[PATCH 1/2] perf string: Add strcmp_prefix()

[Wei Li <liwei391@huawei.com>]

Add a helper to check whether a string has the given prefix.
This function is stolen from fs/xattr.c

Signed-off-by: Wei Li <liwei391@huawei.com>
---
 tools/perf/util/string.c  | 17 +++++++++++++++++
 tools/perf/util/string2.h |  1 +
 2 files changed, 18 insertions(+)

diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
index f6d90cdd9225..0ed3e2d0b70f 100644
--- a/tools/perf/util/string.c
+++ b/tools/perf/util/string.c
@@ -209,6 +209,23 @@ int strtailcmp(const char *s1, const char *s2)
 	return 0;
 }
 
+/**
+ * strcmp_prefix - check string for given prefix
+ * @str: the target string to check
+ * @prefix: the given prefix to match
+ *
+ * Return the rest string in @str if @str has the given @prefix, return NULL
+ * otherwise.
+ */
+const char *strcmp_prefix(const char *str, const char *prefix)
+{
+	while (*prefix && *str == *prefix) {
+		str++;
+		prefix++;
+	}
+	return *prefix ? NULL : str;
+}
+
 char *asprintf_expr_inout_ints(const char *var, bool in, size_t nints, int *ints)
 {
 	/*
diff --git a/tools/perf/util/string2.h b/tools/perf/util/string2.h
index 56c30fef9682..58929ad928f7 100644
--- a/tools/perf/util/string2.h
+++ b/tools/perf/util/string2.h
@@ -20,6 +20,7 @@ static inline bool strisglob(const char *str)
 	return strpbrk(str, "*?[") != NULL;
 }
 int strtailcmp(const char *s1, const char *s2);
+const char *strcmp_prefix(const char *str, const char *prefix);
 
 char *asprintf_expr_inout_ints(const char *var, bool in, size_t nints, int *ints);
 
-- 
2.25.1