gecko-dev/third_party/rust/rust_decimal

Decimal  

A Decimal implementation written in pure Rust suitable for financial calculations that require significant integral and fractional digits with no round-off errors.

The binary representation consists of a 96 bit integer number, a scaling factor used to specify the decimal fraction and a 1 bit sign. Because of this representation, trailing zeros are preserved and may be exposed when in string form. These can be truncated using the normalize or round_dp functions.

Documentation

Usage

Decimal numbers can be created in a few distinct ways. The easiest and most optimal method of creating a Decimal is to use the procedural macro within the rust_decimal_macros crate:

// Procedural macros need importing directly
use rust_decimal_macros::*;

let number = dec!(-1.23);

Alternatively you can also use one of the Decimal number convenience functions:

use rust_decimal::prelude::*;

// Using an integer followed by the decimal points
let scaled = Decimal::new(202, 2); // 2.02

// From a string representation
let from_string = Decimal::from_str("2.02").unwrap(); // 2.02

// Using the `Into` trait
let my_int : Decimal = 3i32.into();

// Using the raw decimal representation
// 3.1415926535897932384626433832
let pi = Decimal::from_parts(1102470952, 185874565, 1703060790, false, 28);

Features

• db-postgres
• db-tokio-postgres
• db-diesel-postgres
• serde-float
• serde-bincode

db-postgres

This feature enables a PostgreSQL communication module. It allows for reading and writing the Decimal type by transparently serializing/deserializing into the NUMERIC data type within PostgreSQL.

db-tokio-postgres

Enables the tokio postgres module allowing for async communication with PostgreSQL.

db-diesel-postgres

Enable diesel PostgreSQL support.

serde-float

Enable this so that JSON serialization of Decimal types are sent as a float instead of a string (default).

e.g. with this turned on, JSON serialization would output:

{
  "value": 1.234
}

serde-bincode

Since bincode does not specify type information, we need to ensure that a type hint is provided in order to correctly be able to deserialize. Enabling this feature on it's own will force deserialization to use deserialize_str instead of deserialize_any.

If, for some reason, you also have serde-float enabled then this will use deserialize_f64 as a type hint. Because converting to f64 loses precision, it's highly recommended that you do NOT enable this feature when working with bincode. That being said, this will only use 8 bytes so is slightly more efficient in regards to storage size.