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random: added random_bytes function

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This commit is contained in:
tobhe 2017-09-27 14:11:33 +02:00
parent 81bfb0c97a
commit 7af07bacff
2 changed files with 46 additions and 1 deletions
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6
sys/include/random.h
View File

@ -27,6 +27,7 @@
#define RANDOM_H
#include <inttypes.h>
#include <stddef.h>
#ifdef __cplusplus
extern "C" {
@ -67,6 +68,11 @@ void random_init_by_array(uint32_t init_key[], int key_length);
*/
uint32_t random_uint32(void);
/**
* @brief writes random bytes in the [0,0xff]-interval to memory
*/
void random_bytes(uint8_t *buf, size_t size);
/**
* @brief generates a random number r with a <= r < b.
*

41
sys/random/tinymt32.c
View File

@ -6,7 +6,7 @@
* directory for more details.
*/
/**
/**
* @ingroup sys_random
* @{
* @file
@ -20,9 +20,18 @@
*/
#include <stdint.h>
#include <string.h>
#include "tinymt32/tinymt32.h"
#define _ALIGNMENT_MASK (sizeof(uint32_t) - 1)
/* fits size to byte alignment */
static inline uint8_t *_align(uint8_t *buf)
{
return (uint8_t *)(((size_t) buf + _ALIGNMENT_MASK) & ~(_ALIGNMENT_MASK));
}
static tinymt32_t _random;
void random_init(uint32_t seed)
@ -35,6 +44,36 @@ uint32_t random_uint32(void)
return tinymt32_generate_uint32(&_random);
}
void random_bytes(uint8_t *buf, size_t size)
{
size_t iter = size;
size_t diff = _align(buf) - buf;
uint32_t tmp;
/* Fill first <4 unaligned bytes */
if (diff) {
tmp = tinymt32_generate_uint32(&_random);
if (diff > size) {
diff = size;
}
memcpy(buf, &tmp, diff);
iter -= diff;
}
/* Fill aligned bytes */
while (iter >= sizeof(uint32_t)) {
*((uint32_t *) buf) = tinymt32_generate_uint32(&_random);
buf += sizeof(uint32_t);
iter -= sizeof(uint32_t);
}
/* Fill last bytes */
if (iter) {
tmp = tinymt32_generate_uint32(&_random);
memcpy(buf, &tmp, iter);
}
}
void random_init_by_array(uint32_t init_key[], int key_length)
{
tinymt32_init_by_array(&_random, init_key, key_length);