in.c

   1 /* reading input */
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include "eqn.h"
   6
   7 #define NARGS           10
   8 #define NMACROS         512
   9
  10 /* eqn input stream */
  11 struct ein {
  12         struct ein *prev;       /* previous buffer */
  13         char *buf;              /* input buffer; NULL for stdin */
  14         int pos;                /* current position in buf */
  15         int unbuf[LNLEN];       /* push-back buffer */
  16         int uncnt;
  17         char *args[NARGS];      /* macro arguments */
  18         int call;               /* is a macro call */
  19 };
  20
  21 static struct ein ein_stdin;    /* the default input stream */
  22 static struct ein *ein = &ein_stdin;
  23
  24 static char *in_strdup(char *s)
  25 {
  26         char *d = malloc(strlen(s) + 1);
  27         strcpy(d, s);
  28         return d;
  29 }
  30
  31 /* push buf in the input stream; this is a macro call if args is not NULL */
  32 static void in_push(char *buf, char **args)
  33 {
  34         struct ein *next = malloc(sizeof(*next));
  35         int i;
  36         memset(next, 0, sizeof(*next));
  37         next->prev = ein;
  38         next->buf = in_strdup(buf);
  39         next->call = args != NULL;
  40         if (args)
  41                 for (i = 0; i < NARGS; i++)
  42                         next->args[i] = args[i] ? in_strdup(args[i]) : NULL;
  43         ein = next;
  44 }
  45
  46 /* back to the previous ein buffer */
  47 static void in_pop(void)
  48 {
  49         struct ein *prev = ein->prev;
  50         int i;
  51         if (prev) {
  52                 for (i = 0; i < NARGS; i++)
  53                         free(ein->args[i]);
  54                 free(ein->buf);
  55                 free(ein);
  56                 ein = prev;
  57         }
  58 }
  59
  60 /* read the next character */
  61 int in_next(void)
  62 {
  63         while (1) {
  64                 if (ein->uncnt)
  65                         return ein->unbuf[--ein->uncnt];
  66                 if (!ein->prev)
  67                         return fgetc(stdin);
  68                 if (ein->buf[ein->pos])
  69                         return ein->buf[ein->pos++];
  70                 in_pop();
  71         }
  72         return 0;
  73 }
  74
  75 /* push back c */
  76 void in_back(int c)
  77 {
  78         if (c > 0)
  79                 ein->unbuf[ein->uncnt++] = c;
  80 }
  81
  82 /* eqn macros */
  83 struct macro {
  84         char name[NMLEN];
  85         char *def;
  86 };
  87 static struct macro macros[NMACROS];
  88 static int nmacros;
  89
  90 static int in_findmacro(char *name)
  91 {
  92         int i;
  93         for (i = 0; i < nmacros; i++)
  94                 if (!strcmp(macros[i].name, name))
  95                         return i;
  96         return -1;
  97 }
  98
  99 /* define a macro */
 100 void in_define(char *name, char *def)
 101 {
 102         int idx = in_findmacro(name);
 103         if (idx < 0 && nmacros < NMACROS)
 104                 idx = nmacros++;
 105         if (idx >= 0) {
 106                 strcpy(macros[idx].name, name);
 107                 free(macros[idx].def);
 108                 macros[idx].def = in_strdup(def);
 109         }
 110 }
 111
 112 /* see if name starts with a macro name followed by a '(' */
 113 int in_macrocall(char *name)
 114 {
 115         int mlen, i;
 116         for (i = 0; i < nmacros; i++) {
 117                 mlen = strlen(macros[i].name);
 118                 if (!strncmp(macros[i].name, name, mlen) && name[mlen] == '(')
 119                         return mlen;
 120         }
 121         return 0;
 122 }
 123
 124 /* expand macro */
 125 int in_expand(char *name, char **args)
 126 {
 127         int i = in_findmacro(name);
 128         if (i >= 0)
 129                 in_push(macros[i].def, args);
 130         return i < 0;
 131 }
 132
 133 /* expand argument */
 134 int in_arg(int i)
 135 {
 136         int call = ein->call;
 137         if (call && ein->args[i - 1])
 138                 in_push(ein->args[i - 1], NULL);
 139         return call ? 0 : 1;
 140 }