Crate js_int

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Crate js_int provides JavaScript-interoperable integer types.

JavaScript does not have native integers. Instead it represents all numeric values with a single Number type which is represented as an IEEE 754 floating-point value.* Rust’s i64 and u64 types can contain values outside the range of what can be represented in a JavaScript Number.

This crate provides the types Int and UInt which wrap i64 and u64, respectively. These types add bounds checking to ensure the contained value is within the range representable by a JavaScript Number. They provide useful trait implementations to easily convert from Rust’s primitive integer types.

* In the upcoming ECMAScript 2020, JavaScript will probably gain support for integers. There is a proposal for a BigInt type type that is not far from becoming part of the JavaScript specification. It won’t make this crate obsolete in any way though, since there will still be lots of JS code using Number, and code in other languages that assumes its use.

§#![no_std]

The js_int crate does not use Rust’s standard library, and is compatible with #![no_std] programs.

§Features

  • serde: Serialization and deserialization support via serde. Disabled by default. You can use js_int + serde in #![no_std] contexts if you use default-features = false for both.
  • float_deserialize: Deserialize via f64, not via u64. If the input has a fraction, deserialization will fail.
  • lax_deserialize: Like float_deserialize, but if the input has a fraction, it is deserialized with the fractional part discarded. Please be aware that serde_json doesn’t losslessly parse large floats with a fractional part by default (even if the fractional part is .0). To fix that, enable its float_roundtrip feature.
  • std: Enable std::error::Error implementations for ParseIntError, TryFromIntError. Enabled by default.

Macros§

  • int
    Creates an Int from a numeric literal.
  • uint
    Creates a UInt from a numeric literal.

Structs§

  • Int
    An integer limited to the range of integers that can be represented exactly by an f64.
  • ParseIntError
    The error type returned when when parsing an integer fails.
  • TryFromIntError
    The error type returned when a checked integral type conversion fails.
  • UInt
    An integer limited to the range of non-negative integers that can be represented exactly by an f64.

Constants§

  • MAX_SAFE_INT
    The largest integer value that can be represented exactly by an f64.
  • MAX_SAFE_UINT
    The same as MAX_SAFE_INT, but with u64 as the type.
  • MIN_SAFE_INT
    The smallest integer value that can be represented exactly by an f64.