/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */

/* util/support/base64.c - base64 encoder and decoder */

/*

 * Copyright (c) 1995-2001 Kungliga Tekniska Högskolan

 * (Royal Institute of Technology, Stockholm, Sweden).

 * 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. Neither the name of the Institute nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

#include <k5-platform.h>

#include <k5-base64.h>

static const char base64_chars[] =

    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

char *

k5_base64_encode(const void *data, size_t len)

{

    char *s, *p;

    size_t i;

    unsigned int c;

    const unsigned char *q;

    if (len > SIZE_MAX / 4)

        return NULL;

    p = s = malloc(len * 4 / 3 + 4);

    if (p == NULL)

        return NULL;

    q = (const unsigned char *)data;

    for (i = 0; i < len;) {

        c = q[i++];

        c *= 256;

        if (i < len)

            c += q[i];

        i++;

        c *= 256;

        if (i < len)

            c += q[i];

        i++;

        p[0] = base64_chars[(c & 0x00fc0000) >> 18];

        p[1] = base64_chars[(c & 0x0003f000) >> 12];

        p[2] = base64_chars[(c & 0x00000fc0) >> 6];

        p[3] = base64_chars[(c & 0x0000003f) >> 0];

        if (i > len)

            p[3] = '=';

        if (i > len + 1)

            p[2] = '=';

        p += 4;

    }

    *p = '\0';

    return s;

}

#define DECODE_ERROR 0xffffffff

/* Decode token, which must be four bytes long. */

static unsigned int

decode_token(const char *token)

{

    int i, marker = 0;

    unsigned int val = 0;

    const char *p;

    for (i = 0; i < 4; i++) {

        val *= 64;

        if (token[i] == '=') {

            marker++;

        } else if (marker > 0) {

            return DECODE_ERROR;

        } else {

            p = strchr(base64_chars, token[i]);

            if (p == NULL)

                return DECODE_ERROR;

            val += p - base64_chars;

        }

    }

    if (marker > 2)

        return DECODE_ERROR;

    return (marker << 24) | val;

}

void *

k5_base64_decode(const char *str, size_t *len_out)

{

    unsigned char *data, *q;

    unsigned int val, marker;

    size_t len;

    *len_out = SIZE_MAX;

    /* Allocate the output buffer. */

    len = strlen(str);

    if (len % 4)

        return NULL;

    q = data = malloc(len / 4 * 3);

    if (data == NULL) {

        *len_out = 0;

        return NULL;

    }

    /* Decode the string. */

    for (; *str != '\0'; str += 4) {

        val = decode_token(str);

        if (val == DECODE_ERROR) {

            free(data);

            return NULL;

        }

        marker = (val >> 24) & 0xff;

        *q++ = (val >> 16) & 0xff;

        if (marker < 2)

            *q++ = (val >> 8) & 0xff;

        if (marker < 1)

            *q++ = val & 0xff;

    }

    *len_out = q - data;

    return data;

}