Introduce pam_str_skip_icase_prefix_len and pam_str_skip_icase_prefix

Every time I see a code like
  if (strncasecmp(argv, "remember=", 9) == 0)
      options->remember = strtol(&argv[9], NULL, 10);
my eyes are bleeding.

Similar to pam_str_skip_prefix_len() and pam_str_skip_prefix(),
introduce a new helper inline function pam_str_skip_icase_prefix_len()
and a new macro pam_str_skip_icase_prefix() on top of it, to be used
in subsequent commits to cleanup the ugliness.

* libpam/include/pam_inline.h (pam_str_skip_icase_prefix_len): New
function.
(pam_str_skip_icase_prefix): New macro.

1 files changed, 15 insertions, 0 deletions

diff --git a/libpam/include/pam_inline.h b/libpam/include/pam_inline.h
index 2e3a8d6a..ec05fe43 100644
--- a/libpam/include/pam_inline.h
+++ b/libpam/include/pam_inline.h
@@ -49,4 +49,19 @@ pam_str_skip_prefix_len(const char *str, const char *prefix, size_t prefix_len)
 #define pam_str_skip_prefix(str_, prefix_)	\
 	pam_str_skip_prefix_len((str_), (prefix_), sizeof(prefix_) - 1 + PAM_MUST_BE_ARRAY(prefix_))
 
+/*
+ * Returns NULL if STR does not start with PREFIX
+ * (ignoring the case of the characters),
+ * or a pointer to the first char in STR after PREFIX.
+ * The length of PREFIX is specified by PREFIX_LEN.
+ */
+static inline const char *
+pam_str_skip_icase_prefix_len(const char *str, const char *prefix, size_t prefix_len)
+{
+	return strncasecmp(str, prefix, prefix_len) ? NULL : str + prefix_len;
+}
+
+#define pam_str_skip_icase_prefix(str_, prefix_)	\
+	pam_str_skip_icase_prefix_len((str_), (prefix_), sizeof(prefix_) - 1 + PAM_MUST_BE_ARRAY(prefix_))
+
 #endif /* PAM_INLINE_H */