/*
    * Copyright (C) 2008-2009, Google Inc.
    * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org>
    * 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.util;
  
  import static java.nio.charset.StandardCharsets.ISO_8859_1;
  import static java.nio.charset.StandardCharsets.UTF_8;
  import static org.eclipse.jgit.lib.ObjectChecker.author;
  import static org.eclipse.jgit.lib.ObjectChecker.committer;
  import static org.eclipse.jgit.lib.ObjectChecker.encoding;
  import static org.eclipse.jgit.lib.ObjectChecker.tagger;
  
  import java.nio.ByteBuffer;
  import java.nio.charset.CharacterCodingException;
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetDecoder;
  import java.nio.charset.CodingErrorAction;
  import java.nio.charset.IllegalCharsetNameException;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.PersonIdent;
  
  /**
   * Handy utility functions to parse raw object contents.
   */
  public final class RawParseUtils {
  	/**
  	 * UTF-8 charset constant.
  	 *
  	 * @since 2.2
  	 */
  	public static final Charset UTF8_CHARSET = UTF_8;
  
  	private static final byte[] digits10;
  
  	private static final byte[] digits16;
  
  	private static final byte[] footerLineKeyChars;
  
  	private static final Map<String, Charset> encodingAliases;
  
  	static {
  		encodingAliases = new HashMap<>();
  		encodingAliases.put("latin-1", ISO_8859_1); //$NON-NLS-1$
  		encodingAliases.put("iso-latin-1", ISO_8859_1); //$NON-NLS-1$
  
  		digits10 = new byte['9' + 1];
  		Arrays.fill(digits10, (byte) -1);
  		for (char i = '0'; i <= '9'; i++)
  			digits10[i] = (byte) (i - '0');
  
  		digits16 = new byte['f' + 1];
  		Arrays.fill(digits16, (byte) -1);
 		for (char i = '0'; i <= '9'; i++)
 			digits16[i] = (byte) (i - '0');
 		for (char i = 'a'; i <= 'f'; i++)
 			digits16[i] = (byte) ((i - 'a') + 10);
 		for (char i = 'A'; i <= 'F'; i++)
 			digits16[i] = (byte) ((i - 'A') + 10);
 
 		footerLineKeyChars = new byte['z' + 1];
 		footerLineKeyChars['-'] = 1;
 		for (char i = '0'; i <= '9'; i++)
 			footerLineKeyChars[i] = 1;
 		for (char i = 'A'; i <= 'Z'; i++)
 			footerLineKeyChars[i] = 1;
 		for (char i = 'a'; i <= 'z'; i++)
 			footerLineKeyChars[i] = 1;
 	}
 
 	/**
 	 * Determine if b[ptr] matches src.
 	 *
 	 * @param b
 	 *            the buffer to scan.
 	 * @param ptr
 	 *            first position within b, this should match src[0].
 	 * @param src
 	 *            the buffer to test for equality with b.
 	 * @return ptr + src.length if b[ptr..src.length] == src; else -1.
 	 */
 	public static final int match(final byte[] b, int ptr, final byte[] src) {
 		if (ptr + src.length > b.length)
 			return -1;
 		for (int i = 0; i < src.length; i++, ptr++)
 			if (b[ptr] != src[i])
 				return -1;
 		return ptr;
 	}
 
 	private static final byte[] base10byte = { '0', '1', '2', '3', '4', '5',
 			'6', '7', '8', '9' };
 
 	/**
 	 * Format a base 10 numeric into a temporary buffer.
 	 * <p>
 	 * Formatting is performed backwards. The method starts at offset
 	 * <code>o-1</code> and ends at <code>o-1-digits</code>, where
 	 * <code>digits</code> is the number of positions necessary to store the
 	 * base 10 value.
 	 * <p>
 	 * The argument and return values from this method make it easy to chain
 	 * writing, for example:
 	 * </p>
 	 *
 	 * <pre>
 	 * final byte[] tmp = new byte[64];
 	 * int ptr = tmp.length;
 	 * tmp[--ptr] = '\n';
 	 * ptr = RawParseUtils.formatBase10(tmp, ptr, 32);
 	 * tmp[--ptr] = ' ';
 	 * ptr = RawParseUtils.formatBase10(tmp, ptr, 18);
 	 * tmp[--ptr] = 0;
 	 * final String str = new String(tmp, ptr, tmp.length - ptr);
 	 * </pre>
 	 *
 	 * @param b
 	 *            buffer to write into.
 	 * @param o
 	 *            one offset past the location where writing will begin; writing
 	 *            proceeds towards lower index values.
 	 * @param value
 	 *            the value to store.
 	 * @return the new offset value <code>o</code>. This is the position of
 	 *         the last byte written. Additional writing should start at one
 	 *         position earlier.
 	 */
 	public static int formatBase10(final byte[] b, int o, int value) {
 		if (value == 0) {
 			b[--o] = '0';
 			return o;
 		}
 		final boolean isneg = value < 0;
 		if (isneg)
 			value = -value;
 		while (value != 0) {
 			b[--o] = base10byte[value % 10];
 			value /= 10;
 		}
 		if (isneg)
 			b[--o] = '-';
 		return o;
 	}
 
 	/**
 	 * Parse a base 10 numeric from a sequence of ASCII digits into an int.
 	 * <p>
 	 * Digit sequences can begin with an optional run of spaces before the
 	 * sequence, and may start with a '+' or a '-' to indicate sign position.
 	 * Any other characters will cause the method to stop and return the current
 	 * result to the caller.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start parsing digits at.
 	 * @param ptrResult
 	 *            optional location to return the new ptr value through. If null
 	 *            the ptr value will be discarded.
 	 * @return the value at this location; 0 if the location is not a valid
 	 *         numeric.
 	 */
 	public static final int parseBase10(final byte[] b, int ptr,
 			final MutableInteger ptrResult) {
 		int r = 0;
 		int sign = 0;
 		try {
 			final int sz = b.length;
 			while (ptr < sz && b[ptr] == ' ')
 				ptr++;
 			if (ptr >= sz)
 				return 0;
 
 			switch (b[ptr]) {
 			case '-':
 				sign = -1;
 				ptr++;
 				break;
 			case '+':
 				ptr++;
 				break;
 			}
 
 			while (ptr < sz) {
 				final byte v = digits10[b[ptr]];
 				if (v < 0)
 					break;
 				r = (r * 10) + v;
 				ptr++;
 			}
 		} catch (ArrayIndexOutOfBoundsException e) {
 			// Not a valid digit.
 		}
 		if (ptrResult != null)
 			ptrResult.value = ptr;
 		return sign < 0 ? -r : r;
 	}
 
 	/**
 	 * Parse a base 10 numeric from a sequence of ASCII digits into a long.
 	 * <p>
 	 * Digit sequences can begin with an optional run of spaces before the
 	 * sequence, and may start with a '+' or a '-' to indicate sign position.
 	 * Any other characters will cause the method to stop and return the current
 	 * result to the caller.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start parsing digits at.
 	 * @param ptrResult
 	 *            optional location to return the new ptr value through. If null
 	 *            the ptr value will be discarded.
 	 * @return the value at this location; 0 if the location is not a valid
 	 *         numeric.
 	 */
 	public static final long parseLongBase10(final byte[] b, int ptr,
 			final MutableInteger ptrResult) {
 		long r = 0;
 		int sign = 0;
 		try {
 			final int sz = b.length;
 			while (ptr < sz && b[ptr] == ' ')
 				ptr++;
 			if (ptr >= sz)
 				return 0;
 
 			switch (b[ptr]) {
 			case '-':
 				sign = -1;
 				ptr++;
 				break;
 			case '+':
 				ptr++;
 				break;
 			}
 
 			while (ptr < sz) {
 				final byte v = digits10[b[ptr]];
 				if (v < 0)
 					break;
 				r = (r * 10) + v;
 				ptr++;
 			}
 		} catch (ArrayIndexOutOfBoundsException e) {
 			// Not a valid digit.
 		}
 		if (ptrResult != null)
 			ptrResult.value = ptr;
 		return sign < 0 ? -r : r;
 	}
 
 	/**
 	 * Parse 4 character base 16 (hex) formatted string to unsigned integer.
 	 * <p>
 	 * The number is read in network byte order, that is, most significant
 	 * nybble first.
 	 *
 	 * @param bs
 	 *            buffer to parse digits from; positions {@code [p, p+4)} will
 	 *            be parsed.
 	 * @param p
 	 *            first position within the buffer to parse.
 	 * @return the integer value.
 	 * @throws java.lang.ArrayIndexOutOfBoundsException
 	 *             if the string is not hex formatted.
 	 */
 	public static final int parseHexInt16(final byte[] bs, final int p) {
 		int r = digits16[bs[p]] << 4;
 
 		r |= digits16[bs[p + 1]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 2]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 3]];
 		if (r < 0)
 			throw new ArrayIndexOutOfBoundsException();
 		return r;
 	}
 
 	/**
 	 * Parse 8 character base 16 (hex) formatted string to unsigned integer.
 	 * <p>
 	 * The number is read in network byte order, that is, most significant
 	 * nybble first.
 	 *
 	 * @param bs
 	 *            buffer to parse digits from; positions {@code [p, p+8)} will
 	 *            be parsed.
 	 * @param p
 	 *            first position within the buffer to parse.
 	 * @return the integer value.
 	 * @throws java.lang.ArrayIndexOutOfBoundsException
 	 *             if the string is not hex formatted.
 	 */
 	public static final int parseHexInt32(final byte[] bs, final int p) {
 		int r = digits16[bs[p]] << 4;
 
 		r |= digits16[bs[p + 1]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 2]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 3]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 4]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 5]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 6]];
 
 		final int last = digits16[bs[p + 7]];
 		if (r < 0 || last < 0)
 			throw new ArrayIndexOutOfBoundsException();
 		return (r << 4) | last;
 	}
 
 	/**
 	 * Parse 16 character base 16 (hex) formatted string to unsigned long.
 	 * <p>
 	 * The number is read in network byte order, that is, most significant
 	 * nibble first.
 	 *
 	 * @param bs
 	 *            buffer to parse digits from; positions {@code [p, p+16)} will
 	 *            be parsed.
 	 * @param p
 	 *            first position within the buffer to parse.
 	 * @return the integer value.
 	 * @throws java.lang.ArrayIndexOutOfBoundsException
 	 *             if the string is not hex formatted.
 	 * @since 4.3
 	 */
 	public static final long parseHexInt64(final byte[] bs, final int p) {
 		long r = digits16[bs[p]] << 4;
 
 		r |= digits16[bs[p + 1]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 2]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 3]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 4]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 5]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 6]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 7]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 8]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 9]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 10]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 11]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 12]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 13]];
 		r <<= 4;
 
 		r |= digits16[bs[p + 14]];
 
 		final int last = digits16[bs[p + 15]];
 		if (r < 0 || last < 0)
 			throw new ArrayIndexOutOfBoundsException();
 		return (r << 4) | last;
 	}
 
 	/**
 	 * Parse a single hex digit to its numeric value (0-15).
 	 *
 	 * @param digit
 	 *            hex character to parse.
 	 * @return numeric value, in the range 0-15.
 	 * @throws java.lang.ArrayIndexOutOfBoundsException
 	 *             if the input digit is not a valid hex digit.
 	 */
 	public static final int parseHexInt4(final byte digit) {
 		final byte r = digits16[digit];
 		if (r < 0)
 			throw new ArrayIndexOutOfBoundsException();
 		return r;
 	}
 
 	/**
 	 * Parse a Git style timezone string.
 	 * <p>
 	 * The sequence "-0315" will be parsed as the numeric value -195, as the
 	 * lower two positions count minutes, not 100ths of an hour.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start parsing digits at.
 	 * @return the timezone at this location, expressed in minutes.
 	 */
 	public static final int parseTimeZoneOffset(final byte[] b, int ptr) {
 		return parseTimeZoneOffset(b, ptr, null);
 	}
 
 	/**
 	 * Parse a Git style timezone string.
 	 * <p>
 	 * The sequence "-0315" will be parsed as the numeric value -195, as the
 	 * lower two positions count minutes, not 100ths of an hour.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start parsing digits at.
 	 * @param ptrResult
 	 *            optional location to return the new ptr value through. If null
 	 *            the ptr value will be discarded.
 	 * @return the timezone at this location, expressed in minutes.
 	 * @since 4.1
 	 */
 	public static final int parseTimeZoneOffset(final byte[] b, int ptr,
 			MutableInteger ptrResult) {
 		final int v = parseBase10(b, ptr, ptrResult);
 		final int tzMins = v % 100;
 		final int tzHours = v / 100;
 		return tzHours * 60 + tzMins;
 	}
 
 	/**
 	 * Locate the first position after a given character.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start looking for chrA at.
 	 * @param chrA
 	 *            character to find.
 	 * @return new position just after chrA.
 	 */
 	public static final int next(final byte[] b, int ptr, final char chrA) {
 		final int sz = b.length;
 		while (ptr < sz) {
 			if (b[ptr++] == chrA)
 				return ptr;
 		}
 		return ptr;
 	}
 
 	/**
 	 * Locate the first position after the next LF.
 	 * <p>
 	 * This method stops on the first '\n' it finds.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start looking for LF at.
 	 * @return new position just after the first LF found.
 	 */
 	public static final int nextLF(final byte[] b, int ptr) {
 		return next(b, ptr, '\n');
 	}
 
 	/**
 	 * Locate the first position after either the given character or LF.
 	 * <p>
 	 * This method stops on the first match it finds from either chrA or '\n'.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start looking for chrA or LF at.
 	 * @param chrA
 	 *            character to find.
 	 * @return new position just after the first chrA or LF to be found.
 	 */
 	public static final int nextLF(final byte[] b, int ptr, final char chrA) {
 		final int sz = b.length;
 		while (ptr < sz) {
 			final byte c = b[ptr++];
 			if (c == chrA || c == '\n')
 				return ptr;
 		}
 		return ptr;
 	}
 
 	/**
 	 * Locate the first position before a given character.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start looking for chrA at.
 	 * @param chrA
 	 *            character to find.
 	 * @return new position just before chrA, -1 for not found
 	 */
 	public static final int prev(final byte[] b, int ptr, final char chrA) {
 		if (ptr == b.length)
 			--ptr;
 		while (ptr >= 0) {
 			if (b[ptr--] == chrA)
 				return ptr;
 		}
 		return ptr;
 	}
 
 	/**
 	 * Locate the first position before the previous LF.
 	 * <p>
 	 * This method stops on the first '\n' it finds.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start looking for LF at.
 	 * @return new position just before the first LF found, -1 for not found
 	 */
 	public static final int prevLF(final byte[] b, int ptr) {
 		return prev(b, ptr, '\n');
 	}
 
 	/**
 	 * Locate the previous position before either the given character or LF.
 	 * <p>
 	 * This method stops on the first match it finds from either chrA or '\n'.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within buffer to start looking for chrA or LF at.
 	 * @param chrA
 	 *            character to find.
 	 * @return new position just before the first chrA or LF to be found, -1 for
 	 *         not found
 	 */
 	public static final int prevLF(final byte[] b, int ptr, final char chrA) {
 		if (ptr == b.length)
 			--ptr;
 		while (ptr >= 0) {
 			final byte c = b[ptr--];
 			if (c == chrA || c == '\n')
 				return ptr;
 		}
 		return ptr;
 	}
 
 	/**
 	 * Index the region between <code>[ptr, end)</code> to find line starts.
 	 * <p>
 	 * The returned list is 1 indexed. Index 0 contains
 	 * {@link java.lang.Integer#MIN_VALUE} to pad the list out.
 	 * <p>
 	 * Using a 1 indexed list means that line numbers can be directly accessed
 	 * from the list, so <code>list.get(1)</code> (aka get line 1) returns
 	 * <code>ptr</code>.
 	 * <p>
 	 * The last element (index <code>map.size()-1</code>) always contains
 	 * <code>end</code>.
 	 * <p>
 	 * If the data contains a '\0' anywhere, the whole region is considered
 	 * binary and a LineMap corresponding to a single line is returned.
 	 * </p>
 	 *
 	 * @param buf
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position within the buffer corresponding to the first byte of
 	 *            line 1.
 	 * @param end
 	 *            1 past the end of the content within <code>buf</code>.
 	 * @return a line map indexing the start position of each line.
 	 */
 	public static final IntList lineMap(final byte[] buf, int ptr, int end) {
 		int start = ptr;
 
 		// Experimentally derived from multiple source repositories
 		// the average number of bytes/line is 36. Its a rough guess
 		// to initially size our map close to the target.
 		IntList map = new IntList((end - ptr) / 36);
 		map.add(Integer.MIN_VALUE);
 		boolean foundLF = true;
 		for (; ptr < end; ptr++) {
 			if (foundLF) {
 				map.add(ptr);
 			}
 
 			if (buf[ptr] == '\0') {
 				// binary data.
 				map = new IntList(3);
 				map.add(Integer.MIN_VALUE);
 				map.add(start);
 				break;
 			}
 
 			foundLF = (buf[ptr] == '\n');
 		}
 		map.add(end);
 		return map;
 	}
 
 	/**
 	 * Locate the "author " header line data.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position in buffer to start the scan at. Most callers should
 	 *            pass 0 to ensure the scan starts from the beginning of the
 	 *            commit buffer and does not accidentally look at message body.
 	 * @return position just after the space in "author ", so the first
 	 *         character of the author's name. If no author header can be
 	 *         located -1 is returned.
 	 */
 	public static final int author(final byte[] b, int ptr) {
 		final int sz = b.length;
 		if (ptr == 0)
 			ptr += 46; // skip the "tree ..." line.
 		while (ptr < sz && b[ptr] == 'p')
 			ptr += 48; // skip this parent.
 		return match(b, ptr, author);
 	}
 
 	/**
 	 * Locate the "committer " header line data.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position in buffer to start the scan at. Most callers should
 	 *            pass 0 to ensure the scan starts from the beginning of the
 	 *            commit buffer and does not accidentally look at message body.
 	 * @return position just after the space in "committer ", so the first
 	 *         character of the committer's name. If no committer header can be
 	 *         located -1 is returned.
 	 */
 	public static final int committer(final byte[] b, int ptr) {
 		final int sz = b.length;
 		if (ptr == 0)
 			ptr += 46; // skip the "tree ..." line.
 		while (ptr < sz && b[ptr] == 'p')
 			ptr += 48; // skip this parent.
 		if (ptr < sz && b[ptr] == 'a')
 			ptr = nextLF(b, ptr);
 		return match(b, ptr, committer);
 	}
 
 	/**
 	 * Locate the "tagger " header line data.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position in buffer to start the scan at. Most callers should
 	 *            pass 0 to ensure the scan starts from the beginning of the tag
 	 *            buffer and does not accidentally look at message body.
 	 * @return position just after the space in "tagger ", so the first
 	 *         character of the tagger's name. If no tagger header can be
 	 *         located -1 is returned.
 	 */
 	public static final int tagger(final byte[] b, int ptr) {
 		final int sz = b.length;
 		if (ptr == 0)
 			ptr += 48; // skip the "object ..." line.
 		while (ptr < sz) {
 			if (b[ptr] == '\n')
 				return -1;
 			final int m = match(b, ptr, tagger);
 			if (m >= 0)
 				return m;
 			ptr = nextLF(b, ptr);
 		}
 		return -1;
 	}
 
 	/**
 	 * Locate the "encoding " header line.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position in buffer to start the scan at. Most callers should
 	 *            pass 0 to ensure the scan starts from the beginning of the
 	 *            buffer and does not accidentally look at the message body.
 	 * @return position just after the space in "encoding ", so the first
 	 *         character of the encoding's name. If no encoding header can be
 	 *         located -1 is returned (and UTF-8 should be assumed).
 	 */
 	public static final int encoding(final byte[] b, int ptr) {
 		final int sz = b.length;
 		while (ptr < sz) {
 			if (b[ptr] == '\n')
 				return -1;
 			if (b[ptr] == 'e')
 				break;
 			ptr = nextLF(b, ptr);
 		}
 		return match(b, ptr, encoding);
 	}
 
 	/**
 	 * Parse the "encoding " header as a string.
 	 * <p>
 	 * Locates the "encoding " header (if present) and returns its value.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @return the encoding header as specified in the commit; null if the
 	 *         header was not present and should be assumed.
 	 * @since 4.2
 	 */
 	@Nullable
 	public static String parseEncodingName(final byte[] b) {
 		int enc = encoding(b, 0);
 		if (enc < 0) {
 			return null;
 		}
 		int lf = nextLF(b, enc);
 		return decode(UTF_8, b, enc, lf - 1);
 	}
 
 	/**
 	 * Parse the "encoding " header into a character set reference.
 	 * <p>
 	 * Locates the "encoding " header (if present) by first calling
 	 * {@link #encoding(byte[], int)} and then returns the proper character set
 	 * to apply to this buffer to evaluate its contents as character data.
 	 * <p>
 	 * If no encoding header is present {@code UTF-8} is assumed.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @return the Java character set representation. Never null.
 	 * @throws IllegalCharsetNameException
 	 *             if the character set requested by the encoding header is
 	 *             malformed and unsupportable.
 	 * @throws UnsupportedCharsetException
 	 *             if the JRE does not support the character set requested by
 	 *             the encoding header.
 	 */
 	public static Charset parseEncoding(final byte[] b) {
 		String enc = parseEncodingName(b);
 		if (enc == null) {
 			return UTF_8;
 		}
 
 		String name = enc.trim();
 		try {
 			return Charset.forName(name);
 		} catch (IllegalCharsetNameException
 				| UnsupportedCharsetException badName) {
 			Charset aliased = charsetForAlias(name);
 			if (aliased != null) {
 				return aliased;
 			}
 			throw badName;
 		}
 	}
 
 	/**
 	 * Parse a name string (e.g. author, committer, tagger) into a PersonIdent.
 	 * <p>
 	 * Leading spaces won't be trimmed from the string, i.e. will show up in the
 	 * parsed name afterwards.
 	 *
 	 * @param in
 	 *            the string to parse a name from.
 	 * @return the parsed identity or null in case the identity could not be
 	 *         parsed.
 	 */
 	public static PersonIdent parsePersonIdent(final String in) {
 		return parsePersonIdent(Constants.encode(in), 0);
 	}
 
 	/**
 	 * Parse a name line (e.g. author, committer, tagger) into a PersonIdent.
 	 * <p>
 	 * When passing in a value for <code>nameB</code> callers should use the
 	 * return value of {@link #author(byte[], int)} or
 	 * {@link #committer(byte[], int)}, as these methods provide the proper
 	 * position within the buffer.
 	 *
 	 * @param raw
 	 *            the buffer to parse character data from.
 	 * @param nameB
 	 *            first position of the identity information. This should be the
 	 *            first position after the space which delimits the header field
 	 *            name (e.g. "author" or "committer") from the rest of the
 	 *            identity line.
 	 * @return the parsed identity or null in case the identity could not be
 	 *         parsed.
 	 */
 	public static PersonIdent parsePersonIdent(final byte[] raw, final int nameB) {
 		Charset cs;
 		try {
 			cs = parseEncoding(raw);
 		} catch (IllegalCharsetNameException | UnsupportedCharsetException e) {
 			// Assume UTF-8 for person identities, usually this is correct.
 			// If not decode() will fall back to the ISO-8859-1 encoding.
 			cs = UTF_8;
 		}
 
 		final int emailB = nextLF(raw, nameB, '<');
 		final int emailE = nextLF(raw, emailB, '>');
 		if (emailB >= raw.length || raw[emailB] == '\n' ||
 				(emailE >= raw.length - 1 && raw[emailE - 1] != '>'))
 			return null;
 
 		final int nameEnd = emailB - 2 >= nameB && raw[emailB - 2] == ' ' ?
 				emailB - 2 : emailB - 1;
 		final String name = decode(cs, raw, nameB, nameEnd);
 		final String email = decode(cs, raw, emailB, emailE - 1);
 
 		// Start searching from end of line, as after first name-email pair,
 		// another name-email pair may occur. We will ignore all kinds of
 		// "junk" following the first email.
 		//
 		// We've to use (emailE - 1) for the case that raw[email] is LF,
 		// otherwise we would run too far. "-2" is necessary to position
 		// before the LF in case of LF termination resp. the penultimate
 		// character if there is no trailing LF.
 		final int tzBegin = lastIndexOfTrim(raw, ' ',
 				nextLF(raw, emailE - 1) - 2) + 1;
 		if (tzBegin <= emailE) // No time/zone, still valid
 			return new PersonIdent(name, email, 0, 0);
 
 		final int whenBegin = Math.max(emailE,
 				lastIndexOfTrim(raw, ' ', tzBegin - 1) + 1);
 		if (whenBegin >= tzBegin - 1) // No time/zone, still valid
 			return new PersonIdent(name, email, 0, 0);
 
 		final long when = parseLongBase10(raw, whenBegin, null);
 		final int tz = parseTimeZoneOffset(raw, tzBegin);
 		return new PersonIdent(name, email, when * 1000L, tz);
 	}
 
 	/**
 	 * Parse a name data (e.g. as within a reflog) into a PersonIdent.
 	 * <p>
 	 * When passing in a value for <code>nameB</code> callers should use the
 	 * return value of {@link #author(byte[], int)} or
 	 * {@link #committer(byte[], int)}, as these methods provide the proper
 	 * position within the buffer.
 	 *
 	 * @param raw
 	 *            the buffer to parse character data from.
 	 * @param nameB
 	 *            first position of the identity information. This should be the
 	 *            first position after the space which delimits the header field
 	 *            name (e.g. "author" or "committer") from the rest of the
 	 *            identity line.
 	 * @return the parsed identity. Never null.
 	 */
 	public static PersonIdent parsePersonIdentOnly(final byte[] raw,
 			final int nameB) {
 		int stop = nextLF(raw, nameB);
 		int emailB = nextLF(raw, nameB, '<');
 		int emailE = nextLF(raw, emailB, '>');
 		final String name;
 		final String email;
 		if (emailE < stop) {
 			email = decode(raw, emailB, emailE - 1);
 		} else {
 			email = "invalid"; //$NON-NLS-1$
 		}
 		if (emailB < stop)
 			name = decode(raw, nameB, emailB - 2);
 		else
 			name = decode(raw, nameB, stop);
 
 		final MutableInteger ptrout = new MutableInteger();
 		long when;
 		int tz;
 		if (emailE < stop) {
 			when = parseLongBase10(raw, emailE + 1, ptrout);
 			tz = parseTimeZoneOffset(raw, ptrout.value);
 		} else {
 			when = 0;
 			tz = 0;
 		}
 		return new PersonIdent(name, email, when * 1000L, tz);
 	}
 
 	/**
 	 * Locate the end of a footer line key string.
 	 * <p>
 	 * If the region at {@code raw[ptr]} matches {@code ^[A-Za-z0-9-]+:} (e.g.
 	 * "Signed-off-by: A. U. Thor\n") then this method returns the position of
 	 * the first ':'.
 	 * <p>
 	 * If the region at {@code raw[ptr]} does not match {@code ^[A-Za-z0-9-]+:}
 	 * then this method returns -1.
 	 *
 	 * @param raw
 	 *            buffer to scan.
 	 * @param ptr
 	 *            first position within raw to consider as a footer line key.
 	 * @return position of the ':' which terminates the footer line key if this
 	 *         is otherwise a valid footer line key; otherwise -1.
 	 */
 	public static int endOfFooterLineKey(final byte[] raw, int ptr) {
 		try {
 			for (;;) {
 				final byte c = raw[ptr];
 				if (footerLineKeyChars[c] == 0) {
 					if (c == ':')
 						return ptr;
 					return -1;
 				}
 				ptr++;
 			}
 		} catch (ArrayIndexOutOfBoundsException e) {
 			return -1;
 		}
 	}
 
 	/**
 	 * Decode a buffer under UTF-8, if possible.
 	 *
 	 * If the byte stream cannot be decoded that way, the platform default is tried
 	 * and if that too fails, the fail-safe ISO-8859-1 encoding is tried.
 	 *
 	 * @param buffer
 	 *            buffer to pull raw bytes from.
 	 * @return a string representation of the range <code>[start,end)</code>,
 	 *         after decoding the region through the specified character set.
 	 */
 	public static String decode(final byte[] buffer) {
 		return decode(buffer, 0, buffer.length);
 	}
 
 	/**
 	 * Decode a buffer under UTF-8, if possible.
 	 *
 	 * If the byte stream cannot be decoded that way, the platform default is
 	 * tried and if that too fails, the fail-safe ISO-8859-1 encoding is tried.
 	 *
 	 * @param buffer
 	 *            buffer to pull raw bytes from.
 	 * @param start
 	 *            start position in buffer
 	 * @param end
 	 *            one position past the last location within the buffer to take
 	 *            data from.
 	 * @return a string representation of the range <code>[start,end)</code>,
 	 *         after decoding the region through the specified character set.
 	 */
 	public static String decode(final byte[] buffer, final int start,
 			final int end) {
 		return decode(UTF_8, buffer, start, end);
 	}
 
 	/**
 	 * Decode a buffer under the specified character set if possible.
 	 *
 	 * If the byte stream cannot be decoded that way, the platform default is tried
 	 * and if that too fails, the fail-safe ISO-8859-1 encoding is tried.
 	 *
 	 * @param cs
 	 *            character set to use when decoding the buffer.
 	 * @param buffer
 	 *            buffer to pull raw bytes from.
 	 * @return a string representation of the range <code>[start,end)</code>,
 	 *         after decoding the region through the specified character set.
 	 */
 	public static String decode(final Charset cs, final byte[] buffer) {
 		return decode(cs, buffer, 0, buffer.length);
 	}
 
 	/**
 	 * Decode a region of the buffer under the specified character set if possible.
 	 *
 	 * If the byte stream cannot be decoded that way, the platform default is tried
 	 * and if that too fails, the fail-safe ISO-8859-1 encoding is tried.
 	 *
 	 * @param cs
 	 *            character set to use when decoding the buffer.
 	 * @param buffer
 	 *            buffer to pull raw bytes from.
 	 * @param start
 	 *            first position within the buffer to take data from.
 	 * @param end
 	 *            one position past the last location within the buffer to take
 	 *            data from.
 	 * @return a string representation of the range <code>[start,end)</code>,
 	 *         after decoding the region through the specified character set.
 	 */
 	public static String decode(final Charset cs, final byte[] buffer,
 			final int start, final int end) {
 		try {
 			return decodeNoFallback(cs, buffer, start, end);
 		} catch (CharacterCodingException e) {
 			// Fall back to an ISO-8859-1 style encoding. At least all of
 			// the bytes will be present in the output.
 			//
 			return extractBinaryString(buffer, start, end);
 		}
 	}
 
 	/**
 	 * Decode a region of the buffer under the specified character set if
 	 * possible.
 	 *
 	 * If the byte stream cannot be decoded that way, the platform default is
 	 * tried and if that too fails, an exception is thrown.
 	 *
 	 * @param cs
 	 *            character set to use when decoding the buffer.
 	 * @param buffer
 	 *            buffer to pull raw bytes from.
 	 * @param start
 	 *            first position within the buffer to take data from.
 	 * @param end
 	 *            one position past the last location within the buffer to take
 	 *            data from.
 	 * @return a string representation of the range <code>[start,end)</code>,
 	 *         after decoding the region through the specified character set.
 	 * @throws java.nio.charset.CharacterCodingException
 	 *             the input is not in any of the tested character sets.
 	 */
 	public static String decodeNoFallback(final Charset cs,
 			final byte[] buffer, final int start, final int end)
 			throws CharacterCodingException {
 		ByteBuffer b = ByteBuffer.wrap(buffer, start, end - start);
 		b.mark();
 
 		// Try our built-in favorite. The assumption here is that
 		// decoding will fail if the data is not actually encoded
 		// using that encoder.
 		try {
 			return decode(b, UTF_8);
 		} catch (CharacterCodingException e) {
 			b.reset();
 		}
 
 		if (!cs.equals(UTF_8)) {
 			// Try the suggested encoding, it might be right since it was
 			// provided by the caller.
 			try {
 				return decode(b, cs);
 			} catch (CharacterCodingException e) {
 				b.reset();
 			}
 		}
 
 		// Try the default character set. A small group of people
 		// might actually use the same (or very similar) locale.
 		Charset defcs = Charset.defaultCharset();
 		if (!defcs.equals(cs) && !defcs.equals(UTF_8)) {
 			try {
 				return decode(b, defcs);
 			} catch (CharacterCodingException e) {
 				b.reset();
 			}
 		}
 
 		throw new CharacterCodingException();
 	}
 
 	/**
 	 * Decode a region of the buffer under the ISO-8859-1 encoding.
 	 *
 	 * Each byte is treated as a single character in the 8859-1 character
 	 * encoding, performing a raw binary-&gt;char conversion.
 	 *
 	 * @param buffer
 	 *            buffer to pull raw bytes from.
 	 * @param start
 	 *            first position within the buffer to take data from.
 	 * @param end
 	 *            one position past the last location within the buffer to take
 	 *            data from.
 	 * @return a string representation of the range <code>[start,end)</code>.
 	 */
 	public static String extractBinaryString(final byte[] buffer,
 			final int start, final int end) {
 		final StringBuilder r = new StringBuilder(end - start);
 		for (int i = start; i < end; i++)
 			r.append((char) (buffer[i] & 0xff));
 		return r.toString();
 	}
 
 	private static String decode(final ByteBuffer b, final Charset charset)
 			throws CharacterCodingException {
 		final CharsetDecoder d = charset.newDecoder();
 		d.onMalformedInput(CodingErrorAction.REPORT);
 		d.onUnmappableCharacter(CodingErrorAction.REPORT);
 		return d.decode(b).toString();
 	}
 
 	/**
 	 * Locate the position of the commit message body.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position in buffer to start the scan at. Most callers should
 	 *            pass 0 to ensure the scan starts from the beginning of the
 	 *            commit buffer.
 	 * @return position of the user's message buffer.
 	 */
 	public static final int commitMessage(final byte[] b, int ptr) {
 		final int sz = b.length;
 		if (ptr == 0)
 			ptr += 46; // skip the "tree ..." line.
 		while (ptr < sz && b[ptr] == 'p')
 			ptr += 48; // skip this parent.
 
 		// Skip any remaining header lines, ignoring what their actual
 		// header line type is. This is identical to the logic for a tag.
 		//
 		return tagMessage(b, ptr);
 	}
 
 	/**
 	 * Locate the position of the tag message body.
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param ptr
 	 *            position in buffer to start the scan at. Most callers should
 	 *            pass 0 to ensure the scan starts from the beginning of the tag
 	 *            buffer.
 	 * @return position of the user's message buffer.
 	 */
 	public static final int tagMessage(final byte[] b, int ptr) {
 		final int sz = b.length;
 		if (ptr == 0)
 			ptr += 48; // skip the "object ..." line.
 		while (ptr < sz && b[ptr] != '\n')
 			ptr = nextLF(b, ptr);
 		if (ptr < sz && b[ptr] == '\n')
 			return ptr + 1;
 		return -1;
 	}
 
 	/**
 	 * Locate the end of a paragraph.
 	 * <p>
 	 * A paragraph is ended by two consecutive LF bytes or CRLF pairs
 	 *
 	 * @param b
 	 *            buffer to scan.
 	 * @param start
 	 *            position in buffer to start the scan at. Most callers will
 	 *            want to pass the first position of the commit message (as
 	 *            found by {@link #commitMessage(byte[], int)}.
 	 * @return position of the LF at the end of the paragraph;
 	 *         <code>b.length</code> if no paragraph end could be located.
 	 */
 	public static final int endOfParagraph(final byte[] b, final int start) {
 		int ptr = start;
 		final int sz = b.length;
 		while (ptr < sz && (b[ptr] != '\n' && b[ptr] != '\r'))
 			ptr = nextLF(b, ptr);
 		if (ptr > start && b[ptr - 1] == '\n')
 			ptr--;
 		if (ptr > start && b[ptr - 1] == '\r')
 			ptr--;
 		return ptr;
 	}
 
 	/**
 	 * Get last index of {@code ch} in raw, trimming spaces.
 	 *
 	 * @param raw
 	 *            buffer to scan.
 	 * @param ch
 	 *            character to find.
 	 * @param pos
 	 *            starting position.
 	 * @return last index of {@code ch} in raw, trimming spaces.
 	 * @since 4.1
 	 */
 	public static int lastIndexOfTrim(byte[] raw, char ch, int pos) {
 		while (pos >= 0 && raw[pos] == ' ')
 			pos--;
 
 		while (pos >= 0 && raw[pos] != ch)
 			pos--;
 
 		return pos;
 	}
 
 	private static Charset charsetForAlias(String name) {
 		return encodingAliases.get(StringUtils.toLowerCase(name));
 	}
 
 	private RawParseUtils() {
 		// Don't create instances of a static only utility.
 	}
 }