From: Ben Pfaff <blp@cs.stanford.edu>
Date: Tue, 31 Aug 2004 22:04:08 +0000 (+0000)
Subject: Allow user to provide random seed to random_init().
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commitdiff_plain;h=cf2f40d622b3d18afaf03142dc234de3b6a40c81

Allow user to provide random seed to random_init().
---

diff --git a/src/lib/random.c b/src/lib/random.c
index 39452a9..d4ffa6d 100644
--- a/src/lib/random.c
+++ b/src/lib/random.c
@@ -1,9 +1,11 @@
 #include "random.h"
+#include <stdbool.h>
 #include <stdint.h>
 
 /* RC4-based pseudo-random state. */
 static uint8_t s[256];
 static uint8_t s_i, s_j;
+static bool inited;
 
 static inline void
 swap_byte (uint8_t *a, uint8_t *b) 
@@ -13,27 +15,26 @@ swap_byte (uint8_t *a, uint8_t *b)
   *b = t;
 }
 
-static uint8_t
-key_byte (int idx) 
-{
-  return idx ^ 0xff;
-}
-
 void
-random_init (void)
+random_init (unsigned seed)
 {
+  uint8_t *seedp = (uint8_t *) &seed;
   int i;
   uint8_t j;
 
+  if (inited)
+    return;
+  
   for (i = 0; i < 256; i++) 
     s[i] = i;
   for (i = j = 0; i < 256; i++) 
     {
-      j += s[i] + key_byte (i);
+      j += s[i] + seedp[i % sizeof seed];
       swap_byte (s + i, s + j);
     }
 
   s_i = s_j = 0;
+  inited = true;
 }
 
 void
diff --git a/src/lib/random.h b/src/lib/random.h
index d2f3706..cc6eed4 100644
--- a/src/lib/random.h
+++ b/src/lib/random.h
@@ -3,7 +3,7 @@
 
 #include <stddef.h>
 
-void random_init (void);
+void random_init (unsigned seed);
 void random_bytes (void *, size_t);
 unsigned long random_ulong (void);