AnyObjectId.java
/*
* Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org> 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.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.nio.ByteBuffer;
import org.eclipse.jgit.util.NB;
import org.eclipse.jgit.util.References;
/**
* A (possibly mutable) SHA-1 abstraction.
* <p>
* If this is an instance of {@link org.eclipse.jgit.lib.MutableObjectId} the
* concept of equality with this instance can alter at any time, if this
* instance is modified to represent a different object name.
*/
public abstract class AnyObjectId implements Comparable<AnyObjectId> {
/**
* Compare two object identifier byte sequences for equality.
*
* @param firstObjectId
* the first identifier to compare. Must not be null.
* @param secondObjectId
* the second identifier to compare. Must not be null.
* @return true if the two identifiers are the same.
* @deprecated use {@link #isEqual(AnyObjectId, AnyObjectId)} instead
*/
@Deprecated
@SuppressWarnings("AmbiguousMethodReference")
public static boolean equals(final AnyObjectId firstObjectId,
final AnyObjectId secondObjectId) {
return isEqual(firstObjectId, secondObjectId);
}
/**
* Compare two object identifier byte sequences for equality.
*
* @param firstObjectId
* the first identifier to compare. Must not be null.
* @param secondObjectId
* the second identifier to compare. Must not be null.
* @return true if the two identifiers are the same.
* @since 5.4
*/
public static boolean isEqual(final AnyObjectId firstObjectId,
final AnyObjectId secondObjectId) {
if (References.isSameObject(firstObjectId, secondObjectId)) {
return true;
}
// We test word 3 first since the git file-based ODB
// uses the first byte of w1, and we use w2 as the
// hash code, one of those probably came up with these
// two instances which we are comparing for equality.
// Therefore the first two words are very likely to be
// identical. We want to break away from collisions as
// quickly as possible.
return firstObjectId.w3 == secondObjectId.w3
&& firstObjectId.w4 == secondObjectId.w4
&& firstObjectId.w5 == secondObjectId.w5
&& firstObjectId.w1 == secondObjectId.w1
&& firstObjectId.w2 == secondObjectId.w2;
}
int w1;
int w2;
int w3;
int w4;
int w5;
/**
* Get the first 8 bits of the ObjectId.
*
* This is a faster version of {@code getByte(0)}.
*
* @return a discriminator usable for a fan-out style map. Returned values
* are unsigned and thus are in the range [0,255] rather than the
* signed byte range of [-128, 127].
*/
public final int getFirstByte() {
return w1 >>> 24;
}
/**
* Get any byte from the ObjectId.
*
* Callers hard-coding {@code getByte(0)} should instead use the much faster
* special case variant {@link #getFirstByte()}.
*
* @param index
* index of the byte to obtain from the raw form of the ObjectId.
* Must be in range [0,
* {@link org.eclipse.jgit.lib.Constants#OBJECT_ID_LENGTH}).
* @return the value of the requested byte at {@code index}. Returned values
* are unsigned and thus are in the range [0,255] rather than the
* signed byte range of [-128, 127].
* @throws java.lang.ArrayIndexOutOfBoundsException
* {@code index} is less than 0, equal to
* {@link org.eclipse.jgit.lib.Constants#OBJECT_ID_LENGTH}, or
* greater than
* {@link org.eclipse.jgit.lib.Constants#OBJECT_ID_LENGTH}.
*/
public final int getByte(int index) {
int w;
switch (index >> 2) {
case 0:
w = w1;
break;
case 1:
w = w2;
break;
case 2:
w = w3;
break;
case 3:
w = w4;
break;
case 4:
w = w5;
break;
default:
throw new ArrayIndexOutOfBoundsException(index);
}
return (w >>> (8 * (3 - (index & 3)))) & 0xff;
}
/**
* {@inheritDoc}
* <p>
* Compare this ObjectId to another and obtain a sort ordering.
*/
@Override
public final int compareTo(AnyObjectId other) {
if (this == other)
return 0;
int cmp;
cmp = NB.compareUInt32(w1, other.w1);
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w2, other.w2);
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w3, other.w3);
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w4, other.w4);
if (cmp != 0)
return cmp;
return NB.compareUInt32(w5, other.w5);
}
/**
* Compare this ObjectId 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 a negative integer, zero, or a positive integer as this object is
* less than, equal to, or greater than the specified object.
*/
public final int compareTo(byte[] bs, int p) {
int cmp;
cmp = NB.compareUInt32(w1, NB.decodeInt32(bs, p));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w2, NB.decodeInt32(bs, p + 4));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w3, NB.decodeInt32(bs, p + 8));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w4, NB.decodeInt32(bs, p + 12));
if (cmp != 0)
return cmp;
return NB.compareUInt32(w5, NB.decodeInt32(bs, p + 16));
}
/**
* Compare this ObjectId 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
* integers, starting at this position are required.
* @return a negative integer, zero, or a positive integer as this object is
* less than, equal to, or greater than the specified object.
*/
public final int compareTo(int[] bs, int p) {
int cmp;
cmp = NB.compareUInt32(w1, bs[p]);
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w2, bs[p + 1]);
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w3, bs[p + 2]);
if (cmp != 0)
return cmp;
cmp = NB.compareUInt32(w4, bs[p + 3]);
if (cmp != 0)
return cmp;
return NB.compareUInt32(w5, bs[p + 4]);
}
/**
* Tests if this ObjectId starts with the given abbreviation.
*
* @param abbr
* the abbreviation.
* @return true if this ObjectId begins with the abbreviation; else false.
*/
public boolean startsWith(AbbreviatedObjectId abbr) {
return abbr.prefixCompare(this) == 0;
}
/** {@inheritDoc} */
@Override
public final int hashCode() {
return w2;
}
/**
* Determine if this ObjectId has exactly the same value as another.
*
* @param other
* the other id to compare to. May be null.
* @return true only if both ObjectIds have identical bits.
*/
@SuppressWarnings({ "NonOverridingEquals", "AmbiguousMethodReference" })
public final boolean equals(AnyObjectId other) {
return other != null ? isEqual(this, other) : false;
}
/** {@inheritDoc} */
@Override
public final boolean equals(Object o) {
if (o instanceof AnyObjectId) {
return equals((AnyObjectId) o);
}
return false;
}
/**
* Copy this ObjectId to an output writer in raw binary.
*
* @param w
* the buffer to copy to. Must be in big endian order.
*/
public void copyRawTo(ByteBuffer w) {
w.putInt(w1);
w.putInt(w2);
w.putInt(w3);
w.putInt(w4);
w.putInt(w5);
}
/**
* Copy this ObjectId to a byte array.
*
* @param b
* the buffer to copy to.
* @param o
* the offset within b to write at.
*/
public void copyRawTo(byte[] b, int o) {
NB.encodeInt32(b, o, w1);
NB.encodeInt32(b, o + 4, w2);
NB.encodeInt32(b, o + 8, w3);
NB.encodeInt32(b, o + 12, w4);
NB.encodeInt32(b, o + 16, w5);
}
/**
* Copy this ObjectId to an int array.
*
* @param b
* the buffer to copy to.
* @param o
* the offset within b to write at.
*/
public void copyRawTo(int[] b, int o) {
b[o] = w1;
b[o + 1] = w2;
b[o + 2] = w3;
b[o + 3] = w4;
b[o + 4] = w5;
}
/**
* Copy this ObjectId to an output writer in raw binary.
*
* @param w
* the stream to write to.
* @throws java.io.IOException
* the stream writing failed.
*/
public void copyRawTo(OutputStream w) throws IOException {
writeRawInt(w, w1);
writeRawInt(w, w2);
writeRawInt(w, w3);
writeRawInt(w, w4);
writeRawInt(w, w5);
}
private static void writeRawInt(OutputStream w, int v)
throws IOException {
w.write(v >>> 24);
w.write(v >>> 16);
w.write(v >>> 8);
w.write(v);
}
/**
* Copy this ObjectId to an output writer in hex format.
*
* @param w
* the stream to copy to.
* @throws java.io.IOException
* the stream writing failed.
*/
public void copyTo(OutputStream w) throws IOException {
w.write(toHexByteArray());
}
/**
* Copy this ObjectId to a byte array in hex format.
*
* @param b
* the buffer to copy to.
* @param o
* the offset within b to write at.
*/
public void copyTo(byte[] b, int o) {
formatHexByte(b, o + 0, w1);
formatHexByte(b, o + 8, w2);
formatHexByte(b, o + 16, w3);
formatHexByte(b, o + 24, w4);
formatHexByte(b, o + 32, w5);
}
/**
* Copy this ObjectId to a ByteBuffer in hex format.
*
* @param b
* the buffer to copy to.
*/
public void copyTo(ByteBuffer b) {
b.put(toHexByteArray());
}
private byte[] toHexByteArray() {
final byte[] dst = new byte[Constants.OBJECT_ID_STRING_LENGTH];
formatHexByte(dst, 0, w1);
formatHexByte(dst, 8, w2);
formatHexByte(dst, 16, w3);
formatHexByte(dst, 24, w4);
formatHexByte(dst, 32, w5);
return dst;
}
private static final byte[] hexbyte = { '0', '1', '2', '3', '4', '5', '6',
'7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
private static void formatHexByte(byte[] dst, int p, int w) {
int o = p + 7;
while (o >= p && w != 0) {
dst[o--] = hexbyte[w & 0xf];
w >>>= 4;
}
while (o >= p)
dst[o--] = '0';
}
/**
* Copy this ObjectId to an output writer in hex format.
*
* @param w
* the stream to copy to.
* @throws java.io.IOException
* the stream writing failed.
*/
public void copyTo(Writer w) throws IOException {
w.write(toHexCharArray());
}
/**
* Copy this ObjectId to an output writer in hex format.
*
* @param tmp
* temporary char array to buffer construct into before writing.
* Must be at least large enough to hold 2 digits for each byte
* of object id (40 characters or larger).
* @param w
* the stream to copy to.
* @throws java.io.IOException
* the stream writing failed.
*/
public void copyTo(char[] tmp, Writer w) throws IOException {
toHexCharArray(tmp);
w.write(tmp, 0, Constants.OBJECT_ID_STRING_LENGTH);
}
/**
* Copy this ObjectId to a StringBuilder in hex format.
*
* @param tmp
* temporary char array to buffer construct into before writing.
* Must be at least large enough to hold 2 digits for each byte
* of object id (40 characters or larger).
* @param w
* the string to append onto.
*/
public void copyTo(char[] tmp, StringBuilder w) {
toHexCharArray(tmp);
w.append(tmp, 0, Constants.OBJECT_ID_STRING_LENGTH);
}
private char[] toHexCharArray() {
final char[] dst = new char[Constants.OBJECT_ID_STRING_LENGTH];
toHexCharArray(dst);
return dst;
}
private void toHexCharArray(char[] dst) {
formatHexChar(dst, 0, w1);
formatHexChar(dst, 8, w2);
formatHexChar(dst, 16, w3);
formatHexChar(dst, 24, w4);
formatHexChar(dst, 32, w5);
}
private static final char[] hexchar = { '0', '1', '2', '3', '4', '5', '6',
'7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
static void formatHexChar(char[] dst, int p, int w) {
int o = p + 7;
while (o >= p && w != 0) {
dst[o--] = hexchar[w & 0xf];
w >>>= 4;
}
while (o >= p)
dst[o--] = '0';
}
/** {@inheritDoc} */
@SuppressWarnings("nls")
@Override
public String toString() {
return "AnyObjectId[" + name() + "]";
}
/**
* <p>name.</p>
*
* @return string form of the SHA-1, in lower case hexadecimal.
*/
public final String name() {
return new String(toHexCharArray());
}
/**
* Get string form of the SHA-1, in lower case hexadecimal.
*
* @return string form of the SHA-1, in lower case hexadecimal.
*/
public final String getName() {
return name();
}
/**
* Return an abbreviation (prefix) of this object SHA-1.
* <p>
* This implementation does not guarantee uniqueness. Callers should instead
* use
* {@link org.eclipse.jgit.lib.ObjectReader#abbreviate(AnyObjectId, int)} to
* obtain a unique abbreviation within the scope of a particular object
* database.
*
* @param len
* length of the abbreviated string.
* @return SHA-1 abbreviation.
*/
public AbbreviatedObjectId abbreviate(int len) {
final int a = AbbreviatedObjectId.mask(len, 1, w1);
final int b = AbbreviatedObjectId.mask(len, 2, w2);
final int c = AbbreviatedObjectId.mask(len, 3, w3);
final int d = AbbreviatedObjectId.mask(len, 4, w4);
final int e = AbbreviatedObjectId.mask(len, 5, w5);
return new AbbreviatedObjectId(len, a, b, c, d, e);
}
/**
* Obtain an immutable copy of this current object name value.
* <p>
* Only returns <code>this</code> if this instance is an unsubclassed
* instance of {@link org.eclipse.jgit.lib.ObjectId}; otherwise a new
* instance is returned holding the same value.
* <p>
* This method is useful to shed any additional memory that may be tied to
* the subclass, yet retain the unique identity of the object id for future
* lookups within maps and repositories.
*
* @return an immutable copy, using the smallest memory footprint possible.
*/
public final ObjectId copy() {
if (getClass() == ObjectId.class)
return (ObjectId) this;
return new ObjectId(this);
}
/**
* Obtain an immutable copy of this current object name value.
* <p>
* See {@link #copy()} if <code>this</code> is a possibly subclassed (but
* immutable) identity and the application needs a lightweight identity
* <i>only</i> reference.
*
* @return an immutable copy. May be <code>this</code> if this is already
* an immutable instance.
*/
public abstract ObjectId toObjectId();
}