From 4ae705d2ed448464096ea809156140fdd27d9e59 Mon Sep 17 00:00:00 2001
From: Antonio Ospite <ospite@studenti.unina.it>
Date: Thu, 21 Mar 2013 16:14:50 +0100
Subject: [PATCH] Initial import

---
 .gitignore  |  2 ++
 Makefile    | 41 ++++++++++++++++++++++++++++++++
 fps-limit.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 121 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 fps-limit.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ef7def1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.o
+fps-limit
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..961ef03
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,41 @@
+CFLAGS = -std=c99 -pedantic -pedantic-errors -Wall -g3 -O2 -D_ANSI_SOURCE_
+CFLAGS += -fno-common \
+	  -Wall \
+	  -Wdeclaration-after-statement \
+	  -Wextra \
+	  -Wformat=2 \
+	  -Winit-self \
+	  -Winline \
+	  -Wpacked \
+	  -Wp,-D_FORTIFY_SOURCE=2 \
+	  -Wpointer-arith \
+	  -Wlarger-than-65500 \
+	  -Wmissing-declarations \
+	  -Wmissing-format-attribute \
+	  -Wmissing-noreturn \
+	  -Wmissing-prototypes \
+	  -Wnested-externs \
+	  -Wold-style-definition \
+	  -Wredundant-decls \
+	  -Wsign-compare \
+	  -Wstrict-aliasing=2 \
+	  -Wstrict-prototypes \
+	  -Wswitch-enum \
+	  -Wundef \
+	  -Wunreachable-code \
+	  -Wunsafe-loop-optimizations \
+	  -Wunused-but-set-variable \
+	  -Wwrite-strings
+
+CFLAGS += -DDEBUG
+
+# For clock_nanosleep()
+CFLAGS += -D_POSIX_C_SOURCE=200112L
+
+# for clock_gettime()
+LDLIBS += -lrt
+
+fps-limit: fps-limit.o
+
+clean:
+	rm -rf *~ *.o fps-limit
diff --git a/fps-limit.c b/fps-limit.c
new file mode 100644
index 0000000..746c957
--- /dev/null
+++ b/fps-limit.c
@@ -0,0 +1,78 @@
+/*
+ * fps-limit - Example program to limit frames per seconds
+ *
+ * Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <time.h>
+
+#ifdef DEBUG
+#define dbg(...)                     \
+	do {                         \
+		printf(__VA_ARGS__); \
+		printf("\n");        \
+		fflush(stdout);      \
+	} while(0)
+#else
+#define dbg(...) do {} while(0)
+#endif
+
+#define FPS 60
+
+#define NSEC_PER_SEC 1000000000
+
+#define timespecsub(a, b, result)                                \
+	do {                                                     \
+		(result)->tv_sec = (a)->tv_sec - (b)->tv_sec;    \
+		(result)->tv_nsec = (a)->tv_nsec - (b)->tv_nsec; \
+		if ((result)->tv_nsec < 0) {                     \
+			--(result)->tv_sec;                      \
+			(result)->tv_nsec += 1000000000;         \
+		}                                                \
+	} while(0)
+
+int main(void)
+{
+	struct timespec time_start;
+	struct timespec time_end;
+	struct timespec elapsed;
+	struct timespec remaining = {0, 0};
+
+	struct timespec tmp;
+
+	while (1) {
+		clock_gettime(CLOCK_MONOTONIC, &time_start);
+		dbg("Start time: s: %ld, ns: %ld", time_start.tv_sec, time_start.tv_nsec);
+
+		dbg("Doing some work, max: %d", NSEC_PER_SEC / FPS);
+		tmp.tv_sec = 0;
+		tmp.tv_nsec = (NSEC_PER_SEC / FPS) * 2 / 3;
+		nanosleep(&tmp, NULL);
+
+		clock_gettime(CLOCK_MONOTONIC, &time_end);
+		dbg("End time: s: %ld, ns: %ld", time_end.tv_sec, time_end.tv_nsec);
+		timespecsub(&time_end, &time_start, &elapsed);
+		dbg("Elapsed s: %ld ns: %ld", elapsed.tv_sec, elapsed.tv_nsec);
+		if (elapsed.tv_sec == 0 && elapsed.tv_nsec < NSEC_PER_SEC / FPS) {
+			remaining.tv_nsec = (NSEC_PER_SEC / FPS) - elapsed.tv_nsec;
+			dbg("Sleeping for: ns: %ld", remaining.tv_nsec);
+			clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &remaining, NULL);
+		}
+	}
+
+	return 0;
+}
-- 
2.1.4