Add set_bit to BooleanBufferBuilder to allow mutating bit in index

arrow/src/array/builder.rs

@@ -302,6 +302,15 @@ impl BooleanBufferBuilder {
         self.len
     }
 
+    #[inline]
+    pub fn set_bit(&mut self, index: usize, v: bool) {
+        if v {
+            bit_util::set_bit(self.buffer.as_mut(), index);
+        } else {
+            bit_util::unset_bit(self.buffer.as_mut(), index);
+        }
+    }
+
     #[inline]
     pub fn is_empty(&self) -> bool {
         self.len == 0
@@ -2266,7 +2275,7 @@ mod tests {
     }
 
     #[test]
-    fn test_write_bytes() {
+    fn test_boolean_buffer_builder_write_bytes() {
         let mut b = BooleanBufferBuilder::new(4);
         b.append(false);
         b.append(true);
@@ -2285,6 +2294,83 @@ mod tests {
         assert_eq!(1, buffer.len());
     }
 
+    #[test]
+    fn test_boolean_buffer_builder_unset_first_bit() {
+        let mut buffer = BooleanBufferBuilder::new(4);
+        buffer.append(true);
+        buffer.append(true);
+        buffer.append(false);
+        buffer.append(true);
+        buffer.set_bit(0, false);
+        assert_eq!(buffer.len(), 4);
+        assert_eq!(buffer.finish().as_slice(), &[0b1010_u8]);
+    }
+
+    #[test]
+    fn test_boolean_buffer_builder_unset_last_bit() {
+        let mut buffer = BooleanBufferBuilder::new(4);
+        buffer.append(true);
+        buffer.append(true);
+        buffer.append(false);
+        buffer.append(true);
+        buffer.set_bit(3, false);
+        assert_eq!(buffer.len(), 4);
+        assert_eq!(buffer.finish().as_slice(), &[0b0011_u8]);
+    }
+
+    #[test]
+    fn test_boolean_buffer_builder_unset_an_inner_bit() {
+        let mut buffer = BooleanBufferBuilder::new(5);
+        buffer.append(true);
+        buffer.append(true);
+        buffer.append(false);
+        buffer.append(true);
+        buffer.set_bit(1, false);
+        assert_eq!(buffer.len(), 4);
+        assert_eq!(buffer.finish().as_slice(), &[0b1001_u8]);
+    }
+
+    #[test]
+    fn test_boolean_buffer_builder_unset_several_bits() {
+        let mut buffer = BooleanBufferBuilder::new(5);
+        buffer.append(true);
+        buffer.append(true);
+        buffer.append(true);
+        buffer.append(false);
+        buffer.append(true);
+        buffer.set_bit(1, false);
+        buffer.set_bit(2, false);
+        assert_eq!(buffer.len(), 5);
+        assert_eq!(buffer.finish().as_slice(), &[0b10001_u8]);
+    }
+
+    #[test]
+    fn test_boolean_buffer_builder_unset_several_bits_bigger_than_one_byte() {
+        let mut buffer = BooleanBufferBuilder::new(16);
+        buffer.append_n(10, true);
+        buffer.set_bit(0, false);
+        buffer.set_bit(3, false);
+        buffer.set_bit(9, false);
+        assert_eq!(buffer.len(), 10);
+        assert_eq!(buffer.finish().as_slice(), &[0b11110110_u8, 0b01_u8]);
+    }
+
+    #[test]
+    fn test_boolean_buffer_builder_flip_several_bits_bigger_than_one_byte() {
+        let mut buffer = BooleanBufferBuilder::new(16);
+        buffer.append_n(5, true);
+        buffer.append_n(5, false);
+        buffer.append_n(5, true);
+        buffer.set_bit(0, false);
+        buffer.set_bit(3, false);
+        buffer.set_bit(9, false);
+        buffer.set_bit(6, true);
+        buffer.set_bit(14, true);
+        buffer.set_bit(13, false);
+        assert_eq!(buffer.len(), 15);
+        assert_eq!(buffer.finish().as_slice(), &[0b01010110_u8, 0b1011100_u8]);
+    }
+
     #[test]
     fn test_boolean_array_builder_append_slice() {
         let arr1 =

arrow/src/util/bit_util.rs

@@ -62,7 +62,7 @@ pub unsafe fn get_bit_raw(data: *const u8, i: usize) -> bool {
     (*data.add(i >> 3) & BIT_MASK[i & 7]) != 0
 }
 
-/// Sets bit at position `i` for `data`
+/// Sets bit at position `i` for `data` to 1
 #[inline]
 pub fn set_bit(data: &mut [u8], i: usize) {
     data[i >> 3] |= BIT_MASK[i & 7];