qubit-codec-text 0.1.0

Buffer-oriented text encoding and decoding utilities for Rust
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159

// =============================================================================
//    Copyright (c) 2026 Haixing Hu.
//
//    SPDX-License-Identifier: Apache-2.0.
//
//    Licensed under the Apache License, Version 2.0.
// =============================================================================
use crate::{
    Ascii,
    Charset,
    CharsetCodec,
    CharsetDecodeError,
    CharsetDecodeErrorKind,
    CharsetDecodeResult,
    CharsetEncodeError,
    CharsetEncodeErrorKind,
    CharsetEncodeProbe,
    CharsetEncodeResult,
};
use qubit_codec::Codec;

/// Single-byte ASCII codec for bytes.
///
/// `AsciiCodec` converts between one-byte ASCII-encoded data and Unicode scalar
/// values.
#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq)]
pub struct AsciiCodec;

impl AsciiCodec {
    /// Returns the ASCII charset descriptor.
    ///
    /// # Returns
    ///
    /// Returns [`Charset::ASCII`].
    #[must_use]
    #[inline(always)]
    pub const fn charset(self) -> Charset {
        Charset::ASCII
    }
}

impl CharsetCodec for AsciiCodec {
    /// Returns the charset descriptor for this codec.
    ///
    /// # Returns
    ///
    /// Returns [`Charset::ASCII`].
    #[inline(always)]
    fn charset(&self) -> Charset {
        Charset::ASCII
    }
}

impl CharsetEncodeProbe for AsciiCodec {
    /// Encodes one `char` into one ASCII byte.
    ///
    /// # Parameters
    ///
    /// - `ch`: The character to encode.
    /// - `index`: Input character index used for error context.
    ///
    /// # Returns
    ///
    /// `Ok(1)` when one byte is needed.
    ///
    /// # Errors
    ///
    /// * `CharsetEncodeErrorKind::UnmappableCharacter` if `ch` is not ASCII.
    #[inline]
    fn encode_len(&self, ch: char, index: usize) -> CharsetEncodeResult<usize> {
        if ch > Ascii::MAX_CHAR {
            let kind = CharsetEncodeErrorKind::UnmappableCharacter {
                value: ch as u32,
            };
            return Err(CharsetEncodeError::new(Charset::ASCII, kind, index));
        }
        Ok(1)
    }
}

unsafe impl Codec for AsciiCodec {
    type Value = char;
    type Unit = u8;
    type DecodeError = CharsetDecodeError;
    type EncodeError = CharsetEncodeError;

    #[inline(always)]
    fn min_units_per_value(&self) -> core::num::NonZeroUsize {
        core::num::NonZeroUsize::MIN
    }

    #[inline(always)]
    fn max_units_per_value(&self) -> core::num::NonZeroUsize {
        core::num::NonZeroUsize::MIN
    }

    #[inline]
    unsafe fn decode_unchecked(
        &self,
        input: &[u8],
        index: usize,
    ) -> CharsetDecodeResult<(char, core::num::NonZeroUsize)> {
        if index > input.len() {
            let kind = CharsetDecodeErrorKind::InvalidInputIndex {
                input_len: input.len(),
            };
            return Err(CharsetDecodeError::new(Charset::ASCII, kind, index));
        }
        if index == input.len() {
            let kind = CharsetDecodeErrorKind::IncompleteSequence {
                required: 1,
                available: 0,
            };
            return Err(CharsetDecodeError::new(Charset::ASCII, kind, index));
        }

        let value = input[index];
        if value > Ascii::MAX_BYTE {
            let kind = CharsetDecodeErrorKind::MalformedSequence {
                value: Some(value as u32),
            };
            return Err(CharsetDecodeError::new(Charset::ASCII, kind, index));
        }
        debug_assert!(index < input.len());
        Ok((value as char, core::num::NonZeroUsize::MIN))
    }

    #[inline]
    unsafe fn encode_unchecked(
        &self,
        ch: &char,
        output: &mut [u8],
        index: usize,
    ) -> CharsetEncodeResult<usize> {
        if *ch > Ascii::MAX_CHAR {
            let kind = CharsetEncodeErrorKind::UnmappableCharacter {
                value: *ch as u32,
            };
            return Err(CharsetEncodeError::new(Charset::ASCII, kind, index));
        }
        if index >= output.len() {
            let kind = CharsetEncodeErrorKind::BufferTooSmall {
                required: required_index(index, 1),
                available: 0,
            };
            return Err(CharsetEncodeError::new(Charset::ASCII, kind, index));
        }
        output[index] = *ch as u8;
        Ok(1)
    }
}

#[inline(always)]
const fn required_index(index: usize, required_units: usize) -> usize {
    match index.checked_add(required_units) {
        Some(required) => required,
        None => usize::MAX,
    }
}