commands/mdb/mdbexp.c

   1 /*
   2  * mdbexp.c - MINIX expresion parser
   3  *
   4  * Written by Bruce D. Szablak
   5  *
   6  * This free software is provided for non-commerical use. No warrantee
   7  * of fitness for any use is implied. You get what you pay for. Anyone
   8  * may make modifications and distribute them, but please keep this header
   9  * in the distribution.
  10  */
  11
  12 #include "mdb.h"
  13 #include <ctype.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include "proto.h"
  18
  19 static long value(char *s , char **s_p , int *seg_p );
  20 static long lookup(char *s , char **s_p , int *seg_p );
  21
  22 #define idchar(c) (isalpha(c) || isdigit(c) || (c) == '_')
  23
  24 /*
  25  * Get an expression for mdb
  26  */
  27 char *getexp(buf, exp_p, seg_p)
  28 char *buf;
  29 int *seg_p;
  30 long *exp_p;
  31 {
  32   long v = 0L;
  33
  34   buf = skip(buf);
  35   if ((isalpha(*buf) && (isspace(buf[1]) || buf[1] == ';'))
  36       || *buf == '\n'
  37       || *buf == ';'
  38       || *buf == '/'
  39       || *buf == '!'
  40       || *buf == '?'
  41       || *buf == '@'
  42       || *buf == '#') {
  43         *exp_p = 0L;
  44         return buf;
  45   }
  46   v = value(buf, &buf, seg_p);
  47   buf = skip(buf);
  48   if (*buf == '+')
  49         v += value(skip(buf + 1), &buf, seg_p);
  50   else if (*buf == '-')
  51         v -= value(skip(buf + 1), &buf, seg_p);
  52   *exp_p = v;
  53   return skip(buf);
  54 }
  55
  56 /*
  57  * Get value
  58  *
  59  *      \c      escaped characters
  60  *      digits  number
  61  *      $xx     registers
  62  *      \n      0L
  63  *      then calls lookup for symbols
  64  */
  65 static long value(s, s_p, seg_p)
  66 char *s, **s_p;
  67 int *seg_p;
  68 {
  69   long k;
  70
  71   if (*s == '\'') {             /* handle character constants here */
  72         *s_p = s + 2;
  73         return s[1];
  74   }
  75   if (*s == '-' || isdigit(*s))
  76         return strtol(s, s_p, 0);
  77   if (*s == '$') {
  78         k = reg_addr(s + 1);
  79         *s_p = s + 3;
  80         return get_reg(curpid, k);
  81         k = reg_addr(s + 1);
  82         *s_p = s + 3;
  83         return get_reg(curpid, k);
  84   }
  85   if (*s == '\n') {
  86         *s_p = s + 1;
  87         return 0L;
  88   }
  89   return lookup(s, s_p, seg_p);
  90 }
  91
  92 /*
  93  * Lookup symbol - return value
  94  * Handle special cases: _start T: D: S:
  95  * then call symbolvalue()
  96  */
  97 static long lookup(s, s_p, seg_p)
  98 char *s, **s_p;
  99 int *seg_p;
 100 {
 101   long value;
 102   char c;
 103   int l;
 104
 105   for (l = 1; idchar(s[l]); ++l) {}
 106   c = s[l];
 107   s[l] = 0;
 108
 109   if (strcmp("_start", s) == 0) {
 110         *seg_p = T;
 111         if (c == ':') c = '+';
 112         *(*s_p = s + 6) = c;
 113         return st_addr;
 114   }
 115   if (strcmp("T", s) == 0) {
 116         *seg_p = T;
 117         if (c == ':') c = '+';
 118         *(*s_p = s + 1) = c;
 119         return st_addr;
 120   }
 121   if (strcmp("D", s) == 0) {
 122         *seg_p = D;
 123         if (c == ':') c = '+';
 124         *(*s_p = s + 1) = c;
 125         return sd_addr;
 126   }
 127   if (strcmp("S", s) == 0) {
 128         *seg_p = S;
 129         if (c == ':') c = '+';
 130         *(*s_p = s + 1) = c;
 131         return sk_addr;
 132   }
 133
 134   if ((value = symbolvalue(s, TRUE)) != 0L) {
 135         *seg_p = T;
 136         *(*s_p = s + l) = c;
 137         return value;
 138   }
 139
 140   if ((value = symbolvalue(s, FALSE)) != 0L) {
 141         *seg_p = D;
 142         *(*s_p = s + l) = c;
 143         return value;
 144   }
 145
 146   Printf("%s: ", s);
 147   mdb_error("symbol not found\n");
 148 }
 149
 150 /* Skip spaces */
 151 char *skip(s)
 152 register char *s;
 153 {
 154   while (isspace(*s)) ++s;
 155   return *s ? s : s - 1;
 156 }
 157