cache wide character state

we always check the character width at least once during initial
processing, and we often check it later at least once, so cache it here
since we have spare bits

1 files changed, 28 insertions, 16 deletions

diff --git a/src/cell.rs b/src/cell.rs
index b9d7168..c9470ed 100644
--- a/src/cell.rs
+++ b/src/cell.rs
@@ -17,7 +17,7 @@ impl PartialEq<Cell> for Cell {
         if self.len != other.len {
             return false;
         }
-        let len = self.len as usize;
+        let len = self.len();
         if len > 0 {
             if self.attrs != other.attrs {
                 return false;
@@ -32,18 +32,31 @@ impl PartialEq<Cell> for Cell {
 }
 
 impl Cell {
+    #[inline]
+    fn len(&self) -> usize {
+        (self.len & 0x0f) as usize
+    }
+
+    fn set_len(&mut self, len: u8) {
+        self.len = (self.len & 0x80) | (len & 0x0f);
+    }
+
     pub(crate) fn set(&mut self, c: char, a: crate::attrs::Attrs) {
         self.contents[0] = c;
-        self.len = 1;
+        self.set_len(1);
+        // strings in this context should always be an arbitrary character
+        // followed by zero or more zero-width characters, so we should only
+        // have to look at the first character
+        self.set_wide(c.width().unwrap_or(0) > 1);
         self.attrs = a;
     }
 
     pub(crate) fn append(&mut self, c: char) {
-        if self.len as usize >= CODEPOINTS_IN_CELL {
+        if self.len() >= CODEPOINTS_IN_CELL {
             return;
         }
 
-        self.contents[self.len as usize] = c;
+        self.contents[self.len()] = c;
         self.len += 1;
 
         // some fonts have combined characters but can't render combining
@@ -62,7 +75,7 @@ impl Cell {
             .contents
             .iter()
             .copied()
-            .take(self.len as usize)
+            .take(self.len())
             .nfc()
             .take(CODEPOINTS_IN_CELL)
         {
@@ -70,7 +83,8 @@ impl Cell {
             new_len += 1;
         }
         self.contents = new_contents;
-        self.len = new_len;
+        self.set_len(new_len);
+        self.set_wide(new_contents[0].width().unwrap_or(0) > 1);
     }
 
     pub(crate) fn clear(&mut self, bgcolor: crate::attrs::Color) {
@@ -85,10 +99,7 @@ impl Cell {
     /// used, but will contain at most one character with a non-zero character
     /// width.
     pub fn contents(&self) -> String {
-        self.contents
-            .iter()
-            .take(self.len as usize)
-            .collect::<String>()
+        self.contents.iter().take(self.len()).collect::<String>()
     }
 
     /// Returns whether the cell contains any text data.
@@ -98,13 +109,14 @@ impl Cell {
 
     /// Returns whether the text data in the cell represents a wide character.
     pub fn is_wide(&self) -> bool {
-        // strings in this context should always be an arbitrary character
-        // followed by zero or more zero-width characters, so we should only
-        // have to look at the first character
-        if self.len == 0 {
-            false
+        self.len & 0x80 == 0x80
+    }
+
+    fn set_wide(&mut self, wide: bool) {
+        if wide {
+            self.len |= 0x80;
         } else {
-            self.contents[0].width().unwrap_or(0) > 1
+            self.len &= 0x7f;
         }
     }