util: added strtok_r implementation for old compilers

Visual studios older than 2005 don't have strtok_s() and according to
MSDN vs2005 has NOT thread-safe strtok().

src/sasl.c

@@ -24,10 +24,17 @@
 #include "sha1.h"
 #include "scram.h"
 #include "rand.h"
+#include "util.h"
 
-#ifdef _WIN32
-#define strtok_r strtok_s
-#endif
+/* strtok_s() has appeared in visual studio 2005.
+   Use own implementation for older versions. */
+#ifdef _MSC_VER
+# if (_MSC_VER >= 1400)
+# define strtok_r strtok_s
+# else
+# define strtok_r xmpp_strtok_r
+# endif
+#endif /* _MSC_VER */
 
 
 /** generate authentication string for the SASL PLAIN mechanism */

src/util.c

@@ -55,6 +55,28 @@ char *xmpp_strdup(const xmpp_ctx_t * const ctx, const char * const s)
     return copy;
 }
 
+/** strtok_r(3) implementation.
+ *  This function has appeared in POSIX.1-2001, but not in C standard.
+ *  For example, visual studio older than 2005 doesn't provide strtok_r()
+ *  nor strtok_s().
+ */
+char *xmpp_strtok_r(char *s, const char *delim, char **saveptr)
+{
+    size_t len;
+
+    s = s ? s : *saveptr;
+    len = strspn(s, delim);
+    s += len;
+    if (*s == '\0')
+        return NULL;
+
+    len = strcspn(s, delim);
+    *saveptr = s[len] == '\0' ? &s[len] : &s[len + 1];
+    s[len] = '\0';
+
+    return s;
+}
+
 /** Return an integer based time stamp.
  *  This function uses gettimeofday or timeGetTime (on Win32 platforms) to
  *  compute an integer based time stamp.  This is used internally by the

src/util.h

@@ -18,6 +18,9 @@
 
 #include "ostypes.h"
 
+/* string functions */
+char *xmpp_strtok_r(char *s, const char *delim, char **saveptr);
+
 /* timing functions */
 uint64_t time_stamp(void);
 uint64_t time_elapsed(uint64_t t1, uint64_t t2);