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postgres/src/include/regex/regcustom.h
Thomas Munro db4f21e4a3 Redesign interrupt/cancel API for regex engine. 
Previously, a PostgreSQL-specific callback checked by the regex engine
had a way to trigger a special error code REG_CANCEL if it detected that
the next call to CHECK_FOR_INTERRUPTS() would certainly throw via
ereport().

A later proposed bugfix aims to move some complex logic out of signal
handlers, so that it won't run until the next CHECK_FOR_INTERRUPTS(),
which makes the above design impossible unless we split
CHECK_FOR_INTERRUPTS() into two phases, one to run logic and another to
ereport().  We may develop such a system in the future, but for the
regex code it is no longer necessary.

An earlier commit moved regex memory management over to our
MemoryContext system.  Given that the purpose of the two-phase interrupt
checking was to free memory before throwing, something we don't need to
worry about anymore, it seems simpler to inject CHECK_FOR_INTERRUPTS()
directly into cancelation points, and just let it throw.

Since the plan is to keep PostgreSQL-specific concerns separate from the
main regex engine code (with a view to bein able to stay in sync with
other projects), do this with a new macro INTERRUPT(), customizable in
regcustom.h and defaulting to nothing.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CA%2BhUKGK3PGKwcKqzoosamn36YW-fsuTdOPPF1i_rtEO%3DnEYKSg%40mail.gmail.com
2023-04-08 22:10:39 +12:00

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/*
* Copyright (c) 1998, 1999 Henry Spencer. All rights reserved.
*
* Development of this software was funded, in part, by Cray Research Inc.,
* UUNET Communications Services Inc., Sun Microsystems Inc., and Scriptics
* Corporation, none of whom are responsible for the results. The author
* thanks all of them.
*
* Redistribution and use in source and binary forms -- with or without
* modification -- are permitted for any purpose, provided that
* redistributions in source form retain this entire copyright notice and
* indicate the origin and nature of any modifications.
*
* I'd appreciate being given credit for this package in the documentation
* of software which uses it, but that is not a requirement.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* HENRY SPENCER BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* src/include/regex/regcustom.h
*/
/* headers if any */
/*
* It's against Postgres coding conventions to include postgres.h in a
* header file, but we allow the violation here because the regexp library
* files specifically intend this file to supply application-dependent
* headers, and are careful to include this file before anything else.
*/
#include "postgres.h"
#include <ctype.h>
#include <limits.h>
#include <wctype.h>
#include "mb/pg_wchar.h"
#include "miscadmin.h" /* needed by stacktoodeep */
/* overrides for regguts.h definitions, if any */
#define FUNCPTR(name, args) (*name) args
#define MALLOC(n) palloc_extended((n), MCXT_ALLOC_NO_OOM)
#define FREE(p) pfree(VS(p))
#define REALLOC(p,n) repalloc_extended(VS(p),(n), MCXT_ALLOC_NO_OOM)
#define INTERRUPT(re) CHECK_FOR_INTERRUPTS()
#define assert(x) Assert(x)
/* internal character type and related */
typedef pg_wchar chr; /* the type itself */
typedef unsigned uchr; /* unsigned type that will hold a chr */
#define CHR(c) ((unsigned char) (c)) /* turn char literal into chr literal */
#define DIGITVAL(c) ((c)-'0') /* turn chr digit into its value */
#define CHRBITS 32 /* bits in a chr; must not use sizeof */
#define CHR_MIN 0x00000000 /* smallest and largest chr; the value */
#define CHR_MAX 0x7ffffffe /* CHR_MAX-CHR_MIN+1 must fit in an int, and
* CHR_MAX+1 must fit in a chr variable */
/*
* Check if a chr value is in range. Ideally we'd just write this as
* ((c) >= CHR_MIN && (c) <= CHR_MAX)
* However, if chr is unsigned and CHR_MIN is zero, the first part of that
* is a no-op, and certain overly-nannyish compilers give warnings about it.
* So we leave that out here. If you want to make chr signed and/or CHR_MIN
* not zero, redefine this macro as above. Callers should assume that the
* macro may multiply evaluate its argument, even though it does not today.
*/
#define CHR_IS_IN_RANGE(c) ((c) <= CHR_MAX)
/*
* MAX_SIMPLE_CHR is the cutoff between "simple" and "complicated" processing
* in the color map logic. It should usually be chosen high enough to ensure
* that all common characters are <= MAX_SIMPLE_CHR. However, very large
* values will be counterproductive since they cause more regex setup time.
* Also, small values can be helpful for testing the high-color-map logic
* with plain old ASCII input.
*/
#define MAX_SIMPLE_CHR 0x7FF /* suitable value for Unicode */
/* functions operating on chr */
#define iscalnum(x) pg_wc_isalnum(x)
#define iscalpha(x) pg_wc_isalpha(x)
#define iscdigit(x) pg_wc_isdigit(x)
#define iscspace(x) pg_wc_isspace(x)
/* and pick up the standard header */
#include "regex.h"
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