From b1b2d6903f656ebd687518b1495581decf6810ba Mon Sep 17 00:00:00 2001
From: hasslesstech <hasslesstech@tutanota.com>
Date: Tue, 18 Mar 2025 19:54:50 +0200
Subject: [PATCH] optimize randint() function for massive performance increase

---
 inc/random.h |  1 +
 src/main.c   |  2 ++
 src/random.c | 34 +++++++++++++++++++++++++++-------
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/inc/random.h b/inc/random.h
index 5e8346a..d00be78 100644
--- a/inc/random.h
+++ b/inc/random.h
@@ -1,6 +1,7 @@
 #ifndef RANDOM_HEADER
 #define RANDOM_HEADER
 
+void random_init(void);
 size_t randint(size_t max);
 
 #endif
diff --git a/src/main.c b/src/main.c
index 810d5af..a3d3b89 100644
--- a/src/main.c
+++ b/src/main.c
@@ -25,6 +25,8 @@ main(void)
 {
 	system_time = 0;
 
+	random_init();
+
 	free_pages_cnt = 0;
 	busy_pages_cnt = 0;
 
diff --git a/src/random.c b/src/random.c
index 9f103df..33704a2 100644
--- a/src/random.c
+++ b/src/random.c
@@ -1,14 +1,34 @@
+#include <stdio.h>
 #include <fcntl.h>
 #include <stddef.h>
 #include <unistd.h>
 
-size_t randint(size_t max)
+#define RANDOM_BUFFER_SIZE 16384
+
+static size_t index = RANDOM_BUFFER_SIZE;
+static size_t value_buff[RANDOM_BUFFER_SIZE];
+static int random_fd = -1;
+
+void
+random_init(void)
 {
-	size_t random_value;
+	random_fd = open("/dev/urandom", O_RDONLY);
 
-	int f = open("/dev/urandom", O_RDONLY);
-	read(f, &random_value, 8);
-	close(f);
-
-	return random_value % max;
+	if (random_fd < 0)
+		printf("[random:error] Failed to open /dev/urandom\n");
+}
+
+size_t
+randint(size_t max)
+{
+	if (index >= RANDOM_BUFFER_SIZE) {
+		read(random_fd, value_buff, 8 * RANDOM_BUFFER_SIZE);
+
+		index = 0;
+	}
+
+	size_t rv = value_buff[index] % max;
+	index++;
+
+	return rv;
 }