Packed encoding of enum still includes variant names for non-unit variants #187

joshtriplett · 2020-05-08T22:49:42Z

Test case:

use serde::{Deserialize, Serialize};
use std::io::Write;

#[derive(Debug, Deserialize, Serialize)]
enum Thing {
    Thing1(String),
    Thing2(u64),
    Thing3(Box<[Thing]>),
    Thing4,
}

fn main() -> anyhow::Result<()> {
    let thing = Thing::Thing3(vec![Thing::Thing2(42), Thing::Thing4].into_boxed_slice());
    let v = serde_cbor::ser::to_vec_packed(&thing)?;
    std::fs::File::create("cbor")?.write_all(&v)?;
    Ok(())
}

Hex dump of the resulting file:

00000000  a1 66 54 68 69 6e 67 33  82 a1 66 54 68 69 6e 67  |.fThing3..fThing|
00000010  32 18 2a 03                                       |2.*.|

Notice that it includes Thing3 and Thing2, but not Thing4.

From what I can tell, the serialization of unit variants pays attention to self.packed, but the serialization of non-unit variants does not.

The text was updated successfully, but these errors were encountered:

Fixes pyfisch#187 Legacy enum format supported packed encoding pretty well but with the switch to new enum format there was a regression (pyfisch#173). This commit fixes the new enum format in packed encoding. For example consider the following structure: ```rust enum Enum { Unit, NewType(i32), Tuple(i32, i32), Struct { x: i32, y: i32 }, } ``` Legacy enum packed encodings are: ``` Empty: <variant number> NewType: [<variant number>, value] Tuple: [<variant number>, values..] Struct: [<variant number>, {<struct>}] ``` Non-legacy enum packed encodings before this commit: ``` Empty: <variant number> NewType: {"<variant>": value} Tuple: {"<variant>": [values..]} Struct: {<variant number>: {<struct>}} ``` Notice how NewType and Tuple store the name instead of variant number. Fixed after this commit: ``` Empty: <variant number> NewType: {<variant number>: value} Tuple: {<variant number>: [values..]} Struct: {<variant number>: {<struct>}} ``` After this commit the packed encoding can be briefly described as: All struct fields and enum variants are encoded as their field number rather than name. This applies to all types of members (unit, newtype, tuple and struct).

matix2267 · 2021-06-14T12:10:58Z

I've created a bugfix for this issue (#215) but I don't have high hopes to get it merged given that this project is effectively unmaintained (see #179).

Feel free to use the bugfix repo directly if it fits your use case.

Fixes pyfisch#187 Legacy enum format supported packed encoding pretty well but with the switch to new enum format there was a regression (pyfisch#173). This commit fixes the new enum format in packed encoding. For example consider the following structure: ```rust enum Enum { Unit, NewType(i32), Tuple(i32, i32), Struct { x: i32, y: i32 }, } ``` Legacy enum packed encodings are: ``` Empty: <variant number> NewType: [<variant number>, value] Tuple: [<variant number>, values..] Struct: [<variant number>, {<struct>}] ``` Non-legacy enum packed encodings before this commit: ``` Empty: <variant number> NewType: {"<variant>": value} Tuple: {"<variant>": [values..]} Struct: {<variant number>: {<struct>}} ``` Notice how NewType and Tuple store the name instead of variant number. Fixed after this commit: ``` Empty: <variant number> NewType: {<variant number>: value} Tuple: {<variant number>: [values..]} Struct: {<variant number>: {<struct>}} ``` After this commit the packed encoding can be briefly described as: All struct fields and enum variants are encoded as their field number rather than name. This applies to all types of members (unit, newtype, tuple and struct).

matix2267 linked a pull request Jun 14, 2021 that will close this issue

Fix encoding of packed variants in new enum format #215

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Packed encoding of enum still includes variant names for non-unit variants #187

Packed encoding of enum still includes variant names for non-unit variants #187

joshtriplett commented May 8, 2020

matix2267 commented Jun 14, 2021

Packed encoding of enum still includes variant names for non-unit variants #187

Packed encoding of enum still includes variant names for non-unit variants #187

Comments

joshtriplett commented May 8, 2020

matix2267 commented Jun 14, 2021