Base64 Encoding/Decoding

pjproject-2.10pjlib-utilincludepjlib-utilase64.h

/* $Id$ */
/* 
 * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com)
 * Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
 */
#ifndef __PJLIB_UTIL_BASE64_H__
#define __PJLIB_UTIL_BASE64_H__

/**
 * @file base64.h
 * @brief Base64 encoding and decoding
 */

#include <pjlib-util/types.h>

PJ_BEGIN_DECL

/**
 * @defgroup PJLIB_UTIL_BASE64 Base64 Encoding/Decoding
 * @ingroup PJLIB_UTIL_ENCRYPTION
 * @{
 * This module implements base64 encoding and decoding.
 */

/**
 * Helper macro to calculate the approximate length required for base256 to
 * base64 conversion.
 */
#define PJ_BASE256_TO_BASE64_LEN(len)    (len * 4 / 3 + 3)

/**
 * Helper macro to calculate the approximage length required for base64 to
 * base256 conversion.
 */
#define PJ_BASE64_TO_BASE256_LEN(len)    (len * 3 / 4)


/**
 * Encode a buffer into base64 encoding.
 *
 * @param input        The input buffer.
 * @param in_len    Size of the input buffer.
 * @param output    Output buffer. Caller must allocate this buffer with
 *            the appropriate size.
 * @param out_len   On entry, it specifies the length of the output buffer. 
 *            Upon return, this will be filled with the actual
 *            length of the output buffer.
 *
 * @return        PJ_SUCCESS on success.
 */
PJ_DECL(pj_status_t) pj_base64_encode(const pj_uint8_t *input, int in_len,
                     char *output, int *out_len);


/**
 * Decode base64 string.
 *
 * @param input        Input string.
 * @param out        Buffer to store the output. Caller must allocate
 *            this buffer with the appropriate size.
 * @param out_len   On entry, it specifies the length of the output buffer. 
 *            Upon return, this will be filled with the actual
 *            length of the output.
 */
PJ_DECL(pj_status_t) pj_base64_decode(const pj_str_t *input, 
                      pj_uint8_t *out, int *out_len);



/**
 * @}
 */

PJ_END_DECL


#endif    /* __PJLIB_UTIL_BASE64_H__ */

pjproject-2.10pjlib-utilsrcpjlib-utilase64.c

/* $Id$ */
/* 
 * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com)
 * Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
 */
#include <pjlib-util/base64.h>
#include <pj/assert.h>
#include <pj/errno.h>

#define INV        -1
#define PADDING        '='

static const char base64_char[] = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
    'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
    'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
    'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
    'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', '+', '/' 
};

static int base256_char(char c)
{
    if (c >= 'A' && c <= 'Z')
    return (c - 'A');
    else if (c >= 'a' && c <= 'z')
    return (c - 'a' + 26);
    else if (c >= '0' && c <= '9')
    return (c - '0' + 52);
    else if (c == '+')
    return (62);
    else if (c == '/')
    return (63);
    else {
    /* It *may* happen on bad input, so this is not a good idea.
     * pj_assert(!"Should not happen as '=' should have been filtered");
     */
    return INV;
    }
}


static void base256to64(pj_uint8_t c1, pj_uint8_t c2, pj_uint8_t c3, 
            int padding, char *output)
{
    *output++ = base64_char[c1>>2];
    *output++ = base64_char[((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)];
    switch (padding) {
    case 0:
    *output++ = base64_char[((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6)];
    *output = base64_char[c3 & 0x3F];
    break;
    case 1:
    *output++ = base64_char[((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6)];
    *output = PADDING;
    break;
    case 2:
    default:
    *output++ = PADDING;
    *output = PADDING;
    break;
    }
}


PJ_DEF(pj_status_t) pj_base64_encode(const pj_uint8_t *input, int in_len,
                     char *output, int *out_len)
{
    const pj_uint8_t *pi = input;
    pj_uint8_t c1, c2, c3;
    int i = 0;
    char *po = output;

    PJ_ASSERT_RETURN(input && output && out_len, PJ_EINVAL);
    PJ_ASSERT_RETURN(*out_len >= PJ_BASE256_TO_BASE64_LEN(in_len), 
             PJ_ETOOSMALL);

    while (i < in_len) {
    c1 = *pi++;
    ++i;

    if (i == in_len) {
        base256to64(c1, 0, 0, 2, po);
        po += 4;
        break;
    } else {
        c2 = *pi++;
        ++i;

        if (i == in_len) {
        base256to64(c1, c2, 0, 1, po);
        po += 4;
        break;
        } else {
        c3 = *pi++;
        ++i;
        base256to64(c1, c2, c3, 0, po);
        }
    }

    po += 4;
    }

    *out_len = (int)(po - output);
    return PJ_SUCCESS;
}


PJ_DEF(pj_status_t) pj_base64_decode(const pj_str_t *input, 
                     pj_uint8_t *out, int *out_len)
{
    const char *buf;
    int len;
    int i, j, k;
    int c[4];

    PJ_ASSERT_RETURN(input && out && out_len, PJ_EINVAL);

    buf = input->ptr;
    len = (int)input->slen;
    while (len && buf[len-1] == '=')
    --len;

    PJ_ASSERT_RETURN(*out_len >= PJ_BASE64_TO_BASE256_LEN(len), 
             PJ_ETOOSMALL);

    for (i=0, j=0; i<len; ) {
    /* Fill up c, silently ignoring invalid characters */
    for (k=0; k<4 && i<len; ++k) {
        do {
        c[k] = base256_char(buf[i++]);
        } while (c[k]==INV && i<len);
    }

    if (k<4) {
        if (k > 1) {
        out[j++] = (pj_uint8_t)((c[0]<<2) | ((c[1] & 0x30)>>4));
        if (k > 2) {
            out[j++] = (pj_uint8_t)
                   (((c[1] & 0x0F)<<4) | ((c[2] & 0x3C)>>2));
        }
        }
        break;
    }

    out[j++] = (pj_uint8_t)((c[0]<<2) | ((c[1] & 0x30)>>4));
    out[j++] = (pj_uint8_t)(((c[1] & 0x0F)<<4) | ((c[2] & 0x3C)>>2));
    out[j++] = (pj_uint8_t)(((c[2] & 0x03)<<6) | (c[3] & 0x3F));
    }

    pj_assert(j <= *out_len);
    *out_len = j;

    return PJ_SUCCESS;
}