quasiliterals: buffers in hex, separation for strings and buffers.

In this commit, output variables in the TXR Pattern language and
in TXR Lisp quasiliterals now support separator strings for values
that are strings and buffers.  Values which are buffers appear
differently: they are rendered as a sequence of lower case hex
digit pairs. When a string-valued variable specifies a separator,
the separator appears between characters of the string value.
Previously, the separator was ignored. When a buffer-valued
variable specifies a separator. the separator appears between
pairs of digits, not between digits. For instance if ethaddr
is a variable holding #b'08:00:27:79:c7:f5', then the quasiliteral
`@ethaddr` produces "08002779c7f" whereas `@{ethaddr ":"}`
produces "08:00:27:79:c7:f5".

* buf.[ch] (buf_str_sep): New function.

* lib.[ch] (fmt_str_sep): New function.

* eval.c (fmt_cat): If the argument is a string, and a separator
is present, replace the value with the result of calling
fmt_str_sep. If the argument is a buffer, and a separator is
present, use buf_str_sep to convert to a string, otherwise
use tostringp.

* txr.1: Section on Output Variables updated.

* tests/012/readprint.tl: New tests.

1 files changed, 34 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 7a0d2522..363b55a3 100644
--- a/lib.c
+++ b/lib.c
@@ -6237,6 +6237,40 @@ val fmt_join(varg args)
   return join_with(nil, args);
 }
 
+val fmt_str_sep(val sep, val str, val self)
+{
+  ucnum lsep = c_unum(length_str(sep), self);
+  ucnum lstr = c_unum(length_str(str), self);
+  const wchar_t *csep = c_str(sep, self);
+  const wchar_t *cstr = c_str(str, self);
+  ucnum total = (lstr > 0 ? (lstr - 1) * lsep + lstr : 0) + 1;
+  ucnum i;
+  wchar_t *out = chk_wmalloc(total);
+  wchar_t *ptr = out, *end = out + total;
+
+  for (i = 0; i < lstr; i++) {
+    if (i > 0) {
+      if (end - ptr <= convert(ptrdiff_t, lsep))
+        break;
+      wcscpy(ptr, csep);
+      ptr += lsep;
+    }
+    if (end - ptr <= 1)
+      break;
+    *ptr++ = cstr[i];
+  }
+
+  if (i < lstr) {
+    free(out);
+    uw_throwf(error_s, lit("~a: string length overflow"), self, nao);
+  }
+
+  *ptr = 0;
+
+  return string_own(out);
+}
+
+
 val split_str_keep(val str, val sep, val keep_sep_opt, val count_opt)
 {
   val self = lit("split-str");