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use crate::fail;
use crate::layer::OpenedSpan;
use tracing::Subscriber;
use tracing_subscriber::{registry::LookupSpan, Registry};
use uuid::Uuid;
/// Gets the current [`Uuid`] of an entered span within a `tracing-forest`
/// subscriber.
///
/// # Examples
///
/// Passing in a `Uuid` to a span, and then retreiving it from within the span:
/// ```
/// # use tracing::{info, info_span};
/// # use uuid::Uuid;
/// # tracing_forest::init();
/// let uuid = Uuid::new_v4();
///
/// // Tracing's syntax allows us to omit the redundent naming of the field here
/// info_span!("my_span", %uuid).in_scope(|| {
/// assert!(tracing_forest::id() == uuid);
/// });
/// ```
///
/// # Panics
///
/// This function panics if there is no current subscriber, if the subscriber
/// isn't composed with a [`ForestLayer`], or if the subscriber isn't in a span.
///
/// [`ForestLayer`]: crate::layer::ForestLayer
#[must_use]
pub fn id() -> Uuid {
tracing::dispatcher::get_default(|dispatch| {
let subscriber = dispatch
.downcast_ref::<Registry>()
.unwrap_or_else(fail::subscriber_not_found);
let current = subscriber.current_span();
let id = current.id().expect(fail::NO_CURRENT_SPAN);
subscriber
.span(id)
.expect(fail::SPAN_NOT_IN_CONTEXT)
.extensions()
.get::<OpenedSpan>()
.expect(fail::NO_FOREST_LAYER)
.uuid()
})
}
// Credit: https://github.com/uuid-rs/uuid/blob/main/src/parser.rs
pub(crate) const fn try_parse(input: &[u8]) -> Option<Uuid> {
match (input.len(), input) {
// Inputs of 32 bytes must be a non-hyphenated UUID
(32, s) => parse_simple(s),
// Hyphenated UUIDs may be wrapped in various ways:
// - `{UUID}` for braced UUIDs
// - `urn:uuid:UUID` for URNs
// - `UUID` for a regular hyphenated UUID
(36, s)
| (38, [b'{', s @ .., b'}'])
| (45, [b'u', b'r', b'n', b':', b'u', b'u', b'i', b'd', b':', s @ ..]) => {
parse_hyphenated(s)
}
// Any other shaped input is immediately invalid
_ => None,
}
}
#[inline]
const fn parse_simple(s: &[u8]) -> Option<Uuid> {
// This length check here removes all other bounds
// checks in this function
if s.len() != 32 {
return None;
}
let mut buf: [u8; 16] = [0; 16];
let mut i = 0;
while i < 16 {
// Convert a two-char hex value (like `A8`)
// into a byte (like `10101000`)
let h1 = HEX_TABLE[s[i * 2] as usize];
let h2 = HEX_TABLE[s[i * 2 + 1] as usize];
// We use `0xff` as a sentinel value to indicate
// an invalid hex character sequence (like the letter `G`)
if h1 | h2 == 0xff {
return None;
}
// The upper nibble needs to be shifted into position
// to produce the final byte value
buf[i] = SHL4_TABLE[h1 as usize] | h2;
i += 1;
}
Some(Uuid::from_bytes(buf))
}
#[inline]
const fn parse_hyphenated(s: &[u8]) -> Option<Uuid> {
// This length check here removes all other bounds
// checks in this function
if s.len() != 36 {
return None;
}
// We look at two hex-encoded values (4 chars) at a time because
// that's the size of the smallest group in a hyphenated UUID.
// The indexes we're interested in are:
//
// uuid : 936da01f-9abd-4d9d-80c7-02af85c822a8
// | | || || || || | |
// hyphens : | | 8| 13| 18| 23| | |
// positions: 0 4 9 14 19 24 28 32
// First, ensure the hyphens appear in the right places
match [s[8], s[13], s[18], s[23]] {
[b'-', b'-', b'-', b'-'] => {}
_ => return None,
}
let positions: [u8; 8] = [0, 4, 9, 14, 19, 24, 28, 32];
let mut buf: [u8; 16] = [0; 16];
let mut j = 0;
while j < 8 {
let i = positions[j];
// The decoding here is the same as the simple case
// We're just dealing with two values instead of one
let h1 = HEX_TABLE[s[i as usize] as usize];
let h2 = HEX_TABLE[s[(i + 1) as usize] as usize];
let h3 = HEX_TABLE[s[(i + 2) as usize] as usize];
let h4 = HEX_TABLE[s[(i + 3) as usize] as usize];
if h1 | h2 | h3 | h4 == 0xff {
return None;
}
buf[j * 2] = SHL4_TABLE[h1 as usize] | h2;
buf[j * 2 + 1] = SHL4_TABLE[h3 as usize] | h4;
j += 1;
}
Some(Uuid::from_bytes(buf))
}
const HEX_TABLE: &[u8; 256] = &{
let mut buf = [0; 256];
let mut i: u8 = 0;
loop {
buf[i as usize] = match i {
b'0'..=b'9' => i - b'0',
b'a'..=b'f' => i - b'a' + 10,
b'A'..=b'F' => i - b'A' + 10,
_ => 0xff,
};
if i == 255 {
break buf;
}
i += 1;
}
};
const SHL4_TABLE: &[u8; 256] = &{
let mut buf = [0; 256];
let mut i: u8 = 0;
loop {
buf[i as usize] = i.wrapping_shl(4);
if i == 255 {
break buf;
}
i += 1;
}
};