qubit_codec/value/
json_bytes_value_decoder.rs

1// =============================================================================
2//    Copyright (c) 2026 Haixing Hu.
3//
4//    SPDX-License-Identifier: Apache-2.0
5//
6//    Licensed under the Apache License, Version 2.0.
7// =============================================================================
8//! Serde JSON bytes decoder for one owned value.
9
10use core::marker::PhantomData;
11
12use serde::de::DeserializeOwned;
13use serde_json::Error as JsonError;
14use serde_json::from_slice;
15
16use super::ValueDecoder;
17
18/// Decodes UTF-8 JSON bytes into one owned value via `serde_json`.
19/// Its stateless marker implements `Clone`, `Copy`, and `Default` without
20/// requiring those traits on `T`.
21///
22/// # Type Parameters
23///
24/// - `T`: Target value type deserialized through Serde.
25///
26/// # Examples
27///
28/// ```rust
29/// use qubit_codec::{JsonBytesValueDecoder, ValueDecoder};
30/// use serde::Deserialize;
31///
32/// #[derive(Debug, Deserialize, PartialEq)]
33/// struct Point {
34///     x: i32,
35///     y: i32,
36/// }
37///
38/// let mut decoder = JsonBytesValueDecoder::<Point>::new();
39/// let point = decoder.decode(br#"{"x":1,"y":2}"#).unwrap();
40/// assert_eq!(point, Point { x: 1, y: 2 });
41/// ```
42#[must_use]
43#[derive(Debug)]
44pub struct JsonBytesValueDecoder<T> {
45    /// Associates the decoder with `T` without retaining a value.
46    _marker: PhantomData<T>,
47}
48
49impl<T> Copy for JsonBytesValueDecoder<T> {}
50
51impl<T> Clone for JsonBytesValueDecoder<T> {
52    /// Returns an identical stateless decoder without requiring `T: Clone`.
53    ///
54    /// # Returns
55    ///
56    /// Returns a decoder associated with the same target type.
57    #[inline]
58    fn clone(&self) -> Self {
59        *self
60    }
61}
62
63impl<T> Default for JsonBytesValueDecoder<T> {
64    /// Creates a decoder for `T` without constructing a value of that type.
65    ///
66    /// # Returns
67    ///
68    /// Returns an uninitialized stateless decoder associated with `T`.
69    #[inline]
70    fn default() -> Self {
71        Self::new()
72    }
73}
74
75impl<T> JsonBytesValueDecoder<T> {
76    /// Creates a JSON bytes decoder for values of type `T`.
77    ///
78    /// # Returns
79    ///
80    /// Returns a stateless decoder without allocating or constructing a `T`.
81    #[inline]
82    pub const fn new() -> Self {
83        Self { _marker: PhantomData }
84    }
85}
86
87impl<T> ValueDecoder<[u8]> for JsonBytesValueDecoder<T>
88where
89    T: DeserializeOwned,
90{
91    /// JSON syntax, UTF-8, or target-value deserialization failure.
92    type Error = JsonError;
93    /// Owned value deserialized independently of the input byte slice.
94    type Output = T;
95
96    /// Deserializes `input` from UTF-8 JSON bytes.
97    ///
98    /// # Parameters
99    ///
100    /// - `input`: One complete UTF-8 JSON value, optionally surrounded by
101    ///   whitespace.
102    ///
103    /// # Returns
104    ///
105    /// Returns an owned `T`; decoding may allocate according to the target
106    /// type.
107    ///
108    /// # Errors
109    ///
110    /// Returns a JSON error for invalid UTF-8, malformed or incomplete input,
111    /// trailing non-whitespace data, or a value incompatible with `T`.
112    #[inline]
113    fn decode(&mut self, input: &[u8]) -> Result<Self::Output, Self::Error> {
114        from_slice(input)
115    }
116}
qubit_codec/value/json_bytes_value_decoder.rs

qubit_codec/value/
json_bytes_value_decoder.rs
