qubit-codec-text 0.1.0

Buffer-oriented text encoding and decoding utilities for Rust
Documentation 
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use qubit_codec_text::{
    AsciiCodec,
    Charset,
    CharsetCodec,
    CharsetDecodeError,
    CharsetDecodeErrorKind,
    CharsetDecodeResult,
    CharsetEncodeError,
    CharsetEncodeErrorKind,
    CharsetEncodeProbe,
    CharsetEncodeResult,
    Codec,
};

type DecodedCharResult = CharsetDecodeResult<(char, core::num::NonZeroUsize)>;
type DecodeFn = unsafe fn(&AsciiCodec, &[u8], usize) -> DecodedCharResult;
type EncodeFn = unsafe fn(
    &AsciiCodec,
    &char,
    &mut [u8],
    usize,
) -> CharsetEncodeResult<usize>;

#[test]
fn test_ascii_codec_exposes_identity_and_limits() {
    let codec = AsciiCodec;

    assert_eq!(
        Charset::ASCII,
        <AsciiCodec as CharsetCodec>::charset(&codec)
    );
    assert_eq!(1, codec.min_units_per_value().get());
    assert_eq!(1, codec.max_units_per_value().get());
    assert_eq!(1, codec.encode_len('A', 0).expect("ASCII is mappable"));

    assert_eq!(Charset::ASCII, codec.charset());
    assert_eq!(Charset::ASCII, codec.charset());
}

#[test]
fn test_ascii_codec_decodes_ascii_bytes_and_reports_closed_tail_and_malformed()
{
    let codec = AsciiCodec;

    let (decoded, consumed) =
        unsafe { codec.decode_unchecked(b"A", 0) }.expect("ASCII decode");
    assert_eq!('A', decoded);
    assert_eq!(1, consumed.get());

    let error = unsafe { codec.decode_unchecked(&[], 0) }
        .expect_err("empty closed input is incomplete");
    assert_eq!(
        CharsetDecodeErrorKind::IncompleteSequence {
            required: 1,
            available: 0,
        },
        error.kind()
    );

    let error = unsafe { codec.decode_unchecked(&[0x80], 0) }
        .expect_err("non-ASCII byte is malformed");
    assert_eq!(
        CharsetDecodeErrorKind::MalformedSequence { value: Some(128) },
        error.kind()
    );
    assert_eq!(0, error.index());

    let error = unsafe { codec.decode_unchecked(&[0x41], 2) }
        .expect_err("index out of range is invalid");
    assert_eq!(
        CharsetDecodeErrorKind::InvalidInputIndex { input_len: 1 },
        error.kind()
    );
    assert_eq!(2, error.index());
}

#[test]
fn test_ascii_codec_encodes_ascii_and_reports_limits_and_unmappable_chars() {
    let codec = AsciiCodec;
    let mut output = [0_u8; 2];

    assert_eq!(1, unsafe {
        codec
            .encode_unchecked(&'A', &mut output, 0)
            .expect("encode ASCII")
    });
    assert_eq!(b'A', output[0]);

    let error = codec
        .encode_len('é', 0)
        .expect_err("non-ASCII is unmappable");
    assert!(matches!(
        error.kind(),
        CharsetEncodeErrorKind::UnmappableCharacter { value: _ },
    ));
    assert_eq!(Some('é' as u32), error.value());

    let error = unsafe { codec.encode_unchecked(&'A', &mut [], 0) }
        .expect_err("empty output should fail");
    assert_eq!(
        CharsetEncodeErrorKind::BufferTooSmall {
            required: 1,
            available: 0,
        },
        error.kind()
    );

    let error = unsafe { codec.encode_unchecked(&'A', &mut [], usize::MAX) }
        .expect_err("overflowing output index should fail without panicking");
    assert_eq!(
        CharsetEncodeErrorKind::BufferTooSmall {
            required: usize::MAX,
            available: 0,
        },
        error.kind()
    );
}

#[test]
fn test_ascii_codec_direct_function_items_cover_trait_methods() {
    let codec = AsciiCodec;
    let inherent_charset: fn(AsciiCodec) -> Charset = AsciiCodec::charset;
    let trait_charset: fn(&AsciiCodec) -> Charset =
        <AsciiCodec as CharsetCodec>::charset;
    let min_units: fn(&AsciiCodec) -> core::num::NonZeroUsize =
        <AsciiCodec as Codec>::min_units_per_value;
    let max_units: fn(&AsciiCodec) -> core::num::NonZeroUsize =
        <AsciiCodec as Codec>::max_units_per_value;
    let encode_len: fn(&AsciiCodec, char, usize) -> CharsetEncodeResult<usize> =
        <AsciiCodec as CharsetEncodeProbe>::encode_len;
    let decode: DecodeFn = <AsciiCodec as Codec>::decode_unchecked;
    let encode: EncodeFn = <AsciiCodec as Codec>::encode_unchecked;

    assert_eq!(Charset::ASCII, inherent_charset(codec));
    assert_eq!(Charset::ASCII, trait_charset(&codec));
    assert_eq!(1, min_units(&codec).get());
    assert_eq!(1, max_units(&codec).get());
    assert_eq!(1, encode_len(&codec, 'Z', 0).expect("ASCII is mappable"));

    let (decoded, consumed) =
        unsafe { decode(&codec, b"Z", 0) }.expect("decode ASCII");
    assert_eq!(('Z', 1), (decoded, consumed.get()));
    let error: CharsetDecodeError =
        unsafe { decode(&codec, &[], 0) }.expect_err("closed tail");
    assert_eq!(
        CharsetDecodeErrorKind::IncompleteSequence {
            required: 1,
            available: 0,
        },
        error.kind()
    );

    let mut output = [0_u8; 1];
    assert_eq!(
        1,
        unsafe { encode(&codec, &'Z', &mut output, 0) }.expect("encode ASCII")
    );
    assert_eq!(b'Z', output[0]);
    let error: CharsetEncodeError =
        unsafe { encode(&codec, &'é', &mut output, 0) }
            .expect_err("unmappable");
    assert_eq!(Some('é' as u32), error.value());
}