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Commons Codec example source code file (Base64.java)
The Commons Codec Base64.java source code
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.codec.binary;
import java.math.BigInteger;
import org.apache.commons.codec.BinaryDecoder;
import org.apache.commons.codec.BinaryEncoder;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.EncoderException;
/**
* Provides Base64 encoding and decoding as defined by RFC 2045.
*
* <p>
* This class implements section <cite>6.8. Base64 Content-Transfer-Encoding from RFC 2045 Multipurpose
* Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies</cite> by Freed and Borenstein.
* </p>
* <p>
* The class can be parameterized in the following manner with various constructors:
* <ul>
* <li>URL-safe mode: Default off.
* <li>Line length: Default 76. Line length that aren't multiples of 4 will still essentially end up being multiples of
* 4 in the encoded data.
* <li>Line separator: Default is CRLF ("\r\n")
* </ul>
* </p>
* <p>
* Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode
* character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc).
* </p>
*
* @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045
* @author Apache Software Foundation
* @since 1.0
* @version $Id: Base64.java 801706 2009-08-06 16:27:06Z niallp $
*/
public class Base64 implements BinaryEncoder, BinaryDecoder {
private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
private static final int DEFAULT_BUFFER_SIZE = 8192;
/**
* Chunk size per RFC 2045 section 6.8.
*
* <p>
* The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
* equal signs.
* </p>
*
* @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8
*/
static final int CHUNK_SIZE = 76;
/**
* Chunk separator per RFC 2045 section 2.1.
*
* <p>
* N.B. The next major release may break compatibility and make this field private.
* </p>
*
* @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1
*/
static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
/**
* This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
* equivalents as specified in Table 1 of RFC 2045.
*
* Thanks to "commons" project in ws.apache.org for this code.
* http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
*/
private static final byte[] STANDARD_ENCODE_TABLE = {
'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', '+', '/'
};
/**
* This is a copy of the STANDARD_ENCODE_TABLE above, but with + and /
* changed to - and _ to make the encoded Base64 results more URL-SAFE.
* This table is only used when the Base64's mode is set to URL-SAFE.
*/
private static final byte[] URL_SAFE_ENCODE_TABLE = {
'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', '-', '_'
};
/**
* Byte used to pad output.
*/
private static final byte PAD = '=';
/**
* This array is a lookup table that translates 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 translated to -1.
*
* Note: '+' and '-' both decode to 62. '/' and '_' both decode to 63. This means decoder seamlessly handles both
* URL_SAFE and STANDARD base64. (The encoder, on the other hand, needs to know ahead of time what to emit).
*
* Thanks to "commons" project in ws.apache.org for this code.
* http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
*/
private static final byte[] DECODE_TABLE = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, 62, -1, 63, 52, 53, 54,
55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, -1, -1, -1, -1, 63, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,
35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
};
/** Mask used to extract 6 bits, used when encoding */
private static final int MASK_6BITS = 0x3f;
/** Mask used to extract 8 bits, used in decoding base64 bytes */
private static final int MASK_8BITS = 0xff;
// The static final fields above are used for the original static byte[] methods on Base64.
// The private member fields below are used with the new streaming approach, which requires
// some state be preserved between calls of encode() and decode().
/**
* Encode table to use: either STANDARD or URL_SAFE. Note: the DECODE_TABLE above remains static because it is able
* to decode both STANDARD and URL_SAFE streams, but the encodeTable must be a member variable so we can switch
* between the two modes.
*/
private final byte[] encodeTable;
/**
* Line length for encoding. Not used when decoding. A value of zero or less implies no chunking of the base64
* encoded data.
*/
private final int lineLength;
/**
* Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
*/
private final byte[] lineSeparator;
/**
* Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
* <code>decodeSize = 3 + lineSeparator.length;
*/
private final int decodeSize;
/**
* Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
* <code>encodeSize = 4 + lineSeparator.length;
*/
private final int encodeSize;
/**
* Buffer for streaming.
*/
private byte[] buffer;
/**
* Position where next character should be written in the buffer.
*/
private int pos;
/**
* Position where next character should be read from the buffer.
*/
private int readPos;
/**
* Variable tracks how many characters have been written to the current line. Only used when encoding. We use it to
* make sure each encoded line never goes beyond lineLength (if lineLength > 0).
*/
private int currentLinePos;
/**
* Writes to the buffer only occur after every 3 reads when encoding, an every 4 reads when decoding. This variable
* helps track that.
*/
private int modulus;
/**
* Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this Base64 object becomes useless,
* and must be thrown away.
*/
private boolean eof;
/**
* Place holder for the 3 bytes we're dealing with for our base64 logic. Bitwise operations store and extract the
* base64 encoding or decoding from this variable.
*/
private int x;
/**
* Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
* <p>
* When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
* </p>
*
* <p>
* When decoding all variants are supported.
* </p>
*/
public Base64() {
this(false);
}
/**
* Creates a Base64 codec used for decoding (all modes) and encoding in the given URL-safe mode.
* <p>
* When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.
* </p>
*
* <p>
* When decoding all variants are supported.
* </p>
*
* @param urlSafe
* if <code>true, URL-safe encoding is used. In most cases this should be set to
* <code>false.
* @since 1.4
*/
public Base64(boolean urlSafe) {
this(CHUNK_SIZE, CHUNK_SEPARATOR, urlSafe);
}
/**
* Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
* <p>
* When encoding the line length is given in the constructor, the line separator is CRLF, and the encoding table is
* STANDARD_ENCODE_TABLE.
* </p>
* <p>
* Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
* </p>
* <p>
* When decoding all variants are supported.
* </p>
*
* @param lineLength
* Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
* If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
* @since 1.4
*/
public Base64(int lineLength) {
this(lineLength, CHUNK_SEPARATOR);
}
/**
* Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
* <p>
* When encoding the line length and line separator are given in the constructor, and the encoding table is
* STANDARD_ENCODE_TABLE.
* </p>
* <p>
* Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
* </p>
* <p>
* When decoding all variants are supported.
* </p>
*
* @param lineLength
* Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
* If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
* @param lineSeparator
* Each line of encoded data will end with this sequence of bytes.
* @throws IllegalArgumentException
* Thrown when the provided lineSeparator included some base64 characters.
* @since 1.4
*/
public Base64(int lineLength, byte[] lineSeparator) {
this(lineLength, lineSeparator, false);
}
/**
* Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
* <p>
* When encoding the line length and line separator are given in the constructor, and the encoding table is
* STANDARD_ENCODE_TABLE.
* </p>
* <p>
* Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
* </p>
* <p>
* When decoding all variants are supported.
* </p>
*
* @param lineLength
* Each line of encoded data will be at most of the given length (rounded down to nearest multiple of 4).
* If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
* @param lineSeparator
* Each line of encoded data will end with this sequence of bytes.
* @param urlSafe
* Instead of emitting '+' and '/' we emit '-' and '_' respectively. urlSafe is only applied to encode
* operations. Decoding seamlessly handles both modes.
* @throws IllegalArgumentException
* The provided lineSeparator included some base64 characters. That's not going to work!
* @since 1.4
*/
public Base64(int lineLength, byte[] lineSeparator, boolean urlSafe) {
if (lineSeparator == null) {
lineLength = 0; // disable chunk-separating
lineSeparator = CHUNK_SEPARATOR; // this just gets ignored
}
this.lineLength = lineLength > 0 ? (lineLength / 4) * 4 : 0;
this.lineSeparator = new byte[lineSeparator.length];
System.arraycopy(lineSeparator, 0, this.lineSeparator, 0, lineSeparator.length);
if (lineLength > 0) {
this.encodeSize = 4 + lineSeparator.length;
} else {
this.encodeSize = 4;
}
this.decodeSize = this.encodeSize - 1;
if (containsBase64Byte(lineSeparator)) {
String sep = StringUtils.newStringUtf8(lineSeparator);
throw new IllegalArgumentException("lineSeperator must not contain base64 characters: [" + sep + "]");
}
this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE;
}
/**
* Returns our current encode mode. True if we're URL-SAFE, false otherwise.
*
* @return true if we're in URL-SAFE mode, false otherwise.
* @since 1.4
*/
public boolean isUrlSafe() {
return this.encodeTable == URL_SAFE_ENCODE_TABLE;
}
/**
* Returns true if this Base64 object has buffered data for reading.
*
* @return true if there is Base64 object still available for reading.
*/
boolean hasData() {
return this.buffer != null;
}
/**
* Returns the amount of buffered data available for reading.
*
* @return The amount of buffered data available for reading.
*/
int avail() {
return buffer != null ? pos - readPos : 0;
}
/** Doubles our buffer. */
private void resizeBuffer() {
if (buffer == null) {
buffer = new byte[DEFAULT_BUFFER_SIZE];
pos = 0;
readPos = 0;
} else {
byte[] b = new byte[buffer.length * DEFAULT_BUFFER_RESIZE_FACTOR];
System.arraycopy(buffer, 0, b, 0, buffer.length);
buffer = b;
}
}
/**
* Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
* bytes. Returns how many bytes were actually extracted.
*
* @param b
* byte[] array to extract the buffered data into.
* @param bPos
* position in byte[] array to start extraction at.
* @param bAvail
* amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
* @return The number of bytes successfully extracted into the provided byte[] array.
*/
int readResults(byte[] b, int bPos, int bAvail) {
if (buffer != null) {
int len = Math.min(avail(), bAvail);
if (buffer != b) {
System.arraycopy(buffer, readPos, b, bPos, len);
readPos += len;
if (readPos >= pos) {
buffer = null;
}
} else {
// Re-using the original consumer's output array is only
// allowed for one round.
buffer = null;
}
return len;
}
return eof ? -1 : 0;
}
/**
* Sets the streaming buffer. This is a small optimization where we try to buffer directly to the consumer's output
* array for one round (if the consumer calls this method first) instead of starting our own buffer.
*
* @param out
* byte[] array to buffer directly to.
* @param outPos
* Position to start buffering into.
* @param outAvail
* Amount of bytes available for direct buffering.
*/
void setInitialBuffer(byte[] out, int outPos, int outAvail) {
// We can re-use consumer's original output array under
// special circumstances, saving on some System.arraycopy().
if (out != null && out.length == outAvail) {
buffer = out;
pos = outPos;
readPos = outPos;
}
}
/**
* <p>
* Encodes all of the provided data, starting at inPos, for inAvail bytes. Must be called at least twice: once with
* the data to encode, and once with inAvail set to "-1" to alert encoder that EOF has been reached, so flush last
* remaining bytes (if not multiple of 3).
* </p>
* <p>
* Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
* http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
* </p>
*
* @param in
* byte[] array of binary data to base64 encode.
* @param inPos
* Position to start reading data from.
* @param inAvail
* Amount of bytes available from input for encoding.
*/
void encode(byte[] in, int inPos, int inAvail) {
if (eof) {
return;
}
// inAvail < 0 is how we're informed of EOF in the underlying data we're
// encoding.
if (inAvail < 0) {
eof = true;
if (buffer == null || buffer.length - pos < encodeSize) {
resizeBuffer();
}
switch (modulus) {
case 1 :
buffer[pos++] = encodeTable[(x >> 2) & MASK_6BITS];
buffer[pos++] = encodeTable[(x << 4) & MASK_6BITS];
// URL-SAFE skips the padding to further reduce size.
if (encodeTable == STANDARD_ENCODE_TABLE) {
buffer[pos++] = PAD;
buffer[pos++] = PAD;
}
break;
case 2 :
buffer[pos++] = encodeTable[(x >> 10) & MASK_6BITS];
buffer[pos++] = encodeTable[(x >> 4) & MASK_6BITS];
buffer[pos++] = encodeTable[(x << 2) & MASK_6BITS];
// URL-SAFE skips the padding to further reduce size.
if (encodeTable == STANDARD_ENCODE_TABLE) {
buffer[pos++] = PAD;
}
break;
}
if (lineLength > 0 && pos > 0) {
System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
pos += lineSeparator.length;
}
} else {
for (int i = 0; i < inAvail; i++) {
if (buffer == null || buffer.length - pos < encodeSize) {
resizeBuffer();
}
modulus = (++modulus) % 3;
int b = in[inPos++];
if (b < 0) {
b += 256;
}
x = (x << 8) + b;
if (0 == modulus) {
buffer[pos++] = encodeTable[(x >> 18) & MASK_6BITS];
buffer[pos++] = encodeTable[(x >> 12) & MASK_6BITS];
buffer[pos++] = encodeTable[(x >> 6) & MASK_6BITS];
buffer[pos++] = encodeTable[x & MASK_6BITS];
currentLinePos += 4;
if (lineLength > 0 && lineLength <= currentLinePos) {
System.arraycopy(lineSeparator, 0, buffer, pos, lineSeparator.length);
pos += lineSeparator.length;
currentLinePos = 0;
}
}
}
}
}
/**
* <p>
* Decodes all of the provided data, starting at inPos, for inAvail bytes. Should be called at least twice: once
* with the data to decode, and once with inAvail set to "-1" to alert decoder that EOF has been reached. The "-1"
* call is not necessary when decoding, but it doesn't hurt, either.
* </p>
* <p>
* Ignores all non-base64 characters. This is how chunked (e.g. 76 character) data is handled, since CR and LF are
* silently ignored, but has implications for other bytes, too. This method subscribes to the garbage-in,
* garbage-out philosophy: it will not check the provided data for validity.
* </p>
* <p>
* Thanks to "commons" project in ws.apache.org for the bitwise operations, and general approach.
* http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/
* </p>
*
* @param in
* byte[] array of ascii data to base64 decode.
* @param inPos
* Position to start reading data from.
* @param inAvail
* Amount of bytes available from input for encoding.
*/
void decode(byte[] in, int inPos, int inAvail) {
if (eof) {
return;
}
if (inAvail < 0) {
eof = true;
}
for (int i = 0; i < inAvail; i++) {
if (buffer == null || buffer.length - pos < decodeSize) {
resizeBuffer();
}
byte b = in[inPos++];
if (b == PAD) {
// We're done.
eof = true;
break;
} else {
if (b >= 0 && b < DECODE_TABLE.length) {
int result = DECODE_TABLE[b];
if (result >= 0) {
modulus = (++modulus) % 4;
x = (x << 6) + result;
if (modulus == 0) {
buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
buffer[pos++] = (byte) ((x >> 8) & MASK_8BITS);
buffer[pos++] = (byte) (x & MASK_8BITS);
}
}
}
}
}
// Two forms of EOF as far as base64 decoder is concerned: actual
// EOF (-1) and first time '=' character is encountered in stream.
// This approach makes the '=' padding characters completely optional.
if (eof && modulus != 0) {
x = x << 6;
switch (modulus) {
case 2 :
x = x << 6;
buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
break;
case 3 :
buffer[pos++] = (byte) ((x >> 16) & MASK_8BITS);
buffer[pos++] = (byte) ((x >> 8) & MASK_8BITS);
break;
}
}
}
/**
* Returns whether or not the <code>octet is in the base 64 alphabet.
*
* @param octet
* The value to test
* @return <code>true if the value is defined in the the base 64 alphabet,
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