lily/parse-scm.cc

   1 #include <stdio.h>
   2
   3 #include "lily-guile.hh"
   4 #include "parse-scm.hh"
   5 #include "string.hh"
   6 #include "source-file.hh"
   7
   8 /*
   9   Pass string to scm parser, evaluate one expression.
  10   Return result value and #chars read.
  11
  12   Thanks to Gary Houston <ghouston@freewire.co.uk>
  13
  14   Need guile-1.3.4 (>1.3 anyway) for ftell on str ports -- jcn
  15 */
  16 SCM
  17 internal_ly_parse_scm (Parse_start * ps)
  18 {
  19   Source_file* sf =ps->start_location_.source_file_;
  20   SCM port = sf->get_port();
  21
  22   int off = ps->start_location_.defined_str0_ - sf->to_str0();
  23
  24   scm_seek (port, scm_long2num (off), scm_long2num (SEEK_SET));
  25   SCM from = scm_ftell (port);
  26
  27   SCM form;
  28   SCM answer = SCM_UNSPECIFIED;
  29
  30   /* Read expression from port */
  31   if (!SCM_EOF_OBJECT_P (form = scm_read (port)))
  32     answer = scm_primitive_eval (form);
  33
  34   /*
  35    After parsing
  36
  37  (begin (foo 1 2))
  38
  39    all seems fine, but after parsing
  40
  41  (foo 1 2)
  42
  43    read_buf has been advanced to read_pos - 1,
  44    so that scm_ftell returns 1, instead of #parsed chars
  45    */
  46
  47   /*
  48     urg: reset read_buf for scm_ftell
  49     shouldn't scm_read () do this for us?
  50   */
  51   scm_fill_input (port);
  52   SCM to = scm_ftell (port);
  53   ps->nchars = gh_scm2int (to) - gh_scm2int (from);
  54
  55   /* Don't close the port here; if we re-enter this function via a
  56      continuation, then the next time we enter it, we'll get an error.
  57      It's a string port anyway, so there's no advantage to closing it
  58      early.
  59
  60      scm_close_port (port);
  61   */
  62
  63   return answer;
  64 }
  65
  66
  67 SCM
  68 catch_protected_parse_body (void *p)
  69 {
  70   Parse_start *ps = (Parse_start*) p;
  71   return internal_ly_parse_scm (ps);
  72 }
  73
  74 SCM
  75 parse_handler (void * data, SCM tag, SCM args)
  76 {
  77   Parse_start* ps = (Parse_start*) data;
  78
  79   ps->start_location_.error (_("GUILE signaled an error for the expression beginning here"));
  80
  81   if (scm_ilength (args) > 2)
  82     scm_display_error_message (gh_cadr (args), gh_caddr(args), scm_current_error_port());
  83
  84   /*
  85     The following is a kludge; we should probably search for
  86     [a-z][0-9] (a note), and start before that.
  87    */
  88   ps->nchars = 1;
  89
  90   return SCM_UNDEFINED;
  91 }
  92
  93 /*
  94   Do some magical incantations: if not, lily will exit on the first
  95   GUILE error, leaving no location trace.
  96  */
  97
  98
  99 #if GUILE_MINOR_VERSION < 7
 100   #define READ_ERROR "misc-error"
 101   #else
 102   #define READ_ERROR "read-error"
 103 #endif
 104
 105 SCM
 106 protected_ly_parse_scm (Parse_start *ps)
 107 {
 108   return scm_internal_catch (ly_symbol2scm (READ_ERROR),
 109                              &catch_protected_parse_body,
 110                              (void*)ps,
 111                              &parse_handler, (void*)ps);
 112 }
 113
 114 bool  parse_protect_global  = true;
 115
 116 /*
 117   Try parsing. If failure, then return SCM_UNDEFINED.
 118  */
 119 SCM
 120 ly_parse_scm (char const* s, int *n, Input i)
 121 {
 122
 123   Parse_start ps ;
 124   ps.str = s;
 125   ps.start_location_ = i;
 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