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WebSVN – planix.SVN – Blame – /os/branches/feature_fixcpp/sys/src/cmd/ip/snoopy/filter.y – Rev 2

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%{
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#include <u.h>
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#include <libc.h>
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#include <ctype.h>
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#include "dat.h"
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char	*yylp;		/* next character to be lex'd */
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char	*yybuffer;
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char	*yyend;		/* end of buffer to be parsed */
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%}
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%term LOR
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%term LAND
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%term WORD
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%term NE
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%right '!'
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%left '|'
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%left '&'
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%left LOR
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%left LAND
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%start filter
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%%
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filter		: expr
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			{ filter = $$; }
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		;
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expr		: WORD
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			{ $$ = $1; }
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		| WORD '=' WORD
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			{ $2->l = $1; $2->r = $3; $$ = $2; }
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		| WORD NE WORD
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			{ $2->l = newfilter();
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			  $2->l->op = '=';
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			  $2->l->l = $1;
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			  $2->l->r = $3;
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			  $2->op = '!';
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			  $$ = $2;
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			}
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		| WORD '(' expr ')'
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			{ $1->l = $3; free($2); free($4); $$ = $1; }
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		| '(' expr ')'
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			{ free($1); free($3); $$ = $2; }
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		| expr LOR expr
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			{ $2->l = $1; $2->r = $3; $$ = $2; }
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		| expr LAND expr
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			{ $2->l = $1; $2->r = $3; $$ = $2; }
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		| '!' expr
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			{ $1->l = $2; $$ = $1; }
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		;
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%%
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/*
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 *  Initialize the parsing.  Done once for each header field.
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 */
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void
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yyinit(char *p)
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{
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	yylp = p;
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}
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int
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yylex(void)
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{
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	char *p;
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	int c;
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	if(yylp == nil)
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		return 0;
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	while(isspace(*yylp))
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		yylp++;
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	if(*yylp == 0)
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		return 0;
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	yylval = newfilter();
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	p = strpbrk(yylp, "!|&()= ");
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	if(p == 0){
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		yylval->op = WORD;
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		yylval->s = strdup(yylp);
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		if(yylval->s == nil)
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			sysfatal("parsing filter: %r");
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		yylp = nil;
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		return WORD;
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	}
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	c = *p;
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	if(p != yylp){
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		yylval->op = WORD;
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		*p = 0;
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		yylval->s = strdup(yylp);
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		if(yylval->s == nil)
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			sysfatal("parsing filter: %r");
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		*p = c;
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		yylp = p;
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		return WORD;
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	}
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	yylp++;
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	if(c == '!' && *yylp == '='){
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		c = NE;
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		yylp++;
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	}
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	else if(c == '&' && *yylp == '&'){
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		c = LAND;
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		yylp++;
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	}
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	else if(c == '|' && *yylp == '|'){
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		c = LOR;
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		yylp++;
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	}
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	yylval->op = c;
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	return c;
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}
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void
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yyerror(char*)
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{
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	sysfatal("error parsing filter");
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}