[GitHub] [arrow] Dandandan commented on a change in pull request #9304: ARROW-11361: [Rust] Build MutableBuffer/Buffer from iterator of bools

[GitBox <gi...@apache.org>]

Dandandan commented on a change in pull request #9304:
URL: https://github.com/apache/arrow/pull/9304#discussion_r563279700



##########
File path: rust/arrow/src/buffer.rs
##########
@@ -1188,6 +1209,57 @@ impl Drop for SetLenOnDrop<'_> {
     }
 }
 
+/// Creating a `MutableBuffer` instance by setting bits according to the boolean values
+impl std::iter::FromIterator<bool> for MutableBuffer {
+    fn from_iter<I>(iter: I) -> Self
+    where
+        I: IntoIterator<Item = bool>,
+    {
+        let mut iterator = iter.into_iter();
+        let mut result = {
+            let byte_capacity: usize = iterator.size_hint().0.saturating_add(7) / 8;
+            MutableBuffer::new(byte_capacity)
+        };
+
+        while let Some(value) = iterator.next() {
+            //we have the first bit of the byte
+            let mut exhausted = false;
+            let mut byte_accum: u8 = match value {

Review comment:
       I think you could merge the `iterator.next()` loops here.
   and maybe do the bit masking loop like this:
   
   ```rust
   loop {
       let mut byte_accum  = 0;
       let mut mask = 1;
   
       while mask <= 0b10000000 {
           if let Some(value) = iterator.next() {
               byte_accum |= match value {
                   true => mask,
                   false => 0,
               };
               mask <<= 1;
           } else {
               exhausted = true;
               break;
          }
      }
   }
   
   ```
   




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