perf tools: Move timestamp creation to util

Timestamp generation becomes a public available helper. Which will
be used by 'perf record', help it output to split output file based
on time.

For example:

 perf.data.2015122620363710
 perf.data.2015122620364092
 perf.data.2015122620365423
 ...

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1453715801-7732-27-git-send-email-wangnan0@huawei.com
Signed-off-by: He Kuang <hekuang@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-buildid-cache.c

@@ -38,19 +38,7 @@ static int build_id_cache__kcore_buildid(const char *proc_dir, char *sbuildid)
 
 static int build_id_cache__kcore_dir(char *dir, size_t sz)
 {
-	struct timeval tv;
-	struct tm tm;
-	char dt[32];
-
-	if (gettimeofday(&tv, NULL) || !localtime_r(&tv.tv_sec, &tm))
-		return -1;
-
-	if (!strftime(dt, sizeof(dt), "%Y%m%d%H%M%S", &tm))
-		return -1;
-
-	scnprintf(dir, sz, "%s%02u", dt, (unsigned)tv.tv_usec / 10000);
-
-	return 0;
+	return fetch_current_timestamp(dir, sz);
 }
 
 static bool same_kallsyms_reloc(const char *from_dir, char *to_dir)

tools/perf/util/util.c

@@ -701,3 +701,20 @@ bool is_regular_file(const char *file)
 
 	return S_ISREG(st.st_mode);
 }
+
+int fetch_current_timestamp(char *buf, size_t sz)
+{
+	struct timeval tv;
+	struct tm tm;
+	char dt[32];
+
+	if (gettimeofday(&tv, NULL) || !localtime_r(&tv.tv_sec, &tm))
+		return -1;
+
+	if (!strftime(dt, sizeof(dt), "%Y%m%d%H%M%S", &tm))
+		return -1;
+
+	scnprintf(buf, sz, "%s%02u", dt, (unsigned)tv.tv_usec / 10000);
+
+	return 0;
+}

tools/perf/util/util.h

@@ -344,5 +344,6 @@ int fetch_kernel_version(unsigned int *puint,
 
 const char *perf_tip(const char *dirpath);
 bool is_regular_file(const char *file);
+int fetch_current_timestamp(char *buf, size_t sz);
 
 #endif /* GIT_COMPAT_UTIL_H */