tower_web/util/buf_stream/
size_hint.rs

1//! `SizeHint` type and builder
2
3/// A `BufStream` size hint
4///
5/// The default implementation returns:
6///
7/// * 0 for `available`
8/// * 0 for `lower`
9/// * `None` for `upper`.
10#[derive(Debug, Default, Clone)]
11pub struct SizeHint {
12    available: usize,
13    lower: usize,
14    upper: Option<usize>,
15}
16
17/// Build a `SizeHint`
18#[derive(Debug)]
19pub struct Builder {
20    hint: SizeHint,
21}
22
23impl Builder {
24    /// Create a new `Builder` configured with default values.
25    pub fn new() -> Builder {
26        Builder {
27            hint: SizeHint {
28                available: 0,
29                lower: 0,
30                upper: None,
31            },
32        }
33    }
34
35    /// Sets the `available` hint value.
36    pub fn available(&mut self, val: usize) -> &mut Self {
37        self.hint.available = val;
38
39        if self.hint.lower < val {
40            self.hint.lower = val;
41
42            match self.hint.upper {
43                Some(ref mut upper) if *upper < val => {
44                    *upper = val;
45                }
46                _ => {}
47            }
48        }
49
50        self
51    }
52
53    /// Sets the `lower` hint value.
54    ///
55    /// # Panics
56    ///
57    /// This function panics if `val` is smaller than `available`.
58    pub fn lower(&mut self, val: usize) -> &mut Self {
59        assert!(val >= self.hint.available);
60
61        self.hint.lower = val;
62        self
63    }
64
65    /// Set the `upper` hint value.
66    ///
67    /// # Panics
68    ///
69    /// This function panics if `val` is smaller than `lower`.
70    pub fn upper(&mut self, val: usize) -> &mut Self {
71        // There is no need to check `available` as that is guaranteed to be
72        // less than or equal to `lower`.
73        assert!(val >= self.hint.lower, "`val` is smaller than `lower`");
74
75        self.hint.upper = Some(val);
76        self
77    }
78
79    /// Build the `SizeHint`
80    pub fn build(&self) -> SizeHint {
81        self.hint.clone()
82    }
83}
84
85impl SizeHint {
86    /// Returns the **lower bound** of the amount of data that can be read from
87    /// the `BufStream` without `NotReady` being returned.
88    ///
89    /// It is possible that more data is currently available.
90    pub fn available(&self) -> usize {
91        self.available
92    }
93
94    /// Returns the lower bound of data that the `BufStream` will yield before
95    /// completing.
96    pub fn lower(&self) -> usize {
97        self.lower
98    }
99
100    /// Returns the upper bound of data the `BufStream` will yield before
101    /// completing, or `None` if the value is unknown.
102    pub fn upper(&self) -> Option<usize> {
103        self.upper
104    }
105}
tower_web/util/buf_stream/size_hint.rs

tower_web/util/buf_stream/
size_hint.rs
