From: moudgill@cs.cornell.edu ( Mayan Moudgill)
Subject: Flex++
Organization: Cornell Univ. CS Dept, Ithaca NY 14853
Date: Fri, 28 Aug 1992 14:03:35 GMT

I've modified the flex skeleton so that it uses the following features of C++
   1] C++ iostreams
   2] new and delete
   3] made yy_buffer_state into a ``class''.

I've also mucked around with some other stuff in the process, so there's
no guarantee that it will work on existing flex inputs which try to add
modify some #defines etc.

Has anyone else done a full conversion?
------------------------ cut here---------------------------------------

/* A lexical scanner generated by flex */

/* scanner skeleton version:
 * $Header: /usr/fsys/odin/a/vern/flex/RCS/flex.skel,v 2.10 90/03/27 12:03:55 vern Exp $
 */

#define FLEX_SCANNER

#include <iostream.h>
extern istream * yyin;
extern ostream * yyout;


#include <stdlib.h>
#include <osfcn.h>

/* use prototypes in function declarations */
#define YY_USE_PROTOS

/* the "const" storage-class-modifier is valid */
#define YY_USE_CONST



/* amount of stuff to slurp up with each read */
#ifndef YY_READ_BUF_SIZE
#define YY_READ_BUF_SIZE 8192
#endif

/* returned upon end-of-file */
#define YY_END_TOK 0

/* copy whatever the last rule matched to the standard output */

/* cast to (char *) is because for 8-bit chars, yytext is (unsigned char *) */
/* this used to be an fputs(), but since the string might contain NUL's,
 * we now use fwrite()
 */
#define ECHO (yyout->write(yytext, yyleng))

/* report a fatal error */
inline void YY_FATAL_ERROR(char * msg)
{
   cerr << msg << "\n";
   exit(1);
}

/* gets input and stuffs it into "buf".  number of characters read, or YY_NULL,
 * is returned in "result".
 */
#define YY_NULL 0
inline void YY_INPUT(char * buf, int& result, int max_size)
{
   if( yyin->eof() || yyin->fail() ) {
     result = YY_NULL;
   }
   else {
     yyin->read(buf, max_size);
     result = yyin->gcount();
     if( yyin->bad() ) {
	 YY_FATAL_ERROR( "read() in flex scanner failed" );
     }
   }
}

/* no semi-colon after return; correct usage is to write "yyterminate();" -
 * we don't want an extra ';' after the "return" because that will cause
 * some compilers to complain about unreachable statements.
 */
#define yyterminate() return ( YY_NULL )

/* default yywrap function - always treat EOF as an EOF */
#define yywrap() 1

/* enter a start condition.  This macro really ought to take a parameter,
 * but we do it the disgusting crufty way forced on us by the ()-less
 * definition of BEGIN
 */
#define BEGIN yy_start = 1 + 2 *

/* action number for EOF rule of a given start state */
#define YY_STATE_EOF(state) (YY_END_OF_BUFFER + state + 1)

/* special action meaning "start processing a new file" */
#define YY_NEW_FILE { \
   yy_current_buffer->yy_init_buffer( yyin ); \
   yy_load_buffer_state(); \
}

/* default declaration of generated scanner - a define so the user can
 * easily add parameters
 */
#define YY_DECL int yylex ( void ) 

/* code executed at the end of each rule */
#define YY_BREAK break;

#define YY_END_OF_BUFFER_CHAR 0

#ifndef YY_BUF_SIZE
#define YY_BUF_SIZE (YY_READ_BUF_SIZE * 2) /* size of default input buffer */
#endif

typedef struct yy_buffer_state *YY_BUFFER_STATE;

%% section 1 definitions go here

/* done after the current pattern has been matched and before the
 * corresponding action - sets up yytext
 */
#define YY_DO_BEFORE_ACTION \
	yytext = yy_bp; \
%% code to fiddle yytext and yyleng for yymore() goes here
	yy_hold_char = *yy_cp; \
	*yy_cp = '\0'; \
	yy_c_buf_p = yy_cp;

#define EOB_ACT_CONTINUE_SCAN 0
#define EOB_ACT_END_OF_FILE 1
#define EOB_ACT_LAST_MATCH 2

/* return all but the first 'n' matched characters back to the input stream */
#define yyless(n) \
	{ \
	/* undo effects of setting up yytext */ \
	*yy_cp = yy_hold_char; \
	yy_c_buf_p = yy_cp = yy_bp + n; \
	YY_DO_BEFORE_ACTION; /* set up yytext again */ \
	}

#define unput(c) yyunput( c, yytext )


struct yy_buffer_state
   {
   istream * yy_input_file;

   YY_CHAR *yy_ch_buf;		/* input buffer */
   YY_CHAR *yy_buf_pos;	/* current position in input buffer */

   /* size of input buffer in bytes, not including room for EOB characters*/
   int yy_buf_size;	

   /* number of characters read into yy_ch_buf, not including EOB characters */
   int yy_n_chars;

   int yy_eof_status;		/* whether we've seen an EOF on this buffer */
#define EOF_NOT_SEEN 0
   /* "pending" happens when the EOF has been seen but there's still
    * some text process
    */
#define EOF_PENDING 1
#define EOF_DONE 2
   
	   yy_buffer_state(istream * , int );
	   ~yy_buffer_state();
   void    yy_init_buffer(istream *);
   };

static YY_BUFFER_STATE yy_current_buffer;

/* we provide macros for accessing buffer states in case in the
 * future we want to put the buffer states in a more general
 * "scanner state"
 */
#define YY_CURRENT_BUFFER yy_current_buffer


/* yy_hold_char holds the character lost when yytext is formed */
static YY_CHAR yy_hold_char;

static int yy_n_chars;		/* number of characters read into yy_ch_buf */



#ifndef YY_USER_ACTION
#define YY_USER_ACTION
#endif

extern YY_CHAR *yytext;
extern int yyleng;
extern istream * yyin;
extern ostream * yyout;

YY_CHAR *yytext;
int yyleng;

istream * yyin = 0;
ostream * yyout =  0;

%% data tables for the DFA go here

/* these variables are all declared out here so that section 3 code can
 * manipulate them
 */
/* points to current character in buffer */
static YY_CHAR *yy_c_buf_p = (YY_CHAR *) 0;
static int yy_init = 1;		/* whether we need to initialize */
static int yy_start = 0;	/* start state number */

static yy_state_type yy_get_previous_state ( void );
static yy_state_type yy_try_NUL_trans ( yy_state_type current_state );
static int yy_get_next_buffer ( void );
static void yyunput ( YY_CHAR c, YY_CHAR *buf_ptr );
void yyrestart ( istream * input_file );
void yy_switch_to_buffer ( YY_BUFFER_STATE new_buffer );
void yy_load_buffer_state ( void );
//CC YY_BUFFER_STATE yy_create_buffer ( istream * file, int size );
//CC void yy_delete_buffer ( YY_BUFFER_STATE b );
//CC void yy_init_buffer ( YY_BUFFER_STATE b, istream * file );

#ifdef __cplusplus
static int yyinput ( void );
#else
static int input ( void );
#endif

YY_DECL
   {
   register yy_state_type yy_current_state;
   register YY_CHAR *yy_cp, *yy_bp;
   register int yy_act;

%% user's declarations go here

   if ( yy_init )
	{
	if ( ! yy_start )
	   yy_start = 1;	/* first start state */

	if ( ! yyin )
	   yyin = &cin;

	if ( ! yyout )
	   yyout = &cout;

	 if ( yy_current_buffer ) {
	    yy_current_buffer->yy_init_buffer( yyin );
	 }
	else
//CC	   yy_current_buffer = yy_create_buffer( yyin, YY_BUF_SIZE );
	   yy_current_buffer = new yy_buffer_state( yyin, YY_BUF_SIZE );

	yy_load_buffer_state();

	yy_init = 0;
	}

   while ( 1 )		/* loops until end-of-file is reached */
	{
%% yymore()-related code goes here
	yy_cp = yy_c_buf_p;

	/* support of yytext */
	*yy_cp = yy_hold_char;

	/* yy_bp points to the position in yy_ch_buf of the start of the
	 * current run.
	 */
	yy_bp = yy_cp;

%% code to set up and find next match goes here

yy_find_action:
%% code to find the action number goes here

	YY_DO_BEFORE_ACTION;
	YY_USER_ACTION;

do_action:	/* this label is used only to access EOF actions */

%% debug code goes here

	switch ( yy_act )
	   {
%% actions go here

	   case YY_END_OF_BUFFER:
		{
		/* amount of text matched not including the EOB char */
		int yy_amount_of_matched_text = yy_cp - yytext - 1;

		/* undo the effects of YY_DO_BEFORE_ACTION */
		*yy_cp = yy_hold_char;

		/* note that here we test for yy_c_buf_p "<=" to the position
		 * of the first EOB in the buffer, since yy_c_buf_p will
		 * already have been incremented past the NUL character
		 * (since all states make transitions on EOB to the end-
		 * of-buffer state).  Contrast this with the test in yyinput().
		 */
		if ( yy_c_buf_p <= &yy_current_buffer->yy_ch_buf[yy_n_chars] )
		   /* this was really a NUL */
		   {
		   yy_state_type yy_next_state;

		   yy_c_buf_p = yytext + yy_amount_of_matched_text;

		   yy_current_state = yy_get_previous_state();

		   /* okay, we're now positioned to make the
		    * NUL transition.  We couldn't have
		    * yy_get_previous_state() go ahead and do it
		    * for us because it doesn't know how to deal
		    * with the possibility of jamming (and we
		    * don't want to build jamming into it because
		    * then it will run more slowly)
		    */

		   yy_next_state = yy_try_NUL_trans( yy_current_state );

		   yy_bp = yytext + YY_MORE_ADJ;

		   if ( yy_next_state )
			{
			/* consume the NUL */
			yy_cp = ++yy_c_buf_p;
			yy_current_state = yy_next_state;
			goto yy_match;
			}

		   else
			{
%% code to do backtracking for compressed tables and set up yy_cp goes here
			goto yy_find_action;
			}
		   }

		else switch ( yy_get_next_buffer() )
		   {
		   case EOB_ACT_END_OF_FILE:
			{
			if ( yywrap() )
			   {
			   /* note: because we've taken care in
			    * yy_get_next_buffer() to have set up yytext,
			    * we can now set up yy_c_buf_p so that if some
			    * total hoser (like flex itself) wants
			    * to call the scanner after we return the
			    * YY_NULL, it'll still work - another YY_NULL
			    * will get returned.
			    */
			   yy_c_buf_p = yytext + YY_MORE_ADJ;

			   yy_act = YY_STATE_EOF((yy_start - 1) / 2);
			   goto do_action;
			   }

			else
			   YY_NEW_FILE;
			}
			break;

		   case EOB_ACT_CONTINUE_SCAN:
			yy_c_buf_p = yytext + yy_amount_of_matched_text;

			yy_current_state = yy_get_previous_state();

			yy_cp = yy_c_buf_p;
			yy_bp = yytext + YY_MORE_ADJ;
			goto yy_match;

		   case EOB_ACT_LAST_MATCH:
			yy_c_buf_p =
			   &yy_current_buffer->yy_ch_buf[yy_n_chars];

			yy_current_state = yy_get_previous_state();

			yy_cp = yy_c_buf_p;
			yy_bp = yytext + YY_MORE_ADJ;
			goto yy_find_action;
		   }
		break;
		}

	   default:
#ifdef FLEX_DEBUG
		printf( "action # %d\n", yy_act );
#endif
		YY_FATAL_ERROR(
			"fatal flex scanner internal error--no action found" );
	   }
	}
   }


/* yy_get_next_buffer - try to read in a new buffer
 *
 * synopsis
 *    int yy_get_next_buffer();
 *    
 * returns a code representing an action
 *    EOB_ACT_LAST_MATCH - 
 *    EOB_ACT_CONTINUE_SCAN - continue scanning from current position
 *    EOB_ACT_END_OF_FILE - end of file
 */

static int yy_get_next_buffer()

   {
   register YY_CHAR *dest = yy_current_buffer->yy_ch_buf;
   register YY_CHAR *source = yytext - 1; /* copy prev. char, too */
   register int number_to_move, i;
   int ret_val;

   if ( yy_c_buf_p > &yy_current_buffer->yy_ch_buf[yy_n_chars + 1] )
	YY_FATAL_ERROR(
		"fatal flex scanner internal error--end of buffer missed" );

   /* try to read more data */

   /* first move last chars to start of buffer */
   number_to_move = yy_c_buf_p - yytext;

   for ( i = 0; i < number_to_move; ++i )
	*(dest++) = *(source++);

   if ( yy_current_buffer->yy_eof_status != EOF_NOT_SEEN )
	/* don't do the read, it's not guaranteed to return an EOF,
	 * just force an EOF
	 */
	yy_n_chars = 0;

   else
	{
	int num_to_read = yy_current_buffer->yy_buf_size - number_to_move - 1;

	if ( num_to_read > YY_READ_BUF_SIZE )
	   num_to_read = YY_READ_BUF_SIZE;

	else if ( num_to_read <= 0 )
	   YY_FATAL_ERROR( "fatal error - scanner input buffer overflow" );

	/* read in more data */
	YY_INPUT( (&yy_current_buffer->yy_ch_buf[number_to_move]),
		  yy_n_chars, num_to_read );
	}

   if ( yy_n_chars == 0 )
	{
	if ( number_to_move == 1 )
	   {
	   ret_val = EOB_ACT_END_OF_FILE;
	   yy_current_buffer->yy_eof_status = EOF_DONE;
	   }

	else
	   {
	   ret_val = EOB_ACT_LAST_MATCH;
	   yy_current_buffer->yy_eof_status = EOF_PENDING;
	   }
	}

   else
	ret_val = EOB_ACT_CONTINUE_SCAN;

   yy_n_chars += number_to_move;
   yy_current_buffer->yy_ch_buf[yy_n_chars] = YY_END_OF_BUFFER_CHAR;
   yy_current_buffer->yy_ch_buf[yy_n_chars + 1] = YY_END_OF_BUFFER_CHAR;

   /* yytext begins at the second character in yy_ch_buf; the first
    * character is the one which preceded it before reading in the latest
    * buffer; it needs to be kept around in case it's a newline, so
    * yy_get_previous_state() will have with '^' rules active
    */

   yytext = &yy_current_buffer->yy_ch_buf[1];

   return ( ret_val );
   }


/* yy_get_previous_state - get the state just before the EOB char was reached
 *
 * synopsis
 *    yy_state_type yy_get_previous_state();
 */

static yy_state_type yy_get_previous_state()

   {
   register yy_state_type yy_current_state;
   register YY_CHAR *yy_cp;

%% code to get the start state into yy_current_state goes here

   for ( yy_cp = yytext + YY_MORE_ADJ; yy_cp < yy_c_buf_p; ++yy_cp )
	{
%% code to find the next state goes here
	}

   return ( yy_current_state );
   }


/* yy_try_NUL_trans - try to make a transition on the NUL character
 *
 * synopsis
 *    next_state = yy_try_NUL_trans( current_state );
 */

static yy_state_type yy_try_NUL_trans( register yy_state_type yy_current_state )
   {
   register int yy_is_jam;
%% code to find the next state, and perhaps do backtracking, goes here

   return ( yy_is_jam ? 0 : yy_current_state );
   }


static void yyunput( YY_CHAR c, register YY_CHAR *yy_bp )
   {
   register YY_CHAR *yy_cp = yy_c_buf_p;

   /* undo effects of setting up yytext */
   *yy_cp = yy_hold_char;

   if ( yy_cp < yy_current_buffer->yy_ch_buf + 2 )
	{ /* need to shift things up to make room */
	register int number_to_move = yy_n_chars + 2; /* +2 for EOB chars */
	register YY_CHAR *dest =
	   &yy_current_buffer->yy_ch_buf[yy_current_buffer->yy_buf_size + 2];
	register YY_CHAR *source =
	   &yy_current_buffer->yy_ch_buf[number_to_move];

	while ( source > yy_current_buffer->yy_ch_buf )
	   *--dest = *--source;

	yy_cp += dest - source;
	yy_bp += dest - source;
	yy_n_chars = yy_current_buffer->yy_buf_size;

	if ( yy_cp < yy_current_buffer->yy_ch_buf + 2 )
	   YY_FATAL_ERROR( "flex scanner push-back overflow" );
	}

   if ( yy_cp > yy_bp && yy_cp[-1] == '\n' )
	yy_cp[-2] = '\n';

   *--yy_cp = c;

   /* note: the formal parameter *must* be called "yy_bp" for this
    *      macro to now work correctly
    */
   YY_DO_BEFORE_ACTION; /* set up yytext again */
   }


#ifdef __cplusplus
static int yyinput()
#else
static int input()
#endif

   {
   int c;
   YY_CHAR *yy_cp = yy_c_buf_p;

   *yy_cp = yy_hold_char;

   if ( *yy_c_buf_p == YY_END_OF_BUFFER_CHAR )
	{
	/* yy_c_buf_p now points to the character we want to return.
	 * If this occurs *before* the EOB characters, then it's a
	 * valid NUL; if not, then we've hit the end of the buffer.
	 */
	if ( yy_c_buf_p < &yy_current_buffer->yy_ch_buf[yy_n_chars] )
	   /* this was really a NUL */
	   *yy_c_buf_p = '\0';

	else
	   { /* need more input */
	   yytext = yy_c_buf_p;
	   ++yy_c_buf_p;

	   switch ( yy_get_next_buffer() )
		{
		case EOB_ACT_END_OF_FILE:
		   {
		   if ( yywrap() )
			{
			yy_c_buf_p = yytext + YY_MORE_ADJ;
			return ( EOF );
			}

		   YY_NEW_FILE;

#ifdef __cplusplus
		   return ( yyinput() );
#else
		   return ( input() );
#endif
		   }
		   break;

		case EOB_ACT_CONTINUE_SCAN:
		   yy_c_buf_p = yytext + YY_MORE_ADJ;
		   break;

		case EOB_ACT_LAST_MATCH:
#ifdef __cplusplus
		   YY_FATAL_ERROR( "unexpected last match in yyinput()" );
#else
		   YY_FATAL_ERROR( "unexpected last match in input()" );
#endif
		}
	   }
	}

   c = *yy_c_buf_p;
   yy_hold_char = *++yy_c_buf_p;

   return ( c );
   }


void yyrestart( istream * input_file )
{
   yy_current_buffer->yy_init_buffer( input_file );
   yy_load_buffer_state();
}


void yy_switch_to_buffer( YY_BUFFER_STATE new_buffer )
   {
   if ( yy_current_buffer == new_buffer )
	return;

   if ( yy_current_buffer )
	{
	/* flush out information for old buffer */
	*yy_c_buf_p = yy_hold_char;
	yy_current_buffer->yy_buf_pos = yy_c_buf_p;
	yy_current_buffer->yy_n_chars = yy_n_chars;
	}

   yy_current_buffer = new_buffer;
   yy_load_buffer_state();
   }


void yy_load_buffer_state( void )
{
   yy_n_chars = yy_current_buffer->yy_n_chars;
   yytext = yy_c_buf_p = yy_current_buffer->yy_buf_pos;
   yyin = yy_current_buffer->yy_input_file;
   yy_hold_char = *yy_c_buf_p;
}


yy_buffer_state::yy_buffer_state( istream * file, int size )
: yy_buf_size(size)
{
//CC  if ( ! b )
//CC	   YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );

   /* yy_ch_buf has to be 2 characters longer than the size given because
    * we need to put in 2 end-of-buffer characters.
    */
   yy_ch_buf = new YY_CHAR [yy_buf_size + 2];

//CC   if ( !yy_ch_buf )
//CC	YY_FATAL_ERROR( "out of dynamic memory in yy_create_buffer()" );

   yy_init_buffer( file );
}


yy_buffer_state::~yy_buffer_state()
{
   if( this == yy_current_buffer ) {
      yy_current_buffer = 0;
   }
   delete[] yy_ch_buf;
}

void yy_buffer_state::yy_init_buffer( istream *file )
{
   yy_input_file = file;

   /* we put in the '\n' and start reading from [1] so that an
    * initial match-at-newline will be true.
    */

   yy_ch_buf[0] = '\n';
   yy_n_chars = 1;

   /* we always need two end-of-buffer characters.  The first causes
    * a transition to the end-of-buffer state.  The second causes
    * a jam in that state.
    */
   yy_ch_buf[1] = YY_END_OF_BUFFER_CHAR;
   yy_ch_buf[2] = YY_END_OF_BUFFER_CHAR;

   yy_buf_pos = &yy_ch_buf[1];

   yy_eof_status = EOF_NOT_SEEN;
}
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