1 files changed, 43 insertions, 6 deletions

diff --git a/lib.c b/lib.c
index d0667a57..ed0a47fe 100644
--- a/lib.c
+++ b/lib.c
@@ -5384,6 +5384,15 @@ val downcase_str(val str)
   return out;
 }
 
+static val us_length_STR(val str, val self)
+{
+  if (!str->st.len) {
+    set(mkloc(str->st.len, str), num(wcslen(str->st.str)));
+    str->st.alloc = c_num(str->st.len, self) + 1;
+  }
+  return str->st.len;
+}
+
 val string_extend(val str, val tail, val finish_in)
 {
   val self = lit("string-extend");
@@ -5391,7 +5400,7 @@ val string_extend(val str, val tail, val finish_in)
   type_check(self, str, STR);
   {
     val finish = default_null_arg(finish_in);
-    cnum len = c_fixnum(length_str(str), self);
+    cnum len = c_fixnum(us_length_STR(str, self), self);
     cnum oalloc = str->st.alloc;
     cnum alloc = oalloc, delta, needed;
 
@@ -5436,6 +5445,38 @@ val string_extend(val str, val tail, val finish_in)
   return str;
 }
 
+val us_string_extend_STR_CHR(val str, val ch, val finish, val self)
+{
+  cnum len = c_fixnum(us_length_STR(str, self), self);
+  cnum oalloc = str->st.alloc;
+  cnum alloc = oalloc, needed;
+
+  if (NUM_MAX - 2 < len)
+    uw_throwf(alloc_error_s, lit("~a: overflow"), self, nao);
+
+  needed = len + 2;
+
+  if (needed > alloc || finish) {
+    if (finish)
+      alloc = needed;
+    else if (alloc >= (NUM_MAX - NUM_MAX / 3))
+      alloc = NUM_MAX;
+    else
+      alloc = max(alloc + alloc / 2, needed);
+
+    if (alloc != oalloc) {
+      str->st.str = chk_wrealloc(str->st.str, alloc);
+      str->st.alloc = alloc;
+    }
+  }
+
+  str->st.len = num_fast(len + 1);
+  str->st.str[len] = convert(wchar_t, c_n(ch));
+  str->st.str[len + 1] = 0;
+
+  return str;
+}
+
 val string_finish(val str)
 {
   val self = lit("string-finish");
@@ -5528,11 +5569,7 @@ val length_str(val str)
     lazy_str_force(str);
     return length_str(str->ls.prefix);
   case STR:
-    if (!str->st.len) {
-      set(mkloc(str->st.len, str), num(wcslen(str->st.str)));
-      str->st.alloc = c_num(str->st.len, self) + 1;
-    }
-    return str->st.len;
+    return us_length_STR(str, self);
   default:
     type_mismatch(lit("length-str: ~s is not a string"), str, nao);
   }