How to decode and encode a float in Rust?

rust f64 to u8
rust float to decimal
rust float 32
rust f64 mod
rust rounding float
rust format float
rust float to int
rust floor float to int

I want to decode, store and encode a float in Rust. I know about num::Float::integer_decode() but I'd rather not lose any precision. That is, unless the format I encode into is smaller than the format I encode from of course.

Interpret the floating point bits as an integer and print out the value as hex:

use std::mem;

fn main() {
    let a_third: f64 = 1.0 / 3.0;

    let as_int: u64 = unsafe { mem::transmute(a_third) };
    println!("{}", as_int);

    let as_string = format!("{:016x}", as_int);
    println!("{}", as_string);

    let back_to_int = u64::from_str_radix(&as_string, 16).expect("Not an integer");
    println!("{}", back_to_int);

    let back_to_float: f64 = unsafe { mem::transmute(back_to_int) };
    println!("{}", back_to_float);

    assert_eq!(back_to_float, a_third);
}

How to decode and encode a float in Rust? - floating-point - html, Interpret the floating point bits as an integer and print out the value as hex: use std::mem; fn main() { let a_third: f64 = 1.0 / 3.0; let as_int: u64 = unsafe� Decode from string reference as octets. Returns a Result containing a Vec. decode_config_buf: Decode from string reference as octets. Writes into the supplied buffer to avoid allocation. Returns a Result containing an empty tuple, aka (). decode_config_slice: Decode the input into the provided output slice. encode: Encode arbitrary octets as

How to decode and encode a float in Rust?, I want to decode, store and encode a float in Rust. Interpret the floating point bits as an integer and print out the value as hex: use std::mem; fn main() { let� An encoding as defined in the Encoding Standard. An encoding defines a mapping from a u8 sequence to a char sequence and, in most cases, vice versa. Each encoding has a name, an output encoding, and one or more labels. Labels are ASCII-case-insensitive strings that are used to identify an encoding in formats and protocols.

What's wrong with integer_decode()? It is lossless and works for finite numbers as well as NaN and infinities:

use std::mem;

fn integer_decode(val: f64) -> (u64, i16, i8) {
    let bits: u64 = unsafe { mem::transmute(val) };
    let sign: i8 = if bits >> 63 == 0 { 1 } else { -1 };
    let mut exponent: i16 = ((bits >> 52) & 0x7ff) as i16;
    let mantissa = if exponent == 0 {
        (bits & 0xfffffffffffff) << 1
    } else {
        (bits & 0xfffffffffffff) | 0x10000000000000
    };

    exponent -= 1023 + 52;
    (mantissa, exponent, sign)
}

fn main() {
    println!("{:?}", integer_decode(std::f64::NAN));
    println!("{:?}", integer_decode(std::f64::INFINITY));
    println!("{:?}", integer_decode(std::f64::NEG_INFINITY));
}

f64, I want to decode, store and encode a float in Rust. I know about num::Float:: integer_decode() but I'd rather not lose any precision. That is, unless the format I � Decode. The Decode trait is used for deserialization/decoding of encoded data into the respective types. fn decode<I: Input>(value: &mut I)-> Result<Self, Error>: Tries to decode the value from SCALE format to the type it is called on. Returns an Err if the decoding fails. CompactAs

If you don't intend to transfer serialized data between machines or you're certain that float representation is the same on all platforms you target, you can store byte representation of the number:

use std::io::{Read, Write};

fn main() {
  {
    let num: f64 = 1.0 / 3.0;
    let bytes: [u8; 8] = unsafe { std::mem::transmute(num) };
    let mut file = std::fs::File::create("/tmp/1").unwrap();
    file.write_all(&bytes).unwrap();
  }
  {
    let mut file = std::fs::File::open("/tmp/1").unwrap();
    let mut bytes: [u8; 8] = unsafe { std::mem::uninitialized() };
    file.read_exact(&mut bytes).unwrap();
    let num: f64 = unsafe { std::mem::transmute(bytes) };
    println!("result: {}", num);
  }
}

You can also use existing serialization framework, like serde. If you don't want the entire framework and just want to serialize floats, you can use dtoa (it's used by serde_json), although I'm not sure if it provides strong precision guarantees.

blurhash - Rust, API documentation for the Rust `f64` primitive in crate `std`. However, due to a floating point round-off error it can result in r == rhs.abs() , violating This means that any payloads encoded in NaNs will be preserved even if the result of this� A binary encoder / decoder implementation in Rust. - servo/bincode. Details. The encoding (and thus decoding) proceeds unsurprisingly -- primitive types are encoded according to the underlying Writer, tuples and structs are encoded by encoding their fields one-by-one, and enums are encoded by first writing out the tag representing the variant and then the contents.

prost::encoding - Rust, API documentation for the Rust `blurhash` crate. Encoding. use blurhash:: encode; use image::GenericImageView; let img Decoding. use blurhash:: decode; let pixels linear 0.0-1.0 floating point to srgb 0-255 integer conversion. Converts a slice of bytes to a string slice. A string slice (&str) is made of bytes (u8), and a byte slice (&[u8]) is made of bytes, so this function converts between the two.

Boscop/mincode: A minimal binary encoder / decoder , Utility functions and types for encoding and decoding Protobuf types. Modules. bool � bytes � double � fixed32 � fixed64 � float. A Rust library for doing URL percentage encoding. Contribute to bt/rust_urlencoding development by creating an account on GitHub.

servo/bincode: A binary encoder / decoder implementation , FloatEncoding}; use mincode::rustc_serialize::{encode, decode}; #[derive( RustcEncodable, RustcDecodable, PartialEq)] struct Entity { x: f32,� From here we can see where we create the decoder. The programming language that we need to use is JavaScript, and with it, we can easily create a JSON value. The encoder can be used to encode values downlinked to your Pycom, but for this tutorial, we will focus on uplink data. Encoder and Decoder Examples Short: 2 bytes, 0-65,536.

Comments
  • integer_decode() does not lose precision -- it's merely a deconstruction of the floating-point number into its components.
  • @trentcl I'm aware, but it appears encoding as in the documentation of the aforementioned function does.
  • Why not just transmute f64 to [u8; 8] and store it without unnecessary conversions?
  • @PavelStrakhov sounds like a prime candidate for an answer!
  • Oh! I was hoping for f32 and f64 to be directly encodable as hexadecimal (which is the easiest way to get a portable representation) but apparently they do not implement LowerHex or UpperHex. Disappointment :(
  • @MatthieuM. yeah, and there's no hex floating point literal either, so if you need to have a very specific float, you have to go through a transmute :-(
  • @Shepmaster: I think it would be worth raising a RFC here; both for support of literals and formatting/parsing. The formatting/parsing is much simpler than decimal format; literal parsing might require some tricks however (to avoid ambiguities with integrals).
  • Going from the docs that come with the function, it can lose precision during encoding.
  • @JeroenBollen can you link these docs? I can't find this information in std. I implemented fn integer_encode((mantissa, exponent, sign): (u64, i16, i8)) -> f64 { (sign as f64) * (mantissa as f64) * (2f64.powf(exponent as f64)) } and it works for any X I feed into integer_encode(integer_decode(X)) except for NaN (maybe there is something wrong with my integer_encode, though).
  • I did link to it in the OP.
  • @JeroenBollen that link doesn't provide any information about loss of precision.
  • @JeroenBollen maybe that's only a case with f32? I can't reproduce any difference for f64, at least not enough to break assert_eq!(2.0, integer_encode(integer_decode(2.0))); like in the example in the docs you linked.