bug#20109: Incompatible API change in 2.0 series for string port encoding

[Mark H Weaver]

David Kastrup <address@hidden> writes:

> In 2.0.9, the following patch/code for getting what amounts to a binary
> string port worked.
>
> commit 7f7a124d3470b0d566f796e88f4e2ad5aa043f16
> Author: David Kastrup <address@hidden>
> Date:   Sun Sep 21 18:40:06 2014 +0200
>
>     Source_file::init_port: Keep GUILEv2 from redecoding string input
>
> diff --git a/lily/source-file.cc b/lily/source-file.cc
> index 1118b9d..75ed0d9 100644
> --- a/lily/source-file.cc
> +++ b/lily/source-file.cc
> @@ -152,7 +152,11 @@ Source_file::init_port ()
>    // we do our own utf8 encoding and verification in the parser, so we
>    // use the no-conversion equivalent of latin1
>    SCM str = scm_from_latin1_string (c_str ());
> -  str_port_ = scm_mkstrport (SCM_INUM0, str, SCM_OPN | SCM_RDNG, 
> __FUNCTION__);
> +  scm_dynwind_begin ((scm_t_dynwind_flags)0);
> +  // Why doesn't scm_set_port_encoding_x work here?
> +  scm_dynwind_fluid (ly_lily_module_constant ("%default-port-encoding"), 
> SCM_BOOL_F);
> +  str_port_ = scm_open_input_string (str);
> +  scm_dynwind_end ();
>    scm_set_port_filename_x (str_port_, ly_string2scm (name_));
>  }

This hack of giving Guile a buffer containing UTF-8, but claiming that
it is Latin-1, is not good.  It will cause Guile to see non-ASCII
characters as garbage.  However, if you insist on doing this, I would
suggest using a bytevector input port instead, like this: (untested)

  char *buf = c_str ();
  SCM bv = scm_c_make_bytevector (strlen (buf) + 1);
  strcpy (SCM_BYTEVECTOR_CONTENTS (bv), buf);
  str_port_ = scm_open_bytevector_input_port (bv, SCM_UNDEFINED);

       Mark