From da6f343032cb01597dc7866e66f091adf3243a62 Mon Sep 17 00:00:00 2001
From: Michael Smith <mikesmiffy128@gmail.com>
Date: Sat, 20 Nov 2021 03:10:50 +0000
Subject: Initial public snapshot

With code from Bill. Thanks Bill!
---
 src/os.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 src/os.c

(limited to 'src/os.c')

diff --git a/src/os.c b/src/os.c
new file mode 100644
index 0000000..96e3c48
--- /dev/null
+++ b/src/os.c
@@ -0,0 +1,56 @@
+/*
+ * Copyright © 2021 Michael Smith <mikesmiffy128@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdbool.h>
+
+#include "intdefs.h"
+#include "os.h"
+
+#ifdef _WIN32
+// SystemFunction036 is the *real* name of "RtlGenRandom," and is also
+// incorrectly defined in system headers. Yay, Windows.
+int __stdcall SystemFunction036(void *buf, ulong sz);
+#endif
+
+bool os_mprot(void *addr, int len, int fl) {
+#ifdef _WIN32
+	ulong old;
+	return !!VirtualProtect(addr, len, fl, &old);
+#else
+	// round down address and round up size
+	addr = (void *)((ulong)addr & ~(4095));
+	len = len + 4095 & ~(4095);
+	return mprotect(addr, len, fl) != -1;
+#endif
+}
+
+#ifdef _WIN32
+void *os_dlsym(void *m, const char *s) {
+	return (void *)GetProcAddress(m, s);
+}
+#endif
+
+void os_randombytes(void *buf, int sz) {
+	// if these calls ever fail, the system is fundamentally broken with no
+	// recourse, so just loop until success. hopefully nothing will go wrong.
+#ifdef _WIN32
+	while (!SystemFunction036(buf, sz));
+#else
+	while (getentropy(buf, sz) == -1);
+#endif
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80
-- 
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