Btrblocks overflow with custom row block size.

[duarten]

Issue Description

I'm seeing a crash due to attempt to multiply with overflow at vortex-btrblocks/src/integer.rs:600 (in debug mode), when specifying a custom row block size.

Expected Behavior

No overflow.

Actual Behavior

Overflow.

Reproduction Steps

The following test reproduces the issue.

use vortex::{
    VortexSessionDefault,
    array::{
        IntoArray,
        arrays::ListArray,
        builders::{ArrayBuilder, PrimitiveBuilder},
        validity::Validity,
    },
    dtype::Nullability,
    io::session::RuntimeSessionExt,
    session::VortexSession,
};
use vortex_file::{VortexWriteOptions, WriteStrategyBuilder};

const NUM_LISTS: usize = 10_000;
const ELEMENTS_PER_LIST: usize = 5_000;

#[tokio::test]
async fn btrblocks_overflow_list_f64() {
    let total_elements = NUM_LISTS * ELEMENTS_PER_LIST;

    let mut offsets =
        PrimitiveBuilder::<u32>::with_capacity(Nullability::NonNullable, NUM_LISTS + 1);
    for i in 0..=NUM_LISTS {
        offsets.append_value((i * ELEMENTS_PER_LIST) as u32);
    }

    let mut values =
        PrimitiveBuilder::<f64>::with_capacity(Nullability::NonNullable, total_elements);
    for list_idx in 0..NUM_LISTS {
        for elem_idx in 0..ELEMENTS_PER_LIST {
            values.append_value((list_idx * 1000 + elem_idx) as f64);
        }
    }

    let array = ListArray::try_new(
        values.finish().into_array(),
        offsets.finish().into_array(),
        Validity::NonNullable,
    )
    .unwrap();

    let strategy = WriteStrategyBuilder::new()
        .with_row_block_size(array.len()) // This is important to set.
        .build();

    let session = VortexSession::default().with_tokio();
    let mut buffer = Vec::new();
    let result = VortexWriteOptions::new(session)
        .with_strategy(strategy)
        .write(&mut buffer, array.to_array_stream())
        .await;

    assert!(result.is_ok(), "Write should succeed: {:?}", result.err());
}

OS Version Information

macOS

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• I have searched the Vortex repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
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