Add support for use of the system timezone database, rather
than embedding a copy.  Discussed upstream but was not desired.

History:
r4: added "System/Localtime" tzname which uses /etc/localtime
r3: fix a crash if /usr/share/zoneinfo doesn't exist (Raphael Geissert)
r2: add filesystem trawl to set up name alias index
r1: initial revision

--- php-5.2.6/ext/date/lib/parse_tz.c.systzdata
+++ php-5.2.6/ext/date/lib/parse_tz.c
@@ -20,6 +20,16 @@
 
 #include "timelib.h"
 
+#ifdef HAVE_SYSTEM_TZDATA
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "php_scandir.h"
+#endif
+
 #include <stdio.h>
 
 #ifdef HAVE_STRING_H
@@ -27,7 +41,10 @@
 #else
 #include <strings.h>
 #endif
+
+#ifndef HAVE_SYSTEM_TZDATA
 #include "timezonedb.h"
+#endif
 
 #ifdef WORDS_BIGENDIAN
 #define timelib_conv_int(l) (l)
@@ -192,6 +219,211 @@ void timelib_dump_tzinfo(timelib_tzinfo 
 	}
 }
 
+#ifdef HAVE_SYSTEM_TZDATA
+
+#ifdef HAVE_SYSTEM_TZDATA_PREFIX
+#define ZONEINFO_PREFIX HAVE_SYSTEM_TZDATA_PREFIX
+#else
+#define ZONEINFO_PREFIX "/usr/share/zoneinfo"
+#endif
+
+#define SYSTEM_TZFILE "/etc/localtime"
+
+static const timelib_tzdb *timezonedb_system = NULL;
+
+/* Filter out some non-tzdata files and the posix/right databases, if
+ * present. */
+static int index_filter(const struct dirent *ent)
+{
+	return strcmp(ent->d_name, ".") != 0
+		&& strcmp(ent->d_name, "..") != 0
+		&& strcmp(ent->d_name, "posix") != 0
+		&& strcmp(ent->d_name, "posixrules") != 0
+		&& strcmp(ent->d_name, "right") != 0
+		&& strstr(ent->d_name, ".tab") == NULL;
+}
+
+/* Create the zone identifier index by trawling the filesystem. */
+static void create_zone_index(timelib_tzdb *db)
+{
+	size_t dirstack_size,  dirstack_top;
+	size_t index_size, index_next;
+	timelib_tzdb_index_entry *db_index;
+	char **dirstack;
+
+	/* LIFO stack to hold directory entries to scan; each slot is a
+	 * directory name relative to the zoneinfo prefix. */
+	dirstack_size = 32;
+	dirstack = malloc(dirstack_size * sizeof *dirstack);
+	dirstack_top = 1;
+	dirstack[0] = strdup("");
+	
+	/* Index array. */
+	index_size = 64;
+	db_index = malloc(index_size * sizeof *db_index);
+	index_next = 0;
+
+	do {
+		struct dirent **ents;
+		char name[PATH_MAX], *top;
+		int count;
+
+		/* Pop the top stack entry, and iterate through its contents. */
+		top = dirstack[--dirstack_top];
+		snprintf(name, sizeof name, ZONEINFO_PREFIX "/%s", top);
+
+		count = php_scandir(name, &ents, index_filter, php_alphasort);
+
+		while (count > 0) {
+			struct stat st;
+			const char *leaf = ents[count - 1]->d_name;
+
+			snprintf(name, sizeof name, ZONEINFO_PREFIX "/%s/%s", 
+				 top, leaf);
+			
+			if (strlen(name) && stat(name, &st) == 0) {
+				/* Name, relative to the zoneinfo prefix. */
+				const char *root = top;
+
+				if (root[0] == '/') root++;
+
+				snprintf(name, sizeof name, "%s%s%s", root, 
+					 *root ? "/": "", leaf);
+
+				if (S_ISDIR(st.st_mode)) {
+					if (dirstack_top == dirstack_size) {
+						dirstack_size *= 2;
+						dirstack = realloc(dirstack, 
+								   dirstack_size * sizeof *dirstack);
+					}
+					dirstack[dirstack_top++] = strdup(name);
+				}
+				else {
+					if (index_next == index_size) {
+						index_size *= 2;
+						db_index = realloc(db_index,
+								   index_size * sizeof *db_index);
+					}
+
+					db_index[index_next].id = strdup(name);
+					db_index[index_next++].pos = 0;
+				}
+			}
+
+			free(ents[--count]);
+		}
+		
+		if (count != -1) free(ents);
+		free(top);
+	} while (dirstack_top);
+
+	db->index = db_index;
+	db->index_size = index_next;
+
+	free(dirstack);
+}
+
+/* Return the mmap()ed tzfile if found, else NULL.  On success, the
+ * length of the mapped data is placed in *length. */
+static char *map_tzfile(const char *timezone, size_t *length)
+{
+	char fname[PATH_MAX];
+	const char *fn;
+	struct stat st;
+	char *p;
+	int fd;
+	
+	if (strcmp(timezone, TIMELIB_SYSTEM_TZID) == 0) {
+		fn = SYSTEM_TZFILE;
+	}
+	else {
+		if (strstr(timezone, "..") != NULL) {
+			return NULL;
+		}
+	    
+		snprintf(fname, sizeof fname, ZONEINFO_PREFIX "/%s", timezone);
+		fn = fname;
+	}
+	
+	fd = open(fn, O_RDONLY);
+	if (fd == -1) {
+		return NULL;
+	} else if (fstat(fd, &st) != 0 || st.st_size < 21) {
+		close(fd);
+		return NULL;
+	}
+
+	*length = st.st_size;
+	p = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
+	close(fd);
+	
+	return p != MAP_FAILED ? p : NULL;
+}
+
+const timelib_tzdb *timelib_builtin_db(void)
+{
+	if (timezonedb_system == NULL) {
+		timelib_tzdb *tmp = malloc(sizeof *tmp);
+
+		tmp->version = "0.system";
+		tmp->data = NULL;
+		create_zone_index(tmp);
+		timezonedb_system = tmp;
+	}
+			
+	return timezonedb_system;
+}
+
+const timelib_tzdb_index_entry *timelib_timezone_builtin_identifiers_list(int *count)
+{
+	*count = timezonedb_system->index_size;
+	return timezonedb_system->index;
+}
+
+int timelib_timezone_id_is_valid(char *timezone, const timelib_tzdb *tzdb)
+{
+	char fname[PATH_MAX];
+	const char *fn;
+
+	if (strcmp(timezone, TIMELIB_SYSTEM_TZID) == 0) {
+		fn = SYSTEM_TZFILE;
+	}
+	else {
+		if (strstr(timezone, "..") != NULL) {
+			return 0;
+		}
+		
+		snprintf(fname, sizeof fname, ZONEINFO_PREFIX "/%s", timezone);
+		fn = fname;
+	}
+
+	return access(fn, R_OK) == 0 ? 1 : 0;
+}
+
+timelib_tzinfo *timelib_parse_tzfile(char *timezone, const timelib_tzdb *tzdb)
+{
+	char *tzf, *orig;
+	timelib_tzinfo *tmp;
+	size_t len;
+
+	orig = map_tzfile(timezone, &len);
+	if (orig == NULL) {
+		return NULL;
+	}
+
+	tmp = timelib_tzinfo_ctor(timezone);
+
+	tzf = orig + 20;
+	read_header(&tzf, tmp);
+	read_transistions(&tzf, tmp);
+	read_types(&tzf, tmp);
+
+	munmap(orig, len);
+
+	return tmp;
+}
+#else /* !HAVE_SYSTEM_TZDATA */
+
 static int tz_search(char *timezone, int left, int right, const timelib_tzdb *tzdb)
 {
 	int mid, cmp;
@@ -261,6 +497,7 @@ timelib_tzinfo *timelib_parse_tzfile(cha
 
 	return tmp;
 }
+#endif
 
 static ttinfo* fetch_timezone_offset(timelib_tzinfo *tz, timelib_sll ts, timelib_sll *transition_time)
 {
--- php-5.2.6/ext/date/lib/timelib.h.systzdata
+++ php-5.2.6/ext/date/lib/timelib.h
@@ -28,6 +31,10 @@
 
 #define TIMELIB_SPECIAL_WEEKDAY  0x01
 
+#ifdef HAVE_SYSTEM_TZDATA
+#define TIMELIB_SYSTEM_TZID "System/Localtime"
+#endif
+
 #ifndef LONG_MAX
 #define LONG_MAX 2147483647L
 #endif
--- php-5.2.6/ext/date/lib/timelib.m4.systzdata
+++ php-5.2.6/ext/date/lib/timelib.m4
@@ -78,3 +78,17 @@ stdlib.h
 
 dnl Check for strtoll, atoll
 AC_CHECK_FUNCS(strtoll atoll strftime)
+
+PHP_ARG_WITH(system-tzdata, for use of system timezone data,
+[  --with-system-tzdata[=DIR]      to specify use of system timezone data],
+no, no)
+
+if test "$PHP_SYSTEM_TZDATA" != "no"; then
+   AC_DEFINE(HAVE_SYSTEM_TZDATA, 1, [Define if system timezone data is used])
+
+   if test "$PHP_SYSTEM_TZDATA" != "yes"; then
+      AC_DEFINE_UNQUOTED(HAVE_SYSTEM_TZDATA_PREFIX, "$PHP_SYSTEM_TZDATA",
+                         [Define for location of system timezone data])
+   fi
+fi
+
--- php-5.2.6/ext/date/php_date.c.systzdata
+++ php-5.2.6/ext/date/php_date.c
@@ -571,6 +584,11 @@ static char* guess_timezone(const timeli
 	if (DATEG(default_timezone) && (strlen(DATEG(default_timezone)) > 0) && timelib_timezone_id_is_valid(DATEG(default_timezone), tzdb)) {
 		return DATEG(default_timezone);
 	}
+#ifdef TIMELIB_SYSTEM_TZID
+	if (timelib_timezone_id_is_valid(TIMELIB_SYSTEM_TZID, tzdb)) {
+		return TIMELIB_SYSTEM_TZID;
+	}
+#endif
 #if HAVE_TM_ZONE
 	/* Try to guess timezone from system information */
 	{