From 71811470be4f182b623510cf92ea5cfff16df172 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Sun, 28 Jan 2024 16:34:27 +0100
Subject: Add libsimple_generate_seed and libsimple_srand
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
 Makefile           |  3 +++
 generate_seed.c    | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 libsimple.h        |  1 +
 libsimple/random.h | 22 ++++++++++++++++++++
 srand.c            | 18 +++++++++++++++++
 5 files changed, 103 insertions(+)
 create mode 100644 generate_seed.c
 create mode 100644 libsimple/random.h
 create mode 100644 srand.c

diff --git a/Makefile b/Makefile
index cc99bc0..38f2537 100644
--- a/Makefile
+++ b/Makefile
@@ -44,6 +44,7 @@ SUBHDR =\
 	libsimple/printf.h\
 	libsimple/pvalloc.h\
 	libsimple/pvallocz.h\
+	libsimple/random.h\
 	libsimple/realloc.h\
 	libsimple/search.h\
 	libsimple/str.h\
@@ -224,6 +225,7 @@ OBJ =\
 	ewcsdup.o\
 	ewcsndup.o\
 	ewmemdup.o\
+	generate_seed.o\
 	getenv_e.o\
 	getenv_ne.o\
 	gmtime.o\
@@ -318,6 +320,7 @@ OBJ =\
 	reallocf.o\
 	reallocfn.o\
 	reallocn.o\
+	srand.o\
 	stpmove.o\
 	stpnmove.o\
 	stpnset.o\
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
diff --git a/libsimple.h b/libsimple.h
index 9cc0f8f..1cd7806 100644
--- a/libsimple.h
+++ b/libsimple.h
@@ -165,6 +165,7 @@
 #include "libsimple/strn.h"
 #include "libsimple/strtoint.h"
 #include "libsimple/search.h"
+#include "libsimple/random.h"
 
 
 /**
diff --git a/libsimple/random.h b/libsimple/random.h
new file mode 100644
index 0000000..3c09d7a
--- /dev/null
+++ b/libsimple/random.h
@@ -0,0 +1,22 @@
+/* See LICENSE file for copyright and license details. */
+
+
+/**
+ * Creates a pseudo-random seed
+ *
+ * @return  The pseudo-random seed
+ */
+LIBSIMPLE_GCC_ONLY__(__attribute__((__warn_unused_result__)))
+unsigned int libsimple_generate_seed(void); /* TODO add man page */
+
+
+/**
+ * Wrapper for srand(3) that creates a pseudo-random
+ * seed with which it seeds the pseudo-random number
+ * generator
+ */
+inline void
+libsimple_srand(void) /* TODO add man page */
+{
+	srand(libsimple_generate_seed());
+}
diff --git a/srand.c b/srand.c
new file mode 100644
index 0000000..e1648cb
--- /dev/null
+++ b/srand.c
@@ -0,0 +1,18 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+extern inline void libsimple_srand(void); /* TODO add test */
+
+
+#else
+#include "test.h"
+
+int
+main(void)
+{
+	return 0;
+}
+
+#endif
-- 
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