Add missing shrunk check in integer_at (#212)

Author: kou

ext/strscan/strscan.c

@@ -1862,8 +1862,13 @@ strscan_integer_at(int argc, VALUE *argv, VALUE self)
 returnQnil;
 
 beg=adjust_register_position(p, p->regs.beg[i]);
+if (beg>S_LEN(p))
+returnQnil;
 end=adjust_register_position(p, p->regs.end[i]);
+end=minl(end, S_LEN(p));
 len=end-beg;
+if (len==0)
+returnQnil;
 ptr=S_PBEG(p) +beg;
 #ifdefHAVE_RB_INT_PARSE_CSTR
  {

test/strscan/test_stringscanner.rb

@@ -578,6 +578,26 @@ def test_integer_at_base_auto
 assert_integer_at(s,0,0)# 0xaf
 end
 
+deftest_integer_at_shrunk
+omit("not supported on TruffleRuby")ifRUBY_ENGINE == "truffleruby"
+
+s=create_string_scanner(+"before 29 after")
+s.skip_until(" ")
+assert_equal("29",s.scan(/\d+/))
+s.string.replace("before ")
+assert_nil(s.integer_at(0))
+end
+
+deftest_integer_at_shrunk_partial
+omit("not supported on TruffleRuby")ifRUBY_ENGINE == "truffleruby"
+
+s=create_string_scanner(+"before 29 after")
+s.skip_until(" ")
+assert_equal("29",s.scan(/\d+/))
+s.string.replace("before 2")
+assert_integer_at(s,2)
+end
+
 deftest_pre_match
 s=create_string_scanner('a b c d e')
 s.scan(/\w/)