自学Android开发 Java和Android SDK的Base64
聂溪叠
一、问题
在Android开发使用AES加密时，会发现Android SDK自带了Base64，但是它加密的结果和Java JDK的Base64 不一致，所以造成了Java 服务后端的加密数据，用SDK的Base64无法解密，造成了异常。后来Android 开发也引入了Java JDK的Base64, 但是有API限制 ，必须是SDK API 26（Android 8.0）以上才能使用。使用在Android 开发项目时不方便兼容处理。最终我的解决方案是直接引用 JDK的Base64。
二、JDK Base64 源码
为了方便大家使用 这里直接提供 java的Base64源码
import java.io.FilterOutputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Objects;
/**
* 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 name="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 name="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 name="mime"><b>MIME</b></a>
* <p> Uses the "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 Base64.Encoder} that encodes using the
* <a href="#basic">Basic</a> type base64 encoding scheme.
*
* @return A Base64 encoder.
*/
public static Base64.Encoder getEncoder() {
return Base64.Encoder.RFC4648;
}
/**
* Returns a {@link Base64.Encoder} that encodes using the
* <a href="#url">URL and Filename safe</a> type base64
* encoding scheme.
*
* @return A Base64 encoder.
*/
public static Base64.Encoder getUrlEncoder() {
return Base64.Encoder.RFC4648_URLSAFE;
}
/**
* Returns a {@link Base64.Encoder} that encodes using the
* <a href="#mime">MIME</a> type base64 encoding scheme.
*
* @return A Base64 encoder.
*/
public static Base64.Encoder getMimeEncoder() {
return Base64.Encoder.RFC2045;
}
/**
* Returns a {@link Base64.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 {@code lineLength <= 0} 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 Base64.Encoder getMimeEncoder(int lineLength, byte[] lineSeparator) {
Objects.requireNonNull(lineSeparator);
int[] base64 = 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));
}
if (lineLength <= 0) {
return Base64.Encoder.RFC4648;
}
return new Base64.Encoder(false, lineSeparator, lineLength >> 2 << 2, true);
}
/**
* Returns a {@link Base64.Decoder} that decodes using the
* <a href="#basic">Basic</a> type base64 encoding scheme.
*
* @return A Base64 decoder.
*/
public static Base64.Decoder getDecoder() {
return Base64.Decoder.RFC4648;
}
/**
* Returns a {@link Base64.Decoder} that decodes using the
* <a href="#url">URL and Filename safe</a> type base64
* encoding scheme.
*
* @return A Base64 decoder.
*/
public static Base64.Decoder getUrlDecoder() {
return Base64.Decoder.RFC4648_URLSAFE;
}
/**
* Returns a {@link Base64.Decoder} that decodes using the
* <a href="#mime">MIME</a> type base64 decoding scheme.
*
* @return A Base64 decoder.
*/
public static Base64.Decoder getMimeDecoder() {
return Base64.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 Base64.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.
*
* @see Base64.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 Base64.Encoder RFC4648 = new Base64.Encoder(false, null, -1, true);
static final Base64.Encoder RFC4648_URLSAFE = new Base64.Encoder(true, null, -1, true);
static final Base64.Encoder RFC2045 = new Base64.Encoder(false, CRLF, MIMELINEMAX, true);
private final int outLength(int srclen) {
int len = 0;
if (doPadding) {
len = 4 * ((srclen + 2) / 3);
} else {
int n = srclen % 3;
len = 4 * (srclen / 3) + (n == 0 ? 0 : n + 1);
}
if (linemax > 0) // line separators
len += (len - 1) / linemax * newline.length;
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 = outLength(src.length); // 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 = outLength(src.length); // dst array size
if (dst.length < len)
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 = outLength(buffer.remaining());
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 Base64.Encoder withoutPadding() {
if (!doPadding)
return this;
return new Base64.Encoder(isURL, newline, linemax, false);
}
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);
for (int sp0 = sp, dp0 = dp ; sp0 < sl0; ) {
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];
}
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 Base64.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.
*
* @see Base64.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 < Base64.Encoder.toBase64.length; i++)
fromBase64[Base64.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 < Base64.Encoder.toBase64URL.length; i++)
fromBase64URL[Base64.Encoder.toBase64URL[i]] = i;
fromBase64URL['='] = -2;
}
static final Base64.Decoder RFC4648 = new Base64.Decoder(false, false);
static final Base64.Decoder RFC4648_URLSAFE = new Base64.Decoder(true, false);
static final Base64.Decoder RFC2045 = new Base64.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[outLength(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(StandardCharsets.ISO_8859_1));
}
/**
* 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 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 = outLength(src, 0, src.length);
if (dst.length < len)
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 src} 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[outLength(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);
}
private int outLength(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);
return 3 * ((len + 3) / 4) - paddings;
}
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) {
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++]] < 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;
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;
}
@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;
}
}
@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();
out.write(base64[b0 >> 2]);
out.write(base64[(b0 << 4) & 0x3f | (b1 >> 4)]);
out.write(base64[(b1 << 2) & 0x3f | (b2 >> 6)]);
out.write(base64[b2 & 0x3f]);
linepos += 4;
}
int nBits24 = len / 3;
leftover = len - (nBits24 * 3);
while (nBits24-- > 0) {
checkNewline();
int bits = (b[off++] & 0xff) << 16 |
(b[off++] & 0xff) << 8 |
(b[off++] & 0xff);
out.write(base64[(bits >>> 18) & 0x3f]);
out.write(base64[(bits >>> 12) & 0x3f]);
out.write(base64[(bits >>> 6) & 0x3f]);
out.write(base64[bits & 0x3f]);
linepos += 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
private int nextin = 18; // next available "off" in "bits" for input;
// -> 18, 12, 6, 0
private int nextout = -8; // next available "off" in "bits" for output;
// -> 8, 0, -8 (no byte for output)
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;
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (closed)
throw new IOException("Stream is closed");
if (eof && nextout < 0) // eof and no leftover
return -1;
if (off < 0 || len < 0 || len > b.length - off)
throw new IndexOutOfBoundsException();
int oldOff = off;
if (nextout >= 0) { // leftover output byte(s) in bits buf
do {
if (len == 0)
return off - oldOff;
b[off++] = (byte)(bits >> nextout);
len--;
nextout -= 8;
} while (nextout >= 0);
bits = 0;
}
while (len > 0) {
int v = is.read();
if (v == -1) {
eof = true;
if (nextin != 18) {
if (nextin == 12)
throw new IOException("Base64 stream has one un-decoded dangling byte.");
// treat ending xx/xxx without padding character legal.
// same logic as v == '=' below
b[off++] = (byte)(bits >> (16));
len--;
if (nextin == 0) { // only one padding byte
if (len == 0) { // no enough output space
bits >>= 8; // shift to lowest byte
nextout = 0;
} else {
b[off++] = (byte) (bits >> 8);
}
}
}
if (off == oldOff)
return -1;
else
return off - oldOff;
}
if (v == '=') { // padding byte(s)
// = shiftto==18 unnecessary padding
// x= shiftto==12 dangling x, invalid unit
// xx= shiftto==6 && missing last '='
// xx=y or last is not '='
if (nextin == 18 || nextin == 12 ||
nextin == 6 && is.read() != '=') {
throw new IOException("Illegal base64 ending sequence:" + nextin);
}
b[off++] = (byte)(bits >> (16));
len--;
if (nextin == 0) { // only one padding byte
if (len == 0) { // no enough output space
bits >>= 8; // shift to lowest byte
nextout = 0;
} else {
b[off++] = (byte) (bits >> 8);
}
}
eof = true;
break;
}
if ((v = base64[v]) == -1) {
if (isMIME) // skip if for rfc2045
continue;
else
throw new IOException("Illegal base64 character " +
Integer.toString(v, 16));
}
bits |= (v << nextin);
if (nextin == 0) {
nextin = 18; // clear for next
nextout = 16;
while (nextout >= 0) {
b[off++] = (byte)(bits >> nextout);
len--;
nextout -= 8;
if (len == 0 && nextout >= 0) { // don't clean "bits"
return off - oldOff;
}
}
bits = 0;
} else {
nextin -= 6;
}
}
return off - oldOff;
}
@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();
}
}
}
}如果对您有一些意义，希望您给博主一些鼓励（点赞、关注、收藏），如果有错误欢迎大家评论。
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