/*
* Intermediate filter between parser and base lexer (base_yylex in scan.l).
*
* The filter is needed because in some cases SQL92 requires more than one
* token lookahead. We reduce these cases to one-token lookahead by combining
* tokens here, in order to keep the grammar LR(1).
*
* Using a filter is simpler than trying to recognize multiword tokens
* directly in scan.l, because we'd have to allow for comments between the
* words ...
*/
int
yylex(void)
{
int cur_token;
/* Get next token --- we might already have it */
if (have_lookahead)
{
cur_token = lookahead_token;
have_lookahead = false;
}
else
cur_token = base_yylex();
/* Do we need to look ahead for a possible multiword token? */
switch (cur_token)
{
case UNION:
/* UNION JOIN must be reduced to a single UNIONJOIN token */
lookahead_token = base_yylex();
if (lookahead_token == JOIN)
cur_token = UNIONJOIN;
else
have_lookahead = true;
break;
default:
break;
}
return cur_token;
}
/*
* pg_parse_string_token - get the value represented by a string literal
*
* Given the textual form of a SQL string literal, produce the represented
* value as a palloc'd string. It is caller's responsibility that the
* passed string does represent one single string literal.
*
* We export this function to avoid having plpgsql depend on internal details
* of the core grammar (such as the token code assigned to SCONST). Note
* that since the scanner isn't presently re-entrant, this cannot be used
* during use of the main parser/scanner.
*/
char *
pg_parse_string_token(const char *token)
{
int ctoken;
scanner_init(token);
ctoken = base_yylex();
if (ctoken != SCONST) /* caller error */
elog(ERROR, "expected string constant, got token code %d", ctoken);
scanner_finish();
return base_yylval.str;
}
/*
* Intermediate filter between parser and base lexer (base_yylex in scan.l).
*
* The filter is needed because in some cases the standard SQL grammar
* requires more than one token lookahead. We reduce these cases to one-token
* lookahead by combining tokens here, in order to keep the grammar LALR(1).
*
* Using a filter is simpler than trying to recognize multiword tokens
* directly in scan.l, because we'd have to allow for comments between the
* words. Furthermore it's not clear how to do it without re-introducing
* scanner backtrack, which would cost more performance than this filter
* layer does.
*/
int
filtered_base_yylex(void)
{
int cur_token;
int next_token;
YYSTYPE cur_yylval;
YYLTYPE cur_yylloc;
/* Get next token --- we might already have it */
if (have_lookahead)
{
cur_token = lookahead_token;
base_yylval = lookahead_yylval;
base_yylloc = lookahead_yylloc;
have_lookahead = false;
}
else
cur_token = base_yylex();
/* Do we need to look ahead for a possible multiword token? */
switch (cur_token)
{
case NULLS_P:
/*
* NULLS FIRST and NULLS LAST must be reduced to one token
*/
cur_yylval = base_yylval;
cur_yylloc = base_yylloc;
next_token = base_yylex();
switch (next_token)
{
case FIRST_P:
cur_token = NULLS_FIRST;
break;
case LAST_P:
cur_token = NULLS_LAST;
break;
default:
/* save the lookahead token for next time */
lookahead_token = next_token;
lookahead_yylval = base_yylval;
lookahead_yylloc = base_yylloc;
have_lookahead = true;
/* and back up the output info to cur_token */
base_yylval = cur_yylval;
base_yylloc = cur_yylloc;
break;
}
break;
case WITH:
/*
* WITH TIME, CASCADED, LOCAL, or CHECK must be reduced to one token
*
* XXX an alternative way is to recognize just WITH_TIME and put
* the ugliness into the datetime datatype productions instead of
* WITH CHECK OPTION. However that requires promoting WITH to a
* fully reserved word. If we ever have to do that anyway
* (perhaps for SQL99 recursive queries), come back and simplify
* this code.
*/
cur_yylval = base_yylval;
cur_yylloc = base_yylloc;
next_token = base_yylex();
switch (next_token)
{
case TIME:
cur_token = WITH_TIME;
break;
case CASCADED:
cur_token = WITH_CASCADED;
break;
case LOCAL:
cur_token = WITH_LOCAL;
break;
case CHECK:
cur_token = WITH_CHECK;
break;
default:
/* save the lookahead token for next time */
lookahead_token = next_token;
lookahead_yylval = base_yylval;
lookahead_yylloc = base_yylloc;
have_lookahead = true;
/* and back up the output info to cur_token */
base_yylval = cur_yylval;
base_yylloc = cur_yylloc;
break;
}
break;
default:
break;
}
return cur_token;
}
