Improve redisAppendCommandArgv performance

OK, perhaps the second time is a charm.  I forgot that I had
hiredis forked from a long time ago, so the initial pull
request was hosed.  :)

* Pulled in sdscatfmt() from Redis, and modified it to accept a
  size_t (%T) style format specifier.

* Pulled in sdsll2str() and sdsull2str() from Redis (needed by
  sdscatfmt).

* Added a new method, redisFormatSdsCommandArgv() which takes
  and sds* as the target, rather than char* (and uses sdscatfmt
  instead of sprintf for the construction).

I get roughly the following improvement:

Old: 1.044806
New: 0.481620

The benchmark code itself can be found here:
https://gist.github.com/michael-grunder/c92ef31bb632b3d0ad81

Closes #260

1 files changed, 2 insertions, 0 deletions

diff --git a/hiredis.h b/hiredis.h
index 7700f4b..fa3a89d 100644
--- a/hiredis.h
+++ b/hiredis.h
@@ -34,6 +34,7 @@
 #include <stdio.h> /* for size_t */
 #include <stdarg.h> /* for va_list */
 #include <sys/time.h> /* for struct timeval */
+#include "sds.h" /* for sds */
 
 #define HIREDIS_MAJOR 0
 #define HIREDIS_MINOR 11
@@ -161,6 +162,7 @@ void freeReplyObject(void *reply);
 int redisvFormatCommand(char **target, const char *format, va_list ap);
 int redisFormatCommand(char **target, const char *format, ...);
 int redisFormatCommandArgv(char **target, int argc, const char **argv, const size_t *argvlen);
+int redisFormatSdsCommandArgv(sds *target, int argc, const char ** argv, const size_t *argvlen);
 
 /* Context for a connection to Redis */
 typedef struct redisContext {