Add timezone host functions.

Cargo.toml

@@ -319,6 +319,8 @@ humantime = "2.0.0"
 postcard = { version = "1.0.8", default-features = false, features = ['alloc'] }
 criterion = { version = "0.5.0", default-features = false, features = ["html_reports", "rayon"] }
 rustc-hash = "1.1.0"
+chrono = "0.4.26"
+chrono-tz = "0.8.3"
 
 # =============================================================================
 #

crates/wasi-http/wit/deps/cli/imports.wit

@@ -1,7 +1,7 @@
 package wasi:cli@0.2.0;
 
 world imports {
-  include wasi:clocks/imports@0.2.0;
+  include wasi:clocks/imports@0.2.1;
   include wasi:filesystem/imports@0.2.0;
   include wasi:sockets/imports@0.2.0;
   include wasi:random/imports@0.2.0;

crates/wasi-http/wit/deps/clocks/monotonic-clock.wit

@@ -1,4 +1,4 @@
-package wasi:clocks@0.2.0;
+package wasi:clocks@0.2.1;
 /// WASI Monotonic Clock is a clock API intended to let users measure elapsed
 /// time.
 ///

crates/wasi-http/wit/deps/clocks/timezone.wit

@@ -0,0 +1,50 @@
+package wasi:clocks@0.2.1;
+
+interface timezone {
+    use wall-clock.{datetime};
+
+    /// Return information needed to display the given `datetime`. This includes
+    /// the UTC offset, the time zone name, and a flag indicating whether
+    /// daylight saving time is active.
+    ///
+    /// If the timezone cannot be determined for the given `datetime`, return a
+    /// `timezone-display` for `UTC` with a `utc-offset` of 0 and no daylight
+    /// saving time.
+    display: func(when: datetime) -> timezone-display;
+
+    /// The same as `display`, but only return the UTC offset.
+    utc-offset: func(when: datetime) -> s32;
+
+    /// Information useful for displaying the timezone of a specific `datetime`.
+    ///
+    /// This information may vary within a single `timezone` to reflect daylight
+    /// saving time adjustments.
+    record timezone-display {
+        /// The number of seconds difference between UTC time and the local
+        /// time of the timezone.
+        ///
+        /// The returned value will always be less than 86400 which is the
+        /// number of seconds in a day (24*60*60).
+        ///
+        /// In implementations that do not expose an actual time zone, this
+        /// should return 0.
+        utc-offset: s32,
+
+        /// The abbreviated name of the timezone to display to a user. The name
+        /// `UTC` indicates Coordinated Universal Time. Otherwise, this should
+        /// reference local standards for the name of the time zone.
+        ///
+        /// In implementations that do not expose an actual time zone, this
+        /// should be the string `UTC`.
+        ///
+        /// In time zones that do not have an applicable name, a formatted
+        /// representation of the UTC offset may be returned, such as `-04:00`.
+        name: string,
+
+        /// Whether daylight saving time is active.
+        ///
+        /// In implementations that do not expose an actual time zone, this
+        /// should return false.
+        in-daylight-saving-time: bool,
+    }
+}

crates/wasi-http/wit/deps/clocks/wall-clock.wit

@@ -1,4 +1,4 @@
-package wasi:clocks@0.2.0;
+package wasi:clocks@0.2.1;
 /// WASI Wall Clock is a clock API intended to let users query the current
 /// time. The name "wall" makes an analogy to a "clock on the wall", which
 /// is not necessarily monotonic as it may be reset.

crates/wasi-http/wit/deps/clocks/world.wit

@@ -1,6 +1,7 @@
-package wasi:clocks@0.2.0;
+package wasi:clocks@0.2.1;
 
 world imports {
     import monotonic-clock;
     import wall-clock;
+    import timezone;
 }

crates/wasi-http/wit/deps/filesystem/types.wit

@@ -25,7 +25,7 @@ package wasi:[email protected];
 /// [WASI filesystem path resolution]: https://github.com/WebAssembly/wasi-filesystem/blob/main/path-resolution.md
 interface types {
     use wasi:io/streams@0.2.0.{input-stream, output-stream, error};
-    use wasi:clocks/wall-clock@0.2.0.{datetime};
+    use wasi:clocks/wall-clock@0.2.1.{datetime};
 
     /// File size or length of a region within a file.
     type filesize = u64;

crates/wasi-http/wit/deps/http/proxy.wit

@@ -6,7 +6,7 @@ package wasi:[email protected];
 /// outgoing HTTP requests.
 world proxy {
   /// HTTP proxies have access to time and randomness.
-  include wasi:clocks/imports@0.2.0;
+  include wasi:clocks/imports@0.2.1;
   import wasi:random/random@0.2.0;
 
   /// Proxies have standard output and error streams which are expected to

crates/wasi-http/wit/deps/http/types.wit

@@ -2,7 +2,7 @@
 /// HTTP Requests and Responses, both incoming and outgoing, as well as
 /// their headers, trailers, and bodies.
 interface types {
-  use wasi:clocks/monotonic-clock@0.2.0.{duration};
+  use wasi:clocks/monotonic-clock@0.2.1.{duration};
   use wasi:io/streams@0.2.0.{input-stream, output-stream};
   use wasi:io/error@0.2.0.{error as io-error};
   use wasi:io/poll@0.2.0.{pollable};

crates/wasi-http/wit/deps/sockets/tcp.wit

@@ -2,7 +2,7 @@
 interface tcp {
     use wasi:io/streams@0.2.0.{input-stream, output-stream};
     use wasi:io/poll@0.2.0.{pollable};
-    use wasi:clocks/monotonic-clock@0.2.0.{duration};
+    use wasi:clocks/monotonic-clock@0.2.1.{duration};
     use network.{network, error-code, ip-socket-address, ip-address-family};
 
     enum shutdown-type {

crates/wasi/Cargo.toml

@@ -27,6 +27,8 @@ cap-rand = { workspace = true }
 cap-fs-ext = { workspace = true }
 cap-net-ext = { workspace = true }
 cap-time-ext = { workspace = true }
+chrono = { workspace = true }
+chrono-tz = { workspace = true }
 io-lifetimes = { workspace = true }
 fs-set-times = { workspace = true }
 bitflags = { workspace = true }

crates/wasi/src/clocks.rs

@@ -1,4 +1,5 @@
 pub mod host;
+use crate::bindings::clocks::timezone::TimezoneDisplay;
 use cap_std::time::Duration;
 
 pub trait HostWallClock: Send {
@@ -10,3 +11,8 @@ pub trait HostMonotonicClock: Send {
     fn resolution(&self) -> u64;
     fn now(&self) -> u64;
 }
+
+pub trait HostTimezone: Send {
+    fn display(&self, datetime: Duration) -> TimezoneDisplay;
+    fn utc_offset(&self, datetime: Duration) -> i32;
+}

crates/wasi/src/clocks/host.rs

@@ -1,7 +1,10 @@
-use super::{HostMonotonicClock, HostWallClock};
+use super::{HostMonotonicClock, HostTimezone, HostWallClock};
+use crate::bindings::clocks::timezone::TimezoneDisplay;
 use cap_std::time::{Duration, Instant, SystemClock};
 use cap_std::{ambient_authority, AmbientAuthority};
 use cap_time_ext::{MonotonicClockExt, SystemClockExt};
+use chrono::{NaiveDateTime, TimeZone};
+use chrono_tz::{OffsetComponents, Tz, TZ_VARIANTS};
 
 pub struct WallClock {
     /// The underlying system clock.
@@ -64,10 +67,61 @@ impl HostMonotonicClock for MonotonicClock {
     }
 }
 
+pub struct Timezone {
+    // The underlying system timezone.
+    timezone: cap_time_ext::Timezone,
+}
+
+impl Timezone {
+    pub fn new(ambient_authority: AmbientAuthority) -> Self {
+        Self {
+            timezone: cap_time_ext::Timezone::new(ambient_authority),
+        }
+    }
+
+    fn timezone_from_duration(&self, datetime: Duration) -> Option<TimezoneDisplay> {
+        let name = self.timezone.timezone_name().ok()?;
+        let tz: Tz = TZ_VARIANTS.into_iter().find(|tz| tz.to_string() == name)?;
+        let naive_datetime = NaiveDateTime::from_timestamp_opt(datetime.as_secs() as i64, 0)?;
+        let tz_offset = tz.offset_from_local_datetime(&naive_datetime).single()?;
+        let utc_offset = tz_offset.base_utc_offset().num_hours() as i32;
+        let in_daylight_saving_time = !tz_offset.dst_offset().is_zero();
+        Some(TimezoneDisplay {
+            utc_offset,
+            name,
+            in_daylight_saving_time,
+        })
+    }
+}
+
+impl HostTimezone for Timezone {
+    fn display(&self, datetime: Duration) -> TimezoneDisplay {
+        match self.timezone_from_duration(datetime) {
+            None => TimezoneDisplay {
+                utc_offset: 0,
+                name: "UTC".to_string(),
+                in_daylight_saving_time: false,
+            },
+            Some(timezone_display) => timezone_display,
+        }
+    }
+
+    fn utc_offset(&self, datetime: Duration) -> i32 {
+        match self.timezone_from_duration(datetime) {
+            None => 0,
+            Some(timezone_display) => timezone_display.utc_offset,
+        }
+    }
+}
+
 pub fn monotonic_clock() -> Box<dyn HostMonotonicClock + Send> {
     Box::new(MonotonicClock::new(ambient_authority()))
 }
 
 pub fn wall_clock() -> Box<dyn HostWallClock + Send> {
     Box::new(WallClock::new(ambient_authority()))
 }
+
+pub fn timezone() -> Box<dyn HostTimezone + Send> {
+    Box::new(Timezone::new(ambient_authority()))
+}