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|
#![cfg(feature="sval_derive")]
/*!
Tags can be used to define new data types for streams to interpret differently.
Some tags are built-in to `sval`, but libraries can define their own.
This example defines a tag for Unix timestamps, where a 64bit number is interpreted
as seconds since the Unix Epoch.
*/
#[macro_use]
extern crate sval_derive;
pub const UNIX_TIMESTAMP: sval::Tag = sval::Tag::new("unixts");
#[derive(Value)]
#[sval(tag = "UNIX_TIMESTAMP")]
pub struct Timestamp(u64);
fn main() -> sval::Result {
stream(Timestamp(1675154443))?;
Ok(())
}
// This is the same stream as the `stream_simple` case, except with an extra
// `u64` method that handles our timestamps
pub struct MyStream {
is_unix_ts: bool,
}
impl<'sval> sval::Stream<'sval> for MyStream {
fn tagged_begin(
&mut self,
tag: Option<&sval::Tag>,
_: Option<&sval::Label>,
_: Option<&sval::Index>,
) -> sval::Result {
if let Some(&UNIX_TIMESTAMP) = tag {
self.is_unix_ts = true;
}
Ok(())
}
fn tagged_end(
&mut self,
tag: Option<&sval::Tag>,
_: Option<&sval::Label>,
_: Option<&sval::Index>,
) -> sval::Result {
if let Some(&UNIX_TIMESTAMP) = tag {
self.is_unix_ts = false;
}
Ok(())
}
fn u64(&mut self, v: u64) -> sval::Result {
// If the value is tagged as a Unix timestamp then print it using a human-readable RFC3339 format
if self.is_unix_ts {
print!(
"{}",
humantime::format_rfc3339(
std::time::SystemTime::UNIX_EPOCH + std::time::Duration::from_secs(v)
)
);
} else {
print!("{}", v);
}
Ok(())
}
fn null(&mut self) -> sval::Result {
print!("null");
Ok(())
}
fn bool(&mut self, v: bool) -> sval::Result {
print!("{}", v);
Ok(())
}
fn i64(&mut self, v: i64) -> sval::Result {
print!("{}", v);
Ok(())
}
fn f64(&mut self, v: f64) -> sval::Result {
print!("{}", v);
Ok(())
}
fn text_begin(&mut self, _: Option<usize>) -> sval::Result {
print!("\"");
Ok(())
}
fn text_fragment_computed(&mut self, fragment: &str) -> sval::Result {
print!("{}", fragment.escape_debug());
Ok(())
}
fn text_end(&mut self) -> sval::Result {
print!("\"");
Ok(())
}
fn seq_begin(&mut self, _: Option<usize>) -> sval::Result {
print!("[ ");
Ok(())
}
fn seq_value_begin(&mut self) -> sval::Result {
Ok(())
}
fn seq_value_end(&mut self) -> sval::Result {
print!(", ");
Ok(())
}
fn seq_end(&mut self) -> sval::Result {
print!("]");
Ok(())
}
}
fn stream(v: impl sval::Value) -> sval::Result {
v.stream(&mut MyStream { is_unix_ts: false })?;
println!();
Ok(())
}
|
