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/*********************************************************************
* Filename: base64.c
* Author: Brad Conte (brad AT bradconte.com)
* Copyright:
* Disclaimer: This code is presented "as is" without any guarantees.
* Details: Implementation of the Base64 encoding algorithm.
*********************************************************************/
/*************************** HEADER FILES ***************************/
#include <stdlib.h>
#include "base64.h"
/****************************** MACROS ******************************/
#define NEWLINE_INVL 76
/**************************** VARIABLES *****************************/
// Note: To change the charset to a URL encoding, replace the '+' and '/' with '*' and '-'
static const BYTE charset[]={"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"};
/*********************** FUNCTION DEFINITIONS ***********************/
BYTE revchar(char ch)
{
if (ch >= 'A' && ch <= 'Z')
ch -= 'A';
else if (ch >= 'a' && ch <='z')
ch = ch - 'a' + 26;
else if (ch >= '0' && ch <='9')
ch = ch - '0' + 52;
else if (ch == '+')
ch = 62;
else if (ch == '/')
ch = 63;
return(ch);
}
size_t base64_encode(const BYTE in[], BYTE out[], size_t len, int newline_flag)
{
size_t idx, idx2, blks, blk_ceiling, left_over, newline_count = 0;
blks = (len / 3);
left_over = len % 3;
if (out == NULL) {
idx2 = blks * 4 ;
if (left_over)
idx2 += 4;
if (newline_flag)
idx2 += len / 57; // (NEWLINE_INVL / 4) * 3 = 57. One newline per 57 input bytes.
}
else {
// Since 3 input bytes = 4 output bytes, determine out how many even sets of
// 3 bytes the input has.
blk_ceiling = blks * 3;
for (idx = 0, idx2 = 0; idx < blk_ceiling; idx += 3, idx2 += 4) {
out[idx2] = charset[in[idx] >> 2];
out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)];
out[idx2 + 2] = charset[((in[idx + 1] & 0x0f) << 2) | (in[idx + 2] >> 6)];
out[idx2 + 3] = charset[in[idx + 2] & 0x3F];
// The offical standard requires a newline every 76 characters.
// (Eg, first newline is character 77 of the output.)
if (((idx2 - newline_count + 4) % NEWLINE_INVL == 0) && newline_flag) {
out[idx2 + 4] = '\n';
idx2++;
newline_count++;
}
}
if (left_over == 1) {
out[idx2] = charset[in[idx] >> 2];
out[idx2 + 1] = charset[(in[idx] & 0x03) << 4];
out[idx2 + 2] = '=';
out[idx2 + 3] = '=';
idx2 += 4;
}
else if (left_over == 2) {
out[idx2] = charset[in[idx] >> 2];
out[idx2 + 1] = charset[((in[idx] & 0x03) << 4) | (in[idx + 1] >> 4)];
out[idx2 + 2] = charset[(in[idx + 1] & 0x0F) << 2];
out[idx2 + 3] = '=';
idx2 += 4;
}
}
return(idx2);
}
size_t base64_decode(const BYTE in[], BYTE out[], size_t len)
{
BYTE ch;
size_t idx, idx2, blks, blk_ceiling, left_over;
if (in[len - 1] == '=')
len--;
if (in[len - 1] == '=')
len--;
blks = len / 4;
left_over = len % 4;
if (out == NULL) {
if (len >= 77 && in[NEWLINE_INVL] == '\n') // Verify that newlines where used.
len -= len / (NEWLINE_INVL + 1);
blks = len / 4;
left_over = len % 4;
idx = blks * 3;
if (left_over == 2)
idx ++;
else if (left_over == 3)
idx += 2;
}
else {
blk_ceiling = blks * 4;
for (idx = 0, idx2 = 0; idx2 < blk_ceiling; idx += 3, idx2 += 4) {
if (in[idx2] == '\n')
idx2++;
out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4);
out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2);
out[idx + 2] = (revchar(in[idx2 + 2]) << 6) | revchar(in[idx2 + 3]);
}
if (left_over == 2) {
out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4);
idx++;
}
else if (left_over == 3) {
out[idx] = (revchar(in[idx2]) << 2) | ((revchar(in[idx2 + 1]) & 0x30) >> 4);
out[idx + 1] = (revchar(in[idx2 + 1]) << 4) | (revchar(in[idx2 + 2]) >> 2);
idx += 2;
}
}
return(idx);
}
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