forgot this

src/cmd/ip/snoopy/filter.y

@@ -0,0 +1,107 @@
+%{
+#include <u.h>
+#include <libc.h>
+#include <ctype.h>
+#include "dat.h"
+
+char	*yylp;		/* next character to be lex'd */
+char	*yybuffer;
+char	*yyend;		/* end of buffer to be parsed */
+%}
+
+%term LOR
+%term LAND
+%term WORD
+%right '!'
+%left '|'
+%left '&'
+%left LOR
+%left LAND
+%start filter
+%%
+
+filter		: expr
+			{ filter = $$; }
+		;
+expr		: WORD
+			{ $$ = $1; }
+		| WORD '=' WORD
+			{ $2->l = $1; $2->r = $3; $$ = $2; }
+		| WORD '(' expr ')'
+			{ $1->l = $3; free($2); free($4); $$ = $1; }
+		| '(' expr ')'
+			{ free($1); free($3); $$ = $2; }
+		| expr LOR expr
+			{ $2->l = $1; $2->r = $3; $$ = $2; }
+		| expr LAND expr
+			{ $2->l = $1; $2->r = $3; $$ = $2; }
+		| '!' expr
+			{ $1->l = $2; $$ = $1; }
+		;
+%%
+
+/*
+ *  Initialize the parsing.  Done once for each header field.
+ */
+void
+yyinit(char *p)
+{
+	yylp = p;
+}
+
+int
+yylex(void)
+{
+	char *p;
+	int c;
+
+	if(yylp == nil || *yylp == 0)
+		return 0;
+	while(isspace(*yylp))
+		yylp++;
+
+	yylval = newfilter();
+
+	p = strpbrk(yylp, "!|&()= ");
+	if(p == 0){
+		yylval->op = WORD;
+		yylval->s = strdup(yylp);
+		if(yylval->s == nil)
+			sysfatal("parsing filter: %r");
+		yylp = nil;
+		return WORD;
+	}
+	c = *p;
+	if(p != yylp){
+		yylval->op = WORD;
+		*p = 0;
+		yylval->s = strdup(yylp);
+		if(yylval->s == nil)
+			sysfatal("parsing filter: %r");
+		*p = c;
+		yylp = p;
+		return WORD;
+	}
+
+	yylp++;
+	if(*yylp == c)
+		switch(c){
+		case '&':
+			c = LAND;
+			yylp++;
+			break;
+		case '|':
+			c = LOR;
+			yylp++;
+			break;
+		}
+	yylval->op = c;
+	return c;
+}
+
+void
+yyerror(char *e)
+{
+	USED(e);
+	sysfatal("error parsing filter");
+}