add osmo_{escape,quote}_str_buf2() for standard args ordering

To be able to append an escaped or quoted string using
OSMO_STRBUF_APPEND_NOLEN(), the function signature must have the buf and len as
first args, like most other *_buf() functions.

Add osmo_escape_str_buf2() and osmo_quote_str_buf2() to match this signature.

A recent patch [1] has changed the return value of osmo_escape_str_buf() to
char*, removing the const. However, the functions may return const strings,
hence re-add the const. The new signatures always return the non-const buffer.

To avoid code duplication, implement osmo_quote_str_buf() and
osmo_escape_str_buf() by calling the new functions.

I decided to allow slight changes to the behavior for current osmo_escape_str()
and osmo_escape_str_buf(), because impact on callers is minimal:

(1) The new implementation uses OSMO_STRBUF_*, and in consequence
osmo_quote_str() no longer prints an ending double quote after truncated
strings; Before, a truncated output was, sic:
  "this string is trunca"
and now this becomes, sic:
  "this string is truncat
I decided to not keep the old behavior because it is questionable to begin
with. It looks like the string actually ended at the truncation boundary
instead of the reason being not enough space in the output buffer.

(2) The new osmo_escape_str_buf2() function obviously cannot pass-thru an
unchanged char* if no escaping was needed. Sacrifice this tiny optimization
feature to avoid code duplication:
- it is an unnoticeable optimization,
- the caller anyway always passes a string buffer,
- the feature caused handling strings and buffers differently depending on
  their content (i.e. code that usually writes out strings in full length
  "suddenly" truncates because a non-printable character is contained, etc.)
I considered adding a skip_if_unescaped flag to the osmo_quote_str_buf2()
function signature, but in the end decided that the API clutter is not worth
having for all the above reasons.

Adjust tests to accomodate above changes.

[1] 4a62eda225ab7f3c9556990c81a6fc5e19b5eec8
    Ibf85f79e93244f53b2684ff6f1095c5b41203e05

Change-Id: Id748b906b0083b1f1887f2be7a53cae705a8a9ae

1 files changed, 8 insertions, 0 deletions

diff --git a/TODO-RELEASE b/TODO-RELEASE
index 5ddc57a3..7c81e323 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -11,3 +11,11 @@ libosmogb	gprs_ns_inst		Adding bss_sns_fi member for IP-SNS support
 libosmogb	gprs_nsvc		Adding sig_weight and data_weight members for IP-SNS support
 libosmogb	various new symbols	Adding functions related to IP-SNS support
 libosmocore	osmo_fsm_inst		Add flag proc.terminating (ABI change)
+libosmocore	osmo_escape_str(),      These now always copy to the buffer instead of returning the
+		osmo_escape_str_buf()	  unchanged input string when no chars needed escaping, hence
+		                          returned strings might now also be truncated even if all chars were printable.
+libosmocore	osmo_escape_str_buf2()	New function signature similar to snprintf(), for use with OSMO_STRBUF_APPEND().
+libosmocore	osmo_quote_str(),       On string truncation, these used to print a closing quote '"' after the
+		osmo_quote_str_buf()	  truncated string. This is no longer the case. e.g. a string 'truncated' in a
+					  9-char buffer used to print '"trunca"\0', which now becomes '"truncat\0'.
+libosmocore	osmo_quote_str_buf2()	New function signature similar to snprintf(), for use with OSMO_STRBUF_APPEND().