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
use crate::{Key, Value};
use std::fmt::{self, Write};
use std::sync::atomic::{AtomicUsize, Ordering};
static ENCODER_ID_COUNTER: AtomicUsize = AtomicUsize::new(0);
pub trait Encoder: fmt::Debug {
fn encode(&self, attributes: &mut dyn Iterator<Item = (&Key, &Value)>) -> String;
fn id(&self) -> EncoderId;
}
#[derive(Debug)]
pub struct EncoderId(usize);
impl EncoderId {
pub fn is_valid(&self) -> bool {
self.0 != 0
}
}
#[derive(Debug)]
pub struct DefaultAttributeEncoder;
impl Encoder for DefaultAttributeEncoder {
fn encode(&self, attributes: &mut dyn Iterator<Item = (&Key, &Value)>) -> String {
attributes
.enumerate()
.fold(String::new(), |mut acc, (idx, (key, value))| {
let offset = acc.len();
if idx > 0 {
acc.push(',')
}
if write!(acc, "{}", key).is_err() {
acc.truncate(offset);
return acc;
}
acc.push('=');
if write!(acc, "{}", value).is_err() {
acc.truncate(offset);
return acc;
}
acc
})
}
fn id(&self) -> EncoderId {
new_encoder_id()
}
}
pub fn default_encoder() -> Box<dyn Encoder + Send + Sync> {
Box::new(DefaultAttributeEncoder)
}
pub fn new_encoder_id() -> EncoderId {
let old_encoder_id = ENCODER_ID_COUNTER.fetch_add(1, Ordering::AcqRel);
EncoderId(old_encoder_id + 1)
}