/*
    * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
    * 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.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.InvalidObjectIdException;
  import org.eclipse.jgit.util.NB;
  import org.eclipse.jgit.util.RawParseUtils;
  
  /**
   * A SHA-1 abstraction.
   */
  public class ObjectId extends AnyObjectId implements Serializable {
  	private static final long serialVersionUID = 1L;
  
  	private static final ObjectId ZEROID;
  
  	private static final String ZEROID_STR;
  
  	static {
  		ZEROID = new ObjectId(0, 0, 0, 0, 0);
  		ZEROID_STR = ZEROID.name();
  	}
  
  	/**
  	 * Get the special all-null ObjectId.
  	 *
  	 * @return the all-null ObjectId, often used to stand-in for no object.
  	 */
  	public static final ObjectId zeroId() {
  		return ZEROID;
  	}
  
  	/**
  	 * 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 ObjectId.
  	 */
  	public static final boolean isId(@Nullable String id) {
  		if (id == null) {
  			return false;
  		}
  		if (id.length() != Constants.OBJECT_ID_STRING_LENGTH)
  			return false;
  		try {
  			for (int i = 0; i < Constants.OBJECT_ID_STRING_LENGTH; i++) {
  				RawParseUtils.parseHexInt4((byte) id.charAt(i));
  			}
  			return true;
  		} catch (ArrayIndexOutOfBoundsException e) {
  			return false;
  		}
  	}
  
  	/**
  	 * Convert an ObjectId into a hex string representation.
  	 *
  	 * @param i
  	 *            the id to convert. May be null.
  	 * @return the hex string conversion of this id's content.
  	 */
  	public static final String toString(ObjectId i) {
  		return i != null ? i.name() : ZEROID_STR;
  	}
  
  	/**
  	 * Compare two object identifier byte sequences for equality.
  	 *
  	 * @param firstBuffer
  	 *            the first buffer to compare against. Must have at least 20
  	 *            bytes from position fi through the end of the buffer.
  	 * @param fi
  	 *            first offset within firstBuffer to begin testing.
  	 * @param secondBuffer
  	 *            the second buffer to compare against. Must have at least 20
  	 *            bytes from position si through the end of the buffer.
  	 * @param si
  	 *            first offset within secondBuffer to begin testing.
  	 * @return true if the two identifiers are the same.
  	 */
  	public static boolean equals(final byte[] firstBuffer, final int fi,
 			final byte[] secondBuffer, final int si) {
 		return firstBuffer[fi] == secondBuffer[si]
 				&& firstBuffer[fi + 1] == secondBuffer[si + 1]
 				&& firstBuffer[fi + 2] == secondBuffer[si + 2]
 				&& firstBuffer[fi + 3] == secondBuffer[si + 3]
 				&& firstBuffer[fi + 4] == secondBuffer[si + 4]
 				&& firstBuffer[fi + 5] == secondBuffer[si + 5]
 				&& firstBuffer[fi + 6] == secondBuffer[si + 6]
 				&& firstBuffer[fi + 7] == secondBuffer[si + 7]
 				&& firstBuffer[fi + 8] == secondBuffer[si + 8]
 				&& firstBuffer[fi + 9] == secondBuffer[si + 9]
 				&& firstBuffer[fi + 10] == secondBuffer[si + 10]
 				&& firstBuffer[fi + 11] == secondBuffer[si + 11]
 				&& firstBuffer[fi + 12] == secondBuffer[si + 12]
 				&& firstBuffer[fi + 13] == secondBuffer[si + 13]
 				&& firstBuffer[fi + 14] == secondBuffer[si + 14]
 				&& firstBuffer[fi + 15] == secondBuffer[si + 15]
 				&& firstBuffer[fi + 16] == secondBuffer[si + 16]
 				&& firstBuffer[fi + 17] == secondBuffer[si + 17]
 				&& firstBuffer[fi + 18] == secondBuffer[si + 18]
 				&& firstBuffer[fi + 19] == secondBuffer[si + 19];
 	}
 
 	/**
 	 * Convert an ObjectId from raw binary representation.
 	 *
 	 * @param bs
 	 *            the raw byte buffer to read from. At least 20 bytes must be
 	 *            available within this byte array.
 	 * @return the converted object id.
 	 */
 	public static final ObjectId fromRaw(byte[] bs) {
 		return fromRaw(bs, 0);
 	}
 
 	/**
 	 * Convert an ObjectId from raw binary representation.
 	 *
 	 * @param bs
 	 *            the raw byte buffer to read from. At least 20 bytes after p
 	 *            must be available within this byte array.
 	 * @param p
 	 *            position to read the first byte of data from.
 	 * @return the converted object id.
 	 */
 	public static final ObjectId fromRaw(byte[] bs, int p) {
 		final int a = NB.decodeInt32(bs, p);
 		final int b = NB.decodeInt32(bs, p + 4);
 		final int c = NB.decodeInt32(bs, p + 8);
 		final int d = NB.decodeInt32(bs, p + 12);
 		final int e = NB.decodeInt32(bs, p + 16);
 		return new ObjectId(a, b, c, d, e);
 	}
 
 	/**
 	 * Convert an ObjectId from raw binary representation.
 	 *
 	 * @param is
 	 *            the raw integers buffer to read from. At least 5 integers must
 	 *            be available within this int array.
 	 * @return the converted object id.
 	 */
 	public static final ObjectId fromRaw(int[] is) {
 		return fromRaw(is, 0);
 	}
 
 	/**
 	 * Convert an ObjectId from raw binary representation.
 	 *
 	 * @param is
 	 *            the raw integers buffer to read from. At least 5 integers
 	 *            after p must be available within this int array.
 	 * @param p
 	 *            position to read the first integer of data from.
 	 * @return the converted object id.
 	 */
 	public static final ObjectId fromRaw(int[] is, int p) {
 		return new ObjectId(is[p], is[p + 1], is[p + 2], is[p + 3], is[p + 4]);
 	}
 
 	/**
 	 * Convert an ObjectId from hex characters (US-ASCII).
 	 *
 	 * @param buf
 	 *            the US-ASCII buffer to read from. At least 40 bytes after
 	 *            offset must be available within this byte array.
 	 * @param offset
 	 *            position to read the first character from.
 	 * @return the converted object id.
 	 */
 	public static final ObjectId fromString(byte[] buf, int offset) {
 		return fromHexString(buf, offset);
 	}
 
 	/**
 	 * Convert an ObjectId from hex characters.
 	 *
 	 * @param str
 	 *            the string to read from. Must be 40 characters long.
 	 * @return the converted object id.
 	 */
 	public static ObjectId fromString(String str) {
 		if (str.length() != Constants.OBJECT_ID_STRING_LENGTH) {
 			throw new InvalidObjectIdException(str);
 		}
 		return fromHexString(Constants.encodeASCII(str), 0);
 	}
 
 	private static final ObjectId fromHexString(byte[] bs, int p) {
 		try {
 			final int a = RawParseUtils.parseHexInt32(bs, p);
 			final int b = RawParseUtils.parseHexInt32(bs, p + 8);
 			final int c = RawParseUtils.parseHexInt32(bs, p + 16);
 			final int d = RawParseUtils.parseHexInt32(bs, p + 24);
 			final int e = RawParseUtils.parseHexInt32(bs, p + 32);
 			return new ObjectId(a, b, c, d, e);
 		} catch (ArrayIndexOutOfBoundsException e) {
 			InvalidObjectIdException e1 = new InvalidObjectIdException(bs, p,
 					Constants.OBJECT_ID_STRING_LENGTH);
 			e1.initCause(e);
 			throw e1;
 		}
 	}
 
 	/**
 	 * Construct an ObjectId from 160 bits provided in 5 words.
 	 *
 	 * @param new_1
 	 *            an int
 	 * @param new_2
 	 *            an int
 	 * @param new_3
 	 *            an int
 	 * @param new_4
 	 *            an int
 	 * @param new_5
 	 *            an int
 	 * @since 4.7
 	 */
 	public ObjectId(int new_1, int new_2, int new_3, int new_4, int new_5) {
 		w1 = new_1;
 		w2 = new_2;
 		w3 = new_3;
 		w4 = new_4;
 		w5 = new_5;
 	}
 
 	/**
 	 * Initialize this instance by copying another existing ObjectId.
 	 * <p>
 	 * This constructor is mostly useful for subclasses who want to extend an
 	 * ObjectId with more properties, but initialize from an existing ObjectId
 	 * instance acquired by other means.
 	 *
 	 * @param src
 	 *            another already parsed ObjectId to copy the value out of.
 	 */
 	protected ObjectId(AnyObjectId src) {
 		w1 = src.w1;
 		w2 = src.w2;
 		w3 = src.w3;
 		w4 = src.w4;
 		w5 = src.w5;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public ObjectId toObjectId() {
 		return this;
 	}
 
 	private void writeObject(ObjectOutputStream os) throws IOException {
 		os.writeInt(w1);
 		os.writeInt(w2);
 		os.writeInt(w3);
 		os.writeInt(w4);
 		os.writeInt(w5);
 	}
 
 	private void readObject(ObjectInputStream ois) throws IOException {
 		w1 = ois.readInt();
 		w2 = ois.readInt();
 		w3 = ois.readInt();
 		w4 = ois.readInt();
 		w5 = ois.readInt();
 	}
 }