Base64 encoding (URL style, with "-_" instead of "+/" and no "=") as a MySQL UDF

b64u.c

/*
 * Copyright (c) 2017, Brian Leishman
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
 */

/*
 * USAGE INSTRUCTIONS:
 *
 * make sure libmysqlclient-dev is installed:
 * apt-get install libmysqlclient-dev
 *
 * Replace "/usr/lib/mysql/plugin" with your MySQL plugins directory (can be found by running "select @@plugin_dir;")
 * gcc -Ofast -I/usr/include/mysql -o b64u.so -shared b64u.c -fPIC && cp b64u.so /usr/lib/mysql/plugin/b64u.so
 *
 * Then, on the server:
 * create function`b64u`returns string soname'b64u.so';
 *
 * And use/test like:
 * select `b64u`('yeet'); -- should return 'eWVldA'
 *
 * Yeet!
 *
 */

#ifdef STANDARD
/* STANDARD is defined, don't use any mysql functions */
#include <string.h>
#ifdef __WIN__
typedef unsigned __int64 ulonglong; /* Microsofts 64 bit types */
typedef __int64 longlong;
#else
typedef unsigned long long ulonglong;
typedef long long longlong;
#endif /*__WIN__*/
#else
#include <my_global.h>
#include <my_sys.h>
#if defined(MYSQL_SERVER)
#include <m_string.h>
#else
/* when compiled as standalone */
#include <string.h>
#endif
#endif
#include <mysql.h>
#include <ctype.h>

#include <stdint.h>
#include <math.h>

#ifdef HAVE_DLOPEN

my_bool b64u_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
void b64u_deinit(UDF_INIT *initid);
char *b64u(UDF_INIT *initid __attribute__ ((unused)), UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *message __attribute__ ((unused)));

my_bool b64u_init(UDF_INIT *initid, UDF_ARGS *args, char *message) {
	if (args->arg_count != 1) {
		strcpy(message, "`b64u`() requires 1 parameters: the string to be encoded");
		return 1;
	}

	args->arg_type[1] = STRING_RESULT;

	initid->maybe_null = 1; //can return null

	return 0;
}

static const char basis_64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

int Base64encode(char *encoded, const char *string, int len) {
    int i;
    char *p;

    p = encoded;
    for (i = 0; i < len - 2; i += 3) {
		*p++ = basis_64[(string[i] >> 2) & 0x3F];
		*p++ = basis_64[((string[i] & 0x3) << 4) |
						((int) (string[i + 1] & 0xF0) >> 4)];
		*p++ = basis_64[((string[i + 1] & 0xF) << 2) |
						((int) (string[i + 2] & 0xC0) >> 6)];
		*p++ = basis_64[string[i + 2] & 0x3F];
    }

    if (i < len) {
		*p++ = basis_64[(string[i] >> 2) & 0x3F];
		if (i == (len - 1)) {
			*p++ = basis_64[((string[i] & 0x3) << 4)];
		} else {
			*p++ = basis_64[((string[i] & 0x3) << 4) |
							((int) (string[i + 1] & 0xF0) >> 4)];
			*p++ = basis_64[((string[i + 1] & 0xF) << 2)];
		}
    }

    return p - encoded;
}

char *b64u(UDF_INIT *initid __attribute__ ((unused)), UDF_ARGS *args, char *result, unsigned long *length, char *is_null, char *message __attribute__ ((unused))) {
	if (args->args[0] == NULL) {
		*is_null = 1;
		return 0;
	}

	*length = (ceil(4.0 * args->lengths[0] / 3.0));

	char *bytes = malloc(sizeof (char) * *length);

	Base64encode(bytes, args->args[0], args->lengths[0]);

	return bytes;
}

#endif /* HAVE_DLOPEN */