scan.l

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

%{
/*-------------------------------------------------------------------------
 *
 * scan.l
 *	  lexical scanner for PostgreSQL
 *
 * NOTE NOTE NOTE:
 *
 * The rules in this file must be kept in sync with psql's lexer!!!
 *
 * The rules are designed so that the scanner never has to backtrack,
 * in the sense that there is always a rule that can match the input
 * consumed so far (the rule action may internally throw back some input
 * with yyless(), however).  As explained in the flex manual, this makes
 * for a useful speed increase --- about a third faster than a plain -CF
 * lexer, in simple testing.  The extra complexity is mostly in the rules
 * for handling float numbers and continued string literals.  If you change
 * the lexical rules, verify that you haven't broken the no-backtrack
 * property by running flex with the "-b" option and checking that the
 * resulting "lex.backup" file says that no backing up is needed.
 *
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/parser/scan.l,v 1.128.2.1 2006/05/21 20:11:02 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include <unistd.h>

#include "parser/gramparse.h"
#include "parser/keywords.h"
/* Not needed now that this file is compiled as part of gram.y */
/* #include "parser/parse.h" */
#include "parser/scansup.h"
#include "mb/pg_wchar.h"


/* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
#undef fprintf
#define fprintf(file, fmt, msg)  ereport(ERROR, (errmsg_internal("%s", msg)))

extern YYSTYPE yylval;

static int		xcdepth = 0;	/* depth of nesting in slash-star comments */
static char    *dolqstart;      /* current $foo$ quote start string */

/*
 * GUC variables.  This is a DIRECT violation of the warning given at the
 * head of gram.y, ie flex/bison code must not depend on any GUC variables;
 * as such, changing their values can induce very unintuitive behavior.
 * But we shall have to live with it as a short-term thing until the switch
 * to SQL-standard string syntax is complete.
 */
BackslashQuoteType backslash_quote = BACKSLASH_QUOTE_SAFE_ENCODING;
bool			escape_string_warning = true;

static bool		warn_on_first_escape;

/*
 * literalbuf is used to accumulate literal values when multiple rules
 * are needed to parse a single literal.  Call startlit to reset buffer
 * to empty, addlit to add text.  Note that the buffer is palloc'd and
 * starts life afresh on every parse cycle.
 */
static char	   *literalbuf;		/* expandable buffer */
static int		literallen;		/* actual current length */
static int		literalalloc;	/* current allocated buffer size */

#define startlit()  (literalbuf[0] = '\0', literallen = 0)
static void addlit(char *ytext, int yleng);
static void addlitchar(unsigned char ychar);
static char *litbufdup(void);
static int	pg_err_position(void);
static void check_escape_warning(void);

/*
 * When we parse a token that requires multiple lexer rules to process,
 * we set token_start to point at the true start of the token, for use
 * by yyerror().  yytext will point at just the text consumed by the last
 * rule, so it's not very helpful (e.g., it might contain just the last
 * quote mark of a quoted identifier).  But to avoid cluttering every rule
 * with setting token_start, we allow token_start = NULL to denote that
 * it's okay to use yytext.
 */
static char	   *token_start;

/* Handles to the buffer that the lexer uses internally */
static YY_BUFFER_STATE scanbufhandle;
static char *scanbuf;

unsigned char unescape_single_char(unsigned char c);

%}

%option 8bit
%option never-interactive
%option nodefault
%option nounput
%option noyywrap
%option prefix="base_yy"

/*
 * OK, here is a short description of lex/flex rules behavior.
 * The longest pattern which matches an input string is always chosen.
 * For equal-length patterns, the first occurring in the rules list is chosen.
 * INITIAL is the starting state, to which all non-conditional rules apply.
 * Exclusive states change parsing rules while the state is active.  When in
 * an exclusive state, only those rules defined for that state apply.
 *
 * We use exclusive states for quoted strings, extended comments,
 * and to eliminate parsing troubles for numeric strings.
 * Exclusive states:
 *  <xb> bit string literal
 *  <xc> extended C-style comments
 *  <xd> delimited identifiers (double-quoted identifiers)
 *  <xh> hexadecimal numeric string
 *  <xq> quoted strings
 *  <xdolq> $foo$ quoted strings
 */

%x xb
%x xc
%x xd
%x xh
%x xq
%x xdolq

/*
 * In order to make the world safe for Windows and Mac clients as well as
 * Unix ones, we accept either \n or \r as a newline.  A DOS-style \r\n
 * sequence will be seen as two successive newlines, but that doesn't cause
 * any problems.  Comments that start with -- and extend to the next
 * newline are treated as equivalent to a single whitespace character.
 *
 * NOTE a fine point: if there is no newline following --, we will absorb
 * everything to the end of the input as a comment.  This is correct.  Older
 * versions of Postgres failed to recognize -- as a comment if the input
 * did not end with a newline.
 *
 * XXX perhaps \f (formfeed) should be treated as a newline as well?
 */

space			[ \t\n\r\f]
horiz_space		[ \t\f]
newline			[\n\r]
non_newline		[^\n\r]

comment			("--"{non_newline}*)

whitespace		({space}+|{comment})

/*
 * SQL requires at least one newline in the whitespace separating
 * string literals that are to be concatenated.  Silly, but who are we
 * to argue?  Note that {whitespace_with_newline} should not have * after
 * it, whereas {whitespace} should generally have a * after it...
 */

special_whitespace		({space}+|{comment}{newline})
horiz_whitespace		({horiz_space}|{comment})
whitespace_with_newline	({horiz_whitespace}*{newline}{special_whitespace}*)

/*
 * To ensure that {quotecontinue} can be scanned without having to back up
 * if the full pattern isn't matched, we include trailing whitespace in
 * {quotestop}.  This matches all cases where {quotecontinue} fails to match,
 * except for {quote} followed by whitespace and just one "-" (not two,
 * which would start a {comment}).  To cover that we have {quotefail}.
 * The actions for {quotestop} and {quotefail} must throw back characters
 * beyond the quote proper.
 */
quote			'
quotestop		{quote}{whitespace}*
quotecontinue	{quote}{whitespace_with_newline}{quote}
quotefail		{quote}{whitespace}*"-"

/* Bit string
 * It is tempting to scan the string for only those characters
 * which are allowed. However, this leads to silently swallowed
 * characters if illegal characters are included in the string.
 * For example, if xbinside is [01] then B'ABCD' is interpreted
 * as a zero-length string, and the ABCD' is lost!
 * Better to pass the string forward and let the input routines
 * validate the contents.
 */
xbstart			[bB]{quote}
xbinside		[^']*

/* Hexadecimal number */
xhstart			[xX]{quote}
xhinside		[^']*

/* National character */
xnstart			[nN]{quote}

/* Quoted string that allows backslash escapes */
xestart			[eE]{quote}

/* Extended quote
 * xqdouble implements embedded quote, ''''
 */
xqstart			{quote}
xqdouble		{quote}{quote}
xqinside		[^\\']+
xqescape		[\\][^0-7]
xqoctesc		[\\][0-7]{1,3}
xqhexesc		[\\]x[0-9A-Fa-f]{1,2}

/* $foo$ style quotes ("dollar quoting")
 * The quoted string starts with $foo$ where "foo" is an optional string
 * in the form of an identifier, except that it may not contain "$", 
 * and extends to the first occurrence of an identical string.  
 * There is *no* processing of the quoted text.
 *
 * {dolqfailed} is an error rule to avoid scanner backup when {dolqdelim}
 * fails to match its trailing "$".
 */
dolq_start		[A-Za-z\200-\377_]
dolq_cont		[A-Za-z\200-\377_0-9]
dolqdelim		\$({dolq_start}{dolq_cont}*)?\$
dolqfailed		\${dolq_start}{dolq_cont}*
dolqinside		[^$]+

/* Double quote
 * Allows embedded spaces and other special characters into identifiers.
 */
dquote			\"
xdstart			{dquote}
xdstop			{dquote}
xddouble		{dquote}{dquote}
xdinside		[^"]+

/* C-style comments
 *
 * The "extended comment" syntax closely resembles allowable operator syntax.
 * The tricky part here is to get lex to recognize a string starting with
 * slash-star as a comment, when interpreting it as an operator would produce
 * a longer match --- remember lex will prefer a longer match!  Also, if we
 * have something like plus-slash-star, lex will think this is a 3-character
 * operator whereas we want to see it as a + operator and a comment start.
 * The solution is two-fold:
 * 1. append {op_chars}* to xcstart so that it matches as much text as
 *    {operator} would. Then the tie-breaker (first matching rule of same
 *    length) ensures xcstart wins.  We put back the extra stuff with yyless()
 *    in case it contains a star-slash that should terminate the comment.
 * 2. In the operator rule, check for slash-star within the operator, and
 *    if found throw it back with yyless().  This handles the plus-slash-star
 *    problem.
 * Dash-dash comments have similar interactions with the operator rule.
 */
xcstart			\/\*{op_chars}*
xcstop			\*+\/
xcinside		[^*/]+

digit			[0-9]
ident_start		[A-Za-z\200-\377_]
ident_cont		[A-Za-z\200-\377_0-9\$]

identifier		{ident_start}{ident_cont}*

typecast		"::"

/*
 * "self" is the set of chars that should be returned as single-character
 * tokens.  "op_chars" is the set of chars that can make up "Op" tokens,
 * which can be one or more characters long (but if a single-char token
 * appears in the "self" set, it is not to be returned as an Op).  Note
 * that the sets overlap, but each has some chars that are not in the other.
 *
 * If you change either set, adjust the character lists appearing in the
 * rule for "operator"!
 */
self			[,()\[\].;\:\+\-\*\/\%\^\<\>\=]
op_chars		[\~\!\@\#\^\&\|\`\?\+\-\*\/\%\<\>\=]
operator		{op_chars}+

/* we no longer allow unary minus in numbers. 
 * instead we pass it separately to parser. there it gets
 * coerced via doNegate() -- Leon aug 20 1999
 *
 * {realfail1} and {realfail2} are added to prevent the need for scanner
 * backup when the {real} rule fails to match completely.
 */

integer			{digit}+
decimal			(({digit}*\.{digit}+)|({digit}+\.{digit}*))
real			({integer}|{decimal})[Ee][-+]?{digit}+
realfail1		({integer}|{decimal})[Ee]
realfail2		({integer}|{decimal})[Ee][-+]

param			\${integer}

other			.

/*
 * Dollar quoted strings are totally opaque, and no escaping is done on them.
 * Other quoted strings must allow some special characters such as single-quote
 *  and newline.
 * Embedded single-quotes are implemented both in the SQL standard
 *  style of two adjacent single quotes "''" and in the Postgres/Java style
 *  of escaped-quote "\'".
 * Other embedded escaped characters are matched explicitly and the leading
 *  backslash is dropped from the string.
 * Note that xcstart must appear before operator, as explained above!
 *  Also whitespace (comment) must appear before operator.
 */

%%

%{
					/* code to execute during start of each call of yylex() */
					token_start = NULL;
%}

{whitespace}	{
					/* ignore */
				}

{xcstart}		{
					token_start = yytext;
					xcdepth = 0;
					BEGIN(xc);
					/* Put back any characters past slash-star; see above */
					yyless(2);
				}

<xc>{xcstart}	{
					xcdepth++;
					/* Put back any characters past slash-star; see above */
					yyless(2);
				}

<xc>{xcstop}	{
					if (xcdepth <= 0)
					{
						BEGIN(INITIAL);
						/* reset token_start for next token */
						token_start = NULL;
					}
					else
						xcdepth--;
				}

<xc>{xcinside}	{
					/* ignore */
				}

<xc>{op_chars}	{
					/* ignore */
				}

<xc>\*+			{
					/* ignore */
				}

<xc><<EOF>>		{ yyerror("unterminated /* comment"); }

{xbstart}		{
					/* Binary bit type.
					 * At some point we should simply pass the string
					 * forward to the parser and label it there.
					 * In the meantime, place a leading "b" on the string
					 * to mark it for the input routine as a binary string.
					 */
					token_start = yytext;
					BEGIN(xb);
					startlit();
					addlitchar('b');
				}
<xb>{quotestop}	|
<xb>{quotefail} {
					yyless(1);
					BEGIN(INITIAL);
					yylval.str = litbufdup();
					return BCONST;
				}
<xh>{xhinside}	|
<xb>{xbinside}	{
					addlit(yytext, yyleng);
				}
<xh>{quotecontinue}	|
<xb>{quotecontinue}	{
					/* ignore */
				}
<xb><<EOF>>		{ yyerror("unterminated bit string literal"); }

{xhstart}		{
					/* Hexadecimal bit type.
					 * At some point we should simply pass the string
					 * forward to the parser and label it there.
					 * In the meantime, place a leading "x" on the string
					 * to mark it for the input routine as a hex string.
					 */
					token_start = yytext;
					BEGIN(xh);
					startlit();
					addlitchar('x');
				}
<xh>{quotestop}	|
<xh>{quotefail} {
					yyless(1);
					BEGIN(INITIAL);
					yylval.str = litbufdup();
					return XCONST;
				}
<xh><<EOF>>		{ yyerror("unterminated hexadecimal string literal"); }

{xnstart}		{
					/* National character.
					 * We will pass this along as a normal character string,
					 * but preceded with an internally-generated "NCHAR".
					 */
					const ScanKeyword *keyword;

					yyless(1);				/* eat only 'n' this time */
					/* nchar had better be a keyword! */
					keyword = ScanKeywordLookup("nchar");
					Assert(keyword != NULL);
					yylval.keyword = keyword->name;
					return keyword->value;
				}

{xqstart}		{
					warn_on_first_escape = true;
					token_start = yytext;
					BEGIN(xq);
					startlit();
				}
{xestart}		{
					warn_on_first_escape = false;
					token_start = yytext;
					BEGIN(xq);
					startlit();
				}
<xq>{quotestop}	|
<xq>{quotefail} {
					yyless(1);
					BEGIN(INITIAL);
					yylval.str = litbufdup();
					return SCONST;
				}
<xq>{xqdouble}  {
					addlitchar('\'');