src/lib/base64.c

	base64.c revision c0435c854a0e7246373b9752d163095cc4fbe985
/* Based on the sources of Cyrus IMAP:
 *
 * Copyright (c) 2000 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any other legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include "lib.h"
#include "base64.h"
#include "buffer.h"

static const char basis_64[] =
   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

int base64_encode(const unsigned char *src, size_t src_size, buffer_t *dest)
{
    size_t src_pos;
    int c1, c2, c3;

    for (src_pos = 0; src_pos < src_size; ) {
        c1 = src[src_pos++];
        if (buffer_append_c(dest, basis_64[c1 >> 2]) != 1)
            return 0;

        c2 = src_pos == src_size ? 0 : src[src_pos];
        if (buffer_append_c(dest, basis_64[((c1 & 0x03) << 4) |
                           ((c2 & 0xf0) >> 4)]) != 1)
            return 0;

        if (src_pos++ == src_size) {
            if (buffer_append(dest, "==", 2) != 2)
                return 0;
            break;
        }

        c3 = src_pos == src_size ? 0 : src[src_pos];
        if (buffer_append_c(dest, basis_64[((c2 & 0x0f) << 2) |
                           ((c3 & 0xc0) >> 6)]) != 1)
            return 0;

        if (src_pos++ == src_size) {
            if (buffer_append_c(dest, '=') != 1)
                return 0;
            break;
        }

        if (buffer_append_c(dest, basis_64[c3 & 0x3f]) != 1)
            return 0;
    }

    return 1;
}

#define XX 127

/* Table for decoding base64 */
static const char index_64[256] = {
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,62, XX,XX,XX,63,
    52,53,54,55, 56,57,58,59, 60,61,XX,XX, XX,XX,XX,XX,
    XX, 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,XX, XX,XX,XX,XX,
    XX,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,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
};

int base64_decode(const unsigned char *src, size_t src_size,
          size_t *src_pos_r, buffer_t *dest)
{
    size_t src_pos;
    unsigned char buf[4];
    int c1, c2, c3, c4;
    size_t ret, size;

    for (src_pos = 0; src_pos+3 < src_size; ) {
        c1 = src[src_pos++];

        if (c1 == '\n' || c1 == '\r' || c1 == ' ' || c1 == '\t')
            continue;

        if (index_64[c1] == XX)
            return -1;

        c2 = src[src_pos++];
        if (index_64[c2] == XX)
            return -1;

        c3 = src[src_pos++];
        if (c3 != '=' && index_64[c3] == XX)
            return -1;

        c4 = src[src_pos++];
        if (c4 != '=' && index_64[c4] == XX)
            return -1;

        buf[0] = (index_64[c1] << 2) | ((index_64[c2] & 0x30) >> 4);
        if (c3 == '=') {
            if (c4 != '=')
                return -1;
            size = 1;
        } else {
            buf[1] = ((index_64[c2] & 0xf) << 4) |
                ((index_64[c3] & 0x3c) >> 2);

            if (c4 == '=')
                size = 2;
            else {
                buf[2] = ((index_64[c3] & 0x3) << 6) |
                    index_64[c4];
                size = 3;
            }
        }

        ret = buffer_append(dest, buf, size);
        if (ret != size) {
            /* buffer full */
            if (src_pos_r != NULL) {
                *src_pos_r = src_pos-4;
                                ret = buffer_get_used_size(dest) - (size-ret);
                buffer_set_used_size(dest, ret);
            }
            return 0;
        }

        if (size < 3) {
            /* end of base64 data */
            break;
        }
    }

    if (src_pos_r != NULL)
        *src_pos_r = src_pos;

    return 1;
}