[tip:perf/core] perf tools: Introduce filename__read_int helper

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  97a07f10c38064dea492794c99445f6260afcdc1
Gitweb:     http://git.kernel.org/tip/97a07f10c38064dea492794c99445f6260afcdc1
Author:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Thu, 17 Oct 2013 16:33:43 -0300
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Thu, 17 Oct 2013 16:33:43 -0300

perf tools: Introduce filename__read_int helper

Just opens a file and calls atoi() in at most its first 64 bytes.

To read things like /proc/sys/kernel/perf_event_paranoid.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-669q04c5tou5pnt8jtiz6y2r@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/util.c | 17 +++++++++++++++++
 tools/perf/util/util.h |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 8dc8cf3..c25e57b 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -394,3 +394,20 @@ unsigned long parse_tag_value(const char *str, struct parse_tag *tags)
 
 	return (unsigned long) -1;
 }
+
+int filename__read_int(const char *filename, int *value)
+{
+	char line[64];
+	int fd = open(filename, O_RDONLY), err = -1;
+
+	if (fd < 0)
+		return -1;
+
+	if (read(fd, line, sizeof(line)) > 0) {
+		*value = atoi(line);
+		err = 0;
+	}
+
+	close(fd);
+	return err;
+}
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 42dfba7..c8f362d 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -305,4 +305,6 @@ struct dso;
 
 char *get_srcline(struct dso *dso, unsigned long addr);
 void free_srcline(char *srcline);
+
+int filename__read_int(const char *filename, int *value);
 #endif /* GIT_COMPAT_UTIL_H */
--
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