base64.c

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/*
 * This code implements the BASE64 algorithm.
 * This code is in the public domain; do with it what you wish.
 *
 * @file base64.c
 * @brief This code implements the BASE64 algorithm
 * @author Matthieu Speder
 */

#include <memory.h>
#include <stdlib.h>
#include "base64.h"

static const char base64_chars[] =
                "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const char base64_digits[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 62, 0, 0, 0, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
                0, 0, 0, -1, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
                14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 0, 0, 26,
                27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44,
                45, 46, 47, 48, 49, 50, 51, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };


char* BASE64Decode(const char* src) {
        unsigned int in_len = strlen(src);
        char* dest;
        char* result;

        if (in_len % 4) {
                /* Wrong base64 string length */
                return NULL;
        }
        result = dest = malloc(in_len / 4 * 3 + 1);
        if (result == NULL)
           return NULL; /* out of memory */
        while (*src) {
                char a = base64_digits[(unsigned char)*(src++)];
                char b = base64_digits[(unsigned char)*(src++)];
                char c = base64_digits[(unsigned char)*(src++)];
                char d = base64_digits[(unsigned char)*(src++)];
                *(dest++) = (a << 2) | ((b & 0x30) >> 4);
                if (c == -1)
                        break;
                *(dest++) = ((b & 0x0f) << 4) | ((c & 0x3c) >> 2);
                if (d == -1)
                        break;
                *(dest++) = ((c & 0x03) << 6) | d;
        }
        *dest = 0;
        return result;
}

/* end of base64.c */