         /**
  46          * Test a string of characters to verify it is a hex format.
  47          * <p>
  48          * If true the string can be parsed with {@link #fromString(String)}.
  49          *
  50          * @param id
  51          *            the string to test.
  52          * @return true if the string can converted into an ObjectId.
  53          */
  54         public static final boolean isId(final String id) {
  55                 if (id.length() != 2 * Constants.OBJECT_ID_LENGTH)
  56                         return false;
  57                 try {
  58                         for (int k = id.length() - 1; k >= 0; k--)
  59                                 if (fromhex[id.charAt(k)] < 0)
  60                                         return false;
  61                         return true;
  62                 } catch (ArrayIndexOutOfBoundsException e) {
  63                         return false;
  64                 }
  65         }
  66
  67         /**
  68          * Convert an ObjectId into a hex string representation.
  69          *
  70          * @param i
  71          *            the id to convert. May be null.
  72          * @return the hex string conversion of this id's content.
  73          */
  74         public static final String toString(final ObjectId i) {
  75                 return i != null ? i.toString() : ZEROID_STR;
  76         }
  77
  78         /**
  79          * Compare to object identifier byte sequences for equality.
  80          *
  81          * @param firstBuffer
  82          *            the first buffer to compare against. Must have at least 20
  83          *            bytes from position ai through the end of the buffer.
  84          * @param fi
  85          *            first offset within firstBuffer to begin testing.
  86          * @param secondBuffer
  87          *            the second buffer to compare against. Must have at least 2
  88          *            bytes from position bi through the end of the buffer.
  89          * @param si
  90          *            first offset within secondBuffer to begin testing.
  91          * @return true if the two identifiers are the same.
  92          */
  93         public static boolean equals(final byte[] firstBuffer, final int fi,
  94                         final byte[] secondBuffer, final int si) {
  95                 return firstBuffer[fi] == secondBuffer[si]
  96                                 && firstBuffer[fi + 1] == secondBuffer[si + 1]
  97                                 && firstBuffer[fi + 2] == secondBuffer[si + 2]
  98                                 && firstBuffer[fi + 3] == secondBuffer[si + 3]
  99                                 && firstBuffer[fi + 4] == secondBuffer[si + 4]
 100                                 && firstBuffer[fi + 5] == secondBuffer[si + 5]
 101                                 && firstBuffer[fi + 6] == secondBuffer[si + 6]
 102                                 && firstBuffer[fi + 7] == secondBuffer[si + 7]
 103                                 && firstBuffer[fi + 8] == secondBuffer[si + 8]
 104                                 && firstBuffer[fi + 9] == secondBuffer[si + 9]
 105                                 && firstBuffer[fi + 10] == secondBuffer[si + 10]
 106                                 && firstBuffer[fi + 11] == secondBuffer[si + 11]
 107                                 && firstBuffer[fi + 12] == secondBuffer[si + 12]
 108                                 && firstBuffer[fi + 13] == secondBuffer[si + 13]
 109                                 && firstBuffer[fi + 14] == secondBuffer[si + 14]
 110                                 && firstBuffer[fi + 15] == secondBuffer[si + 15]
 111                                 && firstBuffer[fi + 16] == secondBuffer[si + 16]
 112                                 && firstBuffer[fi + 17] == secondBuffer[si + 17]
 113                                 && firstBuffer[fi + 18] == secondBuffer[si + 18]
 114                                 && firstBuffer[fi + 19] == secondBuffer[si + 19];
 115         }
 116
 117         /**
 118          * Convert an ObjectId from raw binary representation.
 119          *
 120          * @param bs
 121          *            the raw byte buffer to read from. At least 20 bytes must be
 122          *            available within this byte array.
 123          * @return the converted object id.
 124          */
 125         public static final ObjectId fromRaw(final byte[] bs) {
 126                 return fromRaw(bs, 0);
 127         }
 128
 129         /**
 130          * Convert an ObjectId from raw binary representation.
 131          *
 132          * @param bs
 133          *            the raw byte buffer to read from. At least 20 bytes after p
 134          *            must be available within this byte array.
 135          * @param p
 136          *            position to read the first byte of data from.
 137          * @return the converted object id.
 138          */
 139         public static final ObjectId fromRaw(final byte[] bs, final int p) {
 140                 final int a = NB.decodeInt32(bs, p);
 141                 final int b = NB.decodeInt32(bs, p + 4);
 142                 final int c = NB.decodeInt32(bs, p + 8);
 143                 final int d = NB.decodeInt32(bs, p + 12);
 144                 final int e = NB.decodeInt32(bs, p + 16);
 145                 return new ObjectId(a, b, c, d, e);
 146         }
 147
 148         /**
 149          * Convert an ObjectId from hex characters (US-ASCII).
 150          *
 151          * @param buf
 152          *            the US-ASCII buffer to read from. At least 40 bytes after
 153          *            offset must be available within this byte array.
 154          * @param offset
 155          *            position to read the first character from.
 156          * @return the converted object id.
 157          */
 158         public static final ObjectId fromString(final byte[] buf, final int offset) {
 159                 return fromHexString(buf, offset);
 160         }
 161
 162         /**
 163          * Convert an ObjectId from hex characters.
 164          *
 165          * @param str
 166          *            the string to read from. Must be 40 characters long.
 167          * @return the converted object id.
 168          */
 169         public static final ObjectId fromString(final String str) {
 170                 if (str.length() != STR_LEN)
 171                         throw new IllegalArgumentException("Invalid id: " + str);
 172                 return fromHexString(Constants.encodeASCII(str), 0);
 173         }
 174
 175         private static final ObjectId fromHexString(final byte[] bs, int p) {
 176                 try {
 177                         final int a = hexUInt32(bs, p);
 178                         final int b = hexUInt32(bs, p + 8);
 179                         final int c = hexUInt32(bs, p + 16);
 180                         final int d = hexUInt32(bs, p + 24);
 181                         final int e = hexUInt32(bs, p + 32);
 182                         return new ObjectId(a, b, c, d, e);
 183                 } catch (ArrayIndexOutOfBoundsException e1) {
 184                         try {
 185                                 final String str = new String(bs, p, STR_LEN, "US-ASCII");
 186                                 throw new IllegalArgumentException("Invalid id: " + str);
 187                         } catch (UnsupportedEncodingException e2) {
 188                                 throw new IllegalArgumentException("Invalid id");
 189                         }
 190                 }
 191         }
 192
 193         protected ObjectId(final int new_1, final int new_2, final int new_3,
 194                         final int new_4, final int new_5) {
 195                 w1 = new_1;
 196                 w2 = new_2;
 197                 w3 = new_3;
 198                 w4 = new_4;
 199                 w5 = new_5;
 200         }
 201
 202         /**
 203          * Initialize this instance by copying another existing ObjectId.
 204          * <p>
 205          * This constructor is mostly useful for subclasses who want to extend an
 206          * ObjectId with more properties, but initialize from an existing ObjectId
 207          * instance acquired by other means.
 208          *
 209          * @param src
 210          *            another already parsed ObjectId to copy the value out of.
 211          */
 212         protected ObjectId(final AnyObjectId src) {
 213                 w1 = src.w1;
 214                 w2 = src.w2;
 215                 w3 = src.w3;
 216                 w4 = src.w4;
 217                 w5 = src.w5;
 218         }
 219
 220         @Override
 221         public ObjectId toObjectId() {
 222                 return this;
 223         }
 224 }