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/*-------------------------------------------------------------------------
*
* parser.c
* Main entry point/driver for PostgreSQL grammar
*
* This should match src/backend/parser/parser.c, except that we do not
* need to bother with re-entrant interfaces.
*
*
* Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/interfaces/ecpg/preproc/parser.c
*
*-------------------------------------------------------------------------
*/
#include "postgres_fe.h"
#include "extern.h"
#include "preproc.h"
static bool have_lookahead; /* is lookahead info valid? */
static int lookahead_token; /* one-token lookahead */
static YYSTYPE lookahead_yylval; /* yylval for lookahead token */
static YYLTYPE lookahead_yylloc; /* yylloc for lookahead token */
static char *lookahead_yytext; /* start current token */
static char *lookahead_end; /* end of current token */
static char lookahead_hold_char; /* to be put back at *lookahead_end */
/*
* Intermediate filter between parser and base lexer (base_yylex in scan.l).
*
* This 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 replacing 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 that 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;
int cur_token_length;
YYSTYPE cur_yylval;
YYLTYPE cur_yylloc;
char *cur_yytext;
/* Get next token --- we might already have it */
if (have_lookahead)
{
cur_token = lookahead_token;
base_yylval = lookahead_yylval;
base_yylloc = lookahead_yylloc;
yytext = lookahead_yytext;
*lookahead_end = lookahead_hold_char;
have_lookahead = false;
}
else
cur_token = base_yylex();
/*
* If this token isn't one that requires lookahead, just return it. If it
* does, determine the token length. (We could get that via strlen(), but
* since we have such a small set of possibilities, hardwiring seems
* feasible and more efficient.)
*/
switch (cur_token)
{
case NOT:
cur_token_length = 3;
break;
case NULLS_P:
cur_token_length = 5;
break;
case WITH:
cur_token_length = 4;
break;
default:
return cur_token;
}
/*
* Identify end+1 of current token. base_yylex() has temporarily stored a
* '\0' here, and will undo that when we call it again. We need to redo
* it to fully revert the lookahead call for error reporting purposes.
*/
lookahead_end = yytext + cur_token_length;
Assert(*lookahead_end == '\0');
/* Save and restore lexer output variables around the call */
cur_yylval = base_yylval;
cur_yylloc = base_yylloc;
cur_yytext = yytext;
/* Get next token, saving outputs into lookahead variables */
next_token = base_yylex();
lookahead_token = next_token;
lookahead_yylval = base_yylval;
lookahead_yylloc = base_yylloc;
lookahead_yytext = yytext;
base_yylval = cur_yylval;
base_yylloc = cur_yylloc;
yytext = cur_yytext;
/* Now revert the un-truncation of the current token */
lookahead_hold_char = *lookahead_end;
*lookahead_end = '\0';
have_lookahead = true;
/* Replace cur_token if needed, based on lookahead */
switch (cur_token)
{
case NOT:
/* Replace NOT by NOT_LA if it's followed by BETWEEN, IN, etc */
switch (next_token)
{
case BETWEEN:
case IN_P:
case LIKE:
case ILIKE:
case SIMILAR:
cur_token = NOT_LA;
break;
}
break;
case NULLS_P:
/* Replace NULLS_P by NULLS_LA if it's followed by FIRST or LAST */
switch (next_token)
{
case FIRST_P:
case LAST_P:
cur_token = NULLS_LA;
break;
}
break;
case WITH:
/* Replace WITH by WITH_LA if it's followed by TIME or ORDINALITY */
switch (next_token)
{
case TIME:
case ORDINALITY:
cur_token = WITH_LA;
break;
}
break;
}
return cur_token;
}
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