lily/parse-scm.cc

   1 /*
   2   parse-scm -- Parse a single SCM expression exactly.
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 2004--2009 Han-Wen Nienhuys <hanwen@xs4all.nl>
   7 */
   8
   9 #include "parse-scm.hh"
  10
  11 #include <cstdio>
  12 using namespace std;
  13
  14 #include "lily-parser.hh"
  15 #include "international.hh"
  16 #include "main.hh"
  17 #include "paper-book.hh"
  18 #include "source-file.hh"
  19
  20 /* Pass string to scm parser, evaluate one expression.
  21    Return result value and #chars read.
  22
  23    Thanks to Gary Houston <ghouston@freewire.co.uk>  */
  24 SCM
  25 internal_ly_parse_scm (Parse_start *ps)
  26 {
  27   Source_file *sf = ps->start_location_.get_source_file ();
  28   SCM port = sf->get_port ();
  29
  30   int off = ps->start_location_.start () - sf->c_str ();
  31
  32   scm_seek (port, scm_long2num (off), scm_long2num (SEEK_SET));
  33   SCM from = scm_ftell (port);
  34
  35   scm_set_port_line_x (port,  scm_from_int (ps->start_location_.line_number () -1));
  36   scm_set_port_column_x (port,  scm_from_int (ps->start_location_.column_number () -1));
  37
  38   SCM answer = SCM_UNSPECIFIED;
  39   SCM form = scm_read (port);
  40
  41   SCM to = scm_ftell (port);
  42   ps->nchars = scm_to_int (to) - scm_to_int (from);
  43
  44
  45   /* Read expression from port.  */
  46   if (!SCM_EOF_OBJECT_P (form))
  47     {
  48       if (ps->safe_)
  49         {
  50           static SCM module = SCM_BOOL_F;
  51           if (module == SCM_BOOL_F)
  52             {
  53               SCM function = ly_lily_module_constant ("make-safe-lilypond-module");
  54               module = scm_call_0 (function);
  55             }
  56
  57           // We define the parser so trusted Scheme functions can
  58           // access the real namespace underlying the parser.
  59           if (ps->parser_)
  60             scm_module_define (module, ly_symbol2scm ("parser"),
  61                                ps->parser_->self_scm());
  62           answer = scm_eval (form, module);
  63         }
  64       else
  65         answer = scm_primitive_eval (form);
  66     }
  67
  68   /* Don't close the port here; if we re-enter this function via a
  69      continuation, then the next time we enter it, we'll get an error.
  70      It's a string port anyway, so there's no advantage to closing it
  71      early. */
  72   // scm_close_port (port);
  73
  74   return answer;
  75 }
  76
  77 SCM
  78 catch_protected_parse_body (void *p)
  79 {
  80   Parse_start *ps = (Parse_start *) p;
  81
  82   return internal_ly_parse_scm (ps);
  83 }
  84
  85 SCM
  86 parse_handler (void *data, SCM tag, SCM args)
  87 {
  88   Parse_start *ps = (Parse_start *) data;
  89
  90   ps->start_location_.error (_ ("GUILE signaled an error for the expression beginning here"));
  91
  92   if (scm_ilength (args) > 2)
  93     scm_display_error_message (scm_cadr (args), scm_caddr (args), scm_current_error_port ());
  94
  95   if (tag == ly_symbol2scm ("read-error"))
  96     ps->nchars = 1;
  97
  98   return SCM_UNDEFINED;
  99 }
 100
 101 SCM
 102 protected_ly_parse_scm (Parse_start *ps)
 103 {
 104   /*
 105     Catch #t : catch all Scheme level errors.
 106    */
 107   return scm_internal_catch (SCM_BOOL_T,
 108                              &catch_protected_parse_body,
 109                              (void *) ps,
 110                              &parse_handler, (void *) ps);
 111 }
 112
 113 bool parse_protect_global = true;
 114 bool parsed_objects_should_be_dead = false;
 115
 116 /* Try parsing.  Upon failure return SCM_UNDEFINED.
 117    FIXME: shouldn't we return SCM_UNSCPECIFIED -- jcn  */
 118 SCM
 119 ly_parse_scm (char const *s, int *n, Input i, bool safe, Lily_parser *parser)
 120 {
 121   Parse_start ps;
 122   ps.str = s;
 123   ps.start_location_ = i;
 124   ps.safe_ = safe;
 125   ps.parser_ = parser;
 126
 127   SCM ans = parse_protect_global ? protected_ly_parse_scm (&ps)
 128     : internal_ly_parse_scm (&ps);
 129   *n = ps.nchars;
 130
 131   return ans;
 132 }
 133