AS3的BASE64编码与解码类

最近任务紧，工作忙，好久没来更新我的BLOG了。

今天在国外网站上淘到一个很好用的AS3的BASE64类

感觉写得简洁而强大。很好，赶快放上来。

调用代码：

import
com
.
dynamicflash
.
utils
.
Base64
;

//编码和解码字符串

var
source
:
String

=

"Hello, world"
;

var
encoded
:
String

=

Base64
.
encode
(
source
);

trace
(
encoded
);

var
decoded
:
String

=

Base64
.
decode
(
encoded
);

trace
(
decoded
);

//编码和解码ByteArray

var
obj
:
Object
=

{
name
:
"Dynamic Flash"
,
url
:
"http://dynamicflash.com"
};

var
source
:
ByteArray

=

new

ByteArray
();

source
.
writeObject
(
obj
);

var
encoded
:
String

=

Base64
.
encodeByteArray
(
source
);

trace
(
encoded
);

var
decoded
:
ByteArray

=

Base64
.
decodeToByteArray
(
encoded
);

obj
=
decoded
.
readObject
();

trace
(
obj
.
name
+

"("

+
obj
.
url
+

")"
);

-----------------------------------------------------------------------------------------------------------------
Base64类代码：

package
com
.
dynamicflash
.
util
{

import
flash
.
utils
.
ByteArray
;

public

class

Base64

{

private

static

const
BASE64_CHARS
:
String

=

"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
;

public

static

const
version
:
String

=

"1.0.0"
;

public

static

function
encode
(
data
:
String
):
String

{

// Convert string to ByteArray

var
bytes
:
ByteArray

=

new

ByteArray
();

bytes
.
writeUTFBytes
(
data
);

// Return encoded ByteArray

return
encodeByteArray
(
bytes
);

}

public

static

function
encodeByteArray
(
data
:
ByteArray
):
String

{

// Initialise output

var
output
:
String

=

""
;

// Create data and output buffers

var
dataBuffer
:
Array
;

var
outputBuffer
:
Array

=

new

Array
(
4
);

// Rewind ByteArray

data
.
position
=

0
;

// while there are still bytes to be processed

while

(
data
.
bytesAvailable
>

0
)

{

// Create new data buffer and populate next 3 bytes from data

dataBuffer
=

new

Array
();

for

(
var
i
:
uint

=

0
;
i
<

3

&&
data
.
bytesAvailable
>

0
;
i
++)

{

dataBuffer
[
i
]

=
data
.
readUnsignedByte
();

}

// Convert to data buffer Base64 character positions and

// store in output buffer

outputBuffer
[
0
]

=

(
dataBuffer
[
0
]

&

0xfc
)

>>

2
;

outputBuffer
[
1
]

=

((
dataBuffer
[
0
]

&

0x03
)

<<

4
)

|

((
dataBuffer
[
1
])

>>

4
);

outputBuffer
[
2
]

=

((
dataBuffer
[
1
]

&

0x0f
)

<<

2
)

|

((
dataBuffer
[
2
])

>>

6
);

outputBuffer
[
3
]

=
dataBuffer
[
2
]

&

0x3f
;

// If data buffer was short (i.e not 3 characters) then set

// end character indexes in data buffer to index of '=' symbol.

// This is necessary because Base64 data is always a multiple of

// 4 bytes and is basses with '=' symbols.

for

(
var
j
:
uint

=
dataBuffer
.
length
;
j
<

3
;
j
++)

{

outputBuffer
[
j
+

1
]

=

64
;

}

// Loop through output buffer and add Base64 characters to

// encoded data string for each character.

for

(
var
k
:
uint

=

0
;
k
<
outputBuffer
.
length
;
k
++)

{

output
+=
BASE64_CHARS
.
charAt
(
outputBuffer
[
k
]);

}

}

// Return encoded data

return
output
;

}

public

static

function
decode
(
data
:
String
):
String

{

// Decode data to ByteArray

var
bytes
:
ByteArray

=
decodeToByteArray
(
data
);

// Convert to string and return

return
bytes
.
readUTFBytes
(
bytes
.
length
);

}

public

static

function
decodeToByteArray
(
data
:
String
):
ByteArray

{

// Initialise output ByteArray for decoded data

var
output
:
ByteArray

=

new

ByteArray
();

// Create data and output buffers

var
dataBuffer
:
Array

=

new

Array
(
4
);

var
outputBuffer
:
Array

=

new

Array
(
3
);

// While there are data bytes left to be processed

for

(
var
i
:
uint

=

0
;
i
<
data
.
length
;
i
+=

4
)

{

// Populate data buffer with position of Base64 characters for

// next 4 bytes from encoded data

for

(
var
j
:
uint

=

0
;
j
<

4

&&
i
+
j
<
data
.
length
;
j
++)

{

dataBuffer
[
j
]

=
BASE64_CHARS
.
indexOf
(
data
.
charAt
(
i
+
j
));

}

// Decode data buffer back into bytes

outputBuffer
[
0
]

=

(
dataBuffer
[
0
]

<<

2
)

+

((
dataBuffer
[
1
]

&

0x30
)

>>

4
);

outputBuffer
[
1
]

=

((
dataBuffer
[
1
]

&

0x0f
)

<<

4
)

+

((
dataBuffer
[
2
]

&

0x3c
)

>>

2
);

outputBuffer
[
2
]

=

((
dataBuffer
[
2
]

&

0x03
)

<<

6
)

+
dataBuffer
[
3
];

// Add all non-padded bytes in output buffer to decoded data

for

(
var
k
:
uint

=

0
;
k
<
outputBuffer
.
length
;
k
++)

{

if

(
dataBuffer
[
k
+
1
]

==

64
)

break
;

output
.
writeByte
(
outputBuffer
[
k
]);

}

}

// Rewind decoded data ByteArray

output
.
position
=

0
;

// Return decoded data

return
output
;

}

public

function

Base64
()

{

throw

new

Error
(
"Base64 class is static container only"
);

}

}

}

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