source: rtems/cpukit/httpd/base64.c @ a6b4c0df

/*
 * base64.c -- Base64 Mime encoding
 *
 * Copyright (c) GoAhead Software Inc., 1995-2000. All Rights Reserved.
 *
 * See the file "license.txt" for usage and redistribution license requirements
 */

/******************************** Description *********************************/

/*
 *      The base64 command encodes and decodes a string in mime base64 format
 */

/********************************* Includes ***********************************/

#include        "wsIntrn.h"

/******************************** Local Data **********************************/
/*
 *      Mapping of ANSI chars to base64 Mime encoding alphabet (see below)
 */

static char_t   map64[] = {
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
        -1,  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, -1, -1, -1, -1, -1, 
        -1, 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, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

static char_t   alphabet64[] = {
        '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', '+', '/',
};

/*********************************** Code *************************************/
/*
 *      Decode a buffer from "string" and into "outbuf"
 */

int websDecode64(char_t *outbuf, char_t *string, int outlen)
{
        unsigned long   shiftbuf;
        char_t                  *cp, *op;
        int                             c, i, j, shift;

        op = outbuf;
        *op = '\0';
        cp = string;
        while (*cp && *cp != '=') {
/*
 *              Map 4 (6bit) input bytes and store in a single long (shiftbuf)
 */
                shiftbuf = 0;
                shift = 18;
                for (i = 0; i < 4 && *cp && *cp != '='; i++, cp++) {
                        c = map64[*cp & 0xff];
                        if (c == -1) {
                                error(E_L, E_LOG, T("Bad string: %s at %c index %d"), string,
                                        c, i);
                                return -1;
                        } 
                        shiftbuf = shiftbuf | (c << shift);
                        shift -= 6;
                }
/*
 *              Interpret as 3 normal 8 bit bytes (fill in reverse order).
 *              Check for potential buffer overflow before filling.
 */
                --i;
                if ((op + i) >= &outbuf[outlen]) {
                        gstrcpy(outbuf, T("String too big"));
                        return -1;
                }
                for (j = 0; j < i; j++) {
                        *op++ = (char_t) ((shiftbuf >> (8 * (2 - j))) & 0xff);
                }
                *op = '\0';
        }
        return 0;
}


/******************************************************************************/
/*
 *      Encode a buffer from "string" into "outbuf"
 */

void websEncode64(char_t *outbuf, char_t *string, int outlen)
{
        unsigned long   shiftbuf;
        char_t                  *cp, *op;
        int                             x, i, j, shift;

        op = outbuf;
        *op = '\0';
        cp = string;
        while (*cp) {
/*
 *              Take three characters and create a 24 bit number in shiftbuf
 */
                shiftbuf = 0;
                for (j = 2; j >= 0 && *cp; j--, cp++) {
                        shiftbuf |= ((*cp & 0xff) << (j * 8));
                }
/*
 *              Now convert shiftbuf to 4 base64 letters.  The i,j magic calculates
 *              how many letters need to be output.
 */
                shift = 18;
                for (i = ++j; i < 4 && op < &outbuf[outlen] ; i++) {
                        x = (shiftbuf >> shift) & 0x3f;
                        *op++ = alphabet64[(shiftbuf >> shift) & 0x3f];
                        shift -= 6;
                }
/*
 *              Pad at the end with '='
 */
                while (j-- > 0) {
                        *op++ = '=';
                }
                *op = '\0';
        }
}
/******************************************************************************/