impl From<BufferBuilder<T>> for Buffer (#5202)

arrow-buffer/src/buffer/immutable.rs

@@ -23,6 +23,7 @@ use std::sync::Arc;
 
 use crate::alloc::{Allocation, Deallocation, ALIGNMENT};
 use crate::util::bit_chunk_iterator::{BitChunks, UnalignedBitChunk};
+use crate::BufferBuilder;
 use crate::{bytes::Bytes, native::ArrowNativeType};
 
 use super::ops::bitwise_unary_op_helper;
@@ -371,6 +372,12 @@ impl From<MutableBuffer> for Buffer {
     }
 }
 
+impl<T: ArrowNativeType> From<BufferBuilder<T>> for Buffer {
+    fn from(mut value: BufferBuilder<T>) -> Self {
+        value.finish()
+    }
+}
+
 impl Buffer {
     /// Creates a [`Buffer`] from an [`Iterator`] with a trusted (upper) length.
     /// Prefer this to `collect` whenever possible, as it is ~60% faster.