lib9: rewrite date routines to use /usr/share/zoneinfo directly

src/lib9/zoneinfo.c

@@ -0,0 +1,215 @@
+#include <u.h>
+#include <libc.h>
+
+/*
+ * Access local time entries of zoneinfo files.
+ * Formats 0 and 2 are supported, and 4-byte timestamps
+ * 
+ * Copyright © 2008 M. Teichgräber
+ * Contributed under the terms of the Lucent Public License 1.02.
+ */
+#include "zoneinfo.h"
+
+static
+struct Zoneinfo
+{
+	int	timecnt;		/* # of transition times */
+	int	typecnt;		/* # of local time types */
+	int	charcnt;		/* # of characters of time zone abbreviation strings */
+
+	uchar *ptime;
+	uchar *ptype;
+	uchar *ptt;
+	uchar *pzone;
+} z;
+
+static uchar *tzdata;
+
+static
+uchar*
+readtzfile(char *file)
+{
+	uchar *p;
+	int fd;
+	Dir *d;
+
+	fd = open(file, OREAD);
+	if (fd<0)
+		return nil;
+        d = dirfstat(fd);
+	if (d==nil)
+		return nil;
+	p = malloc(d->length);
+	if (p!=nil)
+		readn(fd, p, d->length);
+	free(d);
+	close(fd);
+	return p;
+}
+static char *zonefile;
+void
+tzfile(char *f)
+{
+	if (tzdata!=nil) {
+		free(tzdata);
+		tzdata = nil;
+	}
+	z.timecnt = 0;
+	zonefile = f;
+}
+
+static
+long
+get4(uchar *p)
+{
+	return (p[0]<<24)+(p[1]<<16)+(p[2]<<8)+p[3];
+}
+
+enum {
+	TTinfosz	= 4+1+1,
+};
+
+static
+int
+parsehead(void)
+{
+	uchar *p;
+	int	ver;
+
+	ver = tzdata[4];
+	if (ver!=0)
+	if (ver!='2')
+		return -1;
+
+	p = tzdata + 4 + 1 + 15;
+
+	z.timecnt = get4(p+3*4);
+	z.typecnt = get4(p+4*4);
+	if (z.typecnt==0)
+		return -1;
+	z.charcnt = get4(p+5*4);
+	z.ptime = p+6*4;
+	z.ptype = z.ptime + z.timecnt*4;
+	z.ptt = z.ptype + z.timecnt;
+	z.pzone = z.ptt + z.typecnt*TTinfosz;
+	return 0;
+}
+
+static
+void
+ttinfo(Tinfo *ti, int tti)
+{
+	uchar *p;
+	int	i;
+
+	i = z.ptype[tti];
+	assert(i<z.typecnt);
+	p = z.ptt + i*TTinfosz;
+	ti->tzoff = get4(p);
+	ti->dlflag = p[4];
+	assert(p[5]<z.charcnt);
+	ti->zone = (char*)z.pzone + p[5];
+}
+
+static
+void
+readtimezone(void)
+{
+	char *tmp;
+
+	z.timecnt = 0;
+	switch (zonefile==nil) {
+	default:
+		if ((tmp=getenv("timezone"))!=nil) {
+			tzdata = readtzfile(tmp);
+			free(tmp);
+			break;
+		}
+		zonefile = "/etc/localtime";
+		/* fall through */
+	case 0:
+		tzdata = readtzfile(zonefile);
+	}
+	if (tzdata==nil)
+		return;
+
+	if (strncmp("TZif", (char*)tzdata, 4)!=0)
+		goto errfree;
+
+	if (parsehead()==-1) {
+	errfree:
+		free(tzdata);
+		tzdata = nil;
+		z.timecnt = 0;
+		return;
+	}
+}
+
+static
+tlong
+gett4(uchar *p)
+{
+	long l;
+
+	l = get4(p);
+	if (l<0)
+		return 0;
+	return l;
+}
+int
+zonetinfo(Tinfo *ti, int i)
+{
+	if (tzdata==nil)
+		readtimezone();
+	if (i<0 || i>=z.timecnt)
+		return -1;
+	ti->t = gett4(z.ptime + 4*i);
+	ttinfo(ti, i);
+	return i;
+}
+
+int
+zonelookuptinfo(Tinfo *ti, tlong t)
+{
+	uchar *p;
+	int	i;
+	tlong	oldtt, tt;
+
+	if (tzdata==nil)
+		readtimezone();
+	oldtt = 0;
+	p = z.ptime;
+	for (i=0; i<z.timecnt; i++) {
+		tt = gett4(p);
+		if (t<tt)
+			break;
+		oldtt = tt;
+		p += 4;
+	}
+	if (i>0) {
+		ttinfo(ti, i-1);
+		ti->t = oldtt;
+//		fprint(2, "t:%ld off:%d dflag:%d %s\n", (long)ti->t, ti->tzoff, ti->dlflag, ti->zone);
+		return i-1;
+	}
+	return -1;
+}
+
+void
+zonedump(int fd)
+{
+	int	i;
+	uchar *p;
+	tlong t;
+	Tinfo ti;
+
+	if (tzdata==nil)
+		readtimezone();
+	p = z.ptime;
+	for (i=0; i<z.timecnt; i++) {
+		t = gett4(p);
+		ttinfo(&ti, i);
+		fprint(fd, "%ld\t%d\t%d\t%s\n", (long)t, ti.tzoff, ti.dlflag, ti.zone);
+		p += 4;
+	}
+}