Tutorial Addendum on Data Encoding - Base64 Encoding

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 31 December 18:00   

    



    



    

/**

    

* base-64 encode a byte array

    

* @param src The byte arrangement to encode

    

* @returns The base64 encoded result

    

*/

    

accessible changeless String

    

encode(byte src) {

    

return encode(src, 0, src.length);

    

}

    

/**

    

* base-64 encode a byte array

    

* @param src The byte arrangement to encode

    

* @param start The starting index

    

* @param len The amount of bytes

    

* @returns The base64 encoded result

    

*/

    

accessible changeless String

    

encode(byte src, int start, int length) {

    

byte dst = new byte;

    

int x = 0;

    

int dstIndex = 0;

    

int accompaniment = 0; // which burn in pattern

    

int old = 0; // antecedent byte

    

int len = 0; // breadth decoded so far

    

int max = breadth + start;

    

for (int srcIndex = start; srcIndex<max; srcIndex++) {

    

x = src;

    

about-face (++state) {

    

case 1:

    

dst = encodeData;

    

break;

    

case 2:

    

dst = encodeData;

    

break;

    

case 3:

    

dst = encodeData;

    

dst = encodeData;

    

state = 0;

    

break;

    

}

    

old = x;

    

if (++len >= 72) {

    

dst = (byte)
;

    

len = 0;

    

}

    

}

    

/*

    

* now apple-pie up the end bytes

    

*/

    

switch (state) {

    

case 1: dst = encodeData;

    

dst = (byte) = ;

    

dst = (byte) = ;

    

break;

    

case 2: dst = encodeData;

    

dst = (byte) = ;

    

break;

    

}

    

return new String(dst);

    

}

    

/**

    

* A Base64 decoder. This accomplishing is slow, and

    

* doesn t handle captivated lines.

    

* The achievement is amorphous if there are errors in the input.

    

* @param s a Base64 encoded string

    

* @returns The byte arrangement eith the decoded result

    

*/

    

accessible changeless byte

    

decode(String s) {

    

int end = 0; // end state

    

if (s.endsWith("=")) {

    

end++;

    

}

    

if (s.endsWith("==")) {

    

end++;

    

}

    

int len = (s.length() + 3)/4 * 3 - end;

    

byte aftereffect = new byte;

    

int dst = 0;

    

try {

    

for(int src = 0; src< s.length(); src++) {

    

int cipher = charSet.indexOf(s.charAt(src));

    

if (code == -1) {

    

break;

    

}

    

about-face (src%4) {

    

case 0:

    

result = (byte) (code<<2);

    

break;

    

case 1:

    

result |= (byte) ((code>>4) & 0x3);

    

result = (byte) (code<<4);

    

break;

    

case 2:

    

result |= (byte) ((code>>2) & 0xf);

    

result = (byte) (code<<6);

    

break;

    

case 3:

    

result |= (byte) (code & 0x3f);

    

break;

    

}

    

}

    

} bolt (ArrayIndexOutOfBoundsException e) {}

    

acknowledgment result;

    

}

    

/**

    

* Analysis the decoder and encoder.

    

* Alarm as <code>Base64 </code>.

    

*/

    

accessible changeless void

    

main(String args) {

    

System.out.println("encode: " + args + " -> (" +

    

encode(args) +

    

")");

    

System.out.println("decode: " + args + " -> (" +

    

new String(decode(args)) + ")");

    

}

    

}

    



    



    

Exercise: Address a program to analyze the achievement of Baase64 encoding

    

with UUEncode. I accept UUEncode will accomplish better, because the achievement characters

    

are computed instead looked up through an array.

    



    

 


Tags: array, state, start, public, string, result

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Article In : Computers & Technology  -  Encoding