#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "cpp.h"

/*
 * lexical FSM encoding
 *   when in state state, and one of the characters
 *   in ch arrives, enter nextstate.
 *   States >= S_SELF are either final, or at least require special action.
 *   In 'fsm' there is a line for each state X charset X nextstate.
 *   List chars that overwrite previous entries later (e.g. C_ALPH
 *   can be overridden by '_' by a later entry; and C_XX is the
 *   the universal set, and should always be first.
 *   States above S_SELF are represented in the big table as negative values.
 *   S_SELF and S_SELFB encode the resulting token type in the upper bits.
 *   These actions differ in that S_SELF doesn't have a lookahead char,
 *   S_SELFB does.
 *
 *   The encoding is blown out into a big table for time-efficiency.
 *   Entries have
 *      nextstate: 6 bits; ?\ marker: 1 bit; tokentype: 9 bits.
 */

#define	MAXSTATE 32
#define	ACT(tok,act)	((tok<<7)+act)
#define	QBSBIT	0100
#define	GETACT(st)	(st>>7)&0x1ff

/* character classes */
#define	C_WS	1
#define	C_ALPH	2
#define	C_NUM	3
#define	C_EOF	4
#define	C_XX	5

enum state
{
	START = 0, NUM1, NUM2, NUM3, ID1, ST1, ST2, ST3, COM1, COM2, COM3, COM4,
	CC1, CC2, WS1, PLUS1, MINUS1, STAR1, SLASH1, PCT1, SHARP1,
	CIRC1, GT1, GT2, LT1, LT2, OR1, AND1, ASG1, NOT1, DOTS1,
	S_SELF = MAXSTATE, S_SELFB, S_EOF, S_NL, S_EOFSTR,
	S_STNL, S_COMNL, S_EOFCOM, S_COMMENT, S_EOB, S_WS, S_NAME
};

int tottok;
int tokkind[256];
struct fsm
{
	int state;	/* if in this state */
	uchar ch[4];	/* and see one of these characters */
	int nextstate;	/* enter this state if +ve */
};

/*const*/ struct fsm fsm[] = {
	/* start state */
	{START, {C_XX}, ACT(UNCLASS, S_SELF)},
	{START, {' ', '\t', '\v'}, WS1},
	{START, {C_NUM}, NUM1},
	{START, {'.'}, NUM3},
	{START, {C_ALPH}, ID1},
	{START, {'L'}, ST1},
	{START, {'"'}, ST2},
	{START, {'\''}, CC1},
	{START, {'/'}, COM1},
	{START, {EOFC}, S_EOF},
	{START, {'\n'}, S_NL},
	{START, {'-'}, MINUS1},
	{START, {'+'}, PLUS1},
	{START, {'<'}, LT1},
	{START, {'>'}, GT1},
	{START, {'='}, ASG1},
	{START, {'!'}, NOT1},
	{START, {'&'}, AND1},
	{START, {'|'}, OR1},
	{START, {'#'}, SHARP1},
	{START, {'%'}, PCT1},
	{START, {'['}, ACT(SBRA, S_SELF)},
	{START, {']'}, ACT(SKET, S_SELF)},
	{START, {'('}, ACT(LP, S_SELF)},
	{START, {')'}, ACT(RP, S_SELF)},
	{START, {'*'}, STAR1},
	{START, {','}, ACT(COMMA, S_SELF)},
	{START, {'?'}, ACT(QUEST, S_SELF)},
	{START, {':'}, ACT(COLON, S_SELF)},
	{START, {';'}, ACT(SEMIC, S_SELF)},
	{START, {'{'}, ACT(CBRA, S_SELF)},
	{START, {'}'}, ACT(CKET, S_SELF)},
	{START, {'~'}, ACT(TILDE, S_SELF)},
	{START, {'^'}, CIRC1},

	/* saw a digit */
	{NUM1, {C_XX}, ACT(NUMBER, S_SELFB)},
	{NUM1, {C_NUM, C_ALPH, '.'}, NUM1},
	{NUM1, {'E', 'e'}, NUM2},
	{NUM1, {'_'}, ACT(NUMBER, S_SELFB)},

	/* saw possible start of exponent, digits-e */
	{NUM2, {C_XX}, ACT(NUMBER, S_SELFB)},
	{NUM2, {'+', '-'}, NUM1},
	{NUM2, {C_NUM, C_ALPH}, NUM1},
	{NUM2, {'_'}, ACT(NUMBER, S_SELFB)},

	/* saw a '.', which could be a number or an operator */
	{NUM3, {C_XX}, ACT(DOT, S_SELFB)},
	{NUM3, {'.'}, DOTS1},
	{NUM3, {C_NUM}, NUM1},

	{DOTS1, {C_XX}, ACT(UNCLASS, S_SELFB)},
	{DOTS1, {C_NUM}, NUM1},
	{DOTS1, {'.'}, ACT(ELLIPS, S_SELF)},

	/* saw a letter or _ */
	{ID1, {C_XX}, ACT(NAME, S_NAME)},
	{ID1, {C_ALPH, C_NUM}, ID1},

	/* saw L (start of wide string?) */
	{ST1, {C_XX}, ACT(NAME, S_NAME)},
	{ST1, {C_ALPH, C_NUM}, ID1},
	{ST1, {'"'}, ST2},
	{ST1, {'\''}, CC1},

	/* saw " beginning string */
	{ST2, {C_XX}, ST2},
	{ST2, {'"'}, ACT(STRING, S_SELF)},
	{ST2, {'\\'}, ST3},
	{ST2, {'\n'}, S_STNL},
	{ST2, {EOFC}, S_EOFSTR},

	/* saw \ in string */
	{ST3, {C_XX}, ST2},
	{ST3, {'\n'}, S_STNL},
	{ST3, {EOFC}, S_EOFSTR},

	/* saw ' beginning character const */
	{CC1, {C_XX}, CC1},
	{CC1, {'\''}, ACT(CCON, S_SELF)},
	{CC1, {'\\'}, CC2},
	{CC1, {'\n'}, S_STNL},
	{CC1, {EOFC}, S_EOFSTR},

	/* saw \ in ccon */
	{CC2, {C_XX}, CC1},
	{CC2, {'\n'}, S_STNL},
	{CC2, {EOFC}, S_EOFSTR},

	/* saw /, perhaps start of comment */
	{COM1, {C_XX}, ACT(SLASH, S_SELFB)},
	{COM1, {'='}, ACT(ASSLASH, S_SELF)},
	{COM1, {'*'}, COM2},
	{COM1, {'/'}, COM4},

	/* saw / then *, start of comment */
	{COM2, {C_XX}, COM2},
	{COM2, {'\n'}, S_COMNL},
	{COM2, {'*'}, COM3},
	{COM2, {EOFC}, S_EOFCOM},

	/* saw the * possibly ending a comment */
	{COM3, {C_XX}, COM2},
	{COM3, {'\n'}, S_COMNL},
	{COM3, {'*'}, COM3},
	{COM3, {'/'}, S_COMMENT},

	/* // comment */
	{COM4, {C_XX}, COM4},
	{COM4, {'\n'}, S_NL},
	{COM4, {EOFC}, S_EOFCOM},

	/* saw white space, eat it up */
	{WS1, {C_XX}, S_WS},
	{WS1, {' ', '\t', '\v'}, WS1},

	/* saw -, check --, -=, -> */
	{MINUS1, {C_XX}, ACT(MINUS, S_SELFB)},
	{MINUS1, {'-'}, ACT(MMINUS, S_SELF)},
	{MINUS1, {'='}, ACT(ASMINUS, S_SELF)},
	{MINUS1, {'>'}, ACT(ARROW, S_SELF)},

	/* saw +, check ++, += */
	{PLUS1, {C_XX}, ACT(PLUS, S_SELFB)},
	{PLUS1, {'+'}, ACT(PPLUS, S_SELF)},
	{PLUS1, {'='}, ACT(ASPLUS, S_SELF)},

	/* saw <, check <<, <<=, <= */
	{LT1, {C_XX}, ACT(LT, S_SELFB)},
	{LT1, {'<'}, LT2},
	{LT1, {'='}, ACT(LEQ, S_SELF)},
	{LT2, {C_XX}, ACT(LSH, S_SELFB)},
	{LT2, {'='}, ACT(ASLSH, S_SELF)},

	/* saw >, check >>, >>=, >= */
	{GT1, {C_XX}, ACT(GT, S_SELFB)},
	{GT1, {'>'}, GT2},
	{GT1, {'='}, ACT(GEQ, S_SELF)},
	{GT2, {C_XX}, ACT(RSH, S_SELFB)},
	{GT2, {'='}, ACT(ASRSH, S_SELF)},

	/* = */
	{ASG1, {C_XX}, ACT(ASGN, S_SELFB)},
	{ASG1, {'='}, ACT(EQ, S_SELF)},

	/* ! */
	{NOT1, {C_XX}, ACT(NOT, S_SELFB)},
	{NOT1, {'='}, ACT(NEQ, S_SELF)},

	/* & */
	{AND1, {C_XX}, ACT(AND, S_SELFB)},
	{AND1, {'&'}, ACT(LAND, S_SELF)},
	{AND1, {'='}, ACT(ASAND, S_SELF)},

	/* | */
	{OR1, {C_XX}, ACT(OR, S_SELFB)},
	{OR1, {'|'}, ACT(LOR, S_SELF)},
	{OR1, {'='}, ACT(ASOR, S_SELF)},

	/* # */
	{SHARP1, {C_XX}, ACT(SHARP, S_SELFB)},
	{SHARP1, {'#'}, ACT(DSHARP, S_SELF)},

	/* % */
	{PCT1, {C_XX}, ACT(PCT, S_SELFB)},
	{PCT1, {'='}, ACT(ASPCT, S_SELF)},

	/* * */
	{STAR1, {C_XX}, ACT(STAR, S_SELFB)},
	{STAR1, {'='}, ACT(ASSTAR, S_SELF)},

	/* ^ */
	{CIRC1, {C_XX}, ACT(CIRC, S_SELFB)},
	{CIRC1, {'='}, ACT(ASCIRC, S_SELF)},

	-1
};

/* first index is char, second is state */
/* increase #states to power of 2 to encourage use of shift */
short bigfsm[256][MAXSTATE];

void expandlex(void)
{
	/*const */ struct fsm *fp;
	int i, j, nstate;

	for (fp = fsm; fp->state >= 0; fp++)
	{
		for (i = 0; fp->ch[i]; i++)
		{
			nstate = fp->nextstate;
			if (nstate >= S_SELF)
				nstate = ~nstate;
			switch (fp->ch[i])
			{

			case C_XX:	/* random characters */
				for (j = 0; j < 256; j++)
					bigfsm[j][fp->state] = nstate;
				continue;
			case C_ALPH:
				for (j = 0; j <= 256; j++)
					if ('a' <= j && j <= 'z' || 'A' <= j && j <= 'Z'
						|| j == '_')
						bigfsm[j][fp->state] = nstate;
				continue;
			case C_NUM:
				for (j = '0'; j <= '9'; j++)
					bigfsm[j][fp->state] = nstate;
				continue;
			default:
				bigfsm[fp->ch[i]][fp->state] = nstate;
			}
		}
	}
	/* install special cases for ? (trigraphs),  \ (splicing), runes, and EOB */
	for (i = 0; i < MAXSTATE; i++)
	{
		for (j = 0; j < 0xFF; j++)
			if (j == '?' || j == '\\')
			{
				if (bigfsm[j][i] > 0)
					bigfsm[j][i] = ~bigfsm[j][i];
				bigfsm[j][i] &= ~QBSBIT;
			}
		bigfsm[EOB][i] = ~S_EOB;
		if (bigfsm[EOFC][i] >= 0)
			bigfsm[EOFC][i] = ~S_EOF;
	}
}

/*
 * fill in a row of tokens from input, terminated by NL or END
 * First token is put at trp->lp.
 * Reset is non-zero when the input buffer can be "rewound."
 * The value is a flag indicating that possible macros have
 * been seen in the row.
 */
int gettokens(Tokenrow * trp, int reset)
{
	register int c, state, oldstate;
	register uchar *ip;
	register Token *tp, *maxp;
	int runelen;
	Source *s = cursource;
	int nmac = 0;

	tp = trp->lp;
	ip = s->inp;
	if (reset)
	{
		s->lineinc = 0;
		if (ip >= s->inl)
		{	/* nothing in buffer */
			s->inl = s->inb;
			fillbuf(s);
			ip = s->inp = s->inb;
		}
		else if (ip >= s->inb + (3 * INS / 4))
		{
			memmove(s->inb, ip, 4 + s->inl - ip);
			s->inl = s->inb + (s->inl - ip);
			ip = s->inp = s->inb;
		}
	}
	maxp = &trp->bp[trp->max];
	runelen = 1;
	for (;;)
	{
	  continue2:
		if (tp >= maxp)
		{
			trp->lp = tp;
			tp = growtokenrow(trp);
			maxp = &trp->bp[trp->max];
		}
		tp->type = UNCLASS;
		tp->hideset = 0;
		tp->t = ip;
		tp->wslen = 0;
		tp->flag = 0;
		state = START;
		for (;;)
		{
			oldstate = state;
			c = *ip;
			if ((state = bigfsm[c][state]) >= 0)
			{
				ip += runelen;
				runelen = 1;
				continue;
			}
			state = ~state;
		  reswitch:
			switch (state & 0177)
			{
			case S_SELF:
				ip += runelen;
				runelen = 1;
			case S_SELFB:
				tp->type = GETACT(state);
				tp->len = ip - tp->t;
				tp++;
				goto continue2;

			case S_NAME:	/* like S_SELFB but with nmac check */
				tp->type = NAME;
				tp->len = ip - tp->t;
				nmac |= quicklook(tp->t[0], tp->len > 1 ? tp->t[1] : 0);
				tp++;
				goto continue2;

			case S_WS:
				tp->wslen = ip - tp->t;
				tp->t = ip;
				state = START;
				continue;

			default:
				if ((state & QBSBIT) == 0)
				{
					ip += runelen;
					runelen = 1;
					continue;
				}
				state &= ~QBSBIT;
				s->inp = ip;
				if (c == '?')
				{	/* check trigraph */
					if (trigraph(s))
					{
						state = oldstate;
						continue;
					}
					goto reswitch;
				}
				if (c == '\\')
				{	/* line-folding */
					if (foldline(s))
					{
						s->lineinc++;
						state = oldstate;
						continue;
					}
					goto reswitch;
				}
				error(WARNING, "Lexical botch in cpp");
				ip += runelen;
				runelen = 1;
				continue;

			case S_EOB:
				s->inp = ip;
				fillbuf(cursource);
				state = oldstate;
				continue;

			case S_EOF:
				tp->type = END;
				tp->len = 0;
				s->inp = ip;
				if (tp != trp->bp && (tp - 1)->type != NL
					&& cursource->fd != -1)
					error(WARNING, "No newline at end of file");
				trp->lp = tp + 1;
				return nmac;

			case S_STNL:
				error(ERROR, "Unterminated string or char const");
			case S_NL:
				tp->t = ip;
				tp->type = NL;
				tp->len = 1;
				tp->wslen = 0;
				s->lineinc++;
				s->inp = ip + 1;
				trp->lp = tp + 1;
				return nmac;

			case S_EOFSTR:
				error(FATAL, "EOF in string or char constant");
				break;

			case S_COMNL:
				s->lineinc++;
				state = COM2;
				ip += runelen;
				runelen = 1;
				if (ip >= s->inb + (7 * INS / 8))
				{	/* very long comment */
					memmove(tp->t, ip, 4 + s->inl - ip);
					s->inl -= ip - tp->t;
					ip = tp->t + 1;
				}
				continue;

			case S_EOFCOM:
				error(WARNING, "EOF inside comment");
				--ip;
			case S_COMMENT:
				++ip;
				tp->t = ip;
				tp->t[-1] = ' ';
				tp->wslen = 1;
				state = START;
				continue;
			}
			break;
		}
		ip += runelen;
		runelen = 1;
		tp->len = ip - tp->t;
		tp++;
	}
}

/* have seen ?; handle the trigraph it starts (if any) else 0 */
int trigraph(Source * s)
{
	int c;

	while (s->inp + 2 >= s->inl && fillbuf(s) != EOF)
		;
	if (s->inp[1] != '?')
		return 0;
	c = 0;
	switch (s->inp[2])
	{
	case '=':
		c = '#';
		break;
	case '(':
		c = '[';
		break;
	case '/':
		c = '\\';
		break;
	case ')':
		c = ']';
		break;
	case '\'':
		c = '^';
		break;
	case '<':
		c = '{';
		break;
	case '!':
		c = '|';
		break;
	case '>':
		c = '}';
		break;
	case '-':
		c = '~';
		break;
	}
	if (c)
	{
		*s->inp = c;
		memmove(s->inp + 1, s->inp + 3, s->inl - s->inp + 2);
		s->inl -= 2;
	}
	return c;
}

int foldline(Source * s)
{
	while (s->inp + 1 >= s->inl && fillbuf(s) != EOF)
		;
	if (s->inp[1] == '\n')
	{
		memmove(s->inp, s->inp + 2, s->inl - s->inp + 3);
		s->inl -= 2;
		return 1;
	}
	return 0;
}

int fillbuf(Source * s)
{
	int n, nr;

	nr = INS / 8;
	if ((char *)s->inl + nr > (char *)s->inb + INS)
		error(FATAL, "Input buffer overflow");
	if (s->fd < 0 || (n = read(s->fd, (char *)s->inl, INS / 8)) <= 0)
		n = 0;
	if ((*s->inp & 0xff) == EOB)	/* sentinel character appears in input */
		*s->inp = EOFC;
	s->inl += n;
	s->inl[0] = s->inl[1] = s->inl[2] = s->inl[3] = EOB;
	if (n == 0)
	{
		s->inl[0] = s->inl[1] = s->inl[2] = s->inl[3] = EOFC;
		return EOF;
	}
	return 0;
}

/*
 * Push down to new source of characters.
 * If fd>0 and str==NULL, then from a file `name';
 * if fd==-1 and str, then from the string.
 */
Source *setsource(char *name, int fd, char *str)
{
	Source *s = new(Source);
	int len;

	s->line = 1;
	s->lineinc = 0;
	s->fd = fd;
	s->filename = name;
	s->next = cursource;
	s->ifdepth = 0;
	cursource = s;
	/* slop at right for EOB */
	if (str)
	{
		len = strlen(str);
		s->inb = (uchar*)domalloc(len + 4);
		s->inp = s->inb;
		strncpy((char *)s->inp, str, len);
	}
	else
	{
		s->inb = (uchar*)domalloc(INS + 4);
		s->inp = s->inb;
		len = 0;
	}
	s->inl = s->inp + len;
	s->inl[0] = s->inl[1] = EOB;
	return s;
}

void unsetsource(void)
{
	Source *s = cursource;

	if (s->fd >= 0)
	{
		close(s->fd);
		dofree(s->inb);
	}
	cursource = s->next;
	dofree(s);
}
