spectrusty_core/memory/
arrays.rs

1/*
2    Copyright (C) 2022  Rafal Michalski
3
4    This file is part of SPECTRUSTY, a Rust library for building emulators.
5
6    For the full copyright notice, see the lib.rs file.
7*/
8//! Utilities for serializing arrays as tuples.
9use std::{marker::PhantomData};
10use std::mem::{MaybeUninit};
11use std::ptr;
12
13use serde::{
14    de::{SeqAccess, Visitor},
15    ser::SerializeTuple,
16    Deserialize, Deserializer, Serialize, Serializer,
17};
18
19pub fn serialize<S: Serializer, T: Serialize, const N: usize>(
20    data: &[T; N],
21    ser: S,
22) -> Result<S::Ok, S::Error> {
23    let mut tuple = ser.serialize_tuple(N)?;
24    for item in data {
25        tuple.serialize_element(item)?;
26    }
27    tuple.end()
28}
29
30struct ArrayVisitor<T, const N: usize>(PhantomData<T>);
31
32impl<'de, T, const N: usize> Visitor<'de> for ArrayVisitor<T, N>
33    where T: Deserialize<'de>,
34{
35    type Value = [T; N];
36
37    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
38        formatter.write_str(&format!("an array of length {}", N))
39    }
40
41    #[inline]
42    fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
43        where A: SeqAccess<'de>,
44    {
45        struct ArrayUninit<T, const N: usize> {
46            data: [MaybeUninit<T>; N],
47            init_len: usize
48        }
49
50        impl<T, const N: usize> Drop for ArrayUninit<T, N> {
51            fn drop(&mut self) {
52                for elem in &mut self.data[0..self.init_len] {
53                    unsafe { ptr::drop_in_place(elem.as_mut_ptr()); }
54                }
55            }
56        }
57
58        let mut ary: ArrayUninit<T, N> = ArrayUninit {
59            data: unsafe { MaybeUninit::uninit().assume_init() },
60            init_len: 0
61        };
62        let mut iter = ary.data.iter_mut();
63        while let Some(val) = seq.next_element()? {
64            if let Some(elem) = iter.next() {
65                elem.write(val);
66                ary.init_len += 1;
67            }
68            else {
69                return Err(serde::de::Error::invalid_length(N, &self));
70            }
71        }
72        if ary.init_len != N {
73            return Err(serde::de::Error::invalid_length(N, &self));
74        }
75        // All elements in, prevent drop of data
76        ary.init_len = 0;
77        Ok(unsafe { (&ary.data as *const _ as *const [T; N]).read() })
78    }
79}
80
81pub fn deserialize<'de, D, T, const N: usize>(deserializer: D) -> Result<[T; N], D::Error>
82where
83    D: Deserializer<'de>,
84    T: Deserialize<'de>,
85{
86    deserializer.deserialize_tuple(N, ArrayVisitor::<T, N>(PhantomData))
87}
88
89#[cfg(test)]
90mod tests {
91    use super::*;
92    #[derive(Clone, Copy, PartialEq, Debug)]
93    #[derive(Serialize, Deserialize)]
94    #[serde(transparent)]
95    struct ArrayWrap<T: Serialize, const N: usize>(
96        #[serde(serialize_with = "serialize", deserialize_with = "deserialize")] [T;N])
97    where for <'a> T: Deserialize<'a>;
98
99    #[test]
100    fn arrays_serde_works() {
101        let ary: ArrayWrap<u8,5> = ArrayWrap([1,2,3,4,5]);
102        let serary = serde_json::to_string(&ary).unwrap();
103        assert_eq!(&serary, "[1,2,3,4,5]");
104        assert!(serde_json::from_str::<ArrayWrap<u8,4>>(&serary).is_err());
105        assert!(serde_json::from_str::<ArrayWrap<u8,6>>(&serary).is_err());
106        let ary_de: ArrayWrap<u8,5> = serde_json::from_str(&serary).unwrap();
107        assert_eq!(&ary, &ary_de);
108
109        let encoded: Vec<u8> = bincode::serialize(&ary).unwrap();
110        assert!(bincode::deserialize::<ArrayWrap<u8,6>>(&encoded).is_err());
111        let ary_de: ArrayWrap<u8,5> = bincode::deserialize(&encoded).unwrap();
112        assert_eq!(&ary, &ary_de);
113
114        let ary: ArrayWrap<String,3> = ArrayWrap(["foo".to_string(), "bar".to_string(), "baz".to_string()]);
115        let serary = serde_json::to_string(&ary).unwrap();
116        assert_eq!(&serary, r#"["foo","bar","baz"]"#);
117        assert!(serde_json::from_str::<ArrayWrap<String,2>>(&serary).is_err());
118        assert!(serde_json::from_str::<ArrayWrap<String,4>>(&serary).is_err());
119        let ary_de: ArrayWrap<String,3> = serde_json::from_str(&serary).unwrap();
120        assert_eq!(&ary, &ary_de);
121    }
122}
spectrusty_core/memory/arrays.rs

spectrusty_core/memory/
arrays.rs
