Import new Cytoplasm library based off of code from Telodendria.

Telodendria doesn't use this library yet, but it will soon.

src/include/Rand.h

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2022-2023 Jordan Bancino <@jordan:bancino.net>
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef CYTOPLASM_RAND_H
+#define CYTOPLASM_RAND_H
+
+/***
+ * @Nm Rand
+ * @Nd Thread-safe random numbers.
+ * @Dd February 16 2023
+ * @Xr Util
+ *
+ * .Nm
+ * is used for generating random numbers in a thread-safe way.
+ * Currently, one generator state is shared across all threads, which
+ * means that only one thread can generate random numbers at a time.
+ * This state is protected with a mutex to guarantee this behavior.
+ * In the future, a seed pool may be maintained to allow multiple
+ * threads to generate random numbers at the same time.
+ * .Pp
+ * The generator state is seeded on the first call to a function that
+ * needs it. The seed is determined by the current timestamp, the ID
+ * of the process, and the thread ID. These should all be sufficiently
+ * random sources, so the seed should be secure enough.
+ * .Pp
+ * .Nm
+ * currently uses a simple Mersenne Twister algorithm to generate
+ * random numbers. This algorithm was chosen because it is extremely
+ * popular and widespread. While it is likely not cryptographically
+ * secure, and does suffer some unfortunate pitfalls, this algorithm
+ * has stood the test of time and is simple enough to implement, so
+ * it was chosen over the alternatives.
+ * .Pp
+ * .Nm
+ * does not use any random number generator functions from the C
+ * standard library, since these are often flawed.
+ */
+
+#include <stddef.h>
+
+/**
+ * Generate a single random integer between 0 and the passed value.
+ */
+extern int RandInt(unsigned int);
+
+/**
+ * Generate the number of integers specified by the second argument
+ * storing them into the buffer pointed to in the first argument.
+ * Ensure that each number is between 0 and the third argument.
+ * .Pp
+ * This function allows a caller to get multiple random numbers at once
+ * in a more efficient manner than repeatedly calling
+ * .Fn RandInt ,
+ * since each call to these functions
+ * has to lock and unlock a mutex. It is therefore better to obtain
+ * multiple random numbers in one pass if multiple are needed.
+ */
+extern void RandIntN(int *, size_t, unsigned int);
+
+#endif                             /* CYTOPLASM_RAND_H */