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/**
* slibc — Yet another C library
* Copyright © 2015, 2016 Mattias Andrée (maandree@member.fsf.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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include <string.h>
#include <stdlib.h>
/* Durstenfeld's algorithm. */
/**
* The number of bits to retain from `rand` output.
*/
#define BITS 8
/**
* Generate a `size_t` uniformly random.
*
* @param max The largest number to generate, inclusive.
* @return A random number between 0 and `max`, inclusively.
*/
static size_t
uniform_random_zu(size_t max)
{
size_t n, r = 0, mask = max, s = 1;
int b;
while (((mask + 1) & ~mask) != mask + 1)
mask |= mask >> s++;
do
for (n = max; n; n >>= BITS)
{
b = rand();
b /= (double)RAND_MAX + 1;
r = (r << BITS) | (int)(b * (1 << BITS));
}
while (r &= mask, r > max);
return r;
}
/**
* Shuffles all bytes in a string.
*
* You should have called `srand` before
* calling this function.
*
* This is a GNU joke extension.
*
* @param anagram An anagram of the output, will be modified.
* @retrun The string, which will `== anagram`.
*
* @since Always.
*/
char* strfry(char* anagram)
{
size_t i, j;
char t;
if (anagram == NULL)
return NULL;
for (i = strlen(anagram); i--;)
{
j = uniform_random_zu(i);
t = anagram[i], anagram[i] = anagram[j], anagram[j] = t;
}
return anagram;
}
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