gedcomkit/

decode.rs

//! Turning the bytes of a GEDCOM file into text.
//!
//! This is a layer of its own because getting it wrong silently rejects most
//! real files. A byte-order mark is the common case — every GEDCOM 7 file
//! gedcom.io publishes carries one, as does every export from Family Tree
//! Maker 24, Legacy 10, `RootsMagic` 8, and Ancestris 11 — and an unstripped mark
//! makes the first line unparseable for a reason that names the wrong thing.
//!
//! Older files are not UTF-8 at all. GEDCOM 5.5 defaults to ANSEL, a 1980s
//! library-cataloguing set whose diacritics *precede* the letter they modify,
//! and files declaring `ANSI` are Windows-1252 in practice.
//!
//! Nothing here guesses in silence. Every decision, and every disagreement
//! between what a file declares and what it contains, is reported so the import
//! preview can show it before anything is written.

use crate::{GedcomError, GedcomErrorKind, Limits, fault};
use std::fmt;

/// How many leading bytes are searched for the `CHAR` declaration. The header
/// is the first record, and no real one approaches this.
const HEADER_SCAN_BYTES: usize = 8 * 1024;

/// The character encoding a GEDCOM file was read as.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
#[non_exhaustive]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
pub enum GedcomEncoding {
    /// Seven-bit ASCII, which every other encoding here agrees with.
    Ascii,
    /// UTF-8, with or without a byte-order mark.
    Utf8,
    /// UTF-16, big-endian.
    Utf16Be,
    /// UTF-16, little-endian.
    Utf16Le,
    /// ANSEL, the GEDCOM 5.5 default.
    Ansel,
    /// Windows-1252, which GEDCOM files call `ANSI`.
    Ansi,
}

impl GedcomEncoding {
    /// The name to show a user.
    #[must_use]
    pub const fn label(self) -> &'static str {
        match self {
            Self::Ascii => "ASCII",
            Self::Utf8 => "UTF-8",
            Self::Utf16Be => "UTF-16 (big-endian)",
            Self::Utf16Le => "UTF-16 (little-endian)",
            Self::Ansel => "ANSEL",
            Self::Ansi => "ANSI (Windows-1252)",
        }
    }
}

impl fmt::Display for GedcomEncoding {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str(self.label())
    }
}

/// What decoding did, and what it had to decide.
#[derive(Clone, Debug, Default, Eq, PartialEq)]
#[non_exhaustive]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "camelCase"))]
pub struct EncodingReport {
    /// The encoding the bytes were read as.
    pub used: Option<GedcomEncoding>,
    /// The `1 CHAR` payload exactly as the file wrote it, when it had one.
    pub declared: Option<String>,
    /// Whether a byte-order mark was found and removed.
    pub byte_order_mark: bool,
    /// Bytes that no mapping covered and that became U+FFFD.
    pub undecodable_bytes: usize,
    /// Everything a user should read before accepting the import.
    pub warnings: Vec<String>,
}

impl EncodingReport {
    /// A report that says only which encoding applies — what a caller that
    /// serialized the document itself (always UTF-8) reports, since nothing
    /// was decoded and there is nothing to warn about.
    #[must_use]
    pub fn for_encoding(encoding: GedcomEncoding) -> Self {
        Self {
            used: Some(encoding),
            ..Self::default()
        }
    }

    /// A one-line summary for the import preview.
    #[must_use]
    pub fn summary(&self) -> String {
        let used = self.used.map_or("unknown", GedcomEncoding::label);
        let mut text = format!("Read as {used}");
        if self.byte_order_mark {
            text.push_str(" (byte-order mark)");
        }
        match &self.declared {
            Some(declared) => {
                let _ = fmt::Write::write_fmt(&mut text, format_args!(", declared {declared}"));
            }
            None => text.push_str(", no CHAR declared"),
        }
        if self.undecodable_bytes > 0 {
            let _ = fmt::Write::write_fmt(
                &mut text,
                format_args!(", {} byte(s) undecodable", self.undecodable_bytes),
            );
        }
        text
    }
}

/// Reads GEDCOM bytes as text, choosing an encoding and reporting the choice.
///
/// The order of authority is: a byte-order mark, then UTF-16 recognized from
/// its null bytes, then the `1 CHAR` declaration, then a fallback that prefers
/// UTF-8 when the bytes are valid UTF-8 and ANSEL when they are not.
///
/// # Errors
///
/// Returns [`GedcomError`] when the input exceeds the limit. A file that
/// cannot be decoded cleanly is *not* an error: undecodable bytes become
/// U+FFFD and are counted, so the user can see the damage and decide, rather
/// than losing the whole file to a few bytes.
pub fn decode_gedcom(bytes: &[u8]) -> Result<(String, EncodingReport), GedcomError> {
    decode_gedcom_with(bytes, Limits::DEFAULT)
}

/// Reads GEDCOM bytes as text with explicit limits.
///
/// # Errors
///
/// As [`decode_gedcom`].
pub fn decode_gedcom_with(
    bytes: &[u8],
    limits: Limits,
) -> Result<(String, EncodingReport), GedcomError> {
    if bytes.len() > limits.input_bytes {
        return Err(fault(
            0,
            GedcomErrorKind::Limit,
            format!(
                "the file is {} MB and the limit is {} MB",
                bytes.len() / (1024 * 1024),
                limits.input_bytes / (1024 * 1024)
            ),
        ));
    }

    let mut report = EncodingReport::default();

    let (body, marked) = strip_byte_order_mark(bytes);
    report.byte_order_mark = marked.is_some();

    // A mark settles it: the file says what it is in its own first bytes.
    if let Some(encoding) = marked {
        report.declared = declared_charset(body, encoding);
        let text = decode_as(body, encoding, &mut report);
        finish(encoding, &mut report);
        return Ok((text, report));
    }

    // UTF-16 without a mark still announces itself: every GEDCOM begins with
    // the ASCII digit `0`, so one half of that code unit is a null byte.
    if let Some(encoding) = unmarked_utf16(body) {
        report.declared = declared_charset(body, encoding);
        report.warnings.push(format!(
            "File is {encoding} but carries no byte-order mark."
        ));
        let text = decode_as(body, encoding, &mut report);
        finish(encoding, &mut report);
        return Ok((text, report));
    }

    // Everything below is byte-oriented, so the header can be read as ASCII.
    report.declared = declared_charset(body, GedcomEncoding::Utf8);
    let declared = report
        .declared
        .as_ref()
        .map(|value| value.trim().to_owned());
    let encoding = match declared.as_deref() {
        Some(declared) => match_declared(declared, body, &mut report),
        None => {
            // No declaration. UTF-8 is a superset of ASCII, so trying it first
            // never damages a plain file, and failing it is good evidence the
            // file is one of the older single-byte sets.
            if std::str::from_utf8(body).is_ok() {
                GedcomEncoding::Utf8
            } else {
                report.warnings.push(
                    "File declares no CHAR and is not valid UTF-8; read as ANSEL, the GEDCOM 5.5 default."
                        .to_owned(),
                );
                GedcomEncoding::Ansel
            }
        }
    };

    let text = decode_as(body, encoding, &mut report);
    finish(encoding, &mut report);
    Ok((text, report))
}

fn finish(encoding: GedcomEncoding, report: &mut EncodingReport) {
    report.used = Some(encoding);
    if report.undecodable_bytes > 0 {
        report.warnings.push(format!(
            "{} byte(s) had no mapping in {encoding} and were replaced with U+FFFD.",
            report.undecodable_bytes
        ));
    }
}

/// Resolves a `CHAR` payload to an encoding, warning when the file's contents
/// contradict it.
fn match_declared(declared: &str, body: &[u8], report: &mut EncodingReport) -> GedcomEncoding {
    let normalized = declared
        .chars()
        .filter(char::is_ascii_alphanumeric)
        .collect::<String>()
        .to_ascii_uppercase();

    match normalized.as_str() {
        "UTF8" => {
            if std::str::from_utf8(body).is_ok() {
                GedcomEncoding::Utf8
            } else {
                // Windows-1252 maps every byte, so it recovers the text rather
                // than losing the file. The mismatch is the story to tell.
                report.warnings.push(
                    "File declares UTF-8 but contains invalid UTF-8; read as Windows-1252 instead."
                        .to_owned(),
                );
                GedcomEncoding::Ansi
            }
        }
        "ANSEL" => GedcomEncoding::Ansel,
        "ANSI" | "WINDOWS1252" | "CP1252" | "IBMWINDOWS" => GedcomEncoding::Ansi,
        "ASCII" | "USASCII" | "ANSIZ3947" => GedcomEncoding::Ascii,
        "UNICODE" | "UTF16" => {
            // 5.5.1 requires a byte-order mark for UNICODE and this file has
            // none, or an earlier branch would have taken it.
            report.warnings.push(
                "File declares UNICODE but has no byte-order mark and no UTF-16 structure; read as UTF-8."
                    .to_owned(),
            );
            GedcomEncoding::Utf8
        }
        _ => {
            report.warnings.push(format!(
                "Unrecognized CHAR value {declared:?}; read as UTF-8."
            ));
            GedcomEncoding::Utf8
        }
    }
}

fn strip_byte_order_mark(bytes: &[u8]) -> (&[u8], Option<GedcomEncoding>) {
    if let Some(rest) = bytes.strip_prefix(&[0xEF, 0xBB, 0xBF]) {
        return (rest, Some(GedcomEncoding::Utf8));
    }
    if let Some(rest) = bytes.strip_prefix(&[0xFE, 0xFF]) {
        return (rest, Some(GedcomEncoding::Utf16Be));
    }
    if let Some(rest) = bytes.strip_prefix(&[0xFF, 0xFE]) {
        return (rest, Some(GedcomEncoding::Utf16Le));
    }
    (bytes, None)
}

const fn unmarked_utf16(bytes: &[u8]) -> Option<GedcomEncoding> {
    match bytes {
        [0x00, second, ..] if *second != 0x00 => Some(GedcomEncoding::Utf16Be),
        [first, 0x00, ..] if *first != 0x00 => Some(GedcomEncoding::Utf16Le),
        _ => None,
    }
}

/// Finds the `1 CHAR` payload by reading the header as ASCII.
///
/// Every encoding here agrees with ASCII on the bytes a header is written in,
/// so this works before the encoding is known — which is the point.
fn declared_charset(bytes: &[u8], encoding: GedcomEncoding) -> Option<String> {
    let head = &bytes[..bytes.len().min(HEADER_SCAN_BYTES)];
    let text = match encoding {
        GedcomEncoding::Utf16Be | GedcomEncoding::Utf16Le => {
            let mut scratch = EncodingReport::default();
            decode_utf16(head, encoding == GedcomEncoding::Utf16Be, &mut scratch)
        }
        _ => head.iter().map(|byte| char::from(*byte)).collect(),
    };

    text.lines()
        .map(str::trim_end)
        .find_map(|line| line.strip_prefix("1 CHAR "))
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .map(str::to_owned)
}

fn decode_as(bytes: &[u8], encoding: GedcomEncoding, report: &mut EncodingReport) -> String {
    match encoding {
        GedcomEncoding::Utf16Be => decode_utf16(bytes, true, report),
        GedcomEncoding::Utf16Le => decode_utf16(bytes, false, report),
        GedcomEncoding::Ansel => decode_ansel(bytes, report),
        GedcomEncoding::Ansi => decode_windows_1252(bytes),
        GedcomEncoding::Ascii => decode_ascii(bytes, report),
        GedcomEncoding::Utf8 => std::str::from_utf8(bytes).map_or_else(
            |_| {
                let text = String::from_utf8_lossy(bytes).into_owned();
                report.undecodable_bytes += text.matches('\u{FFFD}').count();
                text
            },
            str::to_owned,
        ),
    }
}

fn decode_ascii(bytes: &[u8], report: &mut EncodingReport) -> String {
    bytes
        .iter()
        .map(|byte| {
            if byte.is_ascii() {
                char::from(*byte)
            } else {
                report.undecodable_bytes += 1;
                '\u{FFFD}'
            }
        })
        .collect()
}

fn decode_utf16(bytes: &[u8], big_endian: bool, report: &mut EncodingReport) -> String {
    if !bytes.len().is_multiple_of(2) {
        report
            .warnings
            .push("UTF-16 file has an odd number of bytes; the final byte was ignored.".to_owned());
    }
    let units = bytes
        .as_chunks::<2>()
        .0
        .iter()
        .map(|pair| {
            if big_endian {
                u16::from_be_bytes([pair[0], pair[1]])
            } else {
                u16::from_le_bytes([pair[0], pair[1]])
            }
        })
        .collect::<Vec<_>>();

    let mut text = String::with_capacity(units.len());
    for unit in char::decode_utf16(units) {
        text.push(unit.unwrap_or_else(|_| {
            report.undecodable_bytes += 1;
            '\u{FFFD}'
        }));
    }
    text
}

/// Windows-1252, which differs from Latin-1 only in `0x80`–`0x9F`.
fn decode_windows_1252(bytes: &[u8]) -> String {
    bytes
        .iter()
        .map(|byte| match byte {
            0x80..=0x9F => WINDOWS_1252_HIGH[usize::from(byte - 0x80)],
            other => char::from(*other),
        })
        .collect()
}

/// The five positions Windows-1252 leaves undefined map to the C1 control they
/// sit on, which keeps the text the same length and loses nothing meaningful.
pub const WINDOWS_1252_HIGH: [char; 32] = [
    '\u{20AC}', '\u{0081}', '\u{201A}', '\u{0192}', '\u{201E}', '\u{2026}', '\u{2020}', '\u{2021}',
    '\u{02C6}', '\u{2030}', '\u{0160}', '\u{2039}', '\u{0152}', '\u{008D}', '\u{017D}', '\u{008F}',
    '\u{0090}', '\u{2018}', '\u{2019}', '\u{201C}', '\u{201D}', '\u{2022}', '\u{2013}', '\u{2014}',
    '\u{02DC}', '\u{2122}', '\u{0161}', '\u{203A}', '\u{0153}', '\u{009D}', '\u{017E}', '\u{0178}',
];

/// Decodes ANSEL as GEDCOM 5.5 Appendix D defines it.
///
/// The one structural difference from every other encoding here: a diacritic
/// comes *before* the letter it modifies, where Unicode puts it after. So a
/// run of marks is buffered, the base character is emitted, and the marks
/// follow it in the order they were written.
fn decode_ansel(bytes: &[u8], report: &mut EncodingReport) -> String {
    let mut text = String::with_capacity(bytes.len());
    let mut marks = Vec::new();
    let mut index = 0;

    while index < bytes.len() {
        let byte = bytes[index];
        index += 1;

        if let Some(mark) = ansel_combining(byte) {
            marks.push(mark);
            continue;
        }

        let base = if byte.is_ascii() {
            char::from(byte)
        } else if let Some(character) = ansel_graphic(byte) {
            character
        } else {
            report.undecodable_bytes += 1;
            '\u{FFFD}'
        };

        text.push(base);
        // A mark with nothing after it is written anyway rather than dropped;
        // losing evidence silently is worse than an odd-looking character.
        text.extend(marks.iter().copied());
        marks.clear();
    }

    text.extend(marks);
    text
}

/// The combining diacritics, `0xE0`–`0xFB` and `0xFE`.
const fn ansel_combining(byte: u8) -> Option<char> {
    Some(match byte {
        0xE0 => '\u{0309}', // hook above
        0xE1 => '\u{0300}', // grave
        0xE2 => '\u{0301}', // acute
        0xE3 => '\u{0302}', // circumflex
        0xE4 => '\u{0303}', // tilde
        0xE5 => '\u{0304}', // macron
        0xE6 => '\u{0306}', // breve
        0xE7 => '\u{0307}', // dot above
        0xE8 => '\u{0308}', // diaeresis
        0xE9 => '\u{030C}', // caron
        0xEA => '\u{030A}', // ring above
        0xEB => '\u{FE20}', // ligature, left half
        0xEC => '\u{FE21}', // ligature, right half
        0xED => '\u{0315}', // comma above right
        0xEE => '\u{030B}', // double acute
        0xEF => '\u{0310}', // candrabindu
        0xF0 => '\u{0327}', // cedilla
        0xF1 => '\u{0328}', // ogonek
        0xF2 => '\u{0323}', // dot below
        0xF3 => '\u{0324}', // diaeresis below
        0xF4 => '\u{0325}', // ring below
        0xF5 => '\u{0333}', // double low line
        0xF6 => '\u{0332}', // line below
        0xF7 => '\u{0326}', // comma below
        0xF8 => '\u{031C}', // left half ring below
        0xF9 => '\u{032E}', // breve below
        0xFA => '\u{FE22}', // double tilde, left half
        0xFB => '\u{FE23}', // double tilde, right half
        0xFE => '\u{0313}', // comma above
        _ => return None,
    })
}

/// The non-combining graphic characters, `0xA1`–`0xCF`, including the two LDS
/// box extensions and the two midline letters GEDCOM 5.5 adds.
const fn ansel_graphic(byte: u8) -> Option<char> {
    Some(match byte {
        0xA1 => 'Ł',
        0xA2 => 'Ø',
        0xA3 => 'Đ',
        0xA4 => 'Þ',
        0xA5 => 'Æ',
        0xA6 => 'Œ',
        0xA7 => '\u{02B9}', // single prime
        0xA8 => '·',
        0xA9 => '\u{266D}', // musical flat
        0xAA => '®',
        0xAB => '±',
        0xAC => 'Ơ',
        0xAD => 'Ư',
        0xAE => '\u{02BB}', // left half ring
        0xB0 => '\u{02BC}', // right half ring
        0xB1 => 'ł',
        0xB2 => 'ø',
        0xB3 => 'đ',
        0xB4 => 'þ',
        0xB5 => 'æ',
        0xB6 => 'œ',
        0xB7 => '\u{02BA}', // double prime
        0xB8 => 'ı',
        0xB9 => '£',
        0xBA => 'ð',
        0xBC => 'ơ',
        0xBD => 'ư',
        0xBE => '\u{25A1}', // empty box, an LDS extension
        0xBF => '\u{25A0}', // black box, an LDS extension
        0xC0 => '°',
        0xC1 => '\u{2113}', // script l
        0xC2 => '\u{2117}', // phonograph copyright
        0xC3 => '©',
        0xC4 => '\u{266F}', // musical sharp
        0xC5 => '¿',
        0xC6 => '¡',
        0xCD => 'e', // midline e, an LDS extension with no Unicode of its own
        0xCE => 'o', // midline o, likewise
        0xCF => 'ß',
        _ => return None,
    })
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn a_utf8_byte_order_mark_is_stripped_and_reported() {
        let bytes = b"\xEF\xBB\xBF0 HEAD\n0 TRLR\n";

        let (text, report) = decode_gedcom(bytes).expect("decode");

        assert!(
            text.starts_with("0 HEAD"),
            "mark must not survive: {text:?}"
        );
        assert!(report.byte_order_mark);
        assert_eq!(report.used, Some(GedcomEncoding::Utf8));
    }

    #[test]
    fn utf16_is_read_with_or_without_a_byte_order_mark() {
        let marked = b"\xFF\xFE0\x00 \x00H\x00E\x00A\x00D\x00";
        let (text, report) = decode_gedcom(marked).expect("decode marked");
        assert_eq!(text, "0 HEAD");
        assert_eq!(report.used, Some(GedcomEncoding::Utf16Le));
        assert!(report.byte_order_mark);

        let bare = b"\x000\x00 \x00H\x00E\x00A\x00D";
        let (text, report) = decode_gedcom(bare).expect("decode bare");
        assert_eq!(text, "0 HEAD");
        assert_eq!(report.used, Some(GedcomEncoding::Utf16Be));
        assert!(!report.byte_order_mark);
        assert!(
            !report.warnings.is_empty(),
            "a missing mark is worth saying"
        );
    }

    #[test]
    fn ansel_puts_a_diacritic_after_the_letter_it_modifies() {
        // "1 NAME Jos<acute>e" — ANSEL writes the accent first.
        let bytes = b"0 HEAD\n1 CHAR ANSEL\n0 @I1@ INDI\n1 NAME Jos\xE2e\n";

        let (text, report) = decode_gedcom(bytes).expect("decode");

        assert_eq!(report.used, Some(GedcomEncoding::Ansel));
        assert_eq!(report.declared.as_deref(), Some("ANSEL"));
        assert!(text.contains("Jose\u{0301}"), "got {text:?}");
        assert_eq!(report.undecodable_bytes, 0);
    }

    #[test]
    fn ansel_graphic_characters_decode() {
        let bytes = b"0 HEAD\n1 CHAR ANSEL\n1 NOTE \xA2 \xB2 \xCF\n";

        let (text, _) = decode_gedcom(bytes).expect("decode");

        assert!(text.contains("Ø ø ß"), "got {text:?}");
    }

    #[test]
    fn a_declared_charset_that_the_bytes_contradict_is_reported_not_obeyed() {
        // Declares UTF-8, contains a lone 0xE9 — Windows-1252 recovers it.
        let bytes = b"0 HEAD\n1 CHAR UTF-8\n1 NOTE caf\xE9\n";

        let (text, report) = decode_gedcom(bytes).expect("decode");

        assert_eq!(report.used, Some(GedcomEncoding::Ansi));
        assert_eq!(report.declared.as_deref(), Some("UTF-8"));
        assert!(text.contains("café"), "got {text:?}");
        assert!(
            report
                .warnings
                .iter()
                .any(|warning| warning.contains("declares UTF-8")),
            "{:?}",
            report.warnings
        );
    }

    #[test]
    fn an_undeclared_file_prefers_utf8_and_falls_back_to_ansel() {
        let utf8 = "0 HEAD\n1 NOTE café\n".as_bytes();
        let (text, report) = decode_gedcom(utf8).expect("decode utf8");
        assert_eq!(report.used, Some(GedcomEncoding::Utf8));
        assert!(text.contains("café"));
        assert!(report.declared.is_none());

        let ansel = b"0 HEAD\n1 NOTE caf\xE2e\n";
        let (text, report) = decode_gedcom(ansel).expect("decode ansel");
        assert_eq!(report.used, Some(GedcomEncoding::Ansel));
        assert!(text.contains("cafe\u{0301}"), "got {text:?}");
    }

    #[test]
    fn utf16_surrogate_pairs_decode_to_the_characters_they_spell() {
        // "0 HEAD\n1 NOTE 𝄞" — the clef is U+1D11E, a surrogate pair in
        // UTF-16, which the per-unit reader must join rather than replace.
        let mut bytes = vec![0xFFu8, 0xFE];
        for unit in "0 HEAD\n1 NOTE \u{1D11E}\n".encode_utf16() {
            bytes.extend_from_slice(&unit.to_le_bytes());
        }

        let (text, report) = decode_gedcom(&bytes).expect("decode");

        assert_eq!(report.undecodable_bytes, 0);
        assert!(text.contains('\u{1D11E}'), "got {text:?}");
    }

    #[test]
    fn a_char_line_beyond_the_header_scan_window_falls_back_honestly() {
        // The declaration hunt reads a bounded prefix; a CHAR pushed past it
        // by an absurd header is treated as undeclared — valid UTF-8 reads as
        // UTF-8 — rather than making the scan unbounded.
        use std::fmt::Write as _;
        let mut text = String::from("0 HEAD\n");
        for index in 0..600 {
            let _ = writeln!(
                text,
                "1 NOTE padding line number {index} to push the declaration far down"
            );
        }
        text.push_str("1 CHAR ANSEL\n0 TRLR\n");

        let (_, report) = decode_gedcom(text.as_bytes()).expect("decode");

        assert_eq!(report.declared, None, "the declaration is out of reach");
        assert_eq!(report.used, Some(GedcomEncoding::Utf8));
    }

    #[test]
    fn an_oversized_file_is_refused_with_the_limit_named() {
        // The limit is passed in rather than allocating the default one, which
        // is 128 MB and would make this test cost more than it proves.
        let limits = Limits {
            input_bytes: 2 * 1024 * 1024,
            ..Limits::DEFAULT
        };
        let bytes = vec![b'0'; limits.input_bytes + 1];

        let error = decode_gedcom_with(&bytes, limits).expect_err("must refuse");

        let message = error.to_string();
        assert!(message.contains("2 MB"), "limit must be named: {message}");
    }

    #[test]
    fn undecodable_bytes_are_counted_rather_than_failing_the_import() {
        let bytes = b"0 HEAD\n1 CHAR ANSEL\n1 NOTE \xD0\n";

        let (text, report) = decode_gedcom(bytes).expect("decode");

        assert_eq!(report.undecodable_bytes, 1);
        assert!(text.contains('\u{FFFD}'));
        assert!(!report.warnings.is_empty());
    }
}