Allow parsing strings larger than 4GiB

For a reason unknown, even though `pos` is stored as a `long`,
the `#pos` and `#pos=` treat it as an `int`, which prevent
skeeing into strings larger than 4GiB.

Author: byroot

ext/strscan/strscan.c

@@ -524,7 +524,7 @@ strscan_get_pos(VALUE self)
     struct strscanner *p;
 
     GET_SCANNER(self, p);
-    return INT2FIX(p->curr);
+    return LONG2NUM(p->curr);
 }
 
 /*
@@ -554,7 +554,7 @@ strscan_set_pos(VALUE self, VALUE v)
     long i;
 
     GET_SCANNER(self, p);
-    i = NUM2INT(v);
+    i = NUM2LONG(v);
     if (i < 0) i += S_LEN(p);
     if (i < 0) rb_raise(rb_eRangeError, "index out of range");
     if (i > S_LEN(p)) rb_raise(rb_eRangeError, "index out of range");

test/strscan/test_stringscanner.rb

@@ -1128,6 +1128,17 @@ def test_fixed_anchor_false
     assert_equal(false, StringScanner.new("a", fixed_anchor: nil).fixed_anchor?)
     assert_equal(false, StringScanner.new("a", fixed_anchor: false).fixed_anchor?)
   end
+
+  def test_large_string
+    omit("not supported on JRuby") if RUBY_ENGINE == "jruby"
+
+    two_gib = (2 * 1024 * 1024 * 1024) + 100
+    string = "a" * two_gib
+    s = create_string_scanner(string) # 6 GiB string
+    s.pos = two_gib - 1
+    assert_equal(two_gib - 1, s.pos)
+    string.clear
+  end
 end
 
 class TestStringScannerFixedAnchor < Test::Unit::TestCase