From 9f9a4bc3f3ca326bfb8178821f933dbdd742857c Mon Sep 17 00:00:00 2001
From: jp9000 <obs.jim@gmail.com>
Date: Tue, 15 Dec 2015 20:45:19 -0800
Subject: [PATCH] libobs/util: Add uint128 structure/functions

Allows some limited 128bit integer math functions, primarily for the
sake of performing calculations on nanosecond-based intervals of time
---
 libobs/CMakeLists.txt      |   1 +
 libobs/util/util_uint128.h | 100 +++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+)
 create mode 100644 libobs/util/util_uint128.h

diff --git a/libobs/CMakeLists.txt b/libobs/CMakeLists.txt
index 9cfa7f92f..c35fda61e 100644
--- a/libobs/CMakeLists.txt
+++ b/libobs/CMakeLists.txt
@@ -242,6 +242,7 @@ set(libobs_util_HEADERS
 	util/vc/vc_stdint.h
 	util/bmem.h
 	util/c99defs.h
+	util/util_uint128.h
 	util/cf-parser.h
 	util/threading.h
 	util/pipe.h
diff --git a/libobs/util/util_uint128.h b/libobs/util/util_uint128.h
new file mode 100644
index 000000000..511ab0a05
--- /dev/null
+++ b/libobs/util/util_uint128.h
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2015 Hugh Bailey <obs.jim@gmail.com>
+ *
+ * Permission to use, copy, modify, and 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.
+ */
+
+#pragma once
+
+struct util_uint128 {
+	union {
+		uint32_t i32[4];
+		struct {
+			uint64_t low;
+			uint64_t high;
+		};
+	};
+};
+
+typedef struct util_uint128 util_uint128_t;
+
+static inline util_uint128_t util_add128(util_uint128_t a, util_uint128_t b)
+{
+	util_uint128_t out;
+	uint64_t val;
+
+	val = (a.low & 0xFFFFFFFFULL) + (b.low & 0xFFFFFFFFULL);
+	out.i32[0] = (uint32_t)(val & 0xFFFFFFFFULL);
+	val >>= 32;
+
+	val += (a.low >> 32) + (b.low >> 32);
+	out.i32[1] = (uint32_t)val;
+	val >>= 32;
+
+	val += (a.high & 0xFFFFFFFFULL) + (b.high & 0xFFFFFFFFULL);
+	out.i32[2] = (uint32_t)(val & 0xFFFFFFFFULL);
+	val >>= 32;
+
+	val += (a.high >> 32) + (b.high >> 32);
+	out.i32[3] = (uint32_t)val;
+
+	return out;
+}
+
+static inline util_uint128_t util_lshift64(uint64_t a, int num)
+{
+	util_uint128_t val;
+	val.low = a << num;
+	val.high = a >> (64 - num);
+	return val;
+}
+
+static inline util_uint128_t util_mul64_64(uint64_t a, uint64_t b)
+{
+	util_uint128_t out;
+	uint64_t m;
+
+	m = (a & 0xFFFFFFFFULL) * (b & 0xFFFFFFFFULL);
+	out.low = m;
+	out.high = 0;
+
+	m = (a >> 32) * (b & 0xFFFFFFFFULL);
+	out = util_add128(out, util_lshift64(m, 32));
+
+	m = (a & 0xFFFFFFFFULL) * (b >> 32);
+	out = util_add128(out, util_lshift64(m, 32));
+
+	m = (a >> 32) * (b >> 32);
+	out = util_add128(out, util_lshift64(m, 64));
+
+	return out;
+}
+
+static inline util_uint128_t util_div128_32(util_uint128_t a, uint32_t b)
+{
+	util_uint128_t out;
+	uint64_t val = 0;
+
+	for (int i = 3; i >= 0; i--) {
+		val = (val << 32) | a.i32[i];
+		if (val < b) {
+			out.i32[i] = 0;
+			continue;
+		}
+
+		out.i32[i] = (uint32_t)(val / b);
+		val = val % b;
+	}
+
+	return out;
+}