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

[Mark H Weaver <mhw@netris.org>]

Mark H Weaver <mhw@netris.org> writes:

> David Kastrup <dak@gnu.org> writes:
>
>> In 2.0.9, the following patch/code for getting what amounts to a binary
>> string port worked.
>>
>> commit 7f7a124d3470b0d566f796e88f4e2ad5aa043f16
>> Author: David Kastrup <dak@gnu.org>
>> 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);

Sorry, the NUL terminator should not be included:

   char *buf = c_str ();
   size_t len = strlen (buf);
   SCM bv = scm_c_make_bytevector (len);
   memcpy (SCM_BYTEVECTOR_CONTENTS (bv), buf, len);
   str_port_ = scm_open_bytevector_input_port (bv, SCM_UNDEFINED);

      Mark