AbbreviatedObjectId.java
/*
* Copyright (C) 2008-2009, Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.lib;
import java.io.Serializable;
import java.text.MessageFormat;
import org.eclipse.jgit.errors.InvalidObjectIdException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.util.NB;
import org.eclipse.jgit.util.RawParseUtils;
/**
* A prefix abbreviation of an {@link org.eclipse.jgit.lib.ObjectId}.
* <p>
* Sometimes Git produces abbreviated SHA-1 strings, using sufficient leading
* digits from the ObjectId name to still be unique within the repository the
* string was generated from. These ids are likely to be unique for a useful
* period of time, especially if they contain at least 6-10 hex digits.
* <p>
* This class converts the hex string into a binary form, to make it more
* efficient for matching against an object.
*/
public final class AbbreviatedObjectId implements Serializable {
private static final long serialVersionUID = 1L;
/**
* Test a string of characters to verify it is a hex format.
* <p>
* If true the string can be parsed with {@link #fromString(String)}.
*
* @param id
* the string to test.
* @return true if the string can converted into an AbbreviatedObjectId.
*/
public static final boolean isId(String id) {
if (id.length() < 2 || Constants.OBJECT_ID_STRING_LENGTH < id.length())
return false;
try {
for (int i = 0; i < id.length(); i++)
RawParseUtils.parseHexInt4((byte) id.charAt(i));
return true;
} catch (ArrayIndexOutOfBoundsException e) {
return false;
}
}
/**
* Convert an AbbreviatedObjectId from hex characters (US-ASCII).
*
* @param buf
* the US-ASCII buffer to read from.
* @param offset
* position to read the first character from.
* @param end
* one past the last position to read (<code>end-offset</code> is
* the length of the string).
* @return the converted object id.
*/
public static final AbbreviatedObjectId fromString(final byte[] buf,
final int offset, final int end) {
if (end - offset > Constants.OBJECT_ID_STRING_LENGTH)
throw new IllegalArgumentException(MessageFormat.format(
JGitText.get().invalidIdLength,
Integer.valueOf(end - offset),
Integer.valueOf(Constants.OBJECT_ID_STRING_LENGTH)));
return fromHexString(buf, offset, end);
}
/**
* Convert an AbbreviatedObjectId from an
* {@link org.eclipse.jgit.lib.AnyObjectId}.
* <p>
* This method copies over all bits of the Id, and is therefore complete
* (see {@link #isComplete()}).
*
* @param id
* the {@link org.eclipse.jgit.lib.ObjectId} to convert from.
* @return the converted object id.
*/
public static final AbbreviatedObjectId fromObjectId(AnyObjectId id) {
return new AbbreviatedObjectId(Constants.OBJECT_ID_STRING_LENGTH,
id.w1, id.w2, id.w3, id.w4, id.w5);
}
/**
* Convert an AbbreviatedObjectId from hex characters.
*
* @param str
* the string to read from. Must be <= 40 characters.
* @return the converted object id.
*/
public static final AbbreviatedObjectId fromString(String str) {
if (str.length() > Constants.OBJECT_ID_STRING_LENGTH)
throw new IllegalArgumentException(MessageFormat.format(JGitText.get().invalidId, str));
final byte[] b = Constants.encodeASCII(str);
return fromHexString(b, 0, b.length);
}
private static final AbbreviatedObjectId fromHexString(final byte[] bs,
int ptr, final int end) {
try {
final int a = hexUInt32(bs, ptr, end);
final int b = hexUInt32(bs, ptr + 8, end);
final int c = hexUInt32(bs, ptr + 16, end);
final int d = hexUInt32(bs, ptr + 24, end);
final int e = hexUInt32(bs, ptr + 32, end);
return new AbbreviatedObjectId(end - ptr, a, b, c, d, e);
} catch (ArrayIndexOutOfBoundsException e) {
InvalidObjectIdException e1 = new InvalidObjectIdException(bs, ptr,
end - ptr);
e1.initCause(e);
throw e1;
}
}
private static final int hexUInt32(final byte[] bs, int p, final int end) {
if (8 <= end - p)
return RawParseUtils.parseHexInt32(bs, p);
int r = 0, n = 0;
while (n < 8 && p < end) {
r <<= 4;
r |= RawParseUtils.parseHexInt4(bs[p++]);
n++;
}
return r << ((8 - n) * 4);
}
static int mask(int nibbles, int word, int v) {
final int b = (word - 1) * 8;
if (b + 8 <= nibbles) {
// We have all of the bits required for this word.
//
return v;
}
if (nibbles <= b) {
// We have none of the bits required for this word.
//
return 0;
}
final int s = 32 - (nibbles - b) * 4;
return (v >>> s) << s;
}
/** Number of half-bytes used by this id. */
final int nibbles;
final int w1;
final int w2;
final int w3;
final int w4;
final int w5;
AbbreviatedObjectId(final int n, final int new_1, final int new_2,
final int new_3, final int new_4, final int new_5) {
nibbles = n;
w1 = new_1;
w2 = new_2;
w3 = new_3;
w4 = new_4;
w5 = new_5;
}
/**
* Get number of hex digits appearing in this id.
*
* @return number of hex digits appearing in this id.
*/
public int length() {
return nibbles;
}
/**
* Whether this ObjectId is actually a complete id.
*
* @return true if this ObjectId is actually a complete id.
*/
public boolean isComplete() {
return length() == Constants.OBJECT_ID_STRING_LENGTH;
}
/**
* A complete ObjectId; null if {@link #isComplete()} is false
*
* @return a complete ObjectId; null if {@link #isComplete()} is false
*/
public ObjectId toObjectId() {
return isComplete() ? new ObjectId(w1, w2, w3, w4, w5) : null;
}
/**
* Compares this abbreviation to a full object id.
*
* @param other
* the other object id.
* @return <0 if this abbreviation names an object that is less than
* <code>other</code>; 0 if this abbreviation exactly matches the
* first {@link #length()} digits of <code>other.name()</code>;
* >0 if this abbreviation names an object that is after
* <code>other</code>.
*/
public final int prefixCompare(AnyObjectId other) {
int cmp;
cmp = NB.compareUInt32(w1, mask(1, other.w1));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w2, mask(2, other.w2));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w3, mask(3, other.w3));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w4, mask(4, other.w4));
if (cmp != 0)
return cmp;
return NB.compareUInt32(w5, mask(5, other.w5));
}
/**
* Compare this abbreviation to a network-byte-order ObjectId.
*
* @param bs
* array containing the other ObjectId in network byte order.
* @param p
* position within {@code bs} to start the compare at. At least
* 20 bytes, starting at this position are required.
* @return <0 if this abbreviation names an object that is less than
* <code>other</code>; 0 if this abbreviation exactly matches the
* first {@link #length()} digits of <code>other.name()</code>;
* >0 if this abbreviation names an object that is after
* <code>other</code>.
*/
public final int prefixCompare(byte[] bs, int p) {
int cmp;
cmp = NB.compareUInt32(w1, mask(1, NB.decodeInt32(bs, p)));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w2, mask(2, NB.decodeInt32(bs, p + 4)));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w3, mask(3, NB.decodeInt32(bs, p + 8)));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w4, mask(4, NB.decodeInt32(bs, p + 12)));
if (cmp != 0)
return cmp;
return NB.compareUInt32(w5, mask(5, NB.decodeInt32(bs, p + 16)));
}
/**
* Compare this abbreviation to a network-byte-order ObjectId.
*
* @param bs
* array containing the other ObjectId in network byte order.
* @param p
* position within {@code bs} to start the compare at. At least 5
* ints, starting at this position are required.
* @return <0 if this abbreviation names an object that is less than
* <code>other</code>; 0 if this abbreviation exactly matches the
* first {@link #length()} digits of <code>other.name()</code>;
* >0 if this abbreviation names an object that is after
* <code>other</code>.
*/
public final int prefixCompare(int[] bs, int p) {
int cmp;
cmp = NB.compareUInt32(w1, mask(1, bs[p]));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w2, mask(2, bs[p + 1]));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w3, mask(3, bs[p + 2]));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w4, mask(4, bs[p + 3]));
if (cmp != 0)
return cmp;
return NB.compareUInt32(w5, mask(5, bs[p + 4]));
}
/**
* Get value for a fan-out style map, only valid of length >= 2.
*
* @return value for a fan-out style map, only valid of length >= 2.
*/
public final int getFirstByte() {
return w1 >>> 24;
}
private int mask(int word, int v) {
return mask(nibbles, word, v);
}
/** {@inheritDoc} */
@Override
public int hashCode() {
return w1;
}
/** {@inheritDoc} */
@Override
public boolean equals(Object o) {
if (o instanceof AbbreviatedObjectId) {
final AbbreviatedObjectId b = (AbbreviatedObjectId) o;
return nibbles == b.nibbles && w1 == b.w1 && w2 == b.w2
&& w3 == b.w3 && w4 == b.w4 && w5 == b.w5;
}
return false;
}
/**
* Get string form of the abbreviation, in lower case hexadecimal.
*
* @return string form of the abbreviation, in lower case hexadecimal.
*/
public final String name() {
final char[] b = new char[Constants.OBJECT_ID_STRING_LENGTH];
AnyObjectId.formatHexChar(b, 0, w1);
if (nibbles <= 8)
return new String(b, 0, nibbles);
AnyObjectId.formatHexChar(b, 8, w2);
if (nibbles <= 16)
return new String(b, 0, nibbles);
AnyObjectId.formatHexChar(b, 16, w3);
if (nibbles <= 24)
return new String(b, 0, nibbles);
AnyObjectId.formatHexChar(b, 24, w4);
if (nibbles <= 32)
return new String(b, 0, nibbles);
AnyObjectId.formatHexChar(b, 32, w5);
return new String(b, 0, nibbles);
}
/** {@inheritDoc} */
@SuppressWarnings("nls")
@Override
public String toString() {
return "AbbreviatedObjectId[" + name() + "]"; //$NON-NLS-1$
}
}