improve: use adjust_cursor reduce double calc

qingshi163 · qingshi163 · commit 10e51ba68909 · 2024-01-17T16:06:30.000+02:00
diff --git a/src/engine.rs b/src/engine.rs
@@ -7,7 +7,7 @@ use crate::string::{
 
 use super::{SreAtCode, SreCatCode, SreInfo, SreOpcode, StrDrive, StringCursor, MAXREPEAT};
 use optional::Optioned;
-use std::convert::TryFrom;
+use std::{convert::TryFrom, ptr::null};
 
 #[derive(Debug, Clone, Copy)]
 pub struct Request<'a, S> {
@@ -126,17 +126,12 @@ impl State {
         self.marks.clear();
         self.repeat_stack.clear();
         self.start = start;
-        if self.cursor.ptr.is_null() || self.cursor.position > self.start {
-            self.cursor = req.string.create_cursor(self.start);
-        } else if self.cursor.position < self.start {
-            let skip = self.start - self.cursor.position;
-            S::skip(&mut self.cursor, skip);
-        }
+        req.string.adjust_cursor(&mut self.cursor, start);
     }
 
     pub fn pymatch<S: StrDrive>(&mut self, req: &Request<S>) -> bool {
         self.start = req.start;
-        self.cursor = req.string.create_cursor(self.start);
+        req.string.adjust_cursor(&mut self.cursor, self.start);
 
         let ctx = MatchContext {
             cursor: self.cursor,
@@ -151,7 +146,7 @@ impl State {
 
     pub fn search<S: StrDrive>(&mut self, mut req: Request<S>) -> bool {
         self.start = req.start;
-        self.cursor = req.string.create_cursor(self.start);
+        req.string.adjust_cursor(&mut self.cursor, self.start);
 
         if req.start > req.end {
             return false;
@@ -215,7 +210,9 @@ impl State {
                 || ctx.try_peek_code_as::<SreAtCode, _>(&req, 1).unwrap()
                     == SreAtCode::BEGINNING_STRING)
         {
-            self.reset(&req, req.end);
+            self.cursor.position = req.end;
+            self.cursor.ptr = null();
+            // self.reset(&req, req.end);
             return false;
         }
 
diff --git a/src/string.rs b/src/string.rs
@@ -16,6 +16,7 @@ impl Default for StringCursor {
 pub trait StrDrive: Copy {
     fn count(&self) -> usize;
     fn create_cursor(&self, n: usize) -> StringCursor;
+    fn adjust_cursor(&self, cursor: &mut StringCursor, n: usize);
     fn advance(cursor: &mut StringCursor) -> u32;
     fn peek(cursor: &StringCursor) -> u32;
     fn skip(cursor: &mut StringCursor, n: usize);
@@ -38,6 +39,12 @@ impl<'a> StrDrive for &'a [u8] {
         }
     }
 
+    #[inline]
+    fn adjust_cursor(&self, cursor: &mut StringCursor, n: usize) {
+        cursor.position = n;
+        cursor.ptr = self[n..].as_ptr();
+    }
+
     #[inline]
     fn advance(cursor: &mut StringCursor) -> u32 {
         cursor.position += 1;
@@ -83,11 +90,21 @@ impl StrDrive for &str {
 
     #[inline]
     fn create_cursor(&self, n: usize) -> StringCursor {
-        let mut ptr = self.as_ptr();
-        for _ in 0..n {
-            unsafe { next_code_point(&mut ptr) };
+        let mut cursor = StringCursor {
+            ptr: self.as_ptr(),
+            position: 0,
+        };
+        Self::skip(&mut cursor, n);
+        cursor
+    }
+
+    #[inline]
+    fn adjust_cursor(&self, cursor: &mut StringCursor, n: usize) {
+        if cursor.ptr.is_null() || cursor.position > n {
+            *cursor = Self::create_cursor(&self, n);
+        } else if cursor.position < n {
+            Self::skip(cursor, n - cursor.position);
         }
-        StringCursor { ptr, position: n }
     }
 
     #[inline]
