Description for new cstr wrapper is done.

include/sexpr/sexp.h

@@ -567,12 +567,29 @@ typedef struct sexp_iowrap {
   size_t cnt;
 } sexp_iowrap_t;
 
-/* TODO: doxygen? more doxygen */
+/**
+ * \ingroup IO
+ * This structure is a wrapper around a the parsing infrastructure (continuation
+ * and a buffer) required to parse off of it.  This is used so that routines can
+ * hide the loops and details required to accumulate up data read off of the buffer.
+ */
 typedef struct sexp_cstrwrap {
+  /**
+   * Continuation used to parse off of the given buffer
+   */
   pcont_t *cc;
+  /**
+   * A pointer to the cstring data to parse
+   */
   const char *seval;
+  /**
+   * different counters used to have a deal with source and buffer
+   */
   size_t rl, cnt;
   size_t sln;
+  /**
+   * Temproary buffer used to parse
+   */
   char buf[CSTRBUFSIZ];
 } sexp_cstrwrap_t;
 
@@ -742,8 +759,18 @@ extern "C" {
    */
   sexp_t *read_one_sexp(sexp_iowrap_t *iow);
 
+  /**
+   * \ingroup IO
+   * create an wrapper structure around a c string buffer.  A NULL return
+   * value indicates some problem occurred allocating the wrapper, so the
+   * user should check the value of sexp_errno for further information.
+   */
   sexp_cstrwrap_t *init_cstrwrap(const char *);
 
+  /**
+   * \ingroup IO
+   * destroy a wrapper structure.
+   */
   void destroy_cstrwrap(sexp_cstrwrap_t *);
 
   sexp_t *get_one_sexp(sexp_cstrwrap_t *);