[PATCH 05/13] perf tools: Introduce strtobool() to string.c

[Wang Nan]

This patch clones strtobool() from kernel's string.c to perf's string.c,
then add the function entry to tools/perf/util/include/linux/string.h.

string.h in perf utils doesn't have #ifdef guard. This patch fixes it.

This is preparation for enforcing BPF program configuration, which
would allow config string like 'inlines=yes'.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/include/linux/string.h |  5 +++++
 tools/perf/util/string.c               | 28 ++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/tools/perf/util/include/linux/string.h b/tools/perf/util/include/linux/string.h
index 6f19c54..2bb0057 100644
--- a/tools/perf/util/include/linux/string.h
+++ b/tools/perf/util/include/linux/string.h
@@ -1,3 +1,8 @@
+#ifndef PERF_LINUX_STRING_H_
+#define PERF_LINUX_STRING_H_
 #include <string.h>
 
 void *memdup(const void *src, size_t len);
+
+int strtobool(const char *s, bool *res);
+#endif
diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
index fc8781d..c7fd44d 100644
--- a/tools/perf/util/string.c
+++ b/tools/perf/util/string.c
@@ -396,3 +396,31 @@ out_err_overflow:
 	free(expr);
 	return NULL;
 }
+
+/**
+ * strtobool - convert common user inputs into boolean values
+ * @s: input string
+ * @res: result
+ *
+ * This routine returns 0 iff the first character is one of 'Yy1Nn0'.
+ * Otherwise it will return -EINVAL.  Value pointed to by res is
+ * updated upon finding a match.
+ */
+int strtobool(const char *s, bool *res)
+{
+	switch (s[0]) {
+	case 'y':
+	case 'Y':
+	case '1':
+		*res = true;
+		break;
+	case 'n':
+	case 'N':
+	case '0':
+		*res = false;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
-- 
1.8.3.4

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