Struct arrow::array::BufferBuilder
source · [−]pub struct BufferBuilder<T: ArrowNativeType> { /* private fields */ }
Expand description
Builder for creating a Buffer
object.
A Buffer
is the underlying data
structure of Arrow’s Arrays
.
For all supported types, there are type definitions for the
generic version of BufferBuilder<T>
, e.g. UInt8BufferBuilder
.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(100);
builder.append_slice(&[42, 43, 44]);
builder.append(45);
let buffer = builder.finish();
assert_eq!(unsafe { buffer.typed_data::<u8>() }, &[42, 43, 44, 45]);
Implementations
sourceimpl<T: ArrowNativeType> BufferBuilder<T>
impl<T: ArrowNativeType> BufferBuilder<T>
sourcepub fn new(capacity: usize) -> Self
pub fn new(capacity: usize) -> Self
Creates a new builder with initial capacity for at least capacity
elements of type T
.
The capacity can later be manually adjusted with the
reserve()
method.
Also the
append()
,
append_slice()
and
advance()
methods automatically increase the capacity if needed.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
assert!(builder.capacity() >= 10);
sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the current number of array elements in the internal buffer.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.append(42);
assert_eq!(builder.len(), 1);
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns whether the internal buffer is empty.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.append(42);
assert_eq!(builder.is_empty(), false);
sourcepub fn capacity(&self) -> usize
pub fn capacity(&self) -> usize
Returns the actual capacity (number of elements) of the internal buffer.
Note: the internal capacity returned by this method might be larger than
what you’d expect after setting the capacity in the new()
or reserve()
functions.
sourcepub fn advance(&mut self, i: usize)
pub fn advance(&mut self, i: usize)
Increases the number of elements in the internal buffer by n
and resizes the buffer as needed.
The values of the newly added elements are 0.
This method is usually used when appending NULL
values to the buffer
as they still require physical memory space.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.advance(2);
assert_eq!(builder.len(), 2);
sourcepub fn reserve(&mut self, n: usize)
pub fn reserve(&mut self, n: usize)
Reserves memory for at least n
more elements of type T
.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.reserve(10);
assert!(builder.capacity() >= 20);
sourcepub fn append(&mut self, v: T)
pub fn append(&mut self, v: T)
Appends a value of type T
into the builder,
growing the internal buffer as needed.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.append(42);
assert_eq!(builder.len(), 1);
sourcepub fn append_n(&mut self, n: usize, v: T)
pub fn append_n(&mut self, n: usize, v: T)
Appends a value of type T
into the builder N times,
growing the internal buffer as needed.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.append_n(10, 42);
assert_eq!(builder.len(), 10);
sourcepub fn append_slice(&mut self, slice: &[T])
pub fn append_slice(&mut self, slice: &[T])
Appends a slice of type T
, growing the internal buffer as needed.
Example:
use arrow::array::UInt8BufferBuilder;
let mut builder = UInt8BufferBuilder::new(10);
builder.append_slice(&[42, 44, 46]);
assert_eq!(builder.len(), 3);
sourcepub unsafe fn append_trusted_len_iter(
&mut self,
iter: impl IntoIterator<Item = T>
)
pub unsafe fn append_trusted_len_iter(
&mut self,
iter: impl IntoIterator<Item = T>
)
Safety
This requires the iterator be a trusted length. This could instead require
the iterator implement TrustedLen
once that is stabilized.
Trait Implementations
sourceimpl<T: Debug + ArrowNativeType> Debug for BufferBuilder<T>
impl<T: Debug + ArrowNativeType> Debug for BufferBuilder<T>
Auto Trait Implementations
impl<T> RefUnwindSafe for BufferBuilder<T> where
T: RefUnwindSafe,
impl<T> Send for BufferBuilder<T>
impl<T> Sync for BufferBuilder<T>
impl<T> Unpin for BufferBuilder<T> where
T: Unpin,
impl<T> UnwindSafe for BufferBuilder<T> where
T: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more