head: remove clippy::cognitive_complexity by moving some content in a…

… function (#5366)

* head: remove a clippy::cognitive_complexity by moving some content into a function

* Remove duplicate comment

src/uu/head/src/parse.rs

@@ -13,7 +13,6 @@ pub enum ParseError {
 }
 /// Parses obsolete syntax
 /// head -NUM\[kmzv\] // spell-checker:disable-line
-#[allow(clippy::cognitive_complexity)]
 pub fn parse_obsolete(src: &str) -> Option<Result<impl Iterator<Item = OsString>, ParseError>> {
  let mut chars = src.char_indices();
  if let Some((_, '-')) = chars.next() {
@@ -30,72 +29,82 @@ pub fn parse_obsolete(src: &str) -> Option<Result<impl Iterator<Item = OsString>
  }
  }
  if has_num {
- match src[1..=num_end].parse::<usize>() {
- Ok(num) => {
- let mut quiet = false;
- let mut verbose = false;
- let mut zero_terminated = false;
- let mut multiplier = None;
- let mut c = last_char;
- loop {
- // not that here, we only match lower case 'k', 'c', and 'm'
- match c {
- // we want to preserve order
- // this also saves us 1 heap allocation
- 'q' => {
- quiet = true;
- verbose = false;
- }
- 'v' => {
- verbose = true;
- quiet = false;
- }
- 'z' => zero_terminated = true,
- 'c' => multiplier = Some(1),
- 'b' => multiplier = Some(512),
- 'k' => multiplier = Some(1024),
- 'm' => multiplier = Some(1024 * 1024),
- '\0' => {}
- _ => return Some(Err(ParseError::Syntax)),
- }
- if let Some((_, next)) = chars.next() {
- c = next;
- } else {
- break;
- }
- }
- let mut options = Vec::new();
- if quiet {
- options.push(OsString::from("-q"));
- }
- if verbose {
- options.push(OsString::from("-v"));
- }
- if zero_terminated {
- options.push(OsString::from("-z"));
- }
- if let Some(n) = multiplier {
- options.push(OsString::from("-c"));
- let num = match num.checked_mul(n) {
- Some(n) => n,
- None => return Some(Err(ParseError::Overflow)),
- };
- options.push(OsString::from(format!("{num}")));
- } else {
- options.push(OsString::from("-n"));
- options.push(OsString::from(format!("{num}")));
- }
- Some(Ok(options.into_iter()))
- }
- Err(_) => Some(Err(ParseError::Overflow)),
- }
+ process_num_block(&src[1..=num_end], last_char, &mut chars)
  } else {
  None
  }
  } else {
  None
  }
 }
+
+/// Processes the numeric block of the input string to generate the appropriate options.
+fn process_num_block(
+ src: &str,
+ last_char: char,
+ chars: &mut std::str::CharIndices,
+) -> Option<Result<impl Iterator<Item = OsString>, ParseError>> {
+ match src.parse::<usize>() {
+ Ok(num) => {
+ let mut quiet = false;
+ let mut verbose = false;
+ let mut zero_terminated = false;
+ let mut multiplier = None;
+ let mut c = last_char;
+ loop {
+ // note that here, we only match lower case 'k', 'c', and 'm'
+ match c {
+ // we want to preserve order
+ // this also saves us 1 heap allocation
+ 'q' => {
+ quiet = true;
+ verbose = false;
+ }
+ 'v' => {
+ verbose = true;
+ quiet = false;
+ }
+ 'z' => zero_terminated = true,
+ 'c' => multiplier = Some(1),
+ 'b' => multiplier = Some(512),
+ 'k' => multiplier = Some(1024),
+ 'm' => multiplier = Some(1024 * 1024),
+ '\0' => {}
+ _ => return Some(Err(ParseError::Syntax)),
+ }
+ if let Some((_, next)) = chars.next() {
+ c = next;
+ } else {
+ break;
+ }
+ }
+ let mut options = Vec::new();
+ if quiet {
+ options.push(OsString::from("-q"));
+ }
+ if verbose {
+ options.push(OsString::from("-v"));
+ }
+ if zero_terminated {
+ options.push(OsString::from("-z"));
+ }
+ if let Some(n) = multiplier {
+ options.push(OsString::from("-c"));
+ let num = match num.checked_mul(n) {
+ Some(n) => n,
+ None => return Some(Err(ParseError::Overflow)),
+ };
+ options.push(OsString::from(format!("{num}")));
+ } else {
+ options.push(OsString::from("-n"));
+ options.push(OsString::from(format!("{num}")));
+ }
+ Some(Ok(options.into_iter()))
+ }
+ Err(_) => Some(Err(ParseError::Overflow)),
+ }
+}
+
 /// Parses an -c or -n argument,
 /// the bool specifies whether to read from the end
 pub fn parse_num(src: &str) -> Result<(u64, bool), ParseSizeError> {