Hi I have 2 functions to encode a packet in Base64. But the client can not connect with the server. May be the encoding and decoding is in problem. These two programs might not working combinedly. This is for sending a TCP Packet after Base64 Encoding from Android Java Code and receiving and decoded in C.
We are using ToyVPN Android Client and ToyVPNServer. The links are here- https://github.com/LipiLee/ToyVpn and https://github.com/LipiLee/ToyVpnServer Here is Java code for Encoding-
public final static byte[] ALPHABET =
{(byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F',
(byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K',
(byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P',
(byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
(byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
(byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e',
(byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j',
(byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o',
(byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't',
(byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y',
(byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3',
(byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8',
(byte) '9', (byte) '+', (byte) '/'};
/**
* The 64 valid web safe Base64 values.
*/
public static byte[] encode(byte[] source, int off, int len, byte[] alphabet,
int maxLineLength) {
int lenDiv3 = (len + 2) / 3; // ceil(len / 3)
int len43 = lenDiv3 * 4;
byte[] outBuff = new byte[len43 // Main 4:3
+ (len43 / maxLineLength)]; // New lines
int d = 0;
int e = 0;
int len2 = len - 2;
int lineLength = 0;
for (; d < len2; d += 3, e += 4) {
// The following block of code is the same as
// encode3to4( source, d + off, 3, outBuff, e, alphabet );
// but inlined for faster encoding (~20% improvement)
int inBuff =
((source[d + off] << 24) >>> 8)
| ((source[d + 1 + off] << 24) >>> 16)
| ((source[d + 2 + off] << 24) >>> 24);
outBuff[e] = alphabet[(inBuff >>> 18)];
outBuff[e + 1] = alphabet[(inBuff >>> 12) & 0x3f];
outBuff[e + 2] = alphabet[(inBuff >>> 6) & 0x3f];
outBuff[e + 3] = alphabet[(inBuff) & 0x3f];
lineLength += 4;
if (lineLength == maxLineLength) {
outBuff[e + 4] = NEW_LINE;
e++;
lineLength = 0;
} // end if: end of line
} // end for: each piece of array
if (d < len) {
encode3to4(source, d + off, len - d, outBuff, e, alphabet);
lineLength += 4;
if (lineLength == maxLineLength) {
// Add a last newline
outBuff[e + 4] = NEW_LINE;
e++;
}
e += 4;
}
assert (e == outBuff.length);
return outBuff;
}
Here is C Code for Decoding, this is using the same Decoding Alphabet like Java Encoding Alphabet.
//Base64 char table - used internally for encoding
unsigned char b64_chr[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
unsigned int b64_int(unsigned int ch) {
// ASCII to base64_int
// 65-90 Upper Case >> 0-25
// 97-122 Lower Case >> 26-51
// 48-57 Numbers >> 52-61
// 43 Plus (+) >> 62
// 47 Slash (/) >> 63
// 61 Equal (=) >> 64~
if (ch==43)
return 62;
if (ch==47)
return 63;
if (ch==61)
return 64;
if ((ch>47) && (ch<58))
return ch + 4;
if ((ch>64) && (ch<91))
return ch - 'A';
if ((ch>96) && (ch<123))
return (ch - 'a') + 26;
return 0;
}
unsigned int b64_decode(unsigned char* in, unsigned int in_len, unsigned char* out) {
unsigned int i=0, j=0, k=0, s[4];
for (i=0;i<in_len;i++) {
s[j++]=b64_int(*(in+i));
if (j==4) {
out[k+0] = ((s[0]&255)<<2)+((s[1]&0x30)>>4);
if (s[2]!=64) {
out[k+1] = ((s[1]&0x0F)<<4)+((s[2]&0x3C)>>2);
if ((s[3]!=64)) {
out[k+2] = ((s[2]&0x03)<<6)+(s[3]); k+=3;
} else {
k+=2;
}
} else {
k+=1;
}
j=0;
}
}
return k;
}
