From 56d5364fced642aa203bd74b9d92798985d3ca5c Mon Sep 17 00:00:00 2001
From: Kieran Bingham <kieran.bingham@ideasonboard.com>
Date: Thu, 17 Sep 2020 15:04:49 +0100
Subject: src: monotonic-ts: Monotonic timestamp logging

Introduce a new utility which prefixes a monotonic timestamp rendered in the
same format as the kernel logs to all lines fed in through stdin.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 src/.gitignore     |  1 +
 src/Makefile       |  9 +++++++--
 src/monotonic-ts.c | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 2 deletions(-)
 create mode 100644 src/monotonic-ts.c

diff --git a/src/.gitignore b/src/.gitignore
index d42c924..817142c 100644
--- a/src/.gitignore
+++ b/src/.gitignore
@@ -2,3 +2,4 @@
 
 *.o
 gen-image
+monotonic-ts
diff --git a/src/Makefile b/src/Makefile
index d7f901f..c40e95a 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -7,18 +7,23 @@ CFLAGS	?= -O0 -g -W -Wall -Wno-unused-parameter -Iinclude
 LDFLAGS	?=
 LIBS	:= -lm
 GEN-IMAGE := gen-image
+MONOTONIC-TS := monotonic-ts
 
 %.o : %.c
 	$(CC) $(CFLAGS) -c -o $@ $<
 
-all: $(GEN-IMAGE)
+all: $(GEN-IMAGE) $(MONOTONIC-TS)
 
 $(GEN-IMAGE): gen-image.o
 	$(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
 
+$(MONOTONIC-TS): monotonic-ts.o
+	$(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
+
 clean:
 	-rm -f *.o
-	-rm -f $(GEN-IMAGE)
+	-rm -f $(GEN-IMAGE) $(MONOTONIC_TS)
 
 install:
 	cp $(GEN-IMAGE) $(INSTALL_DIR)/
+	cp $(MONOTONIC-TS) $(INSTALL_DIR)/
diff --git a/src/monotonic-ts.c b/src/monotonic-ts.c
new file mode 100644
index 0000000..69a1809
--- /dev/null
+++ b/src/monotonic-ts.c
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SPDX-FileCopyrightText: 2020 Kieran Bingham <kieran.bingham@ideasonboard.com> */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+int main(int argc, char ** argv)
+{
+	struct timespec tp;
+	char *line = NULL;
+	size_t size = 0;
+	const char *label = "";
+
+	if (argc > 1)
+		label = argv[1];
+
+	/*
+	 * Explicitly set line buffering on stdin to be sure it is delivered
+	 * in a timely fashion for our timestamping purposes when data is fed
+	 * through a pipe.
+	 */
+	setlinebuf(stdin);
+
+	do {
+		if (getline(&line, &size, stdin) <= 0)
+			break;
+
+		clock_gettime(CLOCK_MONOTONIC, &tp);
+		printf("[%ld.%.9ld]%s %s", tp.tv_sec, tp.tv_nsec, label, line);
+	} while (!feof(stdin));
+
+	free(line);
+
+	return 0;
+}
-- 
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