AbbreviatedLongObjectId.java
/*
* Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com>
* and other copyright owners as documented in the project's IP log.
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Distribution License v1.0 which
* accompanies this distribution, is reproduced below, and is
* available at http://www.eclipse.org/org/documents/edl-v10.php
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
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* - Neither the name of the Eclipse Foundation, Inc. nor the
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package org.eclipse.jgit.lfs.lib;
import java.io.Serializable;
import java.text.MessageFormat;
import org.eclipse.jgit.lfs.errors.InvalidLongObjectIdException;
import org.eclipse.jgit.lfs.internal.LfsText;
import org.eclipse.jgit.util.NB;
import org.eclipse.jgit.util.RawParseUtils;
/**
* A prefix abbreviation of an {@link org.eclipse.jgit.lfs.lib.LongObjectId}.
* <p>
* Enable abbreviating SHA-256 strings used by Git LFS, using sufficient leading
* digits from the LongObjectId 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.
*
* Ported to SHA-256 from {@link org.eclipse.jgit.lib.AbbreviatedObjectId}
*
* @since 4.3
*/
public final class AbbreviatedLongObjectId 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.LONG_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 AbbreviatedLongObjectId fromString(final byte[] buf,
final int offset, final int end) {
if (end - offset > Constants.LONG_OBJECT_ID_STRING_LENGTH)
throw new IllegalArgumentException(MessageFormat.format(
LfsText.get().invalidLongIdLength,
Integer.valueOf(end - offset),
Integer.valueOf(Constants.LONG_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 AbbreviatedLongObjectId fromLongObjectId(
AnyLongObjectId id) {
return new AbbreviatedLongObjectId(
Constants.LONG_OBJECT_ID_STRING_LENGTH, id.w1, id.w2, id.w3,
id.w4);
}
/**
* Convert an AbbreviatedLongObjectId from hex characters.
*
* @param str
* the string to read from. Must be <= 64 characters.
* @return the converted object id.
*/
public static final AbbreviatedLongObjectId fromString(String str) {
if (str.length() > Constants.LONG_OBJECT_ID_STRING_LENGTH)
throw new IllegalArgumentException(
MessageFormat.format(LfsText.get().invalidLongId, str));
final byte[] b = org.eclipse.jgit.lib.Constants.encodeASCII(str);
return fromHexString(b, 0, b.length);
}
private static final AbbreviatedLongObjectId fromHexString(final byte[] bs,
int ptr, final int end) {
try {
final long a = hexUInt64(bs, ptr, end);
final long b = hexUInt64(bs, ptr + 16, end);
final long c = hexUInt64(bs, ptr + 32, end);
final long d = hexUInt64(bs, ptr + 48, end);
return new AbbreviatedLongObjectId(end - ptr, a, b, c, d);
} catch (ArrayIndexOutOfBoundsException e1) {
throw new InvalidLongObjectIdException(bs, ptr, end - ptr);
}
}
private static final long hexUInt64(final byte[] bs, int p, final int end) {
if (16 <= end - p)
return RawParseUtils.parseHexInt64(bs, p);
long r = 0;
int n = 0;
while (n < 16 && p < end) {
r <<= 4;
r |= RawParseUtils.parseHexInt4(bs[p++]);
n++;
}
return r << ((16 - n) * 4);
}
static long mask(int nibbles, long word, long v) {
final long b = (word - 1) * 16;
if (b + 16 <= 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 long s = 64 - (nibbles - b) * 4;
return (v >>> s) << s;
}
/** Number of half-bytes used by this id. */
final int nibbles;
final long w1;
final long w2;
final long w3;
final long w4;
AbbreviatedLongObjectId(final int n, final long new_1, final long new_2,
final long new_3, final long new_4) {
nibbles = n;
w1 = new_1;
w2 = new_2;
w3 = new_3;
w4 = new_4;
}
/**
* Get length
*
* @return number of hex digits appearing in this id.
*/
public int length() {
return nibbles;
}
/**
* Check if this id is complete
*
* @return true if this ObjectId is actually a complete id.
*/
public boolean isComplete() {
return length() == Constants.LONG_OBJECT_ID_STRING_LENGTH;
}
/**
* Convert to LongObjectId
*
* @return a complete ObjectId; null if {@link #isComplete()} is false.
*/
public LongObjectId toLongObjectId() {
return isComplete() ? new LongObjectId(w1, w2, w3, w4) : 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(AnyLongObjectId other) {
int cmp;
cmp = NB.compareUInt64(w1, mask(1, other.w1));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt64(w2, mask(2, other.w2));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt64(w3, mask(3, other.w3));
if (cmp != 0)
return cmp;
return NB.compareUInt64(w4, mask(4, other.w4));
}
/**
* Compare this abbreviation to a network-byte-order LongObjectId.
*
* @param bs
* array containing the other LongObjectId in network byte order.
* @param p
* position within {@code bs} to start the compare at. At least
* 32 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.compareUInt64(w1, mask(1, NB.decodeInt64(bs, p)));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt64(w2, mask(2, NB.decodeInt64(bs, p + 8)));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt64(w3, mask(3, NB.decodeInt64(bs, p + 16)));
if (cmp != 0)
return cmp;
return NB.compareUInt64(w4, mask(4, NB.decodeInt64(bs, p + 24)));
}
/**
* Compare this abbreviation to a network-byte-order LongObjectId.
*
* @param bs
* array containing the other LongObjectId in network byte order.
* @param p
* position within {@code bs} to start the compare at. At least 4
* longs, 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(long[] bs, int p) {
int cmp;
cmp = NB.compareUInt64(w1, mask(1, bs[p]));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt64(w2, mask(2, bs[p + 1]));
if (cmp != 0)
return cmp;
cmp = NB.compareUInt64(w3, mask(3, bs[p + 2]));
if (cmp != 0)
return cmp;
return NB.compareUInt64(w4, mask(4, bs[p + 3]));
}
/**
* Get the first byte of this id
*
* @return value for a fan-out style map, only valid of length >= 2.
*/
public final int getFirstByte() {
return (int) (w1 >>> 56);
}
private long mask(long word, long v) {
return mask(nibbles, word, v);
}
/** {@inheritDoc} */
@Override
public int hashCode() {
return (int) (w1 >> 32);
}
/** {@inheritDoc} */
@Override
public boolean equals(Object o) {
if (o instanceof AbbreviatedLongObjectId) {
final AbbreviatedLongObjectId b = (AbbreviatedLongObjectId) o;
return nibbles == b.nibbles && w1 == b.w1 && w2 == b.w2
&& w3 == b.w3 && w4 == b.w4;
}
return false;
}
/**
* <p>name.</p>
*
* @return string form of the abbreviation, in lower case hexadecimal.
*/
public final String name() {
final char[] b = new char[Constants.LONG_OBJECT_ID_STRING_LENGTH];
AnyLongObjectId.formatHexChar(b, 0, w1);
if (nibbles <= 16)
return new String(b, 0, nibbles);
AnyLongObjectId.formatHexChar(b, 16, w2);
if (nibbles <= 32)
return new String(b, 0, nibbles);
AnyLongObjectId.formatHexChar(b, 32, w3);
if (nibbles <= 48)
return new String(b, 0, nibbles);
AnyLongObjectId.formatHexChar(b, 48, w4);
return new String(b, 0, nibbles);
}
/** {@inheritDoc} */
@SuppressWarnings("nls")
@Override
public String toString() {
return "AbbreviatedLongObjectId[" + name() + "]"; //$NON-NLS-1$
}
}