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

   1 /*
   2  * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
   3  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
   4  *
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or
   8  * without modification, are permitted provided that the following
   9  * conditions are met:
  10  *
  11  * - Redistributions of source code must retain the above copyright
  12  *   notice, this list of conditions and the following disclaimer.
  13  *
  14  * - Redistributions in binary form must reproduce the above
  15  *   copyright notice, this list of conditions and the following
  16  *   disclaimer in the documentation and/or other materials provided
  17  *   with the distribution.
  18  *
  19  * - Neither the name of the Git Development Community nor the
  20  *   names of its contributors may be used to endorse or promote
  21  *   products derived from this software without specific prior
  22  *   written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  25  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  26  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  27  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  29  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  30  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  32  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  33  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  34  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  36  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  */
  38
  39 package org.spearce.jgit.lib;
  40
  41 import java.io.UnsupportedEncodingException;
  42
  43 import org.spearce.jgit.util.NB;
  44
  45 /**
  46  * A SHA-1 abstraction.
  47  */
  48 public class ObjectId extends AnyObjectId {
  49         private static final ObjectId ZEROID;
  50
  51         private static final String ZEROID_STR;
  52
  53         static {
  54                 ZEROID = new ObjectId(0, 0, 0, 0, 0);
  55                 ZEROID_STR = ZEROID.toString();
  56         }
  57
  58         /**
  59          * Get the special all-null ObjectId.
  60          *
  61          * @return the all-null ObjectId, often used to stand-in for no object.
  62          */
  63         public static final ObjectId zeroId() {
  64                 return ZEROID;
  65         }
  66
  67         /**
  68          * Test a string of characters to verify it is a hex format.
  69          * <p>
  70          * If true the string can be parsed with {@link #fromString(String)}.
  71          *
  72          * @param id
  73          *            the string to test.
  74          * @return true if the string can converted into an ObjectId.
  75          */
  76         public static final boolean isId(final String id) {
  77                 if (id.length() != 2 * Constants.OBJECT_ID_LENGTH)
  78                         return false;
  79                 try {
  80                         for (int k = id.length() - 1; k >= 0; k--)
  81                                 if (fromhex[id.charAt(k)] < 0)
  82                                         return false;
  83                         return true;
  84                 } catch (ArrayIndexOutOfBoundsException e) {
  85                         return false;
  86                 }
  87         }
  88
  89         /**
  90          * Convert an ObjectId into a hex string representation.
  91          *
  92          * @param i
  93          *            the id to convert. May be null.
  94          * @return the hex string conversion of this id's content.
  95          */
  96         public static final String toString(final ObjectId i) {
  97                 return i != null ? i.toString() : ZEROID_STR;
  98         }
  99
 100         /**
 101          * Compare to object identifier byte sequences for equality.
 102          *
 103          * @param firstBuffer
 104          *            the first buffer to compare against. Must have at least 20
 105          *            bytes from position ai through the end of the buffer.
 106          * @param fi
 107          *            first offset within firstBuffer to begin testing.
 108          * @param secondBuffer
 109          *            the second buffer to compare against. Must have at least 2
 110          *            bytes from position bi through the end of the buffer.
 111          * @param si
 112          *            first offset within secondBuffer to begin testing.
 113          * @return true if the two identifiers are the same.
 114          */
 115         public static boolean equals(final byte[] firstBuffer, final int fi,
 116                         final byte[] secondBuffer, final int si) {
 117                 return firstBuffer[fi] == secondBuffer[si]
 118                                 && firstBuffer[fi + 1] == secondBuffer[si + 1]
 119                                 && firstBuffer[fi + 2] == secondBuffer[si + 2]
 120                                 && firstBuffer[fi + 3] == secondBuffer[si + 3]
 121                                 && firstBuffer[fi + 4] == secondBuffer[si + 4]
 122                                 && firstBuffer[fi + 5] == secondBuffer[si + 5]
 123                                 && firstBuffer[fi + 6] == secondBuffer[si + 6]
 124                                 && firstBuffer[fi + 7] == secondBuffer[si + 7]
 125                                 && firstBuffer[fi + 8] == secondBuffer[si + 8]
 126                                 && firstBuffer[fi + 9] == secondBuffer[si + 9]
 127                                 && firstBuffer[fi + 10] == secondBuffer[si + 10]
 128                                 && firstBuffer[fi + 11] == secondBuffer[si + 11]
 129                                 && firstBuffer[fi + 12] == secondBuffer[si + 12]
 130                                 && firstBuffer[fi + 13] == secondBuffer[si + 13]
 131                                 && firstBuffer[fi + 14] == secondBuffer[si + 14]
 132                                 && firstBuffer[fi + 15] == secondBuffer[si + 15]
 133                                 && firstBuffer[fi + 16] == secondBuffer[si + 16]
 134                                 && firstBuffer[fi + 17] == secondBuffer[si + 17]
 135                                 && firstBuffer[fi + 18] == secondBuffer[si + 18]
 136                                 && firstBuffer[fi + 19] == secondBuffer[si + 19];
 137         }
 138
 139         /**
 140          * Convert an ObjectId from raw binary representation.
 141          *
 142          * @param bs
 143          *            the raw byte buffer to read from. At least 20 bytes must be
 144          *            available within this byte array.
 145          * @return the converted object id.
 146          */
 147         public static final ObjectId fromRaw(final byte[] bs) {
 148                 return fromRaw(bs, 0);
 149         }
 150
 151         /**
 152          * Convert an ObjectId from raw binary representation.
 153          *
 154          * @param bs
 155          *            the raw byte buffer to read from. At least 20 bytes after p
 156          *            must be available within this byte array.
 157          * @param p
 158          *            position to read the first byte of data from.
 159          * @return the converted object id.
 160          */
 161         public static final ObjectId fromRaw(final byte[] bs, final int p) {
 162                 final int a = NB.decodeInt32(bs, p);
 163                 final int b = NB.decodeInt32(bs, p + 4);
 164                 final int c = NB.decodeInt32(bs, p + 8);
 165                 final int d = NB.decodeInt32(bs, p + 12);
 166                 final int e = NB.decodeInt32(bs, p + 16);
 167                 return new ObjectId(a, b, c, d, e);
 168         }
 169
 170         /**
 171          * Convert an ObjectId from hex characters (US-ASCII).
 172          *
 173          * @param buf
 174          *            the US-ASCII buffer to read from. At least 40 bytes after
 175          *            offset must be available within this byte array.
 176          * @param offset
 177          *            position to read the first character from.
 178          * @return the converted object id.
 179          */
 180         public static final ObjectId fromString(final byte[] buf, final int offset) {
 181                 return fromHexString(buf, offset);
 182         }
 183
 184         /**
 185          * Convert an ObjectId from hex characters.
 186          *
 187          * @param str
 188          *            the string to read from. Must be 40 characters long.
 189          * @return the converted object id.
 190          */
 191         public static final ObjectId fromString(final String str) {
 192                 if (str.length() != STR_LEN)
 193                         throw new IllegalArgumentException("Invalid id: " + str);
 194                 return fromHexString(Constants.encodeASCII(str), 0);
 195         }
 196
 197         private static final ObjectId fromHexString(final byte[] bs, int p) {
 198                 try {
 199                         final int a = hexUInt32(bs, p);
 200                         final int b = hexUInt32(bs, p + 8);
 201                         final int c = hexUInt32(bs, p + 16);
 202                         final int d = hexUInt32(bs, p + 24);
 203                         final int e = hexUInt32(bs, p + 32);
 204                         return new ObjectId(a, b, c, d, e);
 205                 } catch (ArrayIndexOutOfBoundsException e1) {
 206                         try {
 207                                 final String str = new String(bs, p, STR_LEN, "US-ASCII");
 208                                 throw new IllegalArgumentException("Invalid id: " + str);
 209                         } catch (UnsupportedEncodingException e2) {
 210                                 throw new IllegalArgumentException("Invalid id");
 211                         }
 212                 }
 213         }
 214
 215         protected ObjectId(final int new_1, final int new_2, final int new_3,
 216                         final int new_4, final int new_5) {
 217                 w1 = new_1;
 218                 w2 = new_2;
 219                 w3 = new_3;
 220                 w4 = new_4;
 221                 w5 = new_5;
 222         }
 223
 224         /**
 225          * Initialize this instance by copying another existing ObjectId.
 226          * <p>
 227          * This constructor is mostly useful for subclasses who want to extend an
 228          * ObjectId with more properties, but initialize from an existing ObjectId
 229          * instance acquired by other means.
 230          *
 231          * @param src
 232          *            another already parsed ObjectId to copy the value out of.
 233          */
 234         protected ObjectId(final AnyObjectId src) {
 235                 w1 = src.w1;
 236                 w2 = src.w2;
 237                 w3 = src.w3;
 238                 w4 = src.w4;
 239                 w5 = src.w5;
 240         }
 241
 242         @Override
 243         public ObjectId toObjectId() {
 244                 return this;
 245         }
 246 }