cdrs 2.3.3

Cassandra DB driver written in Rust
Documentation 
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use super::{to_int, to_varint};
use crate::frame::traits::IntoBytes;

/// Cassandra Decimal type
#[derive(Debug, Clone, PartialEq)]
pub struct Decimal {
    pub unscaled: i64,
    pub scale: u32,
}

impl Decimal {
    pub fn new(unscaled: i64, scale: u32) -> Self {
        Decimal { unscaled, scale }
    }

    /// Method that returns plain `f64` value.
    pub fn as_plain(&self) -> f64 {
        (self.unscaled as f64) / (10i64.pow(self.scale) as f64)
    }
}

impl IntoBytes for Decimal {
    fn into_cbytes(&self) -> Vec<u8> {
        let mut bytes: Vec<u8> = vec![];
        bytes.extend(to_int(self.scale as i32));
        bytes.extend(to_varint(self.unscaled));

        bytes
    }
}

macro_rules! impl_from_for_decimal {
    ($t:ty) => {
        impl From<$t> for Decimal {
            fn from(i: $t) -> Self {
                Decimal {
                    unscaled: i as i64,
                    scale: 0,
                }
            }
        }
    };
}

impl_from_for_decimal!(i8);
impl_from_for_decimal!(i16);
impl_from_for_decimal!(i32);
impl_from_for_decimal!(i64);
impl_from_for_decimal!(u8);
impl_from_for_decimal!(u16);

impl From<f32> for Decimal {
    fn from(f: f32) -> Decimal {
        let mut scale: u32 = 0;

        loop {
            let unscaled = f * (10i64.pow(scale) as f32);

            if unscaled == unscaled.trunc() {
                return Decimal::new(unscaled as i64, scale);
            }

            scale += 1;
        }
    }
}

impl From<f64> for Decimal {
    fn from(f: f64) -> Decimal {
        let mut scale: u32 = 0;

        loop {
            let unscaled = f * (10i64.pow(scale) as f64);

            if unscaled == unscaled.trunc() {
                return Decimal::new(unscaled as i64, scale);
            }

            scale += 1;
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn into_cbytes_test() {
        assert_eq!(
            Decimal::new(129, 0).into_cbytes(),
            vec![0, 0, 0, 0, 0x00, 0x81]
        );

        assert_eq!(
            Decimal::new(-129, 0).into_cbytes(),
            vec![0, 0, 0, 0, 0xFF, 0x7F]
        );

        let expected: Vec<u8> = vec![0, 0, 0, 1, 0x00, 0x81];
        assert_eq!(Decimal::new(129, 1).into_cbytes(), expected);

        let expected: Vec<u8> = vec![0, 0, 0, 1, 0xFF, 0x7F];
        assert_eq!(Decimal::new(-129, 1).into_cbytes(), expected);
    }

    #[test]
    fn from_f32() {
        assert_eq!(Decimal::from(12300001 as f32), Decimal::new(12300001, 0));
        assert_eq!(Decimal::from(1230000.1 as f32), Decimal::new(12300001, 1));
        assert_eq!(Decimal::from(0.12300001 as f32), Decimal::new(12300001, 8));
    }

    #[test]
    fn from_f64() {
        assert_eq!(
            Decimal::from(1230000000000001i64 as f64),
            Decimal::new(1230000000000001i64, 0)
        );
        assert_eq!(
            Decimal::from(123000000000000.1f64),
            Decimal::new(1230000000000001i64, 1)
        );
        assert_eq!(
            Decimal::from(0.1230000000000001f64),
            Decimal::new(1230000000000001i64, 16)
        );
    }
}