#
http_body/
size_hint.rs

    1/// A `Body` size hint
    2///
    3/// The default implementation returns:
    4///
    5/// * 0 for `lower`
    6/// * `None` for `upper`.
    7#[derive(Debug, Default, Clone)]
    8pub struct SizeHint {
    9    lower: u64,
    10    upper: Option<u64>,
    11}
    12
    13impl SizeHint {
    14    /// Returns a new `SizeHint` with default values
    15    #[inline]
    16    pub fn new() -> SizeHint {
    17        SizeHint::default()
    18    }
    19
    20    /// Returns a new `SizeHint` with both upper and lower bounds set to the
    21    /// given value.
    22    #[inline]
    23    pub fn with_exact(value: u64) -> SizeHint {
    24        SizeHint {
    25            lower: value,
    26            upper: Some(value),
    27        }
    28    }
    29
    30    /// Returns the lower bound of data that the `Body` will yield before
    31    /// completing.
    32    #[inline]
    33    pub fn lower(&self) -> u64 {
    34        self.lower
    35    }
    36
    37    /// Set the value of the `lower` hint.
    38    ///
    39    /// # Panics
    40    ///
    41    /// The function panics if `value` is greater than `upper`.
    42    #[inline]
    43    pub fn set_lower(&mut self, value: u64) {
    44        assert!(value <= self.upper.unwrap_or(u64::MAX));
    45        self.lower = value;
    46    }
    47
    48    /// Returns the upper bound of data the `Body` will yield before
    49    /// completing, or `None` if the value is unknown.
    50    #[inline]
    51    pub fn upper(&self) -> Option<u64> {
    52        self.upper
    53    }
    54
    55    /// Set the value of the `upper` hint value.
    56    ///
    57    /// # Panics
    58    ///
    59    /// This function panics if `value` is less than `lower`.
    60    #[inline]
    61    pub fn set_upper(&mut self, value: u64) {
    62        assert!(value >= self.lower, "`value` is less than than `lower`");
    63
    64        self.upper = Some(value);
    65    }
    66
    67    /// Returns the exact size of data that will be yielded **if** the
    68    /// `lower` and `upper` bounds are equal.
    69    #[inline]
    70    pub fn exact(&self) -> Option<u64> {
    71        if Some(self.lower) == self.upper {
    72            self.upper
    73        } else {
    74            None
    75        }
    76    }
    77
    78    /// Set the value of the `lower` and `upper` bounds to exactly the same.
    79    #[inline]
    80    pub fn set_exact(&mut self, value: u64) {
    81        self.lower = value;
    82        self.upper = Some(value);
    83    }
    84}