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alamb pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/arrow-rs.git
The following commit(s) were added to refs/heads/main by this push:
new 2c0eba46ec Mark `BufferBuilder::new_from_buffer` as unsafe (#9292)
2c0eba46ec is described below
commit 2c0eba46ec447d815ddc7f8185edbedd2ae3596b
Author: Jeffrey Vo <[email protected]>
AuthorDate: Fri Jan 30 01:39:39 2026 +0900
Mark `BufferBuilder::new_from_buffer` as unsafe (#9292)
# Which issue does this PR close?
<!--
We generally require a GitHub issue to be filed for all bug fixes and
enhancements and this helps us generate change logs for our releases.
You can link an issue to this PR using the GitHub syntax.
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- Closes #9287
# Rationale for this change
<!--
Why are you proposing this change? If this is already explained clearly
in the issue then this section is not needed.
Explaining clearly why changes are proposed helps reviewers understand
your changes and offer better suggestions for fixes.
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As identified by the issue, it is possible to use safe APIs to produce
an unaligned buffer in `BufferBuilder`.
# What changes are included in this PR?
<!--
There is no need to duplicate the description in the issue here but it
is sometimes worth providing a summary of the individual changes in this
PR.
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Mark `BufferBuilder::new_from_buffer` as unsafe since there are
alignment invariants that must be upheld to use it correctly.
Also fix some docstrings.
# Are these changes tested?
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1. Prevent the code from being accidentally broken by subsequent changes
2. Serve as another way to document the expected behavior of the code
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Marking API unsafe only.
# Are there any user-facing changes?
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updated before approving the PR.
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Yes.
---
arrow-buffer/src/builder/mod.rs | 24 ++++++++++--------------
1 file changed, 10 insertions(+), 14 deletions(-)
diff --git a/arrow-buffer/src/builder/mod.rs b/arrow-buffer/src/builder/mod.rs
index be877e39dc..72e3865190 100644
--- a/arrow-buffer/src/builder/mod.rs
+++ b/arrow-buffer/src/builder/mod.rs
@@ -78,7 +78,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
///
/// assert!(builder.capacity() >= 10);
@@ -95,7 +94,11 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
}
/// Creates a new builder from a [`MutableBuffer`]
- pub fn new_from_buffer(buffer: MutableBuffer) -> Self {
+ ///
+ /// # Safety
+ ///
+ /// - `buffer` bytes must be aligned to type `T`
+ pub unsafe fn new_from_buffer(buffer: MutableBuffer) -> Self {
let buffer_len = buffer.len();
Self {
buffer,
@@ -110,7 +113,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.append(42);
///
@@ -126,7 +128,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.append(42);
///
@@ -157,7 +158,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.advance(2);
///
@@ -175,7 +175,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.reserve(10);
///
@@ -193,7 +192,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.append(42);
///
@@ -213,7 +211,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.append_n(10, 42);
///
@@ -231,12 +228,12 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u32>::new(10);
/// builder.append_n_zeroed(3);
///
/// assert_eq!(builder.len(), 3);
/// assert_eq!(builder.as_slice(), &[0, 0, 0])
+ /// ```
#[inline]
pub fn append_n_zeroed(&mut self, n: usize) {
self.buffer.extend_zeros(n * std::mem::size_of::<T>());
@@ -249,7 +246,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u8>::new(10);
/// builder.append_slice(&[42, 44, 46]);
///
@@ -265,7 +261,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<f64>::new(10);
/// builder.append(1.3);
/// builder.append_n(2, 2.3);
@@ -288,7 +283,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<f32>::new(10);
///
/// builder.append_slice(&[1., 2., 3.4]);
@@ -315,7 +309,6 @@ impl<T: ArrowNativeType> BufferBuilder<T> {
///
/// ```
/// # use arrow_buffer::builder::BufferBuilder;
- ///
/// let mut builder = BufferBuilder::<u16>::new(10);
///
/// builder.append_slice(&[42, 44, 46]);
@@ -402,7 +395,10 @@ impl<T: ArrowNativeType> Extend<T> for BufferBuilder<T> {
impl<T: ArrowNativeType> From<Vec<T>> for BufferBuilder<T> {
fn from(value: Vec<T>) -> Self {
- Self::new_from_buffer(MutableBuffer::from(value))
+ let buffer = MutableBuffer::from(value);
+ // SAFETY
+ // - buffer is aligned to T
+ unsafe { Self::new_from_buffer(buffer) }
}
}
