Add libsimple_generate_seed and libsimple_srand

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 59 insertions, 0 deletions

diff --git a/generate_seed.c b/generate_seed.c
new file mode 100644
index 0000000..cce274f
--- /dev/null
+++ b/generate_seed.c
@@ -0,0 +1,59 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+#include <sys/auxv.h>
+
+
+unsigned int
+libsimple_generate_seed(void) /* TODO add test */
+{
+	uintptr_t longseed = 1;
+	void *ptr;
+	uintptr_t ptri;
+	unsigned int seed;
+	struct timespec ts;
+	uint8_t (*at_random)[16];
+	size_t i;
+
+	if (!clock_gettime(CLOCK_REALTIME, &ts))
+		longseed ^= (uintptr_t)ts.tv_sec * (uintptr_t)1000000000UL + (uintptr_t)ts.tv_nsec;
+
+	ptr = malloc(1);
+	ptri = (uintptr_t)ptr;
+	free(ptr);
+	longseed ^= ptri;
+	longseed ^= (uintptr_t)&ptri;
+	longseed ^= (uintptr_t)clock();
+
+	if (!clock_gettime(CLOCK_MONOTONIC_RAW, &ts))
+		longseed ^= (uintptr_t)ts.tv_sec * (uintptr_t)1000000000UL + (uintptr_t)ts.tv_nsec;
+
+	ptri = (uintptr_t)getauxval(AT_RANDOM);
+	if (ptri) {
+		at_random = (void *)ptri;
+		for (i = 0; i < ELEMSOF(*at_random); i++)
+			longseed ^= (*at_random)[i] << (i % sizeof(longseed) * (size_t)CHAR_BIT);
+	}
+
+	seed = 0;
+	while (longseed) {
+		seed ^= (unsigned int)longseed;
+		longseed >>= sizeof(unsigned int) * (CHAR_BIT - 1);
+		longseed >>= sizeof(unsigned int);
+	}
+
+	return seed;
+}
+
+
+#else
+#include "test.h"
+
+int
+main(void)
+{
+	return 0;
+}
+
+#endif