java.lang.Object
- com.alibaba.nacos.common.codec.Base64

```
public class Base64
extends java.lang.Object
```
Provides Base64 encoding and decoding as defined by RFC 2045.
This class implements section 6.8. Base64 Content-Transfer-Encoding from RFC 2045 Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies by Freed and Borenstein.

The class can be parameterized in the following manner with various constructors:
- URL-safe mode: Default off.
- 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.
- Line separator: Default is CRLF ("\r\n")
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).

This class is not thread-safe. Each thread should use its own instance.
从以下版本开始:

1.0

版本:

$Revision: 1080712 $

作者:

Apache Software Foundation

另请参阅:

RFC 2045

字段概要

字段
修饰符和类型	字段	说明
`private static int`	`BITS_PER_ENCODED_BYTE`	BASE32 characters are 6 bits in length.
`private int`	`bitWorkArea`	Place holder for the bytes we're dealing with for our based logic.
`private byte[]`	`buffer`	Buffer for streaming.
`private static int`	`BYTES_PER_ENCODED_BLOCK`
`private static int`	`BYTES_PER_UNENCODED_BLOCK`
`(专用程序包) static byte[]`	`CHUNK_SEPARATOR`	Chunk separator per RFC 2045 section 2.1.
`private int`	`chunkSeparatorLength`	Size of chunk separator.
`private int`	`currentLinePos`	Variable tracks how many characters have been written to the current line.
`private static byte[]`	`DECODE_TABLE`	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.
`private int`	`decodeSize`	Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
`private byte[]`	`decodeTable`	Only one decode table currently; keep for consistency with Base32 code.
`private static int`	`DEFAULT_BUFFER_RESIZE_FACTOR`
`private static int`	`DEFAULT_BUFFER_SIZE`	Defines the default buffer size - currently 8192 - must be large enough for at least one encoded block+separator.
`private int`	`encodedBlockSize`	Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32
`private int`	`encodeSize`	Convenience variable to help us determine when our buffer is going to run out of room and needs resizing.
`private byte[]`	`encodeTable`	Encode table to use: either STANDARD or URL_SAFE.
`private boolean`	`eof`	Boolean flag to indicate the EOF has been reached.
`private int`	`lineLength`	Chunksize for encoding.
`private byte[]`	`lineSeparator`	Line separator for encoding.
`private static int`	`MASK_6BITS`	Base64 uses 6-bit fields.
`private static int`	`MASK_8BITS`	Mask used to extract 8 bits, used in decoding bytes.
`private static int`	`MIME_CHUNK_SIZE`	MIME chunk size per RFC 2045 section 6.8.
`private int`	`modulus`	Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding.
`private static byte`	`PAD`
`private static byte`	`PAD_DEFAULT`	Byte used to pad output.
`private int`	`pos`	Position where next character should be written in the buffer.
`private int`	`readPos`	Position where next character should be read from the buffer.
`private static byte[]`	`STANDARD_ENCODE_TABLE`	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.
`private int`	`unencodedBlockSize`	Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32
`private static byte[]`	`URL_SAFE_ENCODE_TABLE`	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.

构造器概要

构造器
构造器	说明
`Base64()`	Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
`Base64(int lineLength, byte[] lineSeparator, boolean urlSafe)`	Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

方法概要

所有方法静态方法实例方法具体方法
修饰符和类型	方法	说明
`private boolean`	`containsAlphabetOrPad(byte[] arrayOctet)`	Tests a given byte array to see if it contains any characters within the alphabet or PAD.
`private byte[]`	`decode(byte[] pArray)`	Decodes a byte[] containing characters in the Base-N alphabet.
`(专用程序包) void`	`decode(byte[] in, int inPos, int inAvail)`	Decodes all of the provided data, starting at inPos, for inAvail bytes.
`static byte[]`	`decodeBase64(byte[] base64Data)`	Decodes Base64 data into octets.
`private byte[]`	`encode(byte[] pArray)`	Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
`(专用程序包) void`	`encode(byte[] in, int inPos, int inAvail)`	Encodes all of the provided data, starting at inPos, for inAvail bytes.
`static byte[]`	`encodeBase64(byte[] binaryData)`	Encodes binary data using the base64 algorithm but does not chunk the output.
`static byte[]`	`encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe, int maxResultSize)`	Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
`private void`	`ensureBufferSize(int size)`	Ensure that the buffer has room for `size` bytes.
`private long`	`getEncodedLength(byte[] pArray)`	Calculates the amount of space needed to encode the supplied array.
`protected boolean`	`isInAlphabet(byte octet)`	Returns whether or not the `octet` is in the Base32 alphabet.
`private int`	`readResults(byte[] b, int bPos, int bAvail)`	Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail bytes.
`private void`	`reset()`	Resets this object to its initial newly constructed state.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 字段详细资料
  - BITS_PER_ENCODED_BYTE
```
private static final int BITS_PER_ENCODED_BYTE
```
    BASE32 characters are 6 bits in length. They are formed by taking a block of 3 octets to form a 24-bit string, which is converted into 4 BASE64 characters.
    
    另请参阅:
    
    常量字段值
  - BYTES_PER_UNENCODED_BLOCK
```
private static final int BYTES_PER_UNENCODED_BLOCK
```
    另请参阅:
    
    常量字段值
  - BYTES_PER_ENCODED_BLOCK
```
private static final int BYTES_PER_ENCODED_BLOCK
```
    另请参阅:
    
    常量字段值
  - CHUNK_SEPARATOR
```
static final byte[] CHUNK_SEPARATOR
```
    Chunk separator per RFC 2045 section 2.1.
    N.B. The next major release may break compatibility and make this field private.
    
    另请参阅:
    
    RFC 2045 section 2.1
  - STANDARD_ENCODE_TABLE
```
private static final byte[] STANDARD_ENCODE_TABLE
```
    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/
  - URL_SAFE_ENCODE_TABLE
```
private static final byte[] URL_SAFE_ENCODE_TABLE
```
    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.
  - DECODE_TABLE
```
private static final byte[] DECODE_TABLE
```
    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/
  - MASK_6BITS
```
private static final int MASK_6BITS
```
    Base64 uses 6-bit fields. Mask used to extract 6 bits, used when encoding
    
    另请参阅:
    
    常量字段值
  - encodeTable
```
private final byte[] encodeTable
```
    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.
  - decodeTable
```
private final byte[] decodeTable
```
    Only one decode table currently; keep for consistency with Base32 code.
  - lineSeparator
```
private final byte[] lineSeparator
```
    Line separator for encoding. Not used when decoding. Only used if lineLength > 0.
  - decodeSize
```
private final int decodeSize
```
    Convenience variable to help us determine when our buffer is going to run out of room and needs resizing. decodeSize = 3 + lineSeparator.length;
  - encodeSize
```
private final int encodeSize
```
    Convenience variable to help us determine when our buffer is going to run out of room and needs resizing. encodeSize = 4 + lineSeparator.length;
  - bitWorkArea
```
private int bitWorkArea
```
    Place holder for the bytes we're dealing with for our based logic. Bitwise operations store and extract the encoding or decoding from this variable.
  - MIME_CHUNK_SIZE
```
private static final int MIME_CHUNK_SIZE
```
    MIME chunk size per RFC 2045 section 6.8.
    The 76 character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.
    
    另请参阅:
    
    RFC 2045 section 6.8, 常量字段值
  - DEFAULT_BUFFER_RESIZE_FACTOR
```
private static final int DEFAULT_BUFFER_RESIZE_FACTOR
```
    另请参阅:
    
    常量字段值
  - DEFAULT_BUFFER_SIZE
```
private static final int DEFAULT_BUFFER_SIZE
```
    Defines the default buffer size - currently 8192 - must be large enough for at least one encoded block+separator.
    
    另请参阅:
    
    常量字段值
  - MASK_8BITS
```
private static final int MASK_8BITS
```
    Mask used to extract 8 bits, used in decoding bytes.
    
    另请参阅:
    
    常量字段值
  - PAD_DEFAULT
```
private static final byte PAD_DEFAULT
```
    Byte used to pad output.
    
    另请参阅:
    
    常量字段值
  - PAD
```
private static final byte PAD
```
    另请参阅:
    
    常量字段值
  - unencodedBlockSize
```
private final int unencodedBlockSize
```
    Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32
  - encodedBlockSize
```
private final int encodedBlockSize
```
    Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32
  - lineLength
```
private final int lineLength
```
    Chunksize for encoding. Not used when decoding. A value of zero or less implies no chunking of the encoded data. Rounded down to nearest multiple of encodedBlockSize.
  - chunkSeparatorLength
```
private final int chunkSeparatorLength
```
    Size of chunk separator. Not used unless lineLength > 0.
  - buffer
```
private byte[] buffer
```
    Buffer for streaming.
  - pos
```
private int pos
```
    Position where next character should be written in the buffer.
  - readPos
```
private int readPos
```
    Position where next character should be read from the buffer.
  - eof
```
private boolean eof
```
    Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless, and must be thrown away.
  - currentLinePos
```
private int currentLinePos
```
    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).
  - modulus
```
private int modulus
```
    Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This variable helps track that.
- 构造器详细资料
  - Base64
```
public Base64()
```
    Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
    When encoding the line length is 0 (no chunking), and the encoding table is STANDARD_ENCODE_TABLE.
    
    When decoding all variants are supported.
  - Base64
```
public Base64(int lineLength,
              byte[] lineSeparator,
              boolean urlSafe)
```
    Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
    When encoding the line length and line separator are given in the constructor, and the encoding table is STANDARD_ENCODE_TABLE.
    
    Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
    
    When decoding all variants are supported.
    
    参数:
    
    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.
    
    lineSeparator - Each line of encoded data will end with this sequence of bytes.
    
    urlSafe - Instead of emitting '+' and '/' we emit '-' and '_' respectively. urlSafe is only applied to encode operations. Decoding seamlessly handles both modes.
    
    抛出:
    
    java.lang.IllegalArgumentException - The provided lineSeparator included some base64 characters. That's not going to work!
    
    从以下版本开始:
    
    1.4
- 方法详细资料
  - encode
```
private byte[] encode(byte[] pArray)
```
    Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
    
    参数:
    
    pArray - a byte array containing binary data
    
    返回:
    
    A byte array containing only the basen alphabetic character data
  - encode
```
void encode(byte[] in,
            int inPos,
            int inAvail)
```
    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).
    
    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/
    
    参数:
    
    in - byte[] array of binary data to base64 encode.
    
    inPos - Position to start reading data from.
    
    inAvail - Amount of bytes available from input for encoding.
  - decode
```
private byte[] decode(byte[] pArray)
```
    Decodes a byte[] containing characters in the Base-N alphabet.
    
    参数:
    
    pArray - A byte array containing Base-N character data
    
    返回:
    
    a byte array containing binary data
  - decode
```
void decode(byte[] in,
            int inPos,
            int inAvail)
```
    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.
    
    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.
    
    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/
    
    参数:
    
    in - byte[] array of ascii data to base64 decode.
    
    inPos - Position to start reading data from.
    
    inAvail - Amount of bytes available from input for encoding.
  - encodeBase64
```
public static byte[] encodeBase64(byte[] binaryData)
```
    Encodes binary data using the base64 algorithm but does not chunk the output.
    
    参数:
    
    binaryData - binary data to encode
    
    返回:
    
    byte[] containing Base64 characters in their UTF-8 representation.
  - encodeBase64
```
public static byte[] encodeBase64(byte[] binaryData,
                                  boolean isChunked,
                                  boolean urlSafe,
                                  int maxResultSize)
```
    Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
    
    参数:
    
    binaryData - Array containing binary data to encode.
    
    isChunked - if true this encoder will chunk the base64 output into 76 character blocks
    
    urlSafe - if true this encoder will emit - and _ instead of the usual + and / characters.
    
    maxResultSize - The maximum result size to accept.
    
    返回:
    
    Base64-encoded data.
    
    抛出:
    
    java.lang.IllegalArgumentException - Thrown when the input array needs an output array bigger than maxResultSize
    
    从以下版本开始:
    
    1.4
  - decodeBase64
```
public static byte[] decodeBase64(byte[] base64Data)
```
    Decodes Base64 data into octets.
    
    参数:
    
    base64Data - Byte array containing Base64 data
    
    返回:
    
    Array containing decoded data.
  - isInAlphabet
```
protected boolean isInAlphabet(byte octet)
```
    Returns whether or not the octet is in the Base32 alphabet.
    
    参数:
    
    octet - The value to test
    
    返回:
    
    true if the value is defined in the the Base32 alphabet false otherwise.
  - ensureBufferSize
```
private void ensureBufferSize(int size)
```
    Ensure that the buffer has room for size bytes.
    
    参数:
    
    size - minimum spare space required
  - readResults
```
private int readResults(byte[] b,
                        int bPos,
                        int bAvail)
```
    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.
    
    参数:
    
    b - byte[] array to extract the buffered data into.
    
    bPos - position in byte[] array to start extraction at.
    
    bAvail - amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
    
    返回:
    
    The number of bytes successfully extracted into the provided byte[] array.
  - reset
```
private void reset()
```
    Resets this object to its initial newly constructed state.
  - containsAlphabetOrPad
```
private boolean containsAlphabetOrPad(byte[] arrayOctet)
```
    Tests a given byte array to see if it contains any characters within the alphabet or PAD.
    Intended for use in checking line-ending arrays
    
    参数:
    
    arrayOctet - byte array to test
    
    返回:
    
    true if any byte is a valid character in the alphabet or PAD; false otherwise
  - getEncodedLength
```
private long getEncodedLength(byte[] pArray)
```
    Calculates the amount of space needed to encode the supplied array.
    
    参数:
    
    pArray - byte[] array which will later be encoded
    
    返回:
    
    amount of space needed to encoded the supplied array. Returns a long since a max-len array will require > Integer.MAX_VALUE

类 Base64

字段概要

构造器概要

方法概要

从类继承的方法 java.lang.Object

字段详细资料

BITS_PER_ENCODED_BYTE

BYTES_PER_UNENCODED_BLOCK

BYTES_PER_ENCODED_BLOCK

CHUNK_SEPARATOR

STANDARD_ENCODE_TABLE

URL_SAFE_ENCODE_TABLE

DECODE_TABLE

MASK_6BITS

encodeTable

decodeTable

lineSeparator

decodeSize

encodeSize

bitWorkArea

MIME_CHUNK_SIZE

DEFAULT_BUFFER_RESIZE_FACTOR

DEFAULT_BUFFER_SIZE

MASK_8BITS

PAD_DEFAULT

PAD

unencodedBlockSize

encodedBlockSize

lineLength

chunkSeparatorLength

buffer

pos

readPos

eof

currentLinePos

modulus

构造器详细资料

Base64

Base64

方法详细资料

encode

encode

decode

decode

encodeBase64

encodeBase64

decodeBase64

isInAlphabet

ensureBufferSize

readResults

reset

containsAlphabetOrPad

getEncodedLength