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--2007 Han-Wen Nienhuys <hanwen@xs4all.nl>
   7 */
   8
   9 #include "parse-scm.hh"
  10
  11 #include <cstdio>
  12 using namespace std;
  13
  14 #include "international.hh"
  15 #include "main.hh"
  16 #include "paper-book.hh"
  17 #include "source-file.hh"
  18
  19 /* Pass string to scm parser, evaluate one expression.
  20    Return result value and #chars read.
  21
  22    Thanks to Gary Houston <ghouston@freewire.co.uk>  */
  23 SCM
  24 internal_ly_parse_scm (Parse_start *ps)
  25 {
  26   Source_file *sf = ps->start_location_.get_source_file ();
  27   SCM port = sf->get_port ();
  28
  29   int off = ps->start_location_.start () - sf->c_str ();
  30
  31   scm_seek (port, scm_long2num (off), scm_long2num (SEEK_SET));
  32   SCM from = scm_ftell (port);
  33
  34   scm_set_port_line_x (port,  scm_from_int (ps->start_location_.line_number () -1));
  35   scm_set_port_column_x (port,  scm_from_int (ps->start_location_.column_number () -1));
  36
  37   SCM answer = SCM_UNSPECIFIED;
  38   SCM form = scm_read (port);
  39
  40
  41   /* Reset read_buf for scm_ftell.
  42      Shouldn't scm_read () do this for us?  */
  43   scm_fill_input (port);
  44   SCM to = scm_ftell (port);
  45   ps->nchars = scm_to_int (to) - scm_to_int (from);
  46
  47
  48   /* Read expression from port.  */
  49   if (!SCM_EOF_OBJECT_P (form))
  50     {
  51       if (ps->safe_)
  52         {
  53           static SCM module = SCM_BOOL_F;
  54           if (module == SCM_BOOL_F)
  55             {
  56               SCM function = ly_lily_module_constant ("make-safe-lilypond-module");
  57               module = scm_call_0 (function);
  58             }
  59           answer = scm_eval (form, module);
  60         }
  61       else
  62         answer = scm_primitive_eval (form);
  63     }
  64
  65   /* Don't close the port here; if we re-enter this function via a
  66      continuation, then the next time we enter it, we'll get an error.
  67      It's a string port anyway, so there's no advantage to closing it
  68      early. */
  69   // scm_close_port (port);
  70
  71   return answer;
  72 }
  73
  74 SCM
  75 catch_protected_parse_body (void *p)
  76 {
  77   Parse_start *ps = (Parse_start *) p;
  78
  79   return internal_ly_parse_scm (ps);
  80 }
  81
  82 SCM
  83 parse_handler (void *data, SCM tag, SCM args)
  84 {
  85   Parse_start *ps = (Parse_start *) data;
  86
  87   ps->start_location_.error (_ ("GUILE signaled an error for the expression beginning here"));
  88
  89   if (scm_ilength (args) > 2)
  90     scm_display_error_message (scm_cadr (args), scm_caddr (args), scm_current_error_port ());
  91
  92   if (tag == ly_symbol2scm ("read-error"))
  93     ps->nchars = 1;
  94
  95   return SCM_UNDEFINED;
  96 }
  97
  98 SCM
  99 protected_ly_parse_scm (Parse_start *ps)
 100 {
 101   /*
 102     Catch #t : catch all Scheme level errors.
 103    */
 104   return scm_internal_catch (SCM_BOOL_T,
 105                              &catch_protected_parse_body,
 106                              (void *) ps,
 107                              &parse_handler, (void *) ps);
 108 }
 109
 110 bool parse_protect_global = true;
 111 bool parsed_objects_should_be_dead = false;
 112
 113 /* Try parsing.  Upon failure return SCM_UNDEFINED.
 114    FIXME: shouldn't we return SCM_UNSCPECIFIED -- jcn  */
 115 SCM
 116 ly_parse_scm (char const *s, int *n, Input i, bool safe)
 117 {
 118   Parse_start ps;
 119   ps.str = s;
 120   ps.start_location_ = i;
 121   ps.safe_ = safe;
 122
 123   SCM ans = parse_protect_global ? protected_ly_parse_scm (&ps)
 124     : internal_ly_parse_scm (&ps);
 125   *n = ps.nchars;
 126
 127   return ans;
 128 }
 129