time-tz 2.0.0

Implementation of tz database (IANA) for the time Rust crate.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135

// Copyright (c) 2022, Yuri6037
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
// * Neither the name of time-tz nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//! Support for getting time zone information from the target system.
//! 
//! Currently only supported for Windows, Unix, and WASM targets.

use crate::timezones::get_by_name;
use crate::Tz;
use thiserror::Error;

#[cfg(target_family = "wasm")]
use js_sys::{ Intl, Reflect, Array, Object };
#[cfg(target_family = "wasm")]
use wasm_bindgen::JsValue;

#[derive(Debug, Error)]
pub enum Error {
    /// An IO error has occurred.
    #[error("io error: {0}")]
    Io(std::io::Error),

    /// An OS level error has occurred (can only happen on Windows).
    #[error("low-level os error")]
    Os,

    /// The timezone is undetermined (means the timezone is not defined or that the system
    /// itself doesn't know the its timezone).
    #[error("undefined timezone")]
    Undetermined,

    /// Somehow the read timezone name contains non unicode...
    #[error("timezone name is not unicode")]
    Unicode,

    /// The timezone doesn't exist in the crate's database.
    #[error("unknown timezone name")]
    Unknown,
    
    /// The target platform is not supported. Windows, Unix, and WASM targets are the only supported for the system feature at this moment.
    #[error("unsupported platform")]
    Unsupported,
}

/// Gets the current timezone from the system.
/// 
/// Currently only supported for Windows, Unix, and WASM targets.
/// 
/// # Errors
/// Returns an [Error](enum@Error) if the timezone cannot be determined.
pub fn get_timezone() -> Result<&'static Tz, Error> {
    cfg_if::cfg_if! {
        if #[cfg(unix)] {
            use std::path::Path;
            let path = Path::new("/etc/localtime");
            let realpath = std::fs::read_link(path).map_err(Error::Io)?;
            // The part of the path we're interested in cannot contain non unicode characters.
            if let Some(iana) = realpath.to_str().ok_or(Error::Unicode)?.split("/zoneinfo/").last() {
                let tz = get_by_name(iana).ok_or(Error::Unknown)?;
                Ok(tz)
            } else {
                Err(Error::Undetermined)
            }
        } else if #[cfg(windows)] {
            unsafe {
                use windows_sys::Win32::System::Time::GetDynamicTimeZoneInformation;
                use windows_sys::Win32::System::Time::DYNAMIC_TIME_ZONE_INFORMATION;
                let mut data: DYNAMIC_TIME_ZONE_INFORMATION = std::mem::zeroed();
                let res = GetDynamicTimeZoneInformation(&mut data as _);
                if res > 2 {
                    return Err(Error::Os);
                } else {
                    let win_name_utf16 = &data.TimeZoneKeyName;
                    let mut len: usize = 0;
                    while win_name_utf16[len] != 0x0 {
                        len += 1;
                    }
                    if len == 0 {
                        return Err(Error::Undetermined);
                    }
                    let win_tz = String::from_utf16(&win_name_utf16[..len]).map_err(|_| Error::Unicode)?;
                    let tz = get_by_name(&win_tz).ok_or(Error::Unknown)?;
                    Ok(tz)
                }
            }
        } else if #[cfg(target_family = "wasm")] {
            let options = Intl::DateTimeFormat::new(&Array::new(), &Object::new())
                .resolved_options();

            let tz = Reflect::get(&options, &JsValue::from("timeZone"))
                .map_err(|_| Error::Undetermined)?
                .as_string()
                .ok_or(Error::Unicode)?;

            let tz = get_by_name(&tz).ok_or(Error::Unknown)?;
            Ok(tz)
        } else {
            Err(Error::Unsupported)
        }
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn get_timezone() {
        let tz = super::get_timezone();
        assert!(tz.is_ok());
    }
}