* ext/stringio/stringio.c (strio_ungetc): should allow ungetc at

  the top of the buffer.  ref #701

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_8@20151 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 17 insertions, 8 deletions

diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 7838c51aa2..3ed7d6b1af 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -781,15 +781,24 @@ strio_ungetc(self, ch)
     int cc = NUM2INT(ch);
     long len, pos = ptr->pos;
 
-    if (cc != EOF && pos > 0) {
-	if ((len = RSTRING(ptr->string)->len) < pos-- ||
-	    (unsigned char)RSTRING(ptr->string)->ptr[pos] !=
-	    (unsigned char)cc) {
-	    strio_extend(ptr, pos, 1);
-	    RSTRING(ptr->string)->ptr[pos] = cc;
-	    OBJ_INFECT(ptr->string, self);
+    if (cc != EOF) {
+	len = RSTRING(ptr->string)->len;
+	if (pos == 0) {
+	    char *p;
+	    rb_str_resize(ptr->string, len + 1);
+	    p = RSTRING(ptr->string)->ptr;
+	    memmove(p + 1, p, len);
+	}
+	else {
+	    if (len < pos-- ||
+		(unsigned char)RSTRING(ptr->string)->ptr[pos] !=
+		(unsigned char)cc) {
+		strio_extend(ptr, pos, 1);
+	    }
+	    --ptr->pos;
 	}
-	--ptr->pos;
+	RSTRING(ptr->string)->ptr[pos] = cc;
+	OBJ_INFECT(ptr->string, self);
 	ptr->flags &= ~STRIO_EOF;
     }
     return Qnil;