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@prestonp
Last active December 21, 2015 21:33
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base64 java

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javac Main.java
java Main
import java.io.ByteArrayOutputStream;
public class Base64
{
public static String encode(byte[] data)
{
char[] tbl = {
'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','+','/' };
StringBuilder buffer = new StringBuilder();
int pad = 0;
for (int i = 0; i < data.length; i += 3) {
int b = ((data[i] & 0xFF) << 16) & 0xFFFFFF;
if (i + 1 < data.length) {
b |= (data[i+1] & 0xFF) << 8;
} else {
pad++;
}
if (i + 2 < data.length) {
b |= (data[i+2] & 0xFF);
} else {
pad++;
}
for (int j = 0; j < 4 - pad; j++) {
int c = (b & 0xFC0000) >> 18;
buffer.append(tbl[c]);
b <<= 6;
}
}
for (int j = 0; j < pad; j++) {
buffer.append("=");
}
return buffer.toString();
}
public static byte[] decode(String data)
{
int[] tbl = {
-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, -1, -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, -1, -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, -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, -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, -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, -1, -1, -1 };
byte[] bytes = data.getBytes();
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
for (int i = 0; i < bytes.length; ) {
int b = 0;
if (tbl[bytes[i]] != -1) {
b = (tbl[bytes[i]] & 0xFF) << 18;
}
// skip unknown characters
else {
i++;
continue;
}
int num = 0;
if (i + 1 < bytes.length && tbl[bytes[i+1]] != -1) {
b = b | ((tbl[bytes[i+1]] & 0xFF) << 12);
num++;
}
if (i + 2 < bytes.length && tbl[bytes[i+2]] != -1) {
b = b | ((tbl[bytes[i+2]] & 0xFF) << 6);
num++;
}
if (i + 3 < bytes.length && tbl[bytes[i+3]] != -1) {
b = b | (tbl[bytes[i+3]] & 0xFF);
num++;
}
while (num > 0) {
int c = (b & 0xFF0000) >> 16;
buffer.write((char)c);
b <<= 8;
num--;
}
i += 4;
}
return buffer.toByteArray();
}
}
public class Main {
public static void main(String []args){
System.out.println("Helo");
// encode byte[]
byte foo[] = new byte[] {'a', 'b', 'c'};
System.out.println(Base64.encode(foo));
// encode string
String bar = "poobear";
System.out.println(Base64.encode(bar.getBytes()));
}
}
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