base64.c

-

/*
 * $Id: base64.c,v 1.16 1998/10/14 02:40:25 wessels Exp $
 */

#include "config.h"

#if HAVE_STDIO_H
#include <stdio.h>
#endif
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif

static void base64_init(void);

static int base64_initialized = 0;
#define BASE64_VALUE_SZ 256
#define BASE64_RESULT_SZ 8192
int base64_value[BASE64_VALUE_SZ];
const char base64_code[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";


static void
base64_init(void)
{
    int i;

    for (i = 0; i < BASE64_VALUE_SZ; i++)
	base64_value[i] = -1;

    for (i = 0; i < 64; i++)
	base64_value[(int) base64_code[i]] = i;
    base64_value['='] = 0;

    base64_initialized = 1;
}

char *
base64_decode(const char *p)
{
    static char result[BASE64_RESULT_SZ];
    int j;
    unsigned int k;
    int c;
    long val;
    if (!p)
	return NULL;
    if (!base64_initialized)
	base64_init();
    val = c = 0;
    for (j = 0; *p && j + 3 < BASE64_RESULT_SZ; p++) {
	k = (int) *p % BASE64_VALUE_SZ;
	if (base64_value[k] < 0)
	    continue;
	val <<= 6;
	val += base64_value[k];
	if (++c < 4)
	    continue;
	/* One quantum of four encoding characters/24 bit */
	result[j++] = val >> 16;	/* High 8 bits */
	result[j++] = (val >> 8) & 0xff;	/* Mid 8 bits */
	result[j++] = val & 0xff;	/* Low 8 bits */
	val = c = 0;
    }
    result[j] = 0;
    return result;
}

/* adopted from http://ftp.sunet.se/pub2/gnu/vm/base64-encode.c with adjustments */
const char *
base64_encode(const char *decoded_str)
{
    static char result[BASE64_RESULT_SZ];
    int bits = 0;
    int char_count = 0;
    int out_cnt = 0;
    int c;

    if (!decoded_str)
	return decoded_str;

    if (!base64_initialized)
	base64_init();

    while ((c = *decoded_str++) && out_cnt < sizeof(result) - 1) {
	bits += c;
	char_count++;
	if (char_count == 3) {
	    result[out_cnt++] = base64_code[bits >> 18];
	    result[out_cnt++] = base64_code[(bits >> 12) & 0x3f];
	    result[out_cnt++] = base64_code[(bits >> 6) & 0x3f];
	    result[out_cnt++] = base64_code[bits & 0x3f];
	    bits = 0;
	    char_count = 0;
	} else {
	    bits <<= 8;
	}
    }
    if (char_count != 0) {
	bits <<= 16 - (8 * char_count);
	result[out_cnt++] = base64_code[bits >> 18];
	result[out_cnt++] = base64_code[(bits >> 12) & 0x3f];
	if (char_count == 1) {
	    result[out_cnt++] = '=';
	    result[out_cnt++] = '=';
	} else {
	    result[out_cnt++] = base64_code[(bits >> 6) & 0x3f];
	    result[out_cnt++] = '=';
	}
    }
    result[out_cnt] = '\0';	/* terminate */
    return result;
}