StringScannerからMatchDataがとれない(2)

indexでは参照できるけど名前では参照できなかったので，参照できるようにしてみた．
(2009-10-25修正)：マッチしてない部分の名前での参照がバグってたので修正．

--- orig_strscan.c	2009-10-18 18:39:10.000000000 +0900
+++ strscan.c	2009-10-25 00:26:44.000000000 +0900
@@ -36,6 +36,7 @@
 
     /* the regexp register; legal only when MATCHED_P(s) */
     struct re_registers regs;
+    VALUE regexp;
 };
 
 #define MATCHED_P(s)          ((s)->flags & FLAG_MATCHED)
@@ -160,6 +161,7 @@
 strscan_mark(struct strscanner *p)
 {
     rb_gc_mark(p->str);
+    rb_gc_mark(p->regexp);
 }
 
 static void
@@ -173,12 +175,13 @@
 strscan_s_allocate(VALUE klass)
 {
     struct strscanner *p;
-    
+
     p = ALLOC(struct strscanner);
     MEMZERO(p, struct strscanner, 1);
     CLEAR_MATCH_STATUS(p);
     onig_region_init(&(p->regs));
     p->str = Qnil;
+    p->regexp = Qnil;
     return Data_Wrap_Struct(klass, strscan_mark, strscan_free, p);
 }
 
@@ -230,6 +233,7 @@
     if (self != orig) {
 	self->flags = orig->flags;
 	self->str = orig->str;
+	self->regexp = orig->regexp;
 	self->prev = orig->prev;
 	self->curr = orig->curr;
 	onig_region_copy(&self->regs, &orig->regs);
@@ -449,6 +453,7 @@
     }
 
     MATCHED(p);
+    p->regexp = regex;
     p->prev = p->curr;
     if (succptr) {
         p->curr += p->regs.end[0];
@@ -955,20 +960,55 @@
  *   s.post_match                       # -> "1975 14:39"
  *   s.pre_match                        # -> ""
  */
+
+static int
+name_to_backref_number(struct re_registers *regs, VALUE regexp, const char* name, const char* name_end)
+{
+    int num;
+
+    num = onig_name_to_backref_number(RREGEXP(regexp)->ptr,
+	(const unsigned char* )name, (const unsigned char* )name_end, regs);
+    if (num >= 1) {
+	return num;
+    }
+    else {
+	VALUE s = rb_str_new(name, (long )(name_end - name));
+	rb_raise(rb_eIndexError, "undefined group name reference: %s",
+				 StringValuePtr(s));
+    }
+}
+
 static VALUE
 strscan_aref(VALUE self, VALUE idx)
 {
     struct strscanner *p;
-    long i;
+    long i = 0;
 
     GET_SCANNER(self, p);
     if (! MATCHED_P(p))        return Qnil;
-    
-    i = NUM2LONG(idx);
-    if (i < 0)
-        i += p->regs.num_regs;
-    if (i < 0)                 return Qnil;
-    if (i >= p->regs.num_regs) return Qnil;
+
+    const char *s;
+    switch (TYPE(idx)) {
+    case T_FIXNUM:
+        i = FIX2LONG(idx);
+        if (i < 0)
+            i += p->regs.num_regs;
+        if (i < 0)                 return Qnil;
+        if (i >= p->regs.num_regs) return Qnil;
+        break;
+    case T_SYMBOL:
+        s = rb_id2name(SYM2ID(idx));
+        goto name_to_backref;
+        break;
+    case T_STRING:
+        s = StringValuePtr(idx);
+
+    name_to_backref:
+        i = name_to_backref_number(&p->regs, p->regexp, s, s + strlen(s));
+        break;
+    default:
+        rb_raise(rb_eTypeError, "wrong argument type %s (expected Fixnum, Symbol or String)", rb_obj_classname(idx));
+    }
     if (p->regs.beg[i] == -1)  return Qnil;
 
     return extract_range(p, p->prev + p->regs.beg[i],

s = StringScanner.new("hoge")
s.scan(/.(?<k>.)./)
p s[:k]  # => "o"

re.cからコードを一部コピペする羽目に．適当なのでちゃんとできてるかよくわからない．