1 #include <u.h>
2 #include <libc.h>
3 
4 /*
5  * Access local time entries of zoneinfo files.
6  * Formats 0 and 2 are supported, and 4-byte timestamps
7  *
8  * Copyright © 2008 M. Teichgräber
9  * Contributed under the MIT license used in the rest of the distribution.
10  */
11 #include "zoneinfo.h"
12 
13 static
14 struct Zoneinfo
15 {
16 	int	timecnt;		/* # of transition times */
17 	int	typecnt;		/* # of local time types */
18 	int	charcnt;		/* # of characters of time zone abbreviation strings */
19 
20 	uchar *ptime;
21 	uchar *ptype;
22 	uchar *ptt;
23 	uchar *pzone;
24 } z;
25 
26 static uchar *tzdata;
27 
28 static
29 uchar*
30 readtzfile(char *file)
31 {
32 	uchar *p;
33 	int fd;
34 	Dir *d;
35 
36 	fd = open(file, OREAD);
37 	if (fd<0)
38 		return nil;
39 	d = dirfstat(fd);
40 	if (d==nil)
41 		return nil;
42 	p = malloc(d->length);
43 	if (p!=nil)
44 		readn(fd, p, d->length);
45 	free(d);
46 	close(fd);
47 	return p;
48 }
49 static char *zonefile;
50 void
51 tzfile(char *f)
52 {
53 	if (tzdata!=nil) {
54 		free(tzdata);
55 		tzdata = nil;
56 	}
57 	z.timecnt = 0;
58 	zonefile = f;
59 }
60 
61 static
62 long
63 get4(uchar *p)
64 {
65 	return (p[0]<<24)+(p[1]<<16)+(p[2]<<8)+p[3];
66 }
67 
68 enum {
69 	TTinfosz	= 4+1+1,
70 };
71 
72 static
73 int
74 parsehead(void)
75 {
76 	uchar *p;
77 	int	ver;
78 
79 	ver = tzdata[4];
80 	if (ver!=0)
81 	if (ver!='2')
82 		return -1;
83 
84 	p = tzdata + 4 + 1 + 15;
85 
86 	z.timecnt = get4(p+3*4);
87 	z.typecnt = get4(p+4*4);
88 	if (z.typecnt==0)
89 		return -1;
90 	z.charcnt = get4(p+5*4);
91 	z.ptime = p+6*4;
92 	z.ptype = z.ptime + z.timecnt*4;
93 	z.ptt = z.ptype + z.timecnt;
94 	z.pzone = z.ptt + z.typecnt*TTinfosz;
95 	return 0;
96 }
97 
98 static
99 void
100 ttinfo(Tinfo *ti, int tti)
101 {
102 	uchar *p;
103 	int	i;
104 
105 	i = z.ptype[tti];
106 	assert(i<z.typecnt);
107 	p = z.ptt + i*TTinfosz;
108 	ti->tzoff = get4(p);
109 	ti->dlflag = p[4];
110 	assert(p[5]<z.charcnt);
111 	ti->zone = (char*)z.pzone + p[5];
112 }
113 
114 static
115 void
116 readtimezone(void)
117 {
118 	char *tmp;
119 
120 	z.timecnt = 0;
121 	if(zonefile==nil) {
122 		if ((tmp=getenv("timezone"))!=nil) {
123 			tzdata = readtzfile(tmp);
124 			free(tmp);
125 			goto havedata;
126 		}
127 		zonefile = "/etc/localtime";
128 	}
129 	tzdata = readtzfile(zonefile);
130 	if (tzdata==nil)
131 		return;
132 
133 havedata:
134 	if (strncmp("TZif", (char*)tzdata, 4)!=0)
135 		goto errfree;
136 
137 	if (parsehead()==-1) {
138 	errfree:
139 		free(tzdata);
140 		tzdata = nil;
141 		z.timecnt = 0;
142 		return;
143 	}
144 }
145 
146 static
147 tlong
148 gett4(uchar *p)
149 {
150 	long l;
151 
152 	l = get4(p);
153 	if (l<0)
154 		return 0;
155 	return l;
156 }
157 int
158 zonetinfo(Tinfo *ti, int i)
159 {
160 	if (tzdata==nil)
161 		readtimezone();
162 	if (i<0 || i>=z.timecnt)
163 		return -1;
164 	ti->t = gett4(z.ptime + 4*i);
165 	ttinfo(ti, i);
166 	return i;
167 }
168 
169 int
170 zonelookuptinfo(Tinfo *ti, tlong t)
171 {
172 	uchar *p;
173 	int	i;
174 	tlong	oldtt, tt;
175 
176 	if (tzdata==nil)
177 		readtimezone();
178 	oldtt = 0;
179 	p = z.ptime;
180 	for (i=0; i<z.timecnt; i++) {
181 		tt = gett4(p);
182 		if (t<tt)
183 			break;
184 		oldtt = tt;
185 		p += 4;
186 	}
187 	if (i>0) {
188 		ttinfo(ti, i-1);
189 		ti->t = oldtt;
190 //		fprint(2, "t:%ld off:%d dflag:%d %s\n", (long)ti->t, ti->tzoff, ti->dlflag, ti->zone);
191 		return i-1;
192 	}
193 	return -1;
194 }
195 
196 void
197 zonedump(int fd)
198 {
199 	int	i;
200 	uchar *p;
201 	tlong t;
202 	Tinfo ti;
203 
204 	if (tzdata==nil)
205 		readtimezone();
206 	p = z.ptime;
207 	for (i=0; i<z.timecnt; i++) {
208 		t = gett4(p);
209 		ttinfo(&ti, i);
210 		fprint(fd, "%ld\t%d\t%d\t%s\n", (long)t, ti.tzoff, ti.dlflag, ti.zone);
211 		p += 4;
212 	}
213 }