rustfilepatterns: refactor the pattern of removing a prefix from a &[u8]

Differential Revision: https://phab.mercurial-scm.org/D6766

rust/hg-core/src/filepatterns.rs

@@ -1,383 +1,384 b''
 // filepatterns.rs
 //
 // Copyright 2019 Raphaël Gomès <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Handling of Mercurial-specific patterns.
 
 use crate::{
     utils::{files::get_path_from_bytes, SliceExt},
     LineNumber, PatternError, PatternFileError,
 };
 use lazy_static::lazy_static;
 use regex::bytes::{NoExpand, Regex};
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::Read;
 use std::vec::Vec;
 
 lazy_static! {
     static ref RE_ESCAPE: Vec<Vec<u8>> = {
         let mut v: Vec<Vec<u8>> = (0..=255).map(|byte| vec![byte]).collect();
         let to_escape = b"()[]{}?*+-|^$\\.&~# \t\n\r\x0b\x0c";
         for byte in to_escape {
             v[*byte as usize].insert(0, b'\\');
         }
         v
     };
 }
 
 /// These are matched in order
 const GLOB_REPLACEMENTS: &[(&[u8], &[u8])] =
     &[(b"*/", b"(?:.*/)?"), (b"*", b".*"), (b"", b"[^/]*")];
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum PatternSyntax {
     Regexp,
     /// Glob that matches at the front of the path
     RootGlob,
     /// Glob that matches at any suffix of the path (still anchored at
     /// slashes)
     Glob,
     Path,
     RelPath,
     RelGlob,
     RelRegexp,
     RootFiles,
 }
 
 /// Transforms a glob pattern into a regex
 fn glob_to_re(pat: &[u8]) -> Vec<u8> {
     let mut input = pat;
     let mut res: Vec<u8> = vec![];
     let mut group_depth = 0;
 
     while let Some((c, rest)) = input.split_first() {
         input = rest;
 
         match c {
             b'*' => {
                 for (source, repl) in GLOB_REPLACEMENTS {
-                    if input.starts_with(source) {
-                        input = &input[source.len()..];
+                    if let Some(rest) = input.drop_prefix(source) {
+                        input = rest;
                         res.extend(*repl);
                         break;
                     }
                 }
             }
             b'?' => res.extend(b"."),
             b'[' => {
                 match input.iter().skip(1).position(|b| *b == b']') {
                     None => res.extend(b"\\["),
                     Some(end) => {
                         // Account for the one we skipped
                         let end = end + 1;
 
                         res.extend(b"[");
 
                         for (i, b) in input[..end].iter().enumerate() {
                             if *b == b'!' && i == 0 {
                                 res.extend(b"^")
                             } else if *b == b'^' && i == 0 {
                                 res.extend(b"\\^")
                             } else if *b == b'\\' {
                                 res.extend(b"\\\\")
                             } else {
                                 res.push(*b)
                             }
                         }
                         res.extend(b"]");
                         input = &input[end + 1..];
                     }
                 }
             }
             b'{' => {
                 group_depth += 1;
                 res.extend(b"(?:")
             }
             b'}' if group_depth > 0 => {
                 group_depth -= 1;
                 res.extend(b")");
             }
             b',' if group_depth > 0 => res.extend(b"|"),
             b'\\' => {
                 let c = {
                     if let Some((c, rest)) = input.split_first() {
                         input = rest;
                         c
                     } else {
                         c
                     }
                 };
                 res.extend(&RE_ESCAPE[*c as usize])
             }
             _ => res.extend(&RE_ESCAPE[*c as usize]),
         }
     }
     res
 }
 
 fn escape_pattern(pattern: &[u8]) -> Vec<u8> {
     pattern
         .iter()
         .flat_map(|c| RE_ESCAPE[*c as usize].clone())
         .collect()
 }
 
 fn parse_pattern_syntax(kind: &[u8]) -> Result<PatternSyntax, PatternError> {
     match kind {
         b"re" => Ok(PatternSyntax::Regexp),
         b"path" => Ok(PatternSyntax::Path),
         b"relpath" => Ok(PatternSyntax::RelPath),
         b"rootfilesin" => Ok(PatternSyntax::RootFiles),
         b"relglob" => Ok(PatternSyntax::RelGlob),
         b"relre" => Ok(PatternSyntax::RelRegexp),
         b"glob" => Ok(PatternSyntax::Glob),
         b"rootglob" => Ok(PatternSyntax::RootGlob),
         _ => Err(PatternError::UnsupportedSyntax(
             String::from_utf8_lossy(kind).to_string(),
         )),
     }
 }
 
 /// Builds the regex that corresponds to the given pattern.
 /// If within a `syntax: regexp` context, returns the pattern,
 /// otherwise, returns the corresponding regex.
 fn _build_single_regex(
     syntax: PatternSyntax,
     pattern: &[u8],
     globsuffix: &[u8],
 ) -> Vec<u8> {
     if pattern.is_empty() {
         return vec![];
     }
     match syntax {
         PatternSyntax::Regexp => pattern.to_owned(),
         PatternSyntax::RelRegexp => {
             if pattern[0] == b'^' {
                 return pattern.to_owned();
             }
             let mut res = b".*".to_vec();
             res.extend(pattern);
             res
         }
         PatternSyntax::Path | PatternSyntax::RelPath => {
             if pattern == b"." {
                 return vec![];
             }
             let mut pattern = escape_pattern(pattern);
             pattern.extend(b"(?:/|$)");
             pattern
         }
         PatternSyntax::RootFiles => {
             let mut res = if pattern == b"." {
                 vec![]
             } else {
                 // Pattern is a directory name.
                 let mut as_vec: Vec<u8> = escape_pattern(pattern);
                 as_vec.push(b'/');
                 as_vec
             };
 
             // Anything after the pattern must be a non-directory.
             res.extend(b"[^/]+$");
             res
         }
         PatternSyntax::Glob
         | PatternSyntax::RelGlob
         | PatternSyntax::RootGlob => {
             let mut res: Vec<u8> = vec![];
             if syntax == PatternSyntax::RelGlob {
                 res.extend(b"(?:|.*/)");
             }
 
             res.extend(glob_to_re(pattern));
             res.extend(globsuffix.iter());
             res
         }
     }
 }
 
 const GLOB_SPECIAL_CHARACTERS: [u8; 7] =
     [b'*', b'?', b'[', b']', b'{', b'}', b'\\'];
 
 /// Wrapper function to `_build_single_regex` that short-circuits 'exact' globs
 /// that don't need to be transformed into a regex.
 pub fn build_single_regex(
     kind: &[u8],
     pat: &[u8],
     globsuffix: &[u8],
 ) -> Result<Vec<u8>, PatternError> {
     let enum_kind = parse_pattern_syntax(kind)?;
     if enum_kind == PatternSyntax::RootGlob
         && !pat.iter().any(|b| GLOB_SPECIAL_CHARACTERS.contains(b))
     {
         let mut escaped = escape_pattern(pat);
         escaped.extend(b"(?:/|$)");
         Ok(escaped)
     } else {
         Ok(_build_single_regex(enum_kind, pat, globsuffix))
     }
 }
 
 lazy_static! {
     static ref SYNTAXES: HashMap<&'static [u8], &'static [u8]> = {
         let mut m = HashMap::new();
 
         m.insert(b"re".as_ref(), b"relre:".as_ref());
         m.insert(b"regexp".as_ref(), b"relre:".as_ref());
         m.insert(b"glob".as_ref(), b"relglob:".as_ref());
         m.insert(b"rootglob".as_ref(), b"rootglob:".as_ref());
         m.insert(b"include".as_ref(), b"include".as_ref());
         m.insert(b"subinclude".as_ref(), b"subinclude".as_ref());
         m
     };
 }
 
 pub type PatternTuple = (Vec<u8>, LineNumber, Vec<u8>);
 type WarningTuple = (Vec<u8>, Vec<u8>);
 
 pub fn parse_pattern_file_contents(
     lines: &[u8],
     file_path: &[u8],
     warn: bool,
 ) -> (Vec<PatternTuple>, Vec<WarningTuple>) {
     let comment_regex = Regex::new(r"((?:^|[^\\])(?:\\\\)*)#.*").unwrap();
     let comment_escape_regex = Regex::new(r"\\#").unwrap();
     let mut inputs: Vec<PatternTuple> = vec![];
     let mut warnings: Vec<WarningTuple> = vec![];
 
     let mut current_syntax = b"relre:".as_ref();
 
     for (line_number, mut line) in lines.split(|c| *c == b'\n').enumerate() {
         let line_number = line_number + 1;
 
         let line_buf;
         if line.contains(&b'#') {
             if let Some(cap) = comment_regex.captures(line) {
                 line = &line[..cap.get(1).unwrap().end()]
             }
             line_buf = comment_escape_regex.replace_all(line, NoExpand(b"#"));
             line = &line_buf;
         }
 
         let mut line = line.trim_end();
 
         if line.is_empty() {
             continue;
         }
 
-        if line.starts_with(b"syntax:") {
-            let syntax = line[b"syntax:".len()..].trim();
+        if let Some(syntax) = line.drop_prefix(b"syntax:") {
+            let syntax = syntax.trim();
 
             if let Some(rel_syntax) = SYNTAXES.get(syntax) {
                 current_syntax = rel_syntax;
             } else if warn {
                 warnings.push((file_path.to_owned(), syntax.to_owned()));
             }
             continue;
         }
 
         let mut line_syntax: &[u8] = &current_syntax;
 
         for (s, rels) in SYNTAXES.iter() {
-            if line.starts_with(rels) {
+            if let Some(rest) = line.drop_prefix(rels) {
                 line_syntax = rels;
-                line = &line[rels.len()..];
+                line = rest;
                 break;
-            } else if line.starts_with(&[s, b":".as_ref()].concat()) {
+            }
+            if let Some(rest) = line.drop_prefix(&[s, &b":"[..]].concat()) {
                 line_syntax = rels;
-                line = &line[s.len() + 1..];
+                line = rest;
                 break;
             }
         }
 
         inputs.push((
             [line_syntax, line].concat(),
             line_number,
             line.to_owned(),
         ));
     }
     (inputs, warnings)
 }
 
 pub fn read_pattern_file(
     file_path: &[u8],
     warn: bool,
 ) -> Result<(Vec<PatternTuple>, Vec<WarningTuple>), PatternFileError> {
     let mut f = File::open(get_path_from_bytes(file_path))?;
     let mut contents = Vec::new();
 
     f.read_to_end(&mut contents)?;
 
     Ok(parse_pattern_file_contents(&contents, file_path, warn))
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn escape_pattern_test() {
         let untouched = br#"!"%',/0123456789:;<=>@ABCDEFGHIJKLMNOPQRSTUVWXYZ_`abcdefghijklmnopqrstuvwxyz"#;
         assert_eq!(escape_pattern(untouched), untouched.to_vec());
         // All escape codes
         assert_eq!(
             escape_pattern(br#"()[]{}?*+-|^$\\.&~# \t\n\r\v\f"#),
             br#"\(\)\[\]\{\}\?\*\+\-\|\^\$\\\\\.\&\~\#\ \\t\\n\\r\\v\\f"#
                 .to_vec()
         );
     }
 
     #[test]
     fn glob_test() {
         assert_eq!(glob_to_re(br#"?"#), br#"."#);
         assert_eq!(glob_to_re(br#"*"#), br#"[^/]*"#);
         assert_eq!(glob_to_re(br#"**"#), br#".*"#);
         assert_eq!(glob_to_re(br#"**/a"#), br#"(?:.*/)?a"#);
         assert_eq!(glob_to_re(br#"a/**/b"#), br#"a/(?:.*/)?b"#);
         assert_eq!(glob_to_re(br#"[a*?!^][^b][!c]"#), br#"[a*?!^][\^b][^c]"#);
         assert_eq!(glob_to_re(br#"{a,b}"#), br#"(?:a|b)"#);
         assert_eq!(glob_to_re(br#".\*\?"#), br#"\.\*\?"#);
     }
 
     #[test]
     fn test_parse_pattern_file_contents() {
         let lines = b"syntax: glob\n*.elc";
 
         assert_eq!(
             vec![(b"relglob:*.elc".to_vec(), 2, b"*.elc".to_vec())],
             parse_pattern_file_contents(lines, b"file_path", false).0,
         );
 
         let lines = b"syntax: include\nsyntax: glob";
 
         assert_eq!(
             parse_pattern_file_contents(lines, b"file_path", false).0,
             vec![]
         );
         let lines = b"glob:**.o";
         assert_eq!(
             parse_pattern_file_contents(lines, b"file_path", false).0,
             vec![(b"relglob:**.o".to_vec(), 1, b"**.o".to_vec())]
         );
     }
 
     #[test]
     fn test_build_single_regex_shortcut() {
         assert_eq!(
             br"(?:/|$)".to_vec(),
             build_single_regex(b"rootglob", b"", b"").unwrap()
         );
         assert_eq!(
             br"whatever(?:/|$)".to_vec(),
             build_single_regex(b"rootglob", b"whatever", b"").unwrap()
         );
         assert_eq!(
             br"[^/]*\.o".to_vec(),
             build_single_regex(b"rootglob", b"*.o", b"").unwrap()
         );
     }
 }

rust/hg-core/src/utils.rs

@@ -1,83 +1,92 b''
 // utils module
 //
 // Copyright 2019 Raphaël Gomès <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Contains useful functions, traits, structs, etc. for use in core.
 
 pub mod files;
 
 /// Replaces the `from` slice with the `to` slice inside the `buf` slice.
 ///
 /// # Examples
 ///
 /// ```
 /// use crate::hg::utils::replace_slice;
 /// let mut line = b"I hate writing tests!".to_vec();
 /// replace_slice(&mut line, b"hate", b"love");
 /// assert_eq!(
 ///     line,
 ///     b"I love writing tests!".to_vec()
 /// );
 /// ```
 pub fn replace_slice<T>(buf: &mut [T], from: &[T], to: &[T])
 where
     T: Clone + PartialEq,
 {
     if buf.len() < from.len() || from.len() != to.len() {
         return;
     }
     for i in 0..=buf.len() - from.len() {
         if buf[i..].starts_with(from) {
             buf[i..(i + from.len())].clone_from_slice(to);
         }
     }
 }
 
 pub trait SliceExt {
     fn trim_end(&self) -> &Self;
     fn trim_start(&self) -> &Self;
     fn trim(&self) -> &Self;
+    fn drop_prefix(&self, needle: &Self) -> Option<&Self>;
 }
 
 fn is_not_whitespace(c: &u8) -> bool {
     !(*c as char).is_whitespace()
 }
 
 impl SliceExt for [u8] {
     fn trim_end(&self) -> &[u8] {
         if let Some(last) = self.iter().rposition(is_not_whitespace) {
             &self[..last + 1]
         } else {
             &[]
         }
     }
     fn trim_start(&self) -> &[u8] {
         if let Some(first) = self.iter().position(is_not_whitespace) {
             &self[first..]
         } else {
             &[]
         }
     }
 
     /// ```
     /// use hg::utils::SliceExt;
     /// assert_eq!(
     ///     b"  to trim  ".trim(),
     ///     b"to trim"
     /// );
     /// assert_eq!(
     ///     b"to trim  ".trim(),
     ///     b"to trim"
     /// );
     /// assert_eq!(
     ///     b"  to trim".trim(),
     ///     b"to trim"
     /// );
     /// ```
     fn trim(&self) -> &[u8] {
         self.trim_start().trim_end()
     }
+
+    fn drop_prefix(&self, needle: &Self) -> Option<&Self> {
+        if self.starts_with(needle) {
+            Some(&self[needle.len()..])
+        } else {
+            None
+        }
+    }
 }