Remove owned String from CustomError.

This is a 15% performance improvement.

src/compare/compare_field.rs

@@ -1,3 +1,5 @@
+use std::borrow::Borrow;
+use std::borrow::Cow;
 use std::collections::BTreeSet;
 use std::fmt::Debug;
 use std::str::FromStr;
@@ -262,11 +264,11 @@ pub(crate) fn compare_property_set_of_quoted_string<
         .iter()
         .map(|e| e.as_atom())
         .collect::<Result<Vec<_>, _>>()?;
-    let value: Vec<String> = value
+    let value: Vec<Cow<'_, str>> = value
         .into_iter()
         .map(unquote)
         .collect::<Result<Vec<_>, _>>()?;
-    let value: BTreeSet<&str> = value.iter().map(|e| e.as_str()).collect();
+    let value: BTreeSet<&str> = value.iter().map(|e| e.borrow()).collect();
     let mismatched: Vec<_> = value.symmetric_difference(&rust_value).copied().collect();
     if !mismatched.is_empty() {
         let this_status = DiffStatus::Bad;

src/compare/sexp.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::collections::HashMap;
 
 use nom::branch::alt;
@@ -36,12 +37,6 @@ pub struct TextWithProperties<'s> {
     pub(crate) properties: Vec<Token<'s>>,
 }
 
-enum ParseState {
-    Normal,
-    Escape,
-    Octal(Vec<u8>),
-}
-
 impl<'s> Token<'s> {
     pub(crate) fn as_vector<'p>(
         &'p self,
@@ -117,8 +112,27 @@ fn get_consumed<'s>(input: &'s str, remaining: &'s str) -> &'s str {
     &input[..offset]
 }
 
-pub(crate) fn unquote(text: &str) -> Result<String, Box<dyn std::error::Error>> {
-    let mut out: Vec<u8> = Vec::with_capacity(text.len());
+#[derive(Debug)]
+enum UnquoteState {
+    Normal,
+    Escape,
+    HasEscape {
+        out: Vec<u8>,
+    },
+    HasEscapeEscape {
+        out: Vec<u8>,
+    },
+    Octal {
+        octal_begin_offset: usize,
+        octal: Vec<u8>,
+    },
+    HasEscapeOctal {
+        out: Vec<u8>,
+        octal: Vec<u8>,
+    },
+}
+
+pub(crate) fn unquote(text: &str) -> Result<Cow<'_, str>, Box<dyn std::error::Error>> {
     if !text.starts_with('"') {
         return Err("Quoted text does not start with quote.".into());
     }
@@ -126,54 +140,143 @@ pub(crate) fn unquote(text: &str) -> Result<String, Box<dyn std::error::Error>>
         return Err("Quoted text does not end with quote.".into());
     }
     let interior_text = &text[1..(text.len() - 1)];
-    let mut state = ParseState::Normal;
-    for current_char in interior_text.bytes() {
+    let mut state = UnquoteState::Normal;
+    for (offset, current_char) in interior_text.bytes().enumerate() {
         // Check to see if octal finished
         state = match (state, current_char) {
-            (ParseState::Octal(octal), b'0'..=b'7') if octal.len() < MAX_OCTAL_LENGTH => {
-                ParseState::Octal(octal)
+            (
+                UnquoteState::Octal {
+                    octal_begin_offset,
+                    octal,
+                },
+                b'0'..=b'7',
+            ) if octal.len() < MAX_OCTAL_LENGTH => UnquoteState::Octal {
+                octal_begin_offset,
+                octal,
+            },
+            (
+                UnquoteState::Octal {
+                    octal_begin_offset,
+                    octal,
+                },
+                _,
+            ) => {
+                let octal_number_string = String::from_utf8(octal)?;
+                let decoded_byte = u8::from_str_radix(&octal_number_string, 8)?;
+                let mut out: Vec<u8> = Vec::with_capacity(interior_text.len());
+                out.extend_from_slice(&interior_text.as_bytes()[..octal_begin_offset]);
+                out.push(decoded_byte);
+                UnquoteState::HasEscape { out }
             }
-            (ParseState::Octal(octal), _) => {
+            (UnquoteState::HasEscapeOctal { out, octal }, b'0'..=b'7')
+                if octal.len() < MAX_OCTAL_LENGTH =>
+            {
+                UnquoteState::HasEscapeOctal { out, octal }
+            }
+            (UnquoteState::HasEscapeOctal { mut out, octal }, _) => {
                 let octal_number_string = String::from_utf8(octal)?;
                 let decoded_byte = u8::from_str_radix(&octal_number_string, 8)?;
                 out.push(decoded_byte);
-                ParseState::Normal
+                UnquoteState::HasEscape { out }
             }
             (state, _) => state,
         };
 
         state = match (state, current_char) {
-            (ParseState::Normal, b'\\') => ParseState::Escape,
-            (ParseState::Normal, _) => {
+            (UnquoteState::Normal, b'\\') => UnquoteState::Escape,
+            (UnquoteState::Normal, _) => UnquoteState::Normal,
+            (UnquoteState::HasEscape { out }, b'\\') => UnquoteState::HasEscapeEscape { out },
+            (UnquoteState::HasEscape { mut out }, _) => {
                 out.push(current_char);
-                ParseState::Normal
+                UnquoteState::HasEscape { out }
             }
-            (ParseState::Escape, b'n') => {
+            (UnquoteState::Escape, b'n') => {
+                let mut out: Vec<u8> = Vec::with_capacity(interior_text.len());
+                // Subtract 1 from offset to account for backslash.
+                out.extend_from_slice(&interior_text.as_bytes()[..(offset - 1)]);
                 out.push(b'\n');
-                ParseState::Normal
+                UnquoteState::HasEscape { out }
             }
-            (ParseState::Escape, b'\\') => {
+            (UnquoteState::HasEscapeEscape { mut out }, b'n') => {
+                out.push(b'\n');
+                UnquoteState::HasEscape { out }
+            }
+            (UnquoteState::Escape, b'\\') => {
+                let mut out: Vec<u8> = Vec::with_capacity(interior_text.len());
+                // Subtract 1 from offset to account for backslash.
+                out.extend_from_slice(&interior_text.as_bytes()[..(offset - 1)]);
                 out.push(b'\\');
-                ParseState::Normal
+                UnquoteState::HasEscape { out }
             }
-            (ParseState::Escape, b'"') => {
+            (UnquoteState::HasEscapeEscape { mut out }, b'\\') => {
+                out.push(b'\\');
+                UnquoteState::HasEscape { out }
+            }
+            (UnquoteState::Escape, b'"') => {
+                let mut out: Vec<u8> = Vec::with_capacity(interior_text.len());
+                // Subtract 1 from offset to account for backslash.
+                out.extend_from_slice(&interior_text.as_bytes()[..(offset - 1)]);
                 out.push(b'"');
-                ParseState::Normal
+                UnquoteState::HasEscape { out }
             }
-            (ParseState::Escape, b'0'..=b'7') => {
+            (UnquoteState::HasEscapeEscape { mut out }, b'"') => {
+                out.push(b'"');
+                UnquoteState::HasEscape { out }
+            }
+            (UnquoteState::Escape, b'0'..=b'7') => {
                 let mut octal = Vec::with_capacity(MAX_OCTAL_LENGTH);
                 octal.push(current_char);
-                ParseState::Octal(octal)
+                // Substract 1 from offset to account for backslash
+                UnquoteState::Octal {
+                    octal_begin_offset: offset - 1,
+                    octal,
                 }
-            (ParseState::Octal(mut octal), b'0'..=b'7') => {
+            }
+            (UnquoteState::HasEscapeEscape { out }, b'0'..=b'7') => {
+                let mut octal = Vec::with_capacity(MAX_OCTAL_LENGTH);
                 octal.push(current_char);
-                ParseState::Octal(octal)
+                // Substract 1 from offset to account for backslash
+                UnquoteState::HasEscapeOctal { out, octal }
             }
-            _ => panic!("Invalid state unquoting string."),
+            (
+                UnquoteState::Octal {
+                    octal_begin_offset,
+                    mut octal,
+                },
+                b'0'..=b'7',
+            ) => {
+                octal.push(current_char);
+                UnquoteState::Octal {
+                    octal_begin_offset,
+                    octal,
+                }
+            }
+            (UnquoteState::HasEscapeOctal { out, mut octal }, b'0'..=b'7') => {
+                octal.push(current_char);
+                UnquoteState::HasEscapeOctal { out, octal }
+            }
+            (state, _) => panic!(
+                "Invalid state unquoting string: {:?} | {} | {:?}",
+                state, offset, interior_text
+            ),
         };
     }
 
-    Ok(String::from_utf8(out)?)
+    match state {
+        UnquoteState::Normal | UnquoteState::Escape | UnquoteState::Octal { .. } => {
+            Ok(Cow::Borrowed(interior_text))
+        }
+        UnquoteState::HasEscape { out } => Ok(Cow::Owned(String::from_utf8(out)?)),
+        UnquoteState::HasEscapeEscape { mut out } => {
+            out.push(b'\\');
+            Ok(Cow::Owned(String::from_utf8(out)?))
+        }
+        UnquoteState::HasEscapeOctal { mut out, octal } => {
+            out.push(b'\\');
+            out.extend(octal);
+            Ok(Cow::Owned(String::from_utf8(out)?))
+        }
+    }
 }
 
 #[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]

src/compare/util.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::str::FromStr;
 
 use super::compare_field::compare_property_list_of_quoted_string;
@@ -206,10 +207,10 @@ pub(crate) fn get_property_unquoted_atom<'s>(
 /// Get a named property containing an quoted string from the emacs token.
 ///
 /// Returns None if key is not found.
-pub(crate) fn get_property_quoted_string(
-    emacs: &Token<'_>,
+pub(crate) fn get_property_quoted_string<'s>(
+    emacs: &Token<'s>,
     key: &str,
-) -> Result<Option<String>, Box<dyn std::error::Error>> {
+) -> Result<Option<Cow<'s, str>>, Box<dyn std::error::Error>> {
     get_property(emacs, key)?
         .map(Token::as_atom)
         .map_or(Ok(None), |r| r.map(Some))?

src/error/error.rs

@@ -6,8 +6,6 @@ pub(crate) type Res<T, U> = IResult<T, U, CustomError>;
 
 #[derive(Debug)]
 pub enum CustomError {
-    #[allow(dead_code)]
-    Text(String),
     Static(&'static str),
     IO(std::io::Error),
     Parser(ErrorKind),
@@ -35,9 +33,3 @@ impl From<&'static str> for CustomError {
         CustomError::Static(value)
     }
 }
-
-impl From<String> for CustomError {
-    fn from(value: String) -> Self {
-        CustomError::Text(value)
-    }
-}

src/parser/in_buffer_settings.rs

@@ -102,7 +102,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
     }) {
         let (_, (in_progress_words, complete_words)) =
             todo_keywords(kw.value).map_err(|err| match err {
-                nom::Err::Incomplete(_) => CustomError::Text(err.to_string()),
+                nom::Err::Incomplete(_) => panic!("This parser does not support streaming."),
                 nom::Err::Error(e) => e,
                 nom::Err::Failure(e) => e,
             })?;
@@ -123,7 +123,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
             kw.value,
         )
         .map_err(|err: nom::Err<_>| match err {
-            nom::Err::Incomplete(_) => CustomError::Text(err.to_string()),
+            nom::Err::Incomplete(_) => panic!("This parser does not support streaming."),
             nom::Err::Error(e) => e,
             nom::Err::Failure(e) => e,
         })?;
@@ -141,7 +141,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
         .filter(|kw| kw.key.eq_ignore_ascii_case("link"))
     {
         let (_, (link_key, link_value)) = link_template(kw.value).map_err(|err| match err {
-            nom::Err::Incomplete(_) => CustomError::Text(err.to_string()),
+            nom::Err::Incomplete(_) => panic!("This parser does not support streaming."),
             nom::Err::Error(e) => e,
             nom::Err::Failure(e) => e,
         })?;