integeruser · September 24, 2023 14:09 · Mar 4, 2017
diff --git a/s-rand.py b/s-rand.py
@@ -0,0 +1,55 @@
+#!/usr/bin/env python2
+from ctypes import c_int, c_uint
+
+# http://www.mscs.dal.ca/~selinger/random/
+
+
+def srand(seed):
+    srand.r = [0 for _ in range(34)]
+    srand.r[0] = c_int(seed).value
+    for i in range(1, 31):
+        srand.r[i] = (16807 * srand.r[i - 1]) % 2147483647
+    for i in range(31, 34):
+        srand.r[i] = srand.r[i - 31]
+    srand.k = 0
+    for _ in range(34, 344):
+        rand()
+
+
+def rand():
+    srand.r[srand.k] = srand.r[(srand.k - 31) % 34] + srand.r[(srand.k - 3) % 34]
+    r = c_uint(srand.r[srand.k]).value >> 1
+    srand.k = (srand.k + 1) % 34
+    return r
+
+
+if __name__ == '__main__':
+    srand(1337)
+    assert [rand() for _ in range(10)] == [
+        292616681, 1638893262, 255706927, 995816787, 588263094, 1540293802, 343418821, 903681492,
+        898530248, 1459533395
+    ]
+
+    srand(0xffffffff + 0xffffffff - 1)
+    assert [rand() for _ in range(10)] == [
+        853660264, 1568971201, 1203662233, 15207980, 1421679843, 1717493552, 811896681, 155106358,
+        1156099704, 428649477
+    ]
+
+    srand(-1337)
+    assert [rand() for _ in range(10)] == [
+        1766598330, 413225925, 1792113474, 2120225281, 1445538174, 488114690, 1678701932,
+        1108308242, 32946609, 1612248994
+    ]
+
+    srand(-0xffffffff - 0xffffffff)
+    assert [rand() for _ in range(10)] == [
+        1505335290, 1738766719, 190686788, 260874575, 747983061, 906156498, 1502820864, 142559277,
+        1261608745, 1380759627
+    ]
+
+    # from ctypes import cdll
+    # from ctypes.util import find_library
+    # libc = cdll.LoadLibrary(find_library('c'))
+    # libc.srand(1337)
+    # print[libc.rand() for _ in range(10)]
diff --git a/test.c b/test.c
@@ -0,0 +1,34 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+
+int main(int argc, char const *argv[])
+{
+    srand(1337);
+    for (int i = 0; i < 10; ++i) {
+        printf("%d\n", rand());
+    }
+
+    printf("\n");
+
+    srand(0xffffffff + 0xffffffff - 1);
+    for (int i = 0; i < 10; ++i) {
+        printf("%d\n", rand());
+    }
+
+    printf("\n");
+
+    srand(-1337);
+    for (int i = 0; i < 10; ++i) {
+        printf("%d\n", rand());
+    }
+
+    printf("\n");
+
+    srand(-0xffffffff - 0xffffffff);
+    for (int i = 0; i < 10; ++i) {
+        printf("%d\n", rand());
+    }
+
+    return 0;
+}