1use std::io::{self, ErrorKind};
2use std::iter;
3use std::num::ParseIntError;
4use std::str::{self, FromStr};
5
6use super::rule::TransitionRule;
7use super::timezone::{LeapSecond, LocalTimeType, TimeZone, Transition};
8use super::Error;
9
10pub(super) fn parse(bytes: &[u8]) -> Result<TimeZone, Error> {
11 let mut cursor = Cursor::new(bytes);
12 let state = State::new(&mut cursor, true)?;
13 let (state, footer) = match state.header.version {
14 Version::V1 => match cursor.is_empty() {
15 true => (state, None),
16 false => {
17 return Err(Error::InvalidTzFile("remaining data after end of TZif v1 data block"))
18 }
19 },
20 Version::V2 | Version::V3 => {
21 let state = State::new(&mut cursor, false)?;
22 (state, Some(cursor.remaining()))
23 }
24 };
25
26 let mut transitions = Vec::with_capacity(state.header.transition_count);
27 for (arr_time, &local_time_type_index) in
28 state.transition_times.chunks_exact(state.time_size).zip(state.transition_types)
29 {
30 let unix_leap_time =
31 state.parse_time(&arr_time[0..state.time_size], state.header.version)?;
32 let local_time_type_index = local_time_type_index as usize;
33 transitions.push(Transition::new(unix_leap_time, local_time_type_index));
34 }
35
36 let mut local_time_types = Vec::with_capacity(state.header.type_count);
37 for arr in state.local_time_types.chunks_exact(6) {
38 let ut_offset = read_be_i32(&arr[..4])?;
39
40 let is_dst = match arr[4] {
41 0 => false,
42 1 => true,
43 _ => return Err(Error::InvalidTzFile("invalid DST indicator")),
44 };
45
46 let char_index = arr[5] as usize;
47 if char_index >= state.header.char_count {
48 return Err(Error::InvalidTzFile("invalid time zone name char index"));
49 }
50
51 let position = match state.names[char_index..].iter().position(|&c| c == b'\0') {
52 Some(position) => position,
53 None => return Err(Error::InvalidTzFile("invalid time zone name char index")),
54 };
55
56 let name = &state.names[char_index..char_index + position];
57 let name = if !name.is_empty() { Some(name) } else { None };
58 local_time_types.push(LocalTimeType::new(ut_offset, is_dst, name)?);
59 }
60
61 let mut leap_seconds = Vec::with_capacity(state.header.leap_count);
62 for arr in state.leap_seconds.chunks_exact(state.time_size + 4) {
63 let unix_leap_time = state.parse_time(&arr[0..state.time_size], state.header.version)?;
64 let correction = read_be_i32(&arr[state.time_size..state.time_size + 4])?;
65 leap_seconds.push(LeapSecond::new(unix_leap_time, correction));
66 }
67
68 let std_walls_iter = state.std_walls.iter().copied().chain(iter::repeat(0));
69 let ut_locals_iter = state.ut_locals.iter().copied().chain(iter::repeat(0));
70 if std_walls_iter.zip(ut_locals_iter).take(state.header.type_count).any(|pair| pair == (0, 1)) {
71 return Err(Error::InvalidTzFile(
72 "invalid couple of standard/wall and UT/local indicators",
73 ));
74 }
75
76 let extra_rule = match footer {
77 Some(footer) => {
78 let footer = str::from_utf8(footer)?;
79 if !(footer.starts_with('\n') && footer.ends_with('\n')) {
80 return Err(Error::InvalidTzFile("invalid footer"));
81 }
82
83 let tz_string = footer.trim_matches(|c: char| c.is_ascii_whitespace());
84 if tz_string.starts_with(':') || tz_string.contains('\0') {
85 return Err(Error::InvalidTzFile("invalid footer"));
86 }
87
88 match tz_string.is_empty() {
89 true => None,
90 false => Some(TransitionRule::from_tz_string(
91 tz_string.as_bytes(),
92 state.header.version == Version::V3,
93 )?),
94 }
95 }
96 None => None,
97 };
98
99 TimeZone::new(transitions, local_time_types, leap_seconds, extra_rule)
100}
101
102/// TZif data blocks
103struct State<'a> {
104 header: Header,
105 /// Time size in bytes
106 time_size: usize,
107 /// Transition times data block
108 transition_times: &'a [u8],
109 /// Transition types data block
110 transition_types: &'a [u8],
111 /// Local time types data block
112 local_time_types: &'a [u8],
113 /// Time zone names data block
114 names: &'a [u8],
115 /// Leap seconds data block
116 leap_seconds: &'a [u8],
117 /// UT/local indicators data block
118 std_walls: &'a [u8],
119 /// Standard/wall indicators data block
120 ut_locals: &'a [u8],
121}
122
123impl<'a> State<'a> {
124 /// Read TZif data blocks
125 fn new(cursor: &mut Cursor<'a>, first: bool) -> Result<Self, Error> {
126 let header = Header::new(cursor)?;
127 let time_size = match first {
128 true => 4, // We always parse V1 first
129 false => 8,
130 };
131
132 Ok(Self {
133 time_size,
134 transition_times: cursor.read_exact(header.transition_count * time_size)?,
135 transition_types: cursor.read_exact(header.transition_count)?,
136 local_time_types: cursor.read_exact(header.type_count * 6)?,
137 names: cursor.read_exact(header.char_count)?,
138 leap_seconds: cursor.read_exact(header.leap_count * (time_size + 4))?,
139 std_walls: cursor.read_exact(header.std_wall_count)?,
140 ut_locals: cursor.read_exact(header.ut_local_count)?,
141 header,
142 })
143 }
144
145 /// Parse time values
146 fn parse_time(&self, arr: &[u8], version: Version) -> Result<i64, Error> {
147 match version {
148 Version::V1 => Ok(read_be_i32(&arr[..4])?.into()),
149 Version::V2 | Version::V3 => read_be_i64(arr),
150 }
151 }
152}
153
154/// TZif header
155#[derive(Debug)]
156struct Header {
157 /// TZif version
158 version: Version,
159 /// Number of UT/local indicators
160 ut_local_count: usize,
161 /// Number of standard/wall indicators
162 std_wall_count: usize,
163 /// Number of leap-second records
164 leap_count: usize,
165 /// Number of transition times
166 transition_count: usize,
167 /// Number of local time type records
168 type_count: usize,
169 /// Number of time zone names bytes
170 char_count: usize,
171}
172
173impl Header {
174 fn new(cursor: &mut Cursor) -> Result<Self, Error> {
175 let magic = cursor.read_exact(4)?;
176 if magic != *b"TZif" {
177 return Err(Error::InvalidTzFile("invalid magic number"));
178 }
179
180 let version = match cursor.read_exact(1)? {
181 [0x00] => Version::V1,
182 [0x32] => Version::V2,
183 [0x33] => Version::V3,
184 _ => return Err(Error::UnsupportedTzFile("unsupported TZif version")),
185 };
186
187 cursor.read_exact(15)?;
188 let ut_local_count = cursor.read_be_u32()?;
189 let std_wall_count = cursor.read_be_u32()?;
190 let leap_count = cursor.read_be_u32()?;
191 let transition_count = cursor.read_be_u32()?;
192 let type_count = cursor.read_be_u32()?;
193 let char_count = cursor.read_be_u32()?;
194
195 if !(type_count != 0
196 && char_count != 0
197 && (ut_local_count == 0 || ut_local_count == type_count)
198 && (std_wall_count == 0 || std_wall_count == type_count))
199 {
200 return Err(Error::InvalidTzFile("invalid header"));
201 }
202
203 Ok(Self {
204 version,
205 ut_local_count: ut_local_count as usize,
206 std_wall_count: std_wall_count as usize,
207 leap_count: leap_count as usize,
208 transition_count: transition_count as usize,
209 type_count: type_count as usize,
210 char_count: char_count as usize,
211 })
212 }
213}
214
215/// A `Cursor` contains a slice of a buffer and a read count.
216#[derive(Debug, Eq, PartialEq)]
217pub(crate) struct Cursor<'a> {
218 /// Slice representing the remaining data to be read
219 remaining: &'a [u8],
220 /// Number of already read bytes
221 read_count: usize,
222}
223
224impl<'a> Cursor<'a> {
225 /// Construct a new `Cursor` from remaining data
226 pub(crate) const fn new(remaining: &'a [u8]) -> Self {
227 Self { remaining, read_count: 0 }
228 }
229
230 pub(crate) fn peek(&self) -> Option<&u8> {
231 self.remaining().first()
232 }
233
234 /// Returns remaining data
235 pub(crate) const fn remaining(&self) -> &'a [u8] {
236 self.remaining
237 }
238
239 /// Returns `true` if data is remaining
240 pub(crate) const fn is_empty(&self) -> bool {
241 self.remaining.is_empty()
242 }
243
244 pub(crate) fn read_be_u32(&mut self) -> Result<u32, Error> {
245 let mut buf = [0; 4];
246 buf.copy_from_slice(self.read_exact(4)?);
247 Ok(u32::from_be_bytes(buf))
248 }
249
250 /// Read exactly `count` bytes, reducing remaining data and incrementing read count
251 pub(crate) fn read_exact(&mut self, count: usize) -> Result<&'a [u8], io::Error> {
252 match (self.remaining.get(..count), self.remaining.get(count..)) {
253 (Some(result), Some(remaining)) => {
254 self.remaining = remaining;
255 self.read_count += count;
256 Ok(result)
257 }
258 _ => Err(io::Error::from(ErrorKind::UnexpectedEof)),
259 }
260 }
261
262 /// Read bytes and compare them to the provided tag
263 pub(crate) fn read_tag(&mut self, tag: &[u8]) -> Result<(), io::Error> {
264 if self.read_exact(tag.len())? == tag {
265 Ok(())
266 } else {
267 Err(io::Error::from(ErrorKind::InvalidData))
268 }
269 }
270
271 /// Read bytes if the remaining data is prefixed by the provided tag
272 pub(crate) fn read_optional_tag(&mut self, tag: &[u8]) -> Result<bool, io::Error> {
273 if self.remaining.starts_with(tag) {
274 self.read_exact(tag.len())?;
275 Ok(true)
276 } else {
277 Ok(false)
278 }
279 }
280
281 /// Read bytes as long as the provided predicate is true
282 pub(crate) fn read_while<F: Fn(&u8) -> bool>(&mut self, f: F) -> Result<&'a [u8], io::Error> {
283 match self.remaining.iter().position(|x| !f(x)) {
284 None => self.read_exact(self.remaining.len()),
285 Some(position) => self.read_exact(position),
286 }
287 }
288
289 // Parse an integer out of the ASCII digits
290 pub(crate) fn read_int<T: FromStr<Err = ParseIntError>>(&mut self) -> Result<T, Error> {
291 let bytes = self.read_while(u8::is_ascii_digit)?;
292 Ok(str::from_utf8(bytes)?.parse()?)
293 }
294
295 /// Read bytes until the provided predicate is true
296 pub(crate) fn read_until<F: Fn(&u8) -> bool>(&mut self, f: F) -> Result<&'a [u8], io::Error> {
297 match self.remaining.iter().position(f) {
298 None => self.read_exact(self.remaining.len()),
299 Some(position) => self.read_exact(position),
300 }
301 }
302}
303
304pub(crate) fn read_be_i32(bytes: &[u8]) -> Result<i32, Error> {
305 if bytes.len() != 4 {
306 return Err(Error::InvalidSlice("too short for i32"));
307 }
308
309 let mut buf: [u8; 4] = [0; 4];
310 buf.copy_from_slice(src:bytes);
311 Ok(i32::from_be_bytes(buf))
312}
313
314pub(crate) fn read_be_i64(bytes: &[u8]) -> Result<i64, Error> {
315 if bytes.len() != 8 {
316 return Err(Error::InvalidSlice("too short for i64"));
317 }
318
319 let mut buf: [u8; 8] = [0; 8];
320 buf.copy_from_slice(src:bytes);
321 Ok(i64::from_be_bytes(buf))
322}
323
324/// TZif version
325#[derive(Debug, Copy, Clone, Eq, PartialEq)]
326enum Version {
327 /// Version 1
328 V1,
329 /// Version 2
330 V2,
331 /// Version 3
332 V3,
333}
334