Add functionality to BooleanBufferBuilder

Author: srh

arrow/src/array/builder.rs

@@ -297,11 +297,24 @@ impl BooleanBufferBuilder {
         Self { buffer, len: 0 }
     }
 
+    #[inline]
+    pub fn new_from_buffer(buffer: MutableBuffer, len: usize) -> BooleanBufferBuilder {
+        assert_eq!(len.div_ceil(8), buffer.len());
+        Self { buffer, len }
+    }
+
     #[inline]
     pub fn len(&self) -> usize {
         self.len
     }
 
+    // TODO: Remove, and don't use the elem-by-elem peek_evaluate function.
+    #[inline]
+    pub fn get_bit(&self, index: usize) -> bool {
+        bit_util::get_bit(self.buffer.as_ref(), index)
+    }
+
+    // TODO: Probably, make set_bit be branchless
     #[inline]
     pub fn set_bit(&mut self, index: usize, v: bool) {
         if v {
@@ -382,6 +395,12 @@ impl BooleanBufferBuilder {
         self.len = 0;
         buf.into()
     }
+
+    #[inline]
+    /// Builds the [Buffer] without resetting the builder.
+    pub fn finish_cloned(&self) -> Buffer {
+        Buffer::from_slice_ref(&self.buffer.as_slice())
+    }
 }
 
 impl From<BooleanBufferBuilder> for Buffer {