xref: /freebsd/contrib/expat/lib/random_arc4random.c (revision 9c77fb6aaa366cbabc80ee1b834bcfe4df135491)
1 /*
2                             __  __            _
3                          ___\ \/ /_ __   __ _| |_
4                         / _ \\  /| '_ \ / _` | __|
5                        |  __//  \| |_) | (_| | |_
6                         \___/_/\_\ .__/ \__,_|\__|
7                                  |_| XML parser
8 
9    Copyright (c) 2017-2026 Sebastian Pipping <sebastian@pipping.org>
10    Copyright (c) 2026      Matthew Fernandez <matthew.fernandez@gmail.com>
11    Licensed under the MIT license:
12 
13    Permission is  hereby granted,  free of charge,  to any  person obtaining
14    a  copy  of  this  software   and  associated  documentation  files  (the
15    "Software"),  to  deal in  the  Software  without restriction,  including
16    without  limitation the  rights  to use,  copy,  modify, merge,  publish,
17    distribute, sublicense, and/or sell copies of the Software, and to permit
18    persons  to whom  the Software  is  furnished to  do so,  subject to  the
19    following conditions:
20 
21    The above copyright  notice and this permission notice  shall be included
22    in all copies or substantial portions of the Software.
23 
24    THE  SOFTWARE  IS  PROVIDED  "AS  IS",  WITHOUT  WARRANTY  OF  ANY  KIND,
25    EXPRESS  OR IMPLIED,  INCLUDING  BUT  NOT LIMITED  TO  THE WARRANTIES  OF
26    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
27    NO EVENT SHALL THE AUTHORS OR  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
28    DAMAGES OR  OTHER LIABILITY, WHETHER  IN AN  ACTION OF CONTRACT,  TORT OR
29    OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
30    USE OR OTHER DEALINGS IN THE SOFTWARE.
31 */
32 
33 #include "random_arc4random.h"
34 
35 #if ! defined(_DEFAULT_SOURCE)
36 #  define _DEFAULT_SOURCE 1 /* for glibc */
37 #endif
38 
39 #include <stdint.h> // for uint32_t
40 #include <stdlib.h> // for arc4random
41 #include <string.h> // for memcpy
42 
43 void
44 writeRandomBytes_arc4random(void *target, size_t count) {
45   size_t bytesWrittenTotal = 0;
46 
47   while (bytesWrittenTotal < count) {
48     const uint32_t random32 = arc4random();
49 
50     size_t toUse = count - bytesWrittenTotal;
51     if (toUse > sizeof(random32))
52       toUse = sizeof(random32);
53     memcpy((char *)target + bytesWrittenTotal, &random32, toUse);
54     bytesWrittenTotal += toUse;
55   }
56 }
57