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/*
This code is based on:
Encode or decode file as MIME base64 (RFC 1341)
by John Walker
http://www.fourmilab.ch/
This program is in the public domain.
*/
#define REVDATE "11th August 1997"
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
typedef unsigned char byte; /* Byte type */
/* ENCODE -- Encode binary file into base64. */
void
Base64Encode(char *dst, char *src, size_t max)
{
int i, n=3;
static byte dtable[64];
if (!dtable[63]) {
/* Fill dtable with character encodings. */
for (i = 0; i < 26; i++) {
dtable[i] = 'A' + i;
dtable[26 + i] = 'a' + i;
}
for (i = 0; i < 10; i++) {
dtable[52 + i] = '0' + i;
}
dtable[62] = '+';
dtable[63] = '/';
}
while (max > 0 && n > 2 && *src) {
byte igroup[4]={0};
strncpy(igroup, src, 3);
n = strlen(igroup);
dst[0] = dtable[igroup[0] >> 2];
dst[1] = dtable[((igroup[0] & 3) << 4) | (igroup[1] >> 4)];
dst[2] = dtable[((igroup[1] & 0xF) << 2) | (igroup[2] >> 6)];
dst[3] = dtable[igroup[2] & 0x3F];
if (n < 3) {
dst[3] = '=';
if (n < 2) {
dst[2] = '=';
dst --;
max ++;
}
}
src += 3;
dst += 4;
max -= 4;
}
*dst = '\0';
}
/* DECODE -- Decode base64. */
void
Base64Decode(char *dst, char *src, size_t max)
{
int i;
static byte dtable[256];
if (!dtable['/']) {
for (i = 0; i < 255; i++) {
dtable[i] = 0x80;
}
for (i = 'A'; i <= 'Z'; i++) {
dtable[i] = 0 + (i - 'A');
}
for (i = 'a'; i <= 'z'; i++) {
dtable[i] = 26 + (i - 'a');
}
for (i = '0'; i <= '9'; i++) {
dtable[i] = 52 + (i - '0');
}
dtable['+'] = 62;
dtable['/'] = 63;
dtable['='] = 0;
}
/*CONSTANTCONDITION*/
while (max > 0 && *src > ' ') {
*dst ++ = (dtable[src[0]] << 2) | (dtable[src[1]] >> 4);
if (src[2] != '=') {
*dst ++ = (dtable[src[1]] << 4) | (dtable[src[2]] >> 2);
if (src[3] != '=')
*dst ++ = (dtable[src[2]] << 6) | dtable[src[3]];
else break;
} else break;
src += 4;
max -= 4;
}
*dst = '\0';
}
#ifdef DEBUG_BASE64
/* Main program */
int main(int argc, char *argv[])
{
char en[256], de[256];
printf("<%s>", argv[1]);
Base64Encode(en, argv[1], sizeof(en));
printf("-><%s>", en);
Base64Decode(de, en, sizeof(de));
printf("-><%s>\n", de);
return 0;
}
#endif
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