1 files changed, 502 insertions, 0 deletions
diff --git a/src/timezone/pgtz.c b/src/timezone/pgtz.c
new file mode 100644
index 0000000..82f14ee
--- /dev/null
+++ b/src/timezone/pgtz.c
@@ -0,0 +1,502 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgtz.c
+ *	  Timezone Library Integration Functions
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/timezone/pgtz.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <ctype.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <time.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 *name)
+{
+	pg_tz_cache *tzp;
+	struct state tzstate;
+	char		uppername[TZ_STRLEN_MAX + 1];
+	char		canonname[TZ_STRLEN_MAX + 1];
+	char	   *p;
+
+	if (strlen(name) > 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 (*name)
+		*p++ = pg_toupper((unsigned char) *name++);
+	*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.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];
+		struct stat statbuf;
+
+		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 (stat(fullname, &statbuf) != 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not stat \"%s\": %m", fullname)));
+
+		if (S_ISDIR(statbuf.st_mode))
+		{
+			/* 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;
+}