syn.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

}

static struct op *
caselist()
{
	register struct op *t, *tl;
	int c;

	c = token(CONTIN|KEYWORD|ALIAS);
	/* A {...} can be used instead of in...esac for case statements */
	if (c == IN)
		c = ESAC;
	else if (c == '{')
		c = '}';
	else
		syntaxerr((char *) 0);
	t = tl = NULL;
	while ((tpeek(CONTIN|KEYWORD|ESACONLY)) != c) { /* no ALIAS here */
		struct op *tc = casepart(c);
		if (tl == NULL)
			t = tl = tc, tl->right = NULL;
		else
			tl->right = tc, tl = tc;
	}
	musthave(c, KEYWORD|ALIAS);
	return (t);
}

static struct op *
casepart(endtok)
	int endtok;
{
	register struct op *t;
	register int c;
	XPtrV ptns;

	XPinit(ptns, 16);
	t = newtp(TPAT);
	c = token(CONTIN|KEYWORD); /* no ALIAS here */
	if (c != '(')
		REJECT;
	do {
		musthave(LWORD, 0);
		XPput(ptns, yylval.cp);
	} while ((c = token(0)) == '|');
	REJECT;
	XPput(ptns, NULL);
	t->vars = (char **) XPclose(ptns);
	musthave(')', 0);

	t->left = c_list(TRUE);
	/* Note: Posix requires the ;; */
	if ((tpeek(CONTIN|KEYWORD|ALIAS)) != endtok)
		musthave(BREAK, CONTIN|KEYWORD|ALIAS);
	return (t);
}

static struct op *
function_body(name, ksh_func)
	char *name;
	int ksh_func;	/* function foo { ... } vs foo() { .. } */
{
	char *sname, *p;
	struct op *t;
	int old_func_parse;

	sname = wdstrip(name);
	/* Check for valid characters in name.  posix and ksh93 say only
	 * allow [a-zA-Z_0-9] but this allows more as old pdksh's have
	 * allowed more (the following were never allowed:
	 *	nul space nl tab $ ' " \ ` ( ) & | ; = < >
	 *  C_QUOTE covers all but = and adds # [ ? *)
	 */
	for (p = sname; *p; p++)
		if (ctype(*p, C_QUOTE) || *p == '=')
			yyerror("%s: invalid function name\n", sname);

	t = newtp(TFUNCT);
	t->str = sname;
	t->u.ksh_func = ksh_func;
	t->lineno = source->line;

	/* Note that POSIX allows only compound statements after foo(), sh and
	 * at&t ksh allow any command, go with the later since it shouldn't
	 * break anything.  However, for function foo, at&t ksh only accepts
	 * an open-brace.
	 */
	if (ksh_func) {
		musthave('{', CONTIN|KEYWORD|ALIAS); /* } */
		REJECT;
	}

	old_func_parse = e->flags & EF_FUNC_PARSE;
	e->flags |= EF_FUNC_PARSE;
	if ((t->left = get_command(CONTIN)) == (struct op *) 0) {
		/*
		 * Probably something like foo() followed by eof or ;.
		 * This is accepted by sh and ksh88.
		 * To make "typset -f foo" work reliably (so its output can
		 * be used as input), we pretend there is a colon here.
		 */
		t->left = newtp(TCOM);
		t->left->args = (char **) alloc(sizeof(char *) * 2, ATEMP);
		t->left->args[0] = alloc(sizeof(char) * 3, ATEMP);
		t->left->args[0][0] = CHAR;
		t->left->args[0][1] = ':';
		t->left->args[0][2] = EOS;
		t->left->args[1] = (char *) 0;
		t->left->vars = (char **) alloc(sizeof(char *), ATEMP);
		t->left->vars[0] = (char *) 0;
		t->left->lineno = 1;
	}
	if (!old_func_parse)
		e->flags &= ~EF_FUNC_PARSE;

	return t;
}

static char **
wordlist()
{
	register int c;
	XPtrV args;

	XPinit(args, 16);
	/* Posix does not do alias expansion here... */
	if ((c = token(CONTIN|KEYWORD|ALIAS)) != IN) {
		if (c != ';') /* non-POSIX, but at&t ksh accepts a ; here */
			REJECT;
		return NULL;
	}
	while ((c = token(0)) == LWORD)
		XPput(args, yylval.cp);
	if (c != '\n' && c != ';')
		syntaxerr((char *) 0);
	if (XPsize(args) == 0) {
		XPfree(args);
		return NULL;
	} else {
		XPput(args, NULL);
		return (char **) XPclose(args);
	}
}

/*
 * supporting functions
 */

static struct op *
block(type, t1, t2, wp)
	int type;
	struct op *t1, *t2;
	char **wp;
{
	register struct op *t;

	t = newtp(type);
	t->left = t1;
	t->right = t2;
	t->vars = wp;
	return (t);
}

const	struct tokeninfo {
	const char *name;
	short	val;
	short	reserved;
} tokentab[] = {
	/* Reserved words */
	{ "if",		IF,	TRUE },
	{ "then",	THEN,	TRUE },
	{ "else",	ELSE,	TRUE },
	{ "elif",	ELIF,	TRUE },
	{ "fi",		FI,	TRUE },
	{ "case",	CASE,	TRUE },
	{ "esac",	ESAC,	TRUE },
	{ "for",	FOR,	TRUE },
#ifdef KSH
	{ "select",	SELECT,	TRUE },
#endif /* KSH */
	{ "while",	WHILE,	TRUE },
	{ "until",	UNTIL,	TRUE },
	{ "do",		DO,	TRUE },
	{ "done",	DONE,	TRUE },
	{ "in",		IN,	TRUE },
	{ "function",	FUNCTION, TRUE },
	{ "time",	TIME,	TRUE },
	{ "{",		'{',	TRUE },
	{ "}",		'}',	TRUE },
	{ "!",		BANG,	TRUE },
#ifdef KSH
	{ "[[",		DBRACKET, TRUE },
#endif /* KSH */
	/* Lexical tokens (0[EOF], LWORD and REDIR handled specially) */
	{ "&&",		LOGAND,	FALSE },
	{ "||",		LOGOR,	FALSE },
	{ ";;",		BREAK,	FALSE },
#ifdef KSH
	{ "((",		MDPAREN, FALSE },
	{ "|&",		COPROC,	FALSE },
#endif /* KSH */
	/* and some special cases... */
	{ "newline",	'\n',	FALSE },
	{ 0 }
};

void
initkeywords()
{
	register struct tokeninfo const *tt;
	register struct tbl *p;

	tinit(&keywords, APERM, 32); /* must be 2^n (currently 20 keywords) */
	for (tt = tokentab; tt->name; tt++) {
		if (tt->reserved) {
			p = tenter(&keywords, tt->name, hash(tt->name));
			p->flag |= DEFINED|ISSET;
			p->type = CKEYWD;
			p->val.i = tt->val;
		}
	}
}

static void
syntaxerr(what)
	const char *what;
{
	char redir[6];	/* 2<<- is the longest redirection, I think */
	const char *s;
	struct tokeninfo const *tt;
	int c;

	if (!what)
		what = "unexpected";
	REJECT;
	c = token(0);
    Again:
	switch (c) {
	case 0:
		if (nesting.start_token) {
			c = nesting.start_token;
			source->errline = nesting.start_line;
			what = "unmatched";
			goto Again;
		}
		/* don't quote the EOF */
		yyerror("syntax error: unexpected EOF\n");
		/*NOTREACHED*/

	case LWORD:
		s = snptreef((char *) 0, 32, "%S", yylval.cp);
		break;

	case REDIR:
		s = snptreef(redir, sizeof(redir), "%R", yylval.iop);
		break;

	default:
		for (tt = tokentab; tt->name; tt++)
			if (tt->val == c)
			    break;
		if (tt->name)
			s = tt->name;
		else {
			if (c > 0 && c < 256) {
				redir[0] = c;
				redir[1] = '\0';
			} else
				shf_snprintf(redir, sizeof(redir),
					"?%d", c);
			s = redir;
		}
	}
	yyerror("syntax error: `%s' %s\n", s, what);
}

static void
nesting_push(save, tok)
	struct nesting_state *save;
	int tok;
{
	*save = nesting;
	nesting.start_token = tok;
	nesting.start_line = source->line;
}

static void
nesting_pop(saved)
	struct nesting_state *saved;
{
	nesting = *saved;
}

static struct op *
newtp(type)
	int type;
{
	register struct op *t;

	t = (struct op *) alloc(sizeof(*t), ATEMP);
	t->type = type;
	t->u.evalflags = 0;
	t->args = t->vars = NULL;
	t->ioact = NULL;
	t->left = t->right = NULL;
	t->str = NULL;
	return (t);
}

struct op *
compile(s)
	Source *s;
{
	nesting.start_token = 0;
	nesting.start_line = 0;
	herep = heres;
	source = s;
	yyparse();
	return outtree;
}

/* This kludge exists to take care of sh/at&t ksh oddity in which
 * the arguments of alias/export/readonly/typeset have no field
 * splitting, file globbing, or (normal) tilde expansion done.
 * at&t ksh seems to do something similar to this since
 *	$ touch a=a; typeset a=[ab]; echo "$a"
 *	a=[ab]
 *	$ x=typeset; $x a=[ab]; echo "$a"
 *	a=a
 *	$ 
 */
static int
assign_command(s)
	char *s;
{
	char c = *s;

	if (Flag(FPOSIX) || !*s)
		return 0;
	return     (c == 'a' && strcmp(s, "alias") == 0)
		|| (c == 'e' && strcmp(s, "export") == 0)
		|| (c == 'r' && strcmp(s, "readonly") == 0)
		|| (c == 't' && strcmp(s, "typeset") == 0);
}

/* Check if we are in the middle of reading an alias */
static int
inalias(s)
	struct source *s;
{
	for (; s && s->type == SALIAS; s = s->next)
		if (!(s->flags & SF_ALIASEND))
			return 1;
	return 0;
}


#ifdef KSH
/* Order important - indexed by Test_meta values
 * Note that ||, &&, ( and ) can't appear in as unquoted strings
 * in normal shell input, so these can be interpreted unambiguously
 * in the evaluation pass.
 */
static const char dbtest_or[] = { CHAR, '|', CHAR, '|', EOS };
static const char dbtest_and[] = { CHAR, '&', CHAR, '&', EOS };
static const char dbtest_not[] = { CHAR, '!', EOS };
static const char dbtest_oparen[] = { CHAR, '(', EOS };
static const char dbtest_cparen[] = { CHAR, ')', EOS };
const char *const dbtest_tokens[] = {
			dbtest_or, dbtest_and, dbtest_not,
			dbtest_oparen, dbtest_cparen
		};
const char db_close[] = { CHAR, ']', CHAR, ']', EOS };
const char db_lthan[] = { CHAR, '<', EOS };
const char db_gthan[] = { CHAR, '>', EOS };

/* Test if the current token is a whatever.  Accepts the current token if
 * it is.  Returns 0 if it is not, non-zero if it is (in the case of
 * TM_UNOP and TM_BINOP, the returned value is a Test_op).
 */
static int
dbtestp_isa(te, meta)
	Test_env *te;
	Test_meta meta;
{
	int c = tpeek(ARRAYVAR | (meta == TM_BINOP ? 0 : CONTIN));
	int uqword = 0;
	char *save = (char *) 0;
	int ret = 0;

	/* unquoted word? */
	uqword = c == LWORD && *ident;

	if (meta == TM_OR)
		ret = c == LOGOR;
	else if (meta == TM_AND)
		ret = c == LOGAND;
	else if (meta == TM_NOT)
		ret = uqword && strcmp(yylval.cp, dbtest_tokens[(int) TM_NOT]) == 0;
	else if (meta == TM_OPAREN)
		ret = c == '(' /*)*/;
	else if (meta == TM_CPAREN)
		ret = c == /*(*/ ')';
	else if (meta == TM_UNOP || meta == TM_BINOP) {
		if (meta == TM_BINOP && c == REDIR
		    && (yylval.iop->flag == IOREAD
			|| yylval.iop->flag == IOWRITE))
		{
			ret = 1;
			save = wdcopy(yylval.iop->flag == IOREAD ?
				db_lthan : db_gthan, ATEMP);
		} else if (uqword && (ret = (int) test_isop(te, meta, ident)))
			save = yylval.cp;
	} else /* meta == TM_END */
		ret = uqword && strcmp(yylval.cp, db_close) == 0;
	if (ret) {
		ACCEPT;
		if (meta != TM_END) {
			if (!save)
				save = wdcopy(dbtest_tokens[(int) meta], ATEMP);
			XPput(*te->pos.av, save);
		}
	}
	return ret;
}

static const char *
dbtestp_getopnd(te, op, do_eval)
	Test_env *te;
	Test_op op;
	int do_eval;
{
	int c = tpeek(ARRAYVAR);

	if (c != LWORD)
		return (const char *) 0;

	ACCEPT;
	XPput(*te->pos.av, yylval.cp);

	return null;
}

static int
dbtestp_eval(te, op, opnd1, opnd2, do_eval)
	Test_env *te;
	Test_op op;
	const char *opnd1;
	const char *opnd2;
	int do_eval;
{
	return 1;
}

static void
dbtestp_error(te, offset, msg)
	Test_env *te;
	int offset;
	const char *msg;
{
	te->flags |= TEF_ERROR;

	if (offset < 0) {
		REJECT;
		/* Kludgy to say the least... */
		symbol = LWORD;
		yylval.cp = *(XPptrv(*te->pos.av) + XPsize(*te->pos.av)
				+ offset);
	}
	syntaxerr(msg);
}
#endif /* KSH */