Java tutorial
/* * Copyright (C) 2008-2009, Google Inc. * 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. * * - Neither the name of the Eclipse Foundation, Inc. nor the * names of its contributors may be used to endorse or promote * products derived from this software without specific prior * written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ 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 e1) { throw new InvalidObjectIdException(bs, ptr, end - ptr); } } 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() + "]"; //$NON-NLS-1$ } }