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	/*
	* Copyright (c) 2012, 2020, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.util;

	import java.io.FilterOutputStream;
	import java.io.InputStream;
	import java.io.IOException;
	import java.io.OutputStream;
	import java.nio.ByteBuffer;

	import sun.nio.cs.ISO_8859_1;

	import jdk.internal.vm.annotation.IntrinsicCandidate;

	/**
	* This class consists exclusively of static methods for obtaining
	* encoders and decoders for the Base64 encoding scheme. The
	* implementation of this class supports the following types of Base64
	* as specified in
	* <a href="http://www.ietf.org/rfc/rfc4648.txt">RFC 4648</a> and
	* <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>.
	*
	* <ul>
	* <li><a id="basic"><b>Basic</b></a>
	* <p> Uses "The Base64 Alphabet" as specified in Table 1 of
	* RFC 4648 and RFC 2045 for encoding and decoding operation.
	* The encoder does not add any line feed (line separator)
	* character. The decoder rejects data that contains characters
	* outside the base64 alphabet.</p></li>
	*
	* <li><a id="url"><b>URL and Filename safe</b></a>
	* <p> Uses the "URL and Filename safe Base64 Alphabet" as specified
	* in Table 2 of RFC 4648 for encoding and decoding. The
	* encoder does not add any line feed (line separator) character.
	* The decoder rejects data that contains characters outside the
	* base64 alphabet.</p></li>
	*
	* <li><a id="mime"><b>MIME</b></a>
	* <p> Uses "The Base64 Alphabet" as specified in Table 1 of
	* RFC 2045 for encoding and decoding operation. The encoded output
	* must be represented in lines of no more than 76 characters each
	* and uses a carriage return {@code '\r'} followed immediately by
	* a linefeed {@code '\n'} as the line separator. No line separator
	* is added to the end of the encoded output. All line separators
	* or other characters not found in the base64 alphabet table are
	* ignored in decoding operation.</p></li>
	* </ul>
	*
	* <p> Unless otherwise noted, passing a {@code null} argument to a
	* method of this class will cause a {@link java.lang.NullPointerException
	* NullPointerException} to be thrown.
	*
	* @author Xueming Shen
	* @since 1.8
	*/

	public class Base64 {

	private Base64() {}

	/**
	* Returns a {@link Encoder} that encodes using the
	* <a href="#basic">Basic</a> type base64 encoding scheme.
	*
	* @return A Base64 encoder.
	*/
	public static Encoder getEncoder() {
	return Encoder.RFC4648;
	}

	/**
	* Returns a {@link Encoder} that encodes using the
	* <a href="#url">URL and Filename safe</a> type base64
	* encoding scheme.
	*
	* @return A Base64 encoder.
	*/
	public static Encoder getUrlEncoder() {
	return Encoder.RFC4648_URLSAFE;
	}

	/**
	* Returns a {@link Encoder} that encodes using the
	* <a href="#mime">MIME</a> type base64 encoding scheme.
	*
	* @return A Base64 encoder.
	*/
	public static Encoder getMimeEncoder() {
	return Encoder.RFC2045;
	}

	/**
	* Returns a {@link Encoder} that encodes using the
	* <a href="#mime">MIME</a> type base64 encoding scheme
	* with specified line length and line separators.
	*
	* @param lineLength
	* the length of each output line (rounded down to nearest multiple
	* of 4). If the rounded down line length is not a positive value,
	* the output will not be separated in lines
	* @param lineSeparator
	* the line separator for each output line
	*
	* @return A Base64 encoder.
	*
	* @throws IllegalArgumentException if {@code lineSeparator} includes any
	* character of "The Base64 Alphabet" as specified in Table 1 of
	* RFC 2045.
	*/
	public static Encoder getMimeEncoder(int lineLength, byte[] lineSeparator) {
	Objects.requireNonNull(lineSeparator);
	int[] base64 = Decoder.fromBase64;
	for (byte b : lineSeparator) {
	if (base64[b & 0xff] != -1)
	throw new IllegalArgumentException(
	"Illegal base64 line separator character 0x" + Integer.toString(b, 16));
	}
	// round down to nearest multiple of 4
	lineLength &= ~0b11;
	if (lineLength <= 0) {
	return Encoder.RFC4648;
	}
	return new Encoder(false, lineSeparator, lineLength, true);
	}

	/**
	* Returns a {@link Decoder} that decodes using the
	* <a href="#basic">Basic</a> type base64 encoding scheme.
	*
	* @return A Base64 decoder.
	*/
	public static Decoder getDecoder() {
	return Decoder.RFC4648;
	}

	/**
	* Returns a {@link Decoder} that decodes using the
	* <a href="#url">URL and Filename safe</a> type base64
	* encoding scheme.
	*
	* @return A Base64 decoder.
	*/
	public static Decoder getUrlDecoder() {
	return Decoder.RFC4648_URLSAFE;
	}

	/**
	* Returns a {@link Decoder} that decodes using the
	* <a href="#mime">MIME</a> type base64 decoding scheme.
	*
	* @return A Base64 decoder.
	*/
	public static Decoder getMimeDecoder() {
	return Decoder.RFC2045;
	}

	/**
	* This class implements an encoder for encoding byte data using
	* the Base64 encoding scheme as specified in RFC 4648 and RFC 2045.
	*
	* <p> Instances of {@link Encoder} class are safe for use by
	* multiple concurrent threads.
	*
	* <p> Unless otherwise noted, passing a {@code null} argument to
	* a method of this class will cause a
	* {@link java.lang.NullPointerException NullPointerException} to
	* be thrown.
	* <p> If the encoded byte output of the needed size can not
	* be allocated, the encode methods of this class will
	* cause an {@link java.lang.OutOfMemoryError OutOfMemoryError}
	* to be thrown.
	*
	* @see Decoder
	* @since 1.8
	*/
	public static class Encoder {

	private final byte[] newline;
	private final int linemax;
	private final boolean isURL;
	private final boolean doPadding;

	private Encoder(boolean isURL, byte[] newline, int linemax, boolean doPadding) {
	this.isURL = isURL;
	this.newline = newline;
	this.linemax = linemax;
	this.doPadding = doPadding;
	}

	/**
	* This array is a lookup table that translates 6-bit positive integer
	* index values into their "Base64 Alphabet" equivalents as specified
	* in "Table 1: The Base64 Alphabet" of RFC 2045 (and RFC 4648).
	*/
	private static final char[] toBase64 = {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
	'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
	'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
	'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
	};

	/**
	* It's the lookup table for "URL and Filename safe Base64" as specified
	* in Table 2 of the RFC 4648, with the '+' and '/' changed to '-' and
	* '_'. This table is used when BASE64_URL is specified.
	*/
	private static final char[] toBase64URL = {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
	'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
	'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
	'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_'
	};

	private static final int MIMELINEMAX = 76;
	private static final byte[] CRLF = new byte[] {'\r', '\n'};

	static final Encoder RFC4648 = new Encoder(false, null, -1, true);
	static final Encoder RFC4648_URLSAFE = new Encoder(true, null, -1, true);
	static final Encoder RFC2045 = new Encoder(false, CRLF, MIMELINEMAX, true);

	/**
	* Calculates the length of the encoded output bytes.
	*
	* @param srclen length of the bytes to encode
	* @param throwOOME if true, throws OutOfMemoryError if the length of
	* the encoded bytes overflows; else returns the
	* length
	* @return length of the encoded bytes, or -1 if the length overflows
	*
	*/
	private final int encodedOutLength(int srclen, boolean throwOOME) {
	int len = 0;
	try {
	if (doPadding) {
	len = Math.multiplyExact(4, (Math.addExact(srclen, 2) / 3));
	} else {
	int n = srclen % 3;
	len = Math.addExact(Math.multiplyExact(4, (srclen / 3)), (n == 0 ? 0 : n + 1));
	}
	if (linemax > 0) { // line separators
	len = Math.addExact(len, (len - 1) / linemax * newline.length);
	}
	} catch (ArithmeticException ex) {
	if (throwOOME) {
	throw new OutOfMemoryError("Encoded size is too large");
	} else {
	// let the caller know that encoded bytes length
	// is too large
	len = -1;
	}
	}
	return len;
	}

	/**
	* Encodes all bytes from the specified byte array into a newly-allocated
	* byte array using the {@link Base64} encoding scheme. The returned byte
	* array is of the length of the resulting bytes.
	*
	* @param src
	* the byte array to encode
	* @return A newly-allocated byte array containing the resulting
	* encoded bytes.
	*/
	public byte[] encode(byte[] src) {
	int len = encodedOutLength(src.length, true); // dst array size
	byte[] dst = new byte[len];
	int ret = encode0(src, 0, src.length, dst);
	if (ret != dst.length)
	return Arrays.copyOf(dst, ret);
	return dst;
	}

	/**
	* Encodes all bytes from the specified byte array using the
	* {@link Base64} encoding scheme, writing the resulting bytes to the
	* given output byte array, starting at offset 0.
	*
	* <p> It is the responsibility of the invoker of this method to make
	* sure the output byte array {@code dst} has enough space for encoding
	* all bytes from the input byte array. No bytes will be written to the
	* output byte array if the output byte array is not big enough.
	*
	* @param src
	* the byte array to encode
	* @param dst
	* the output byte array
	* @return The number of bytes written to the output byte array
	*
	* @throws IllegalArgumentException if {@code dst} does not have enough
	* space for encoding all input bytes.
	*/
	public int encode(byte[] src, byte[] dst) {
	int len = encodedOutLength(src.length, false); // dst array size
	if (dst.length < len \|\| len == -1)
	throw new IllegalArgumentException(
	"Output byte array is too small for encoding all input bytes");
	return encode0(src, 0, src.length, dst);
	}

	/**
	* Encodes the specified byte array into a String using the {@link Base64}
	* encoding scheme.
	*
	* <p> This method first encodes all input bytes into a base64 encoded
	* byte array and then constructs a new String by using the encoded byte
	* array and the {@link java.nio.charset.StandardCharsets#ISO_8859_1
	* ISO-8859-1} charset.
	*
	* <p> In other words, an invocation of this method has exactly the same
	* effect as invoking
	* {@code new String(encode(src), StandardCharsets.ISO_8859_1)}.
	*
	* @param src
	* the byte array to encode
	* @return A String containing the resulting Base64 encoded characters
	*/
	@SuppressWarnings("deprecation")
	public String encodeToString(byte[] src) {
	byte[] encoded = encode(src);
	return new String(encoded, 0, 0, encoded.length);
	}

	/**
	* Encodes all remaining bytes from the specified byte buffer into
	* a newly-allocated ByteBuffer using the {@link Base64} encoding
	* scheme.
	*
	* Upon return, the source buffer's position will be updated to
	* its limit; its limit will not have been changed. The returned
	* output buffer's position will be zero and its limit will be the
	* number of resulting encoded bytes.
	*
	* @param buffer
	* the source ByteBuffer to encode
	* @return A newly-allocated byte buffer containing the encoded bytes.
	*/
	public ByteBuffer encode(ByteBuffer buffer) {
	int len = encodedOutLength(buffer.remaining(), true);
	byte[] dst = new byte[len];
	int ret = 0;
	if (buffer.hasArray()) {
	ret = encode0(buffer.array(),
	buffer.arrayOffset() + buffer.position(),
	buffer.arrayOffset() + buffer.limit(),
	dst);
	buffer.position(buffer.limit());
	} else {
	byte[] src = new byte[buffer.remaining()];
	buffer.get(src);
	ret = encode0(src, 0, src.length, dst);
	}
	if (ret != dst.length)
	dst = Arrays.copyOf(dst, ret);
	return ByteBuffer.wrap(dst);
	}

	/**
	* Wraps an output stream for encoding byte data using the {@link Base64}
	* encoding scheme.
	*
	* <p> It is recommended to promptly close the returned output stream after
	* use, during which it will flush all possible leftover bytes to the underlying
	* output stream. Closing the returned output stream will close the underlying
	* output stream.
	*
	* @param os
	* the output stream.
	* @return the output stream for encoding the byte data into the
	* specified Base64 encoded format
	*/
	public OutputStream wrap(OutputStream os) {
	Objects.requireNonNull(os);
	return new EncOutputStream(os, isURL ? toBase64URL : toBase64,
	newline, linemax, doPadding);
	}

	/**
	* Returns an encoder instance that encodes equivalently to this one,
	* but without adding any padding character at the end of the encoded
	* byte data.
	*
	* <p> The encoding scheme of this encoder instance is unaffected by
	* this invocation. The returned encoder instance should be used for
	* non-padding encoding operation.
	*
	* @return an equivalent encoder that encodes without adding any
	* padding character at the end
	*/
	public Encoder withoutPadding() {
	if (!doPadding)
	return this;
	return new Encoder(isURL, newline, linemax, false);
	}

	@IntrinsicCandidate
	private void encodeBlock(byte[] src, int sp, int sl, byte[] dst, int dp, boolean isURL) {
	char[] base64 = isURL ? toBase64URL : toBase64;
	for (int sp0 = sp, dp0 = dp ; sp0 < sl; ) {
	int bits = (src[sp0++] & 0xff) << 16 \|
	(src[sp0++] & 0xff) << 8 \|
	(src[sp0++] & 0xff);
	dst[dp0++] = (byte)base64[(bits >>> 18) & 0x3f];
	dst[dp0++] = (byte)base64[(bits >>> 12) & 0x3f];
	dst[dp0++] = (byte)base64[(bits >>> 6) & 0x3f];
	dst[dp0++] = (byte)base64[bits & 0x3f];
	}
	}

	private int encode0(byte[] src, int off, int end, byte[] dst) {
	char[] base64 = isURL ? toBase64URL : toBase64;
	int sp = off;
	int slen = (end - off) / 3 * 3;
	int sl = off + slen;
	if (linemax > 0 && slen > linemax / 4 * 3)
	slen = linemax / 4 * 3;
	int dp = 0;
	while (sp < sl) {
	int sl0 = Math.min(sp + slen, sl);
	encodeBlock(src, sp, sl0, dst, dp, isURL);
	int dlen = (sl0 - sp) / 3 * 4;
	dp += dlen;
	sp = sl0;
	if (dlen == linemax && sp < end) {
	for (byte b : newline){
	dst[dp++] = b;
	}
	}
	}
	if (sp < end) { // 1 or 2 leftover bytes
	int b0 = src[sp++] & 0xff;
	dst[dp++] = (byte)base64[b0 >> 2];
	if (sp == end) {
	dst[dp++] = (byte)base64[(b0 << 4) & 0x3f];
	if (doPadding) {
	dst[dp++] = '=';
	dst[dp++] = '=';
	}
	} else {
	int b1 = src[sp++] & 0xff;
	dst[dp++] = (byte)base64[(b0 << 4) & 0x3f \| (b1 >> 4)];
	dst[dp++] = (byte)base64[(b1 << 2) & 0x3f];
	if (doPadding) {
	dst[dp++] = '=';
	}
	}
	}
	return dp;
	}
	}

	/**
	* This class implements a decoder for decoding byte data using the
	* Base64 encoding scheme as specified in RFC 4648 and RFC 2045.
	*
	* <p> The Base64 padding character {@code '='} is accepted and
	* interpreted as the end of the encoded byte data, but is not
	* required. So if the final unit of the encoded byte data only has
	* two or three Base64 characters (without the corresponding padding
	* character(s) padded), they are decoded as if followed by padding
	* character(s). If there is a padding character present in the
	* final unit, the correct number of padding character(s) must be
	* present, otherwise {@code IllegalArgumentException} (
	* {@code IOException} when reading from a Base64 stream) is thrown
	* during decoding.
	*
	* <p> Instances of {@link Decoder} class are safe for use by
	* multiple concurrent threads.
	*
	* <p> Unless otherwise noted, passing a {@code null} argument to
	* a method of this class will cause a
	* {@link java.lang.NullPointerException NullPointerException} to
	* be thrown.
	* <p> If the decoded byte output of the needed size can not
	* be allocated, the decode methods of this class will
	* cause an {@link java.lang.OutOfMemoryError OutOfMemoryError}
	* to be thrown.
	*
	* @see Encoder
	* @since 1.8
	*/
	public static class Decoder {

	private final boolean isURL;
	private final boolean isMIME;

	private Decoder(boolean isURL, boolean isMIME) {
	this.isURL = isURL;
	this.isMIME = isMIME;
	}

	/**
	* Lookup table for decoding unicode characters drawn from the
	* "Base64 Alphabet" (as specified in Table 1 of RFC 2045) into
	* their 6-bit positive integer equivalents. Characters that
	* are not in the Base64 alphabet but fall within the bounds of
	* the array are encoded to -1.
	*
	*/
	private static final int[] fromBase64 = new int[256];
	static {
	Arrays.fill(fromBase64, -1);
	for (int i = 0; i < Encoder.toBase64.length; i++)
	fromBase64[Encoder.toBase64[i]] = i;
	fromBase64['='] = -2;
	}

	/**
	* Lookup table for decoding "URL and Filename safe Base64 Alphabet"
	* as specified in Table2 of the RFC 4648.
	*/
	private static final int[] fromBase64URL = new int[256];

	static {
	Arrays.fill(fromBase64URL, -1);
	for (int i = 0; i < Encoder.toBase64URL.length; i++)
	fromBase64URL[Encoder.toBase64URL[i]] = i;
	fromBase64URL['='] = -2;
	}

	static final Decoder RFC4648 = new Decoder(false, false);
	static final Decoder RFC4648_URLSAFE = new Decoder(true, false);
	static final Decoder RFC2045 = new Decoder(false, true);

	/**
	* Decodes all bytes from the input byte array using the {@link Base64}
	* encoding scheme, writing the results into a newly-allocated output
	* byte array. The returned byte array is of the length of the resulting
	* bytes.
	*
	* @param src
	* the byte array to decode
	*
	* @return A newly-allocated byte array containing the decoded bytes.
	*
	* @throws IllegalArgumentException
	* if {@code src} is not in valid Base64 scheme
	*/
	public byte[] decode(byte[] src) {
	byte[] dst = new byte[decodedOutLength(src, 0, src.length)];
	int ret = decode0(src, 0, src.length, dst);
	if (ret != dst.length) {
	dst = Arrays.copyOf(dst, ret);
	}
	return dst;
	}

	/**
	* Decodes a Base64 encoded String into a newly-allocated byte array
	* using the {@link Base64} encoding scheme.
	*
	* <p> An invocation of this method has exactly the same effect as invoking
	* {@code decode(src.getBytes(StandardCharsets.ISO_8859_1))}
	*
	* @param src
	* the string to decode
	*
	* @return A newly-allocated byte array containing the decoded bytes.
	*
	* @throws IllegalArgumentException
	* if {@code src} is not in valid Base64 scheme
	*/
	public byte[] decode(String src) {
	return decode(src.getBytes(ISO_8859_1.INSTANCE));
	}

	/**
	* Decodes all bytes from the input byte array using the {@link Base64}
	* encoding scheme, writing the results into the given output byte array,
	* starting at offset 0.
	*
	* <p> It is the responsibility of the invoker of this method to make
	* sure the output byte array {@code dst} has enough space for decoding
	* all bytes from the input byte array. No bytes will be written to
	* the output byte array if the output byte array is not big enough.
	*
	* <p> If the input byte array is not in valid Base64 encoding scheme
	* then some bytes may have been written to the output byte array before
	* IllegalargumentException is thrown.
	*
	* @param src
	* the byte array to decode
	* @param dst
	* the output byte array
	*
	* @return The number of bytes written to the output byte array
	*
	* @throws IllegalArgumentException
	* if {@code src} is not in valid Base64 scheme, or {@code dst}
	* does not have enough space for decoding all input bytes.
	*/
	public int decode(byte[] src, byte[] dst) {
	int len = decodedOutLength(src, 0, src.length);
	if (dst.length < len \|\| len == -1)
	throw new IllegalArgumentException(
	"Output byte array is too small for decoding all input bytes");
	return decode0(src, 0, src.length, dst);
	}

	/**
	* Decodes all bytes from the input byte buffer using the {@link Base64}
	* encoding scheme, writing the results into a newly-allocated ByteBuffer.
	*
	* <p> Upon return, the source buffer's position will be updated to
	* its limit; its limit will not have been changed. The returned
	* output buffer's position will be zero and its limit will be the
	* number of resulting decoded bytes
	*
	* <p> {@code IllegalArgumentException} is thrown if the input buffer
	* is not in valid Base64 encoding scheme. The position of the input
	* buffer will not be advanced in this case.
	*
	* @param buffer
	* the ByteBuffer to decode
	*
	* @return A newly-allocated byte buffer containing the decoded bytes
	*
	* @throws IllegalArgumentException
	* if {@code buffer} is not in valid Base64 scheme
	*/
	public ByteBuffer decode(ByteBuffer buffer) {
	int pos0 = buffer.position();
	try {
	byte[] src;
	int sp, sl;
	if (buffer.hasArray()) {
	src = buffer.array();
	sp = buffer.arrayOffset() + buffer.position();
	sl = buffer.arrayOffset() + buffer.limit();
	buffer.position(buffer.limit());
	} else {
	src = new byte[buffer.remaining()];
	buffer.get(src);
	sp = 0;
	sl = src.length;
	}
	byte[] dst = new byte[decodedOutLength(src, sp, sl)];
	return ByteBuffer.wrap(dst, 0, decode0(src, sp, sl, dst));
	} catch (IllegalArgumentException iae) {
	buffer.position(pos0);
	throw iae;
	}
	}

	/**
	* Returns an input stream for decoding {@link Base64} encoded byte stream.
	*
	* <p> The {@code read} methods of the returned {@code InputStream} will
	* throw {@code IOException} when reading bytes that cannot be decoded.
	*
	* <p> Closing the returned input stream will close the underlying
	* input stream.
	*
	* @param is
	* the input stream
	*
	* @return the input stream for decoding the specified Base64 encoded
	* byte stream
	*/
	public InputStream wrap(InputStream is) {
	Objects.requireNonNull(is);
	return new DecInputStream(is, isURL ? fromBase64URL : fromBase64, isMIME);
	}

	/**
	* Calculates the length of the decoded output bytes.
	*
	* @param src the byte array to decode
	* @param sp the source position
	* @param sl the source limit
	*
	* @return length of the decoded bytes
	*
	*/
	private int decodedOutLength(byte[] src, int sp, int sl) {
	int[] base64 = isURL ? fromBase64URL : fromBase64;
	int paddings = 0;
	int len = sl - sp;
	if (len == 0)
	return 0;
	if (len < 2) {
	if (isMIME && base64[0] == -1)
	return 0;
	throw new IllegalArgumentException(
	"Input byte[] should at least have 2 bytes for base64 bytes");
	}
	if (isMIME) {
	// scan all bytes to fill out all non-alphabet. a performance
	// trade-off of pre-scan or Arrays.copyOf
	int n = 0;
	while (sp < sl) {
	int b = src[sp++] & 0xff;
	if (b == '=') {
	len -= (sl - sp + 1);
	break;
	}
	if ((b = base64[b]) == -1)
	n++;
	}
	len -= n;
	} else {
	if (src[sl - 1] == '=') {
	paddings++;
	if (src[sl - 2] == '=')
	paddings++;
	}
	}
	if (paddings == 0 && (len & 0x3) != 0)
	paddings = 4 - (len & 0x3);

	// If len is near to Integer.MAX_VALUE, (len + 3)
	// can possibly overflow, perform this operation as
	// long and cast it back to integer when the value comes under
	// integer limit. The final value will always be in integer
	// limits
	return 3 * (int) ((len + 3L) / 4) - paddings;
	}

	/**
	* Decodes base64 characters, and returns the number of data bytes
	* written into the destination array.
	*
	* It is the fast path for full 4-byte to 3-byte decoding w/o errors.
	*
	* decodeBlock() can be overridden by an arch-specific intrinsic.
	* decodeBlock can choose to decode all, none, or a variable-sized
	* prefix of the src bytes. This allows the intrinsic to decode in
	* chunks of the src that are of a favorable size for the specific
	* processor it's running on.
	*
	* If the intrinsic function does not process all of the bytes in
	* src, it must process a multiple of four of them, making the
	* returned destination length a multiple of three.
	*
	* If any illegal base64 bytes are encountered in src by the
	* intrinsic, the intrinsic must return the actual number of valid
	* data bytes already written to dst. Note that the '=' pad
	* character is treated as an illegal Base64 character by
	* decodeBlock, so it will not process a block of 4 bytes
	* containing pad characters.
	*
	* Given the parameters, no length check is possible on dst, so dst
	* is assumed to be large enough to store the decoded bytes.
	*
	* @param src
	* the source byte array of Base64 encoded bytes
	* @param sp
	* the offset into src array to begin reading
	* @param sl
	* the offset (exclusive) past the last byte to be converted.
	* @param dst
	* the destination byte array of decoded data bytes
	* @param dp
	* the offset into dst array to begin writing
	* @param isURL
	* boolean, when true decode RFC4648 URL-safe base64 characters
	* @return the number of destination data bytes produced
	*/
	@IntrinsicCandidate
	private int decodeBlock(byte[] src, int sp, int sl, byte[] dst, int dp, boolean isURL) {
	int[] base64 = isURL ? fromBase64URL : fromBase64;
	int sl0 = sp + ((sl - sp) & ~0b11);
	int new_dp = dp;
	while (sp < sl0) {
	int b1 = base64[src[sp++] & 0xff];
	int b2 = base64[src[sp++] & 0xff];
	int b3 = base64[src[sp++] & 0xff];
	int b4 = base64[src[sp++] & 0xff];
	if ((b1 \| b2 \| b3 \| b4) < 0) { // non base64 byte
	return new_dp - dp;
	}
	int bits0 = b1 << 18 \| b2 << 12 \| b3 << 6 \| b4;
	dst[new_dp++] = (byte)(bits0 >> 16);
	dst[new_dp++] = (byte)(bits0 >> 8);
	dst[new_dp++] = (byte)(bits0);
	}
	return new_dp - dp;
	}

	private int decode0(byte[] src, int sp, int sl, byte[] dst) {
	int[] base64 = isURL ? fromBase64URL : fromBase64;
	int dp = 0;
	int bits = 0;
	int shiftto = 18; // pos of first byte of 4-byte atom

	while (sp < sl) {
	if (shiftto == 18 && sp < sl - 4) { // fast path
	int dl = decodeBlock(src, sp, sl, dst, dp, isURL);
	/*
	* Calculate how many characters were processed by how many
	* bytes of data were returned.
	*/
	int chars_decoded = (dl / 3) * 4;

	sp += chars_decoded;
	dp += dl;
	}
	if (sp >= sl) {
	// we're done
	break;
	}
	int b = src[sp++] & 0xff;
	if ((b = base64[b]) < 0) {
	if (b == -2) { // padding byte '='
	// = shiftto==18 unnecessary padding
	// x= shiftto==12 a dangling single x
	// x to be handled together with non-padding case
	// xx= shiftto==6&&sp==sl missing last =
	// xx=y shiftto==6 last is not =
	if (shiftto == 6 && (sp == sl \|\| src[sp++] != '=') \|\|
	shiftto == 18) {
	throw new IllegalArgumentException(
	"Input byte array has wrong 4-byte ending unit");
	}
	break;
	}
	if (isMIME) // skip if for rfc2045
	continue;
	else
	throw new IllegalArgumentException(
	"Illegal base64 character " +
	Integer.toString(src[sp - 1], 16));
	}
	bits \|= (b << shiftto);
	shiftto -= 6;
	if (shiftto < 0) {
	dst[dp++] = (byte)(bits >> 16);
	dst[dp++] = (byte)(bits >> 8);
	dst[dp++] = (byte)(bits);
	shiftto = 18;
	bits = 0;
	}
	}
	// reached end of byte array or hit padding '=' characters.
	if (shiftto == 6) {
	dst[dp++] = (byte)(bits >> 16);
	} else if (shiftto == 0) {
	dst[dp++] = (byte)(bits >> 16);
	dst[dp++] = (byte)(bits >> 8);
	} else if (shiftto == 12) {
	// dangling single "x", incorrectly encoded.
	throw new IllegalArgumentException(
	"Last unit does not have enough valid bits");
	}
	// anything left is invalid, if is not MIME.
	// if MIME, ignore all non-base64 character
	while (sp < sl) {
	if (isMIME && base64[src[sp++] & 0xff] < 0)
	continue;
	throw new IllegalArgumentException(
	"Input byte array has incorrect ending byte at " + sp);
	}
	return dp;
	}
	}

	/*
	* An output stream for encoding bytes into the Base64.
	*/
	private static class EncOutputStream extends FilterOutputStream {

	private int leftover = 0;
	private int b0, b1, b2;
	private boolean closed = false;

	private final char[] base64; // byte->base64 mapping
	private final byte[] newline; // line separator, if needed
	private final int linemax;
	private final boolean doPadding;// whether or not to pad
	private int linepos = 0;
	private byte[] buf;

	EncOutputStream(OutputStream os, char[] base64,
	byte[] newline, int linemax, boolean doPadding) {
	super(os);
	this.base64 = base64;
	this.newline = newline;
	this.linemax = linemax;
	this.doPadding = doPadding;
	this.buf = new byte[linemax <= 0 ? 8124 : linemax];
	}

	@Override
	public void write(int b) throws IOException {
	byte[] buf = new byte[1];
	buf[0] = (byte)(b & 0xff);
	write(buf, 0, 1);
	}

	private void checkNewline() throws IOException {
	if (linepos == linemax) {
	out.write(newline);
	linepos = 0;
	}
	}

	private void writeb4(char b1, char b2, char b3, char b4) throws IOException {
	buf[0] = (byte)b1;
	buf[1] = (byte)b2;
	buf[2] = (byte)b3;
	buf[3] = (byte)b4;
	out.write(buf, 0, 4);
	}

	@Override
	public void write(byte[] b, int off, int len) throws IOException {
	if (closed)
	throw new IOException("Stream is closed");
	if (off < 0 \|\| len < 0 \|\| len > b.length - off)
	throw new ArrayIndexOutOfBoundsException();
	if (len == 0)
	return;
	if (leftover != 0) {
	if (leftover == 1) {
	b1 = b[off++] & 0xff;
	len--;
	if (len == 0) {
	leftover++;
	return;
	}
	}
	b2 = b[off++] & 0xff;
	len--;
	checkNewline();
	writeb4(base64[b0 >> 2],
	base64[(b0 << 4) & 0x3f \| (b1 >> 4)],
	base64[(b1 << 2) & 0x3f \| (b2 >> 6)],
	base64[b2 & 0x3f]);
	linepos += 4;
	}
	int nBits24 = len / 3;
	leftover = len - (nBits24 * 3);

	while (nBits24 > 0) {
	checkNewline();
	int dl = linemax <= 0 ? buf.length : buf.length - linepos;
	int sl = off + Math.min(nBits24, dl / 4) * 3;
	int dp = 0;
	for (int sp = off; sp < sl; ) {
	int bits = (b[sp++] & 0xff) << 16 \|
	(b[sp++] & 0xff) << 8 \|
	(b[sp++] & 0xff);
	buf[dp++] = (byte)base64[(bits >>> 18) & 0x3f];
	buf[dp++] = (byte)base64[(bits >>> 12) & 0x3f];
	buf[dp++] = (byte)base64[(bits >>> 6) & 0x3f];
	buf[dp++] = (byte)base64[bits & 0x3f];
	}
	out.write(buf, 0, dp);
	off = sl;
	linepos += dp;
	nBits24 -= dp / 4;
	}
	if (leftover == 1) {
	b0 = b[off++] & 0xff;
	} else if (leftover == 2) {
	b0 = b[off++] & 0xff;
	b1 = b[off++] & 0xff;
	}
	}

	@Override
	public void close() throws IOException {
	if (!closed) {
	closed = true;
	if (leftover == 1) {
	checkNewline();
	out.write(base64[b0 >> 2]);
	out.write(base64[(b0 << 4) & 0x3f]);
	if (doPadding) {
	out.write('=');
	out.write('=');
	}
	} else if (leftover == 2) {
	checkNewline();
	out.write(base64[b0 >> 2]);
	out.write(base64[(b0 << 4) & 0x3f \| (b1 >> 4)]);
	out.write(base64[(b1 << 2) & 0x3f]);
	if (doPadding) {
	out.write('=');
	}
	}
	leftover = 0;
	out.close();
	}
	}
	}

	/*
	* An input stream for decoding Base64 bytes
	*/
	private static class DecInputStream extends InputStream {

	private final InputStream is;
	private final boolean isMIME;
	private final int[] base64; // base64 -> byte mapping
	private int bits = 0; // 24-bit buffer for decoding

	/* writing bit pos inside bits; one of 24 (left, msb), 18, 12, 6, 0 */
	private int wpos = 0;

	/* reading bit pos inside bits: one of 24 (left, msb), 16, 8, 0 */
	private int rpos = 0;

	private boolean eof = false;
	private boolean closed = false;

	DecInputStream(InputStream is, int[] base64, boolean isMIME) {
	this.is = is;
	this.base64 = base64;
	this.isMIME = isMIME;
	}

	private byte[] sbBuf = new byte[1];

	@Override
	public int read() throws IOException {
	return read(sbBuf, 0, 1) == -1 ? -1 : sbBuf[0] & 0xff;
	}

	private int leftovers(byte[] b, int off, int pos, int limit) {
	eof = true;

	/*
	* We use a loop here, as this method is executed only a few times.
	* Unrolling the loop would probably not contribute much here.
	*/
	while (rpos - 8 >= wpos && pos != limit) {
	rpos -= 8;
	b[pos++] = (byte) (bits >> rpos);
	}
	return pos - off != 0 \|\| rpos - 8 >= wpos ? pos - off : -1;
	}

	private int eof(byte[] b, int off, int pos, int limit) throws IOException {
	/*
	* pos != limit
	*
	* wpos == 18: x dangling single x, invalid unit
	* accept ending xx or xxx without padding characters
	*/
	if (wpos == 18) {
	throw new IOException("Base64 stream has one un-decoded dangling byte.");
	}
	rpos = 24;
	return leftovers(b, off, pos, limit);
	}

	private int padding(byte[] b, int off, int pos, int limit) throws IOException {
	/*
	* pos != limit
	*
	* wpos == 24: = (unnecessary padding)
	* wpos == 18: x= (dangling single x, invalid unit)
	* wpos == 12 and missing last '=': xx= (invalid padding)
	* wpos == 12 and last is not '=': xx=x (invalid padding)
	*/
	if (wpos >= 18 \|\| wpos == 12 && is.read() != '=') {
	throw new IOException("Illegal base64 ending sequence:" + wpos);
	}
	rpos = 24;
	return leftovers(b, off, pos, limit);
	}

	@Override
	public int read(byte[] b, int off, int len) throws IOException {
	if (closed) {
	throw new IOException("Stream is closed");
	}
	Objects.checkFromIndexSize(off, len, b.length);
	if (len == 0) {
	return 0;
	}

	/*
	* Rather than keeping 2 running vars (e.g., off and len),
	* we only keep one (pos), while definitely fixing the boundaries
	* of the range [off, limit).
	* More specifically, each use of pos as an index in b meets
	* pos - off >= 0 & limit - pos > 0
	*
	* Note that limit can overflow to Integer.MIN_VALUE. However,
	* as long as comparisons with pos are as coded, there's no harm.
	*/
	int pos = off;
	final int limit = off + len;
	if (eof) {
	return leftovers(b, off, pos, limit);
	}

	/*
	* Leftovers from previous invocation; here, wpos = 0.
	* There can be at most 2 leftover bytes (rpos <= 16).
	* Further, b has at least one free place.
	*
	* The logic could be coded as a loop, (as in method leftovers())
	* but the explicit "unrolling" makes it possible to generate
	* better byte extraction code.
	*/
	if (rpos == 16) {
	b[pos++] = (byte) (bits >> 8);
	rpos = 8;
	if (pos == limit) {
	return len;
	}
	}
	if (rpos == 8) {
	b[pos++] = (byte) bits;
	rpos = 0;
	if (pos == limit) {
	return len;
	}
	}

	bits = 0;
	wpos = 24;
	for (;;) {
	/* pos != limit & rpos == 0 */
	final int i = is.read();
	if (i < 0) {
	return eof(b, off, pos, limit);
	}
	final int v = base64[i];
	if (v < 0) {
	/*
	* i not in alphabet, thus
	* v == -2: i is '=', the padding
	* v == -1: i is something else, typically CR or LF
	*/
	if (v == -1) {
	if (isMIME) {
	continue;
	}
	throw new IOException("Illegal base64 character 0x" +
	Integer.toHexString(i));
	}
	return padding(b, off, pos, limit);
	}
	wpos -= 6;
	bits \|= v << wpos;
	if (wpos != 0) {
	continue;
	}
	if (limit - pos >= 3) {
	/* frequently taken fast path, no need to track rpos */
	b[pos++] = (byte) (bits >> 16);
	b[pos++] = (byte) (bits >> 8);
	b[pos++] = (byte) bits;
	bits = 0;
	wpos = 24;
	if (pos == limit) {
	return len;
	}
	continue;
	}

	/* b has either 1 or 2 free places */
	b[pos++] = (byte) (bits >> 16);
	if (pos == limit) {
	rpos = 16;
	return len;
	}
	b[pos++] = (byte) (bits >> 8);
	/* pos == limit, no need for an if */
	rpos = 8;
	return len;
	}
	}

	@Override
	public int available() throws IOException {
	if (closed)
	throw new IOException("Stream is closed");
	return is.available(); // TBD:
	}

	@Override
	public void close() throws IOException {
	if (!closed) {
	closed = true;
	is.close();
	}
	}
	}
	}

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