sys/src/cmd/ip/snoopy/filter.y

   1 %{
   2 #include <u.h>
   3 #include <libc.h>
   4 #include <ctype.h>
   5 #include "dat.h"
   6
   7 char    *yylp;          /* next character to be lex'd */
   8 char    *yybuffer;
   9 char    *yyend;         /* end of buffer to be parsed */
  10 %}
  11
  12 %term LOR
  13 %term LAND
  14 %term WORD
  15 %term NE
  16 %right '!'
  17 %left '|'
  18 %left '&'
  19 %left LOR
  20 %left LAND
  21 %start filter
  22 %%
  23
  24 filter          : expr
  25                         { filter = $$; }
  26                 ;
  27 expr            : WORD
  28                         { $$ = $1; }
  29                 | WORD '=' WORD
  30                         { $2->l = $1; $2->r = $3; $$ = $2; }
  31                 | WORD NE WORD
  32                         { $2->l = newfilter();
  33                           $2->l->op = '=';
  34                           $2->l->l = $1;
  35                           $2->l->r = $3;
  36                           $2->op = '!';
  37                           $$ = $2;
  38                         }
  39                 | WORD '(' expr ')'
  40                         { $1->l = $3; free($2); free($4); $$ = $1; }
  41                 | '(' expr ')'
  42                         { free($1); free($3); $$ = $2; }
  43                 | expr LOR expr
  44                         { $2->l = $1; $2->r = $3; $$ = $2; }
  45                 | expr LAND expr
  46                         { $2->l = $1; $2->r = $3; $$ = $2; }
  47                 | '!' expr
  48                         { $1->l = $2; $$ = $1; }
  49                 ;
  50 %%
  51
  52 /*
  53  *  Initialize the parsing.  Done once for each header field.
  54  */
  55 void
  56 yyinit(char *p)
  57 {
  58         yylp = p;
  59 }
  60
  61 int
  62 yylex(void)
  63 {
  64         char *p;
  65         int c;
  66
  67         if(yylp == nil)
  68                 return 0;
  69         while(isspace(*yylp))
  70                 yylp++;
  71         if(*yylp == 0)
  72                 return 0;
  73
  74         yylval = newfilter();
  75
  76         p = strpbrk(yylp, "!|&()= ");
  77         if(p == 0){
  78                 yylval->op = WORD;
  79                 yylval->s = strdup(yylp);
  80                 if(yylval->s == nil)
  81                         sysfatal("parsing filter: %r");
  82                 yylp = nil;
  83                 return WORD;
  84         }
  85         c = *p;
  86         if(p != yylp){
  87                 yylval->op = WORD;
  88                 *p = 0;
  89                 yylval->s = strdup(yylp);
  90                 if(yylval->s == nil)
  91                         sysfatal("parsing filter: %r");
  92                 *p = c;
  93                 yylp = p;
  94                 return WORD;
  95         }
  96
  97         yylp++;
  98         if(c == '!' && *yylp == '='){
  99                 c = NE;
 100                 yylp++;
 101         }
 102         else if(c == '&' && *yylp == '&'){
 103                 c = LAND;
 104                 yylp++;
 105         }
 106         else if(c == '|' && *yylp == '|'){
 107                 c = LOR;
 108                 yylp++;
 109         }
 110         yylval->op = c;
 111         return c;
 112 }
 113
 114 void
 115 yyerror(char*)
 116 {
 117         sysfatal("error parsing filter");
 118 }