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--2005 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7 */
   8
   9 #include "parse-scm.hh"
  10
  11 #include <cstdio>
  12
  13 #include "main.hh"
  14 #include "paper-book.hh"
  15 #include "source-file.hh"
  16
  17 /* Pass string to scm parser, evaluate one expression.
  18    Return result value and #chars read.
  19
  20    Thanks to Gary Houston <ghouston@freewire.co.uk>  */
  21 SCM
  22 internal_ly_parse_scm (Parse_start *ps)
  23 {
  24   Source_file *sf = ps->start_location_.get_source_file ();
  25   SCM port = sf->get_port ();
  26
  27   int off = ps->start_location_.start () - sf->to_str0 ();
  28
  29   scm_seek (port, scm_long2num (off), scm_long2num (SEEK_SET));
  30   SCM from = scm_ftell (port);
  31
  32   SCM answer = SCM_UNSPECIFIED;
  33   SCM form = scm_read (port);
  34
  35   /* Read expression from port.  */
  36   if (!SCM_EOF_OBJECT_P (form))
  37     {
  38       if (ps->safe_)
  39         {
  40           static SCM module = SCM_BOOL_F;
  41           if (module == SCM_BOOL_F)
  42             {
  43               SCM function = ly_lily_module_constant ("make-safe-lilypond-module");
  44               module = scm_call_0 (function);
  45             }
  46           answer = scm_eval (form, module);
  47         }
  48       else
  49         answer = scm_primitive_eval (form);
  50     }
  51
  52   /* Reset read_buf for scm_ftell.
  53      Shouldn't scm_read () do this for us?  */
  54   scm_fill_input (port);
  55   SCM to = scm_ftell (port);
  56   ps->nchars = scm_to_int (to) - scm_to_int (from);
  57
  58   /* Don't close the port here; if we re-enter this function via a
  59      continuation, then the next time we enter it, we'll get an error.
  60      It's a string port anyway, so there's no advantage to closing it
  61      early. */
  62   // scm_close_port (port);
  63
  64   return answer;
  65 }
  66
  67 SCM
  68 catch_protected_parse_body (void *p)
  69 {
  70   Parse_start *ps = (Parse_start *) p;
  71
  72   return internal_ly_parse_scm (ps);
  73 }
  74
  75 SCM
  76 parse_handler (void *data, SCM tag, SCM args)
  77 {
  78   Parse_start *ps = (Parse_start *) data;
  79   (void) tag;
  80
  81   ps->start_location_.error (_ ("GUILE signaled an error for the expression beginning here"));
  82
  83   if (scm_ilength (args) > 2)
  84     scm_display_error_message (scm_cadr (args), scm_caddr (args), scm_current_error_port ());
  85
  86   /*
  87     The following is a kludge; we should probably search for
  88     [a-z][0-9] (a note), and start before that.
  89   */
  90   ps->nchars = 1;
  91
  92   return SCM_UNDEFINED;
  93 }
  94
  95 /*
  96   Do some magical incantations: if not, lily will exit on the first
  97   GUILE error, leaving no location trace.
  98 */
  99
 100 #if GUILE_MINOR_VERSION < 7
 101 #define READ_ERROR "misc-error"
 102 #else
 103 #define READ_ERROR "read-error"
 104 #endif
 105
 106 SCM
 107 protected_ly_parse_scm (Parse_start *ps)
 108 {
 109   return scm_internal_catch (ly_symbol2scm (READ_ERROR),
 110                              &catch_protected_parse_body,
 111                              (void *) ps,
 112                              &parse_handler, (void *) ps);
 113 }
 114
 115 bool parse_protect_global = true;
 116
 117 /* Try parsing.  Upon failure return SCM_UNDEFINED.
 118    FIXME: shouldn't we return SCM_UNSCPECIFIED -- jcn  */
 119 SCM
 120 ly_parse_scm (char const *s, int *n, Input i, bool safe)
 121 {
 122   Parse_start ps;
 123   ps.str = s;
 124   ps.start_location_ = i;
 125   ps.safe_ = safe;
 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