From ceb8c1189ef875c193fe1f754a4c7caaf4bf0036 Mon Sep 17 00:00:00 2001
From: h2-addad <hamza2.addad@live.uwe.ac.uk>
Date: Sun, 16 Jul 2023 01:20:55 +0000
Subject: [PATCH] Update
---
src/lib/random.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 83 insertions(+)
create mode 100644 src/lib/random.c
diff --git a/src/lib/random.c b/src/lib/random.c
new file mode 100644
index 0000000..a4761b6
--- /dev/null
+++ b/src/lib/random.c
@@ -0,0 +1,83 @@
+#include "random.h"
+#include <stdbool.h>
+#include <stdint.h>
+#include "debug.h"
+
+/* RC4-based pseudo-random number generator (PRNG).
+
+ RC4 is a stream cipher. We're not using it here for its
+ cryptographic properties, but because it is easy to implement
+ and its output is plenty random for non-cryptographic
+ purposes.
+
+ See http://en.wikipedia.org/wiki/RC4_(cipher) for information
+ on RC4.*/
+
+/* RC4 state. */
+static uint8_t s[256]; /* S[]. */
+static uint8_t s_i, s_j; /* i, j. */
+
+/* Already initialized? */
+static bool inited;
+
+/* Swaps the bytes pointed to by A and B. */
+static inline void
+swap_byte (uint8_t *a, uint8_t *b)
+{
+ uint8_t t = *a;
+ *a = *b;
+ *b = t;
+}
+
+/* Initializes or reinitializes the PRNG with the given SEED. */
+void
+random_init (unsigned seed)
+{
+ uint8_t *seedp = (uint8_t *) &seed;
+ int i;
+ uint8_t j;
+
+ for (i = 0; i < 256; i++)
+ s[i] = i;
+ for (i = j = 0; i < 256; i++)
+ {
+ j += s[i] + seedp[i % sizeof seed];
+ swap_byte (s + i, s + j);
+ }
+
+ s_i = s_j = 0;
+ inited = true;
+}
+
+/* Writes SIZE random bytes into BUF. */
+void
+random_bytes (void *buf_, size_t size)
+{
+ uint8_t *buf;
+
+ if (!inited)
+ random_init (0);
+
+ for (buf = buf_; size-- > 0; buf++)
+ {
+ uint8_t s_k;
+
+ s_i++;
+ s_j += s[s_i];
+ swap_byte (s + s_i, s + s_j);
+
+ s_k = s[s_i] + s[s_j];
+ *buf = s[s_k];
+ }
+}
+
+/* Returns a pseudo-random unsigned long.
+ Use random_ulong() % n to obtain a random number in the range
+ 0...n (exclusive). */
+unsigned long
+random_ulong (void)
+{
+ unsigned long ul;
+ random_bytes (&ul, sizeof ul);
+ return ul;
+}
--
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