add osmo_escape_cstr and osmo_quote_cstr

Provide string escaping that
- returns the required buffer size, so it can be used with OSMO_STRBUF_APPEND().
- uses C compatible string constant escaping sequences.

This is intended as a replacement for all previous osmo_escape_str* and
osmo_quote_str* API. It pains me that I didn't get them right the first nor the
second time:
- The buffer functions do not return the chars needed, which is required for
  allocating sufficient memory in the *_c versions of the functions.
- Because of that, these functions are accurately usable for
  OSMO_STRBUF_APPEND(), producing truncated strings, for example when dumping a
  GSUP message.
- They do not use the C equivalent string constant escaping: for some reason I
  thought "\15" would be valid, but it should be "\x0f".
If I could, I would completely drop those mislead implementations ... but
backwards compat prohibits that.

A previous patch already provided internal static functions that accurately
return the required buffer size. Enhance these to also support C compatible
string escaping, and use them as implementation of the new functions:

osmo_escape_cstr_buf()
osmo_escape_cstr_c()
osmo_quote_cstr_buf()
osmo_quote_cstr_c()

In the tests for these, also test C string equivalence.

Naming: from API versions, it would be kind of logical to call them
osmo_escape_str_buf3() and osmo_escape_str_c2(). Since these anyway return a
different escaping, it makes sense to me to have distinct names instead.

Quasi missing are variants of the non-C-compatible weird legacy escaping that
return the required buffer size, but I refrain from adding those, because we
have enough API cruft as it is. Just always use these new cstr variants.

Change-Id: I3dfb892036e01000033dd8e7e4a6a0c32a3caa9b

1 files changed, 5 insertions, 0 deletions

diff --git a/include/osmocom/core/utils.h b/include/osmocom/core/utils.h
index 1abbe989..01c4de6e 100644
--- a/include/osmocom/core/utils.h
+++ b/include/osmocom/core/utils.h
@@ -148,6 +148,11 @@ bool osmo_identifier_valid(const char *str);
 bool osmo_separated_identifiers_valid(const char *str, const char *sep_chars);
 void osmo_identifier_sanitize_buf(char *str, const char *sep_chars, char replace_with);
 
+size_t osmo_escape_cstr_buf(char *buf, size_t bufsize, const char *str, int in_len);
+char *osmo_escape_cstr_c(void *ctx, const char *str, int in_len);
+size_t osmo_quote_cstr_buf(char *buf, size_t bufsize, const char *str, int in_len);
+char *osmo_quote_cstr_c(void *ctx, const char *str, int in_len);
+
 const char *osmo_escape_str(const char *str, int len);
 char *osmo_escape_str_buf2(char *buf, size_t bufsize, const char *str, int in_len);
 const char *osmo_escape_str_buf(const char *str, int in_len, char *buf, size_t bufsize);