eof? should raise an IOError if it is not opened for reading.

include/mruby/ext/io.h

@@ -13,7 +13,8 @@ struct mrb_io {
   int fd;   /* file descriptor, or -1 */
   int fd2;  /* file descriptor to write if it's different from fd, or -1 */
   int pid;  /* child's pid (for pipes)  */
-  unsigned int writable:1,
+  unsigned int readable:1,
+               writable:1,
                sync:1;
 };
 

mrblib/io.rb

@@ -133,6 +133,7 @@ class IO
   end
 
   def eof?
+    _check_readable
     begin
       buf = _read_buf
       return buf.size == 0

src/io.c

@@ -254,6 +254,7 @@ mrb_io_alloc(mrb_state *mrb)
   fptr->fd = -1;
   fptr->fd2 = -1;
   fptr->pid = 0;
+  fptr->readable = 0;
   fptr->writable = 0;
   fptr->sync = 0;
   return fptr;
@@ -394,6 +395,7 @@ mrb_io_s_popen(mrb_state *mrb, mrb_value klass)
       fptr->fd = fd;
       fptr->fd2 = write_fd;
       fptr->pid = pid;
+      fptr->readable = ((flags & FMODE_READABLE) != 0);
       fptr->writable = ((flags & FMODE_WRITABLE) != 0);
       fptr->sync = 0;
 
@@ -454,6 +456,7 @@ mrb_io_initialize(mrb_state *mrb, mrb_value io)
   DATA_PTR(io) = fptr;
 
   fptr->fd = fd;
+  fptr->readable = ((flags & FMODE_READABLE) != 0);
   fptr->writable = ((flags & FMODE_WRITABLE) != 0);
   fptr->sync = 0;
   return io;
@@ -499,6 +502,16 @@ fptr_finalize(mrb_state *mrb, struct mrb_io *fptr, int quiet)
   }
 }
 
+mrb_value
+mrb_io_check_readable(mrb_state *mrb, mrb_value self)
+{
+  struct mrb_io *fptr = io_get_open_fptr(mrb, self);
+  if (! fptr->readable) {
+    mrb_raise(mrb, E_IO_ERROR, "not opened for reading");
+  }
+  return mrb_nil_value();
+}
+
 mrb_value
 mrb_io_isatty(mrb_state *mrb, mrb_value self)
 {
@@ -772,6 +785,7 @@ mrb_io_s_pipe(mrb_state *mrb, mrb_value klass)
   mrb_iv_set(mrb, r, mrb_intern_cstr(mrb, "@pos"), mrb_fixnum_value(0));
   fptr_r = mrb_io_alloc(mrb);
   fptr_r->fd = pipes[0];
+  fptr_r->readable = 1;
   fptr_r->writable = 0;
   fptr_r->sync = 0;
   DATA_TYPE(r) = &mrb_io_type;
@@ -782,6 +796,7 @@ mrb_io_s_pipe(mrb_state *mrb, mrb_value klass)
   mrb_iv_set(mrb, w, mrb_intern_cstr(mrb, "@pos"), mrb_fixnum_value(0));
   fptr_w = mrb_io_alloc(mrb);
   fptr_w->fd = pipes[1];
+  fptr_w->readable = 0;
   fptr_w->writable = 1;
   fptr_w->sync = 1;
   DATA_TYPE(w) = &mrb_io_type;
@@ -1062,6 +1077,7 @@ mrb_init_io(mrb_state *mrb)
 #endif
 
   mrb_define_method(mrb, io, "initialize", mrb_io_initialize, MRB_ARGS_ANY());    /* 15.2.20.5.21 (x)*/
+  mrb_define_method(mrb, io, "_check_readable", mrb_io_check_readable, MRB_ARGS_NONE());
   mrb_define_method(mrb, io, "isatty",     mrb_io_isatty,     MRB_ARGS_NONE());
   mrb_define_method(mrb, io, "sync",       mrb_io_sync,       MRB_ARGS_NONE());
   mrb_define_method(mrb, io, "sync=",      mrb_io_set_sync,   MRB_ARGS_REQ(1));

test/io.rb

@@ -70,12 +70,11 @@ end
 #assert('IO#each_line', '15.2.20.5.5') do
 
 assert('IO#eof?', '15.2.20.5.6') do
-  if false  # XXX: not implemented yet
-    io = IO.new(IO.sysopen($mrbtest_io_wfname, 'w'), 'w')
-    assert_raise(IOError) do
-      io.eof?
-    end
+  io = IO.new(IO.sysopen($mrbtest_io_wfname, 'w'), 'w')
+  assert_raise(IOError) do
+    io.eof?
   end
+  io.close
 
   # empty file
   io = IO.open(IO.sysopen($mrbtest_io_wfname, 'w'), 'w')