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/*-------------------------------------------------------------------------
*
* pgtz.c
* Timezone Library Integration Functions
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/timezone/pgtz.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <ctype.h>
#include <fcntl.h>
#include <time.h>
#include "common/file_utils.h"
#include "datatype/timestamp.h"
#include "miscadmin.h"
#include "pgtz.h"
#include "storage/fd.h"
#include "utils/hsearch.h"
/* Current session timezone (controlled by TimeZone GUC) */
pg_tz *session_timezone = NULL;
/* Current log timezone (controlled by log_timezone GUC) */
pg_tz *log_timezone = NULL;
static bool scan_directory_ci(const char *dirname,
const char *fname, int fnamelen,
char *canonname, int canonnamelen);
/*
* Return full pathname of timezone data directory
*/
static const char *
pg_TZDIR(void)
{
#ifndef SYSTEMTZDIR
/* normal case: timezone stuff is under our share dir */
static bool done_tzdir = false;
static char tzdir[MAXPGPATH];
if (done_tzdir)
return tzdir;
get_share_path(my_exec_path, tzdir);
strlcpy(tzdir + strlen(tzdir), "/timezone", MAXPGPATH - strlen(tzdir));
done_tzdir = true;
return tzdir;
#else
/* we're configured to use system's timezone database */
return SYSTEMTZDIR;
#endif
}
/*
* Given a timezone name, open() the timezone data file. Return the
* file descriptor if successful, -1 if not.
*
* The input name is searched for case-insensitively (we assume that the
* timezone database does not contain case-equivalent names).
*
* If "canonname" is not NULL, then on success the canonical spelling of the
* given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
*/
int
pg_open_tzfile(const char *name, char *canonname)
{
const char *fname;
char fullname[MAXPGPATH];
int fullnamelen;
int orignamelen;
/* Initialize fullname with base name of tzdata directory */
strlcpy(fullname, pg_TZDIR(), sizeof(fullname));
orignamelen = fullnamelen = strlen(fullname);
if (fullnamelen + 1 + strlen(name) >= MAXPGPATH)
return -1; /* not gonna fit */
/*
* If the caller doesn't need the canonical spelling, first just try to
* open the name as-is. This can be expected to succeed if the given name
* is already case-correct, or if the filesystem is case-insensitive; and
* we don't need to distinguish those situations if we aren't tasked with
* reporting the canonical spelling.
*/
if (canonname == NULL)
{
int result;
fullname[fullnamelen] = '/';
/* test above ensured this will fit: */
strcpy(fullname + fullnamelen + 1, name);
result = open(fullname, O_RDONLY | PG_BINARY, 0);
if (result >= 0)
return result;
/* If that didn't work, fall through to do it the hard way */
fullname[fullnamelen] = '\0';
}
/*
* Loop to split the given name into directory levels; for each level,
* search using scan_directory_ci().
*/
fname = name;
for (;;)
{
const char *slashptr;
int fnamelen;
slashptr = strchr(fname, '/');
if (slashptr)
fnamelen = slashptr - fname;
else
fnamelen = strlen(fname);
if (!scan_directory_ci(fullname, fname, fnamelen,
fullname + fullnamelen + 1,
MAXPGPATH - fullnamelen - 1))
return -1;
fullname[fullnamelen++] = '/';
fullnamelen += strlen(fullname + fullnamelen);
if (slashptr)
fname = slashptr + 1;
else
break;
}
if (canonname)
strlcpy(canonname, fullname + orignamelen + 1, TZ_STRLEN_MAX + 1);
return open(fullname, O_RDONLY | PG_BINARY, 0);
}
/*
* Scan specified directory for a case-insensitive match to fname
* (of length fnamelen --- fname may not be null terminated!). If found,
* copy the actual filename into canonname and return true.
*/
static bool
scan_directory_ci(const char *dirname, const char *fname, int fnamelen,
char *canonname, int canonnamelen)
{
bool found = false;
DIR *dirdesc;
struct dirent *direntry;
dirdesc = AllocateDir(dirname);
while ((direntry = ReadDirExtended(dirdesc, dirname, LOG)) != NULL)
{
/*
* Ignore . and .., plus any other "hidden" files. This is a security
* measure to prevent access to files outside the timezone directory.
*/
if (direntry->d_name[0] == '.')
continue;
if (strlen(direntry->d_name) == fnamelen &&
pg_strncasecmp(direntry->d_name, fname, fnamelen) == 0)
{
/* Found our match */
strlcpy(canonname, direntry->d_name, canonnamelen);
found = true;
break;
}
}
FreeDir(dirdesc);
return found;
}
/*
* We keep loaded timezones in a hashtable so we don't have to
* load and parse the TZ definition file every time one is selected.
* Because we want timezone names to be found case-insensitively,
* the hash key is the uppercased name of the zone.
*/
typedef struct
{
/* tznameupper contains the all-upper-case name of the timezone */
char tznameupper[TZ_STRLEN_MAX + 1];
pg_tz tz;
} pg_tz_cache;
static HTAB *timezone_cache = NULL;
static bool
init_timezone_hashtable(void)
{
HASHCTL hash_ctl;
hash_ctl.keysize = TZ_STRLEN_MAX + 1;
hash_ctl.entrysize = sizeof(pg_tz_cache);
timezone_cache = hash_create("Timezones",
4,
&hash_ctl,
HASH_ELEM | HASH_STRINGS);
if (!timezone_cache)
return false;
return true;
}
/*
* Load a timezone from file or from cache.
* Does not verify that the timezone is acceptable!
*
* "GMT" is always interpreted as the tzparse() definition, without attempting
* to load a definition from the filesystem. This has a number of benefits:
* 1. It's guaranteed to succeed, so we don't have the failure mode wherein
* the bootstrap default timezone setting doesn't work (as could happen if
* the OS attempts to supply a leap-second-aware version of "GMT").
* 2. Because we aren't accessing the filesystem, we can safely initialize
* the "GMT" zone definition before my_exec_path is known.
* 3. It's quick enough that we don't waste much time when the bootstrap
* default timezone setting is later overridden from postgresql.conf.
*/
pg_tz *
pg_tzset(const char *tzname)
{
pg_tz_cache *tzp;
struct state tzstate;
char uppername[TZ_STRLEN_MAX + 1];
char canonname[TZ_STRLEN_MAX + 1];
char *p;
if (strlen(tzname) > TZ_STRLEN_MAX)
return NULL; /* not going to fit */
if (!timezone_cache)
if (!init_timezone_hashtable())
return NULL;
/*
* Upcase the given name to perform a case-insensitive hashtable search.
* (We could alternatively downcase it, but we prefer upcase so that we
* can get consistently upcased results from tzparse() in case the name is
* a POSIX-style timezone spec.)
*/
p = uppername;
while (*tzname)
*p++ = pg_toupper((unsigned char) *tzname++);
*p = '\0';
tzp = (pg_tz_cache *) hash_search(timezone_cache,
uppername,
HASH_FIND,
NULL);
if (tzp)
{
/* Timezone found in cache, nothing more to do */
return &tzp->tz;
}
/*
* "GMT" is always sent to tzparse(), as per discussion above.
*/
if (strcmp(uppername, "GMT") == 0)
{
if (!tzparse(uppername, &tzstate, true))
{
/* This really, really should not happen ... */
elog(ERROR, "could not initialize GMT time zone");
}
/* Use uppercase name as canonical */
strcpy(canonname, uppername);
}
else if (tzload(uppername, canonname, &tzstate, true) != 0)
{
if (uppername[0] == ':' || !tzparse(uppername, &tzstate, false))
{
/* Unknown timezone. Fail our call instead of loading GMT! */
return NULL;
}
/* For POSIX timezone specs, use uppercase name as canonical */
strcpy(canonname, uppername);
}
/* Save timezone in the cache */
tzp = (pg_tz_cache *) hash_search(timezone_cache,
uppername,
HASH_ENTER,
NULL);
/* hash_search already copied uppername into the hash key */
strcpy(tzp->tz.TZname, canonname);
memcpy(&tzp->tz.state, &tzstate, sizeof(tzstate));
return &tzp->tz;
}
/*
* Load a fixed-GMT-offset timezone.
* This is used for SQL-spec SET TIME ZONE INTERVAL 'foo' cases.
* It's otherwise equivalent to pg_tzset().
*
* The GMT offset is specified in seconds, positive values meaning west of
* Greenwich (ie, POSIX not ISO sign convention). However, we use ISO
* sign convention in the displayable abbreviation for the zone.
*
* Caution: this can fail (return NULL) if the specified offset is outside
* the range allowed by the zic library.
*/
pg_tz *
pg_tzset_offset(long gmtoffset)
{
long absoffset = (gmtoffset < 0) ? -gmtoffset : gmtoffset;
char offsetstr[64];
char tzname[128];
snprintf(offsetstr, sizeof(offsetstr),
"%02ld", absoffset / SECS_PER_HOUR);
absoffset %= SECS_PER_HOUR;
if (absoffset != 0)
{
snprintf(offsetstr + strlen(offsetstr),
sizeof(offsetstr) - strlen(offsetstr),
":%02ld", absoffset / SECS_PER_MINUTE);
absoffset %= SECS_PER_MINUTE;
if (absoffset != 0)
snprintf(offsetstr + strlen(offsetstr),
sizeof(offsetstr) - strlen(offsetstr),
":%02ld", absoffset);
}
if (gmtoffset > 0)
snprintf(tzname, sizeof(tzname), "<-%s>+%s",
offsetstr, offsetstr);
else
snprintf(tzname, sizeof(tzname), "<+%s>-%s",
offsetstr, offsetstr);
return pg_tzset(tzname);
}
/*
* Initialize timezone library
*
* This is called before GUC variable initialization begins. Its purpose
* is to ensure that log_timezone has a valid value before any logging GUC
* variables could become set to values that require elog.c to provide
* timestamps (e.g., log_line_prefix). We may as well initialize
* session_timezone to something valid, too.
*/
void
pg_timezone_initialize(void)
{
/*
* We may not yet know where PGSHAREDIR is (in particular this is true in
* an EXEC_BACKEND subprocess). So use "GMT", which pg_tzset forces to be
* interpreted without reference to the filesystem. This corresponds to
* the bootstrap default for these variables in guc_tables.c, although in
* principle it could be different.
*/
session_timezone = pg_tzset("GMT");
log_timezone = session_timezone;
}
/*
* Functions to enumerate available timezones
*
* Note that pg_tzenumerate_next() will return a pointer into the pg_tzenum
* structure, so the data is only valid up to the next call.
*
* All data is allocated using palloc in the current context.
*/
#define MAX_TZDIR_DEPTH 10
struct pg_tzenum
{
int baselen;
int depth;
DIR *dirdesc[MAX_TZDIR_DEPTH];
char *dirname[MAX_TZDIR_DEPTH];
struct pg_tz tz;
};
/* typedef pg_tzenum is declared in pgtime.h */
pg_tzenum *
pg_tzenumerate_start(void)
{
pg_tzenum *ret = (pg_tzenum *) palloc0(sizeof(pg_tzenum));
char *startdir = pstrdup(pg_TZDIR());
ret->baselen = strlen(startdir) + 1;
ret->depth = 0;
ret->dirname[0] = startdir;
ret->dirdesc[0] = AllocateDir(startdir);
if (!ret->dirdesc[0])
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m", startdir)));
return ret;
}
void
pg_tzenumerate_end(pg_tzenum *dir)
{
while (dir->depth >= 0)
{
FreeDir(dir->dirdesc[dir->depth]);
pfree(dir->dirname[dir->depth]);
dir->depth--;
}
pfree(dir);
}
pg_tz *
pg_tzenumerate_next(pg_tzenum *dir)
{
while (dir->depth >= 0)
{
struct dirent *direntry;
char fullname[MAXPGPATH * 2];
direntry = ReadDir(dir->dirdesc[dir->depth], dir->dirname[dir->depth]);
if (!direntry)
{
/* End of this directory */
FreeDir(dir->dirdesc[dir->depth]);
pfree(dir->dirname[dir->depth]);
dir->depth--;
continue;
}
if (direntry->d_name[0] == '.')
continue;
snprintf(fullname, sizeof(fullname), "%s/%s",
dir->dirname[dir->depth], direntry->d_name);
if (get_dirent_type(fullname, direntry, true, ERROR) == PGFILETYPE_DIR)
{
/* Step into the subdirectory */
if (dir->depth >= MAX_TZDIR_DEPTH - 1)
ereport(ERROR,
(errmsg_internal("timezone directory stack overflow")));
dir->depth++;
dir->dirname[dir->depth] = pstrdup(fullname);
dir->dirdesc[dir->depth] = AllocateDir(fullname);
if (!dir->dirdesc[dir->depth])
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open directory \"%s\": %m",
fullname)));
/* Start over reading in the new directory */
continue;
}
/*
* Load this timezone using tzload() not pg_tzset(), so we don't fill
* the cache. Also, don't ask for the canonical spelling: we already
* know it, and pg_open_tzfile's way of finding it out is pretty
* inefficient.
*/
if (tzload(fullname + dir->baselen, NULL, &dir->tz.state, true) != 0)
{
/* Zone could not be loaded, ignore it */
continue;
}
if (!pg_tz_acceptable(&dir->tz))
{
/* Ignore leap-second zones */
continue;
}
/* OK, return the canonical zone name spelling. */
strlcpy(dir->tz.TZname, fullname + dir->baselen,
sizeof(dir->tz.TZname));
/* Timezone loaded OK. */
return &dir->tz;
}
/* Nothing more found */
return NULL;
}
|