src/tools/systemd.rs: implement escape_unit and unescape_unit

src/tools/systemd.rs

@@ -4,3 +4,71 @@ pub mod config;
 mod parse_time;
 pub mod tm_editor;
 pub mod time;
+
+use anyhow::{bail, Error};
+
+/// Escape strings for usage in systemd unit names
+pub fn escape_unit(mut unit: &str, is_path: bool) -> String {
+
+    if is_path {
+        unit = unit.trim_matches('/');
+        if unit.is_empty() {
+            return String::from("-");
+        }
+    }
+
+    let unit = unit.as_bytes();
+
+    let mut escaped = String::new();
+
+    for (i, c) in unit.iter().enumerate() {
+        if *c == b'/' {
+            escaped.push('-');
+            continue;
+        }
+        if (i == 0 && *c == b'.') || !((*c >= b'0' && *c <= b'9') || (*c >= b'A' && *c <= b'Z') || (*c >= b'a' && *c <= b'z')) {
+            escaped.push_str(&format!("\\x{:0x}", c));
+        } else {
+            escaped.push(*c as char);
+        }
+    }
+    escaped
+}
+
+fn parse_hex_digit(d: u8) ->  Result<u8, Error> {
+    if d >= b'0' && d <= b'9' { return Ok(d - b'0'); }
+    if d >= b'A' && d <= b'F' {  return Ok(d - b'A' + 10); }
+    if d >= b'a' && d <= b'f' { return Ok(d - b'a' + 10); }
+    bail!("got invalid hex digit");
+}
+
+/// Unescape strings used in systemd unit names
+pub fn unescape_unit(text: &str) -> Result<String, Error> {
+
+    let mut i = text.as_bytes();
+
+    let mut data: Vec<u8> = Vec::new();
+
+    loop {
+        if i.is_empty() { break; }
+        let next = i[0];
+        if next == b'\\' {
+            if i.len() < 4 { bail!("short input"); }
+            if i[1] != b'x' { bail!("unkwnown escape sequence"); }
+            let h1 = parse_hex_digit(i[2])?;
+            let h0 = parse_hex_digit(i[3])?;
+            data.push(h1<<4|h0);
+            i = &i[4..]
+        } else if next == b'-' {
+            data.push(b'/');
+            i = &i[1..]
+        } else {
+            data.push(next);
+            i = &i[1..]
+        }
+    }
+
+    let text = String::from_utf8(data)?;
+
+    Ok(text)
+}