JasonLi-cn commented on code in PR #9268:
URL: https://github.com/apache/arrow-datafusion/pull/9268#discussion_r1501743637
##########
datafusion/sql/src/utils.rs:
##########
@@ -246,3 +246,168 @@ pub(crate) fn normalize_ident(id: Ident) -> String {
None => id.value.to_ascii_lowercase(),
}
}
+
+pub(crate) fn unescape(s: &str) -> Option<String> {
+ let mut queue: VecDeque<_> = String::from(s).chars().collect();
+ let mut unescaped = String::new();
+
+ while let Some(c) = queue.pop_front() {
+ if c != '\\' {
+ unescaped.push(c);
+ continue;
+ }
+
+ let ch = match queue.pop_front() {
+ Some(c) => match c {
+ 'b' => '\u{0008}',
+ 'f' => '\u{000C}',
+ 'n' => '\n',
+ 'r' => '\r',
+ 't' => '\t',
+ 'u' => unescape_unicode_16(&mut queue)?,
+ 'U' => unescape_unicode_32(&mut queue)?,
+ 'x' => unescape_byte(&mut queue)?,
+ c if c.is_digit(8) => unescape_octal(c, &mut queue)?,
+ c => c,
+ },
+ None => return None,
+ };
+ unescaped.push(ch);
+ }
+
+ Some(unescaped)
+}
+
+// Hexadecimal byte value. \xh, \xhh (h = 0–9, A–F)
+fn unescape_byte(queue: &mut VecDeque<char>) -> Option<char> {
+ let mut s = String::new();
+
+ for _ in 0..2 {
+ match next_hex_digit(queue) {
+ Some(c) => s.push(c),
+ None => break,
+ }
+ }
+
+ if s.is_empty() {
+ return Some('x');
+ }
+
+ to_char::<16>(&s)
+}
+
+#[inline]
+fn next_hex_digit(queue: &mut VecDeque<char>) -> Option<char> {
+ match queue.front() {
+ Some(c) if c.is_ascii_hexdigit() => queue.pop_front(),
+ _ => None,
+ }
+}
+
+// 16-bit hexadecimal Unicode character value. \uxxxx (x = 0–9, A–F)
+fn unescape_unicode_16(queue: &mut VecDeque<char>) -> Option<char> {
+ unescape_unicode::<4>(queue)
+}
+
+// 32-bit hexadecimal Unicode character value. \Uxxxxxxxx (x = 0–9, A–F)
+fn unescape_unicode_32(queue: &mut VecDeque<char>) -> Option<char> {
+ unescape_unicode::<8>(queue)
+}
+
+fn unescape_unicode<const NUM: usize>(queue: &mut VecDeque<char>) ->
Option<char> {
+ let mut s = String::new();
+ for _ in 0..NUM {
+ s.push(queue.pop_front()?);
+ }
+ to_char::<16>(&s)
+}
+
+// Octal byte value. \o, \oo, \ooo (o = 0–7)
+fn unescape_octal(c: char, queue: &mut VecDeque<char>) -> Option<char> {
+ let mut s = String::new();
+
+ match c {
+ '0' | '1' | '2' | '3' => {
+ s.push(c);
+ for _ in 0..2 {
+ match next_octal_digest(queue) {
+ Some(c) => s.push(c),
+ None => break,
+ }
+ }
+ }
+ '4' | '5' | '6' | '7' => {
+ s.push(c);
+ if let Some(c) = next_octal_digest(queue) {
+ s.push(c);
+ }
+ }
+ _ => return None,
+ }
+ to_char::<8>(&s)
+}
+
+#[inline]
+fn next_octal_digest(queue: &mut VecDeque<char>) -> Option<char> {
+ match queue.front() {
+ Some(c) if c.is_digit(8) => queue.pop_front(),
+ _ => None,
+ }
+}
+
+#[inline]
+fn to_char<const RADIX: u32>(s: &str) -> Option<char> {
+ match u32::from_str_radix(s, RADIX) {
+ Err(_) => None,
+ Ok(n) => char::from_u32(n),
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::unescape;
+
+ fn check_unescape(s: &str, expected: Option<&str>) {
+ assert_eq!(unescape(s), expected.map(|s| s.to_string()));
+ }
+
+ #[test]
+ fn test_unescape() {
+ check_unescape(r"\b", Some("\u{0008}"));
+ check_unescape(r"\f", Some("\u{000C}"));
+ check_unescape(r"\t", Some("\t"));
+ check_unescape(r"\r\n", Some("\r\n"));
+ check_unescape(r"\/", Some("/"));
+ check_unescape(r"/", Some("/"));
+ check_unescape(r"\\", Some("\\"));
+
+ // 16 and 32-bit hexadecimal Unicode character value
+ check_unescape(r"\u4c91", Some("\u{4c91}"));
+ check_unescape(r"\u4c916", Some("\u{4c91}6"));
+ check_unescape(r"\U0010FFFF", Some("\u{10FFFF}"));
+ check_unescape(r"\u", None);
+ check_unescape(r"\U", None);
+ check_unescape(r"\U1010FFFF", None);
+
+ // hexadecimal byte value
+ check_unescape(r"\xCAD", Some("\u{00ca}D"));
+ check_unescape(r"\xA9", Some("\u{00a9}"));
+ check_unescape(r"\x4B", Some("\u{004b}"));
+ check_unescape(r"\x4", Some("\u{0004}"));
+ check_unescape(r"\x4L", Some("\u{0004}L"));
+ check_unescape(r"\x", Some("x"));
+ check_unescape(r"\xP", Some("xP"));
+
+ // octal byte value
+ check_unescape(r"\1", Some("\u{0001}"));
+ check_unescape(r"\12", Some("\u{000a}"));
+ check_unescape(r"\123", Some("\u{0053}"));
+ check_unescape(r"\1232", Some("\u{0053}2"));
+ check_unescape(r"\4", Some("\u{0004}"));
+ check_unescape(r"\45", Some("\u{0025}"));
+ check_unescape(r"\450", Some("\u{0025}0"));
Review Comment:
When I wrote this `unescape` function, I was referring to the behavior of pg.
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