Base64.cpp

#include "Base64.h"

const char b64_alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";

/* 'Private' declarations */
inline void a3_to_a4(unsigned char * a4, unsigned char * a3);
inline void a4_to_a3(unsigned char * a3, unsigned char * a4);
inline unsigned char b64_lookup(char c);

int base64_encode(char *output, char *input, int inputLen) {
int i = 0, j = 0;
int encLen = 0;
unsigned char a3[3];
unsigned char a4[4];

while(inputLen--) {
a3[i++] = *(input++);
if(i == 3) {
a3_to_a4(a4, a3);

for(i = 0; i < 4; i++) {
output[encLen++] = b64_alphabet[a4[i]];
}

i = 0;
}
}

if(i) {
for(j = i; j < 3; j++) {
a3[j] = '\0';
}

a3_to_a4(a4, a3);

for(j = 0; j < i + 1; j++) {
output[encLen++] = b64_alphabet[a4[j]];
}

while((i++ < 3)) {
output[encLen++] = '=';
}
}
output[encLen] = '\0';
return encLen;
}

int base64_decode(char * output, char * input, int inputLen) {
int i = 0, j = 0;
int decLen = 0;
unsigned char a3[3];
unsigned char a4[4];


while (inputLen--) {
if(*input == '=') {
break;
}

a4[i++] = *(input++);
if (i == 4) {
for (i = 0; i <4; i++) {
a4[i] = b64_lookup(a4[i]);
}

a4_to_a3(a3,a4);

for (i = 0; i < 3; i++) {
output[decLen++] = a3[i];
}
i = 0;
}
}

if (i) {
for (j = i; j < 4; j++) {
a4[j] = '\0';
}

for (j = 0; j <4; j++) {
a4[j] = b64_lookup(a4[j]);
}

a4_to_a3(a3,a4);

for (j = 0; j < i - 1; j++) {
output[decLen++] = a3[j];
}
}
output[decLen] = '\0';
return decLen;
}

int base64_enc_len(int plainLen) {
int n = plainLen;
return (n + 2 - ((n + 2) % 3)) / 3 * 4;
}

int base64_dec_len(char * input, int inputLen) {
int i = 0;
int numEq = 0;
for(i = inputLen - 1; input[i] == '='; i--) {
numEq++;
}

return ((6 * inputLen) / 8) - numEq;
}

inline void a3_to_a4(unsigned char * a4, unsigned char * a3) {
a4[0] = (a3[0] & 0xfc) >> 2;
a4[1] = ((a3[0] & 0x03) << 4) + ((a3[1] & 0xf0) >> 4);
a4[2] = ((a3[1] & 0x0f) << 2) + ((a3[2] & 0xc0) >> 6);
a4[3] = (a3[2] & 0x3f);
}

inline void a4_to_a3(unsigned char * a3, unsigned char * a4) {
a3[0] = (a4[0] << 2) + ((a4[1] & 0x30) >> 4);
a3[1] = ((a4[1] & 0xf) << 4) + ((a4[2] & 0x3c) >> 2);
a3[2] = ((a4[2] & 0x3) << 6) + a4[3];
}

inline unsigned char b64_lookup(char c) {
int i;
for(i = 0; i < 64; i++) {
if(b64_alphabet[i] == c) {
return i;
}
}

return -1;
}