grit-lib 0.1.3

Core library for the grit Git implementation
Documentation 
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//! C-style path quoting compatible with Git's `quote.c` / `core.quotepath`.
//!
//! Git quotes pathnames for human-facing output (`ls-files`, `diff --name-only`,
//! `ls-tree --name-only`) using a byte lookup table and optional full octal
//! escaping for non-ASCII bytes when `quote_path_fully` is set (`core.quotepath`,
//! default true).

/// Lookup table from Git `quote.c` (`cq_lookup`). Values:
/// - `1`: emit as `\<ooo>` three-digit octal
/// - `-1`: safe byte (no escape needed inside a quoted string)
/// - `>= 32`: letter escape (`\n`, `\t`, `\"`, …)
/// - `0` for `0x80..=0xFF`: octal only when `quote_fully` is true
const fn cq_byte(b: u8) -> i8 {
    match b {
        0x00..=0x06 => 1,
        0x07 => b'a' as i8,
        0x08 => b'b' as i8,
        0x09 => b't' as i8,
        0x0a => b'n' as i8,
        0x0b => b'v' as i8,
        0x0c => b'f' as i8,
        0x0d => b'r' as i8,
        0x0e..=0x1f => 1,
        0x20 | 0x21 => -1,
        0x22 => b'"' as i8,
        0x23..=0x5b => -1,
        0x5c => b'\\' as i8,
        0x5d..=0x7e => -1,
        0x7f => 1,
        0x80..=0xff => 0,
    }
}

const fn cq_lookup_table() -> [i8; 256] {
    let mut t = [0i8; 256];
    let mut i = 0usize;
    while i < 256 {
        t[i] = cq_byte(i as u8);
        i += 1;
    }
    t
}

static CQ_LOOKUP: [i8; 256] = cq_lookup_table();

#[inline]
fn cq_must_quote(byte: u8, quote_fully: bool) -> bool {
    i32::from(CQ_LOOKUP[byte as usize]) + i32::from(quote_fully) > 0
}

/// Quote `path` in Git C style when needed, matching `quote_c_style` + `core.quotepath`.
///
/// When `quote_fully` is true (Git default, `core.quotepath=true`), non-ASCII bytes are
/// emitted as `\ooo` escapes. When false, UTF-8 / high bytes are copied literally and only
/// ASCII special characters are escaped.
#[must_use]
pub fn quote_c_style(path: &str, quote_fully: bool) -> String {
    let bytes = path.as_bytes();
    let mut any = false;
    for &b in bytes {
        if cq_must_quote(b, quote_fully) {
            any = true;
            break;
        }
    }
    if !any {
        return path.to_owned();
    }

    let mut out = String::with_capacity(path.len() + 2);
    out.push('"');
    let mut p = 0usize;
    while p < bytes.len() {
        let mut len = 0usize;
        while p + len < bytes.len() && !cq_must_quote(bytes[p + len], quote_fully) {
            len += 1;
        }
        out.push_str(path.get(p..p + len).unwrap_or(""));
        p += len;
        if p >= bytes.len() {
            break;
        }
        let ch = bytes[p];
        p += 1;
        out.push('\\');
        let cq = CQ_LOOKUP[ch as usize];
        if cq >= b' ' as i8 {
            out.push(cq as u8 as char);
        } else {
            out.push(char::from(((ch >> 6) & 3) + b'0'));
            out.push(char::from(((ch >> 3) & 7) + b'0'));
            out.push(char::from((ch & 7) + b'0'));
        }
    }
    out.push('"');
    out
}

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

    #[test]
    fn ascii_safe_unchanged() {
        assert_eq!(quote_c_style("Name", true), "Name");
        assert_eq!(quote_c_style("With SP in it", true), "With SP in it");
    }

    #[test]
    fn t3902_expect_quoted() {
        assert_eq!(quote_c_style("Name and a\nLF", true), "\"Name and a\\nLF\"");
        assert_eq!(
            quote_c_style("Name and an\tHT", true),
            "\"Name and an\\tHT\""
        );
        assert_eq!(quote_c_style("Name\"", true), "\"Name\\\"\"");
    }

    #[test]
    fn t3902_expect_raw_mode() {
        let s = "濱野\t純";
        assert_eq!(quote_c_style(s, false), "\"濱野\\t純\"");
        let s2 = "濱野 純";
        assert_eq!(quote_c_style(s2, false), "濱野 純");
    }
}