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/*
 * mfpp.y
 *
 * magicfilter config file preprocessor
 * Using cpp was getting very tedious...
 * 
 * Copyright  1996 H. Peter Anvin
 */

%{
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <stdarg.h>
#include <ctype.h>
#include "mfpp.h"

static void do_include(char *file);
static void do_cinclude(char *file);
static int yylex(void);

%}

%union {
  char *idsym;			/* ID symbol */
  char *file;			/* file name */
  char *txt;			/* plain text */
  struct listhdr *list;		/* list of values */
  int flag;			/* truth value */
}

%token <file> FILENAME		/* <filename> */
%token <idsym> ID		/* identifier */
%token <txt> TEXT		/* %define text */
%token <txt> STRING		/* quoted string */
%token IF			/* %if */
%token ELIF			/* %elif */
%token ELSE			/* %else */
%token ENDIF			/* %endif */
%token IFDEF			/* %ifdef  - for similarity with cpp */
%token IFNDEF			/* %ifndef - ditto */
%token FOR			/* %for */
%token IN			/* in (keyword in %for statements) */
%token NEXT			/* %next */
%token INCLUDE			/* %include */
%token CINCLUDE			/* %cinclude */
%token DEFINE			/* %define */
%token UNDEF			/* %undef */
%token BOGUS			/* invalid token */

%left '|'			/* || */
%left '&'			/* && */
%right '!'			/* not */
%left '#'			/* ## */
%right '*'			/* reference */

%type <flag> cond;
%type <flag> purecond;
%type <idsym> idexpr;
%type <list> value;
%type <list> values;

%%

file:	  lines line
	;

lines:    /* nothing */
	| lines line '\n'
	;

line:	  /* nothing */
        | IF cond 			{ do_if($2); }
	| ELIF cond 			{ do_elif($2); }
	| ELSE 				{ do_else(); }
	| ENDIF 			{ do_endif(); }
	| IFDEF cond			{ do_if($2); }
	| IFNDEF cond			{ do_if(!$2); }
	| FOR idexpr IN values		{ do_for($2,$3); }
	| NEXT				{ do_next(); }
	| INCLUDE FILENAME		{ do_include($2); }
	| CINCLUDE FILENAME		{ do_cinclude($2); }
	| DEFINE idexpr ':' TEXT	{ do_define($2,$4); }
	| DEFINE idexpr			{ do_define($2,xstrdup("")); }
	| DEFINE idexpr values		{ do_define_list($2,$3); }
	| UNDEF idexpr 			{ do_define($2,NULL); }
	;

cond:	  idexpr			{ $$ = (id_lookup($1)!=NULL); }
	| purecond			{ $$ = $1; }
	;

purecond: cond '&' cond			{ $$ = $1 && $3; }
	| cond '|' cond			{ $$ = $1 || $3; }
	| '!' cond			{ $$ = ! $2; }
	| '(' purecond ')'		{ $$ = $2; }
	;

values:	  value				{ $$ = $1; }
	| values value			{ $$ = listjoin($1,$2); }
	;

value:	  idexpr			{ $$ = id_ref_list($2,1); }
	STRING				{ $$ = makelist($1); }
	;

idexpr:	  ID				{ $$ = $1; }
	| '*' idexpr			{ $$ = id_ref($2); }
	| '(' idexpr ')'		{ $$ = $2; }
	| idexpr '#' idexpr		{ $$ = xstrcat($1,$3);
					  free($1);  free($3); }
	;

%%

/*
 * Bail out with style
 */

static int errflg = 0;

void yyerror(char *msg,...)
{
  va_list va;

  va_start(va,msg);
  vfprintf(stderr, msg, va);
  va_end(va);
  putc('\n', stderr);
  errflg = 1;			/* Error occurred */
}

/*
 * Support code for the lexer
 */

/* Character class buffer */
static int idchar[(1 << CHAR_BIT)+1];
static const unsigned char *idchars =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_";
#define is_idchar(X) (idchar[((unsigned char)(X))+1])

/* Stack for %include files */
#define MAX_INCLUDE 15
static FILE *istack[MAX_INCLUDE+1];
static long llmemory[MAX_INCLUDE+1];
static int nincl;
static FILE *infile;

static void llremember(void);

static void do_include(char *file)
{
  FILE *f;

  if ( !killcount )
    {
      if ( nincl >= MAX_INCLUDE )
	yyerror("Too many nested %%include files");
      else
	{
	  f = fopen(file, "rt");
	  if ( f )
	    {
	      istack[++nincl] = infile = f;
	      llremember();	/* Initialize file-position memory */
	      if ( debug > 1 )
		fprintf(stderr, "%%include <%s>\n", file);
	    }
	  else
	    yyerror("Could not open %%include file %s", file);
	}
    }
}

/* Primitive support for cpp-style include files.  We're just looking
   for #define's, really; this is here to support autoconf-generated
   headers. */

static void do_cinclude(char *file)
{
  FILE *f;
  char linebuf[8192], *id, *p;

  if ( !killcount )
    {
      f = fopen(file, "rt");
      
      if ( !f )
	yyerror("Could not open %%cinclude file %s", file);
      else
	{
	  if ( debug > 1 )
	    fprintf(stderr, "%%cinclude <%s>\n", file);
	  
	  while ( fgets(linebuf, 8192, f) )
	    {
	      if ( p = strchr(linebuf, '\n') )
		*p = '\0';
	      
	      if ( !strncmp(linebuf, "#define", 7) )
		{
		  p = linebuf+7;
		  if ( *p != ' ' && *p != '\t' )
		    continue;
		  while ( *p == ' ' || *p == '\t' )
		    p++;
		  id = p;
		  while ( *p != ' ' && *p != '\t' && *p != '\n' && *p )
		    p++;
		  if ( *p )
		    {
		      *(p++) = '\0';
		      while ( *p == ' ' && *p == '\t' )
			p++;
		    }
		  id_define(xstrdup(id), xstrdup(p));
		}
	    }
	  fclose(f);
	  if ( debug > 1 )
	    fprintf(stderr, "-- End of %%cinclude --\n", file);
	}
    }
}

/* Character I/O */
static int llungetc_buf[4];
static int llungetc_ctr = 0;

static int llgetc(void)
{
  int c;

  if ( llungetc_ctr )
    return llungetc_buf[--llungetc_ctr];

  while ( (c = getc(infile)) == EOF )
    {
      fclose(infile);
      if ( nincl < 1 )
	{
	  balance_blocks();
	  break;
	}
      if ( debug > 1 )
	fprintf(stderr, "-- End of %%include --\n");

      infile = istack[--nincl];
    }
  if ( debug > 3 )
    if ( isprint(c) )
      fprintf(stderr, "Got: %c\n", c); 
    else
      fprintf(stderr, "Got: %02x\n", c);

  return c;
}

static void llungetc(int c)
{
  llungetc_buf[llungetc_ctr++] = c;
}

static void llremember(void)
{
  llmemory[nincl] = ftell(infile);
}

static void llreturn(void)
{
  llungetc_ctr = 0;
  fseek(infile, llmemory[nincl], SEEK_SET);
}

/*
 * Keyword to YACC token lookup - somewhat unsophisticated
 */
static int keyword_lookup(char *str)
{
  char *cand;
  int val;

#define HV(X,Y) (((X) << CHAR_BIT) + (Y))
#define CAND(X,Y,STR,VAL) case HV(X,Y): cand = STR; val = VAL; break
  switch ( HV(str[0], str[2]) )
    {
      CAND('i','\0',"if",IF);
      CAND('i','d',"ifdef",IFDEF);
      CAND('i','n',"ifndef",IFNDEF);
      CAND('e','i',"elif",ELIF);
      CAND('e','s',"else",ELSE);
      CAND('e','d',"endif",ENDIF);
      CAND('i','c',"include",INCLUDE);
      CAND('c','n',"cinclude",CINCLUDE); 
      CAND('d','f',"define",DEFINE);
      CAND('u','d',"undef",UNDEF);
    default:
      cand = "";  val = 0;  break;
    }

  return strcmp(cand, str) ? 0 : val;
#undef HV
#undef CAND
}

/*
 * The lexer itself
 */

static char tokenbuf[32768];
static enum {
  st_linestart,			/* at the start of a line */
  st_definetext,		/* text for a %define */
  st_expr			/* an expression (body of most lines) */
} lexstate;

static void dtext(void)
{
  lexstate = st_definetext;
}

/*
 * Expand a possible single macro token
 */

static void expand_macro(char *str)
{
  struct identifier *id;
  char *mbuf, *p, *tbptr;

  id = id_lookup(str);
  if ( !id )
    {
      fputs(str, stdout);
    }
  else
    {
      tbptr = tokenbuf;
      for ( p = id->txt ; ; )
	{
	  if ( is_idchar(*p) )
	    *(tbptr++) = *(p++);
	  else
	    {
	      if ( tbptr > tokenbuf )
		{
		  *tbptr = '\0';
		  expand_macro(tokenbuf);
		  tbptr = tokenbuf;
		}
	      if ( *p )
		putchar(*(p++));
	      else
		break;
	    }
	}
    }
}

static int yylex(void)
{
  int c, c2;			/* input character */
  int bslash;			/* backslash encounter? */
  char *tbptr;			/* token buffer pointer */
  struct identifier *id;	/* identifier lookup */

  switch ( lexstate )
    {
    case st_linestart:
      {
	llremember();
	do
	  c = llgetc();
	while ( c == ' ' || c == '\t' );

	if ( c != '%' )
	  {
	    /* Not a preprocessor command - output line */
	    llreturn();
	    tbptr = tokenbuf;
	    do
	      {
		c = llgetc();
		if ( !killcount )
		  { 
		    if ( is_idchar(c) )
		      *(tbptr++) = c;
		    else
		      {
			if ( tbptr > tokenbuf )
			  {
			    *tbptr = '\0';
			    expand_macro(tokenbuf);
			    tbptr = tokenbuf;
			  }
			if ( c == EOF )
			  break;
			putchar(c);
		      }
		  }
	      }
	    while ( c != '\n' );
	    
	    return ( c == EOF ) ? 0 : c;
	  }
	else
	  {
	    /* Must be a preprocessor command */
	    
	    c = llgetc();
	    if ( !is_idchar(c) )
	      {
		/* Preprocessor comment */
		while ( c != '\n' && c != EOF )
		  c = llgetc();
		return ( c == EOF ) ? 0 : c;
	      }

	    tbptr = tokenbuf;
	    while ( is_idchar(c) )
	      {
		*(tbptr++) = c;
		c = llgetc();
	      }
	    llungetc(c);
	    
	    *tbptr = '\0';
	    
	    c = keyword_lookup(tokenbuf);
	    if ( !c )
	      {
		yyerror("Unknown preprocessor directive %%%s", tokenbuf);
		c = BOGUS;
	      }

	    lexstate = st_expr;
	    return c;
	  }
      }
    case st_expr:
      {      
	do
	  c = llgetc();
	while ( c == ' ' || c == '\t' );

	switch ( c )
	  {
	  case '<':
	    tbptr = tokenbuf;
	    while (1)
	      {
		c = llgetc();
		if ( c == '\n' || c == EOF )
		  {
		    yyerror("Unterminated filename in %%include");
		    return ( c == EOF ) ? 0 : c;
		  }
		if ( c < ' ' )
		  {
		    yyerror("Bad character in filename");
		    return BOGUS;
		  }
		if ( c == '>' )
		  break;
		*(tbptr++) = c;
	      }
	    *tbptr = '\0';
	    yylval = xstrdup(tokenbuf);
	    /*
	     * Kluge: normally, \n wouldn't be reduced until the rule was
	     * reduced, at which point we've already switched input.  Handle
	     * by reading ahead and stuffing the input buffer.
	     */
	    do
	      {
		c = llgetc();
		if ( c != '\n' && c != EOF && c != ' ' && c != '\t' )
		  yyerror("Junk at the end of %%include line");
	      }
	    while ( c != '\n' && c != EOF );
	    llremember();
	    llungetc(c);
	    return FILENAME;

	  case '\"':
	    tbptr = tokenbuf;
	    while(1)
	      {
		c = llgetc();
		if ( c == '\"' )
		  {
		    c = llgetc();
		    if ( c != '\"' )
		      {
			llungetc(c);
			break;
		      }
		  }
		*(tbptr++) = c;
	      }
	    *tbptr = '\0';
	    yylval.txt = xstrdup(tokenbuf);
	    return STRING;

	  case '\n':
	    lexstate = st_linestart;
	    return c;

	  case '!':
	  case '*':
	  case '(':
	  case ')':
	    return c;

	  case EOF:
	    return 0;

	  case ':':
	    lexstate = st_definetext;
	    return c;

	  case '&':
	  case '|':
	  case '#':
	    c2 = llgetc();
	    if ( c == c2 )
	      return c;
	    else
	      {
		yyerror("Unrecognized token: %c%c", c, c2);
		return BOGUS;
	      }

	  default:
	    if ( is_idchar(c) )
	      {
		tbptr = tokenbuf;
		while ( is_idchar(c) )
		  {
		    *(tbptr++) = c;
		    c = llgetc();
		  }
		*tbptr = '\0';
		llungetc(c);
		yylval.idsym = xstrdup(tokenbuf);
		return ID;
	      }
	    else
	      {
		if ( isprint(c) )
		  yyerror("Unknown character `%c'", c);
		else
		  yyerror("Unknown character %02x", (unsigned char)c);
		return BOGUS;
	      }
	  }
      }
    case st_definetext:
      {
	int oldc = 0;

	do
	  c = llgetc();
	while ( c == ' ' || c == '\t' );

	tbptr = tokenbuf;
	while(1)
	  {
	    if ( (c == '\n' && oldc != '\\') || c == EOF )
	      break;
	    *(tbptr++) = c;
	    oldc = c;
	    c = llgetc();
	  }
	*tbptr = '\0';
	llungetc(c);
	lexstate = st_expr;
	yylval.txt = xstrdup(tokenbuf);
	return TEXT;
      }
    }
}

/*
 * This is the entry point for the lexer-parser - do initalization
 * and call yyparse()
 */

int ppfile(FILE *f)
{
  unsigned const char *p;

  symtab_init();

  memset(idchar, 0, 1<<CHAR_BIT);
  for ( p = idchars ; *p ; p++ )
    idchar[*p+1] = 1;

  lexstate = st_linestart;

  istack[0] = infile = f;
  nincl = 0;
  llremember();			/* Initialize file-position memory */
  yyparse();
  return errflg;
}