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Remove harmful table lookup optimization for bitmap operations #5772

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May 16, 2024
Merged

Remove harmful table lookup optimization for bitmap operations #5772

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24 changes: 6 additions & 18 deletions arrow-buffer/src/util/bit_util.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,18 +17,6 @@

//! Utils for working with bits

const BIT_MASK: [u8; 8] = [1, 2, 4, 8, 16, 32, 64, 128];
const UNSET_BIT_MASK: [u8; 8] = [
255 - 1,
255 - 2,
255 - 4,
255 - 8,
255 - 16,
255 - 32,
255 - 64,
255 - 128,
];

/// Returns the nearest number that is `>=` than `num` and is a multiple of 64
#[inline]
pub fn round_upto_multiple_of_64(num: usize) -> usize {
Expand All @@ -47,7 +35,7 @@ pub fn round_upto_power_of_2(num: usize, factor: usize) -> usize {
/// Returns whether bit at position `i` in `data` is set or not
#[inline]
pub fn get_bit(data: &[u8], i: usize) -> bool {
(data[i >> 3] & BIT_MASK[i & 7]) != 0
data[i / 8] & (1 << (i % 8)) != 0
}

/// Returns whether bit at position `i` in `data` is set or not.
Expand All @@ -58,13 +46,13 @@ pub fn get_bit(data: &[u8], i: usize) -> bool {
/// responsible to guarantee that `i` is within bounds.
#[inline]
pub unsafe fn get_bit_raw(data: *const u8, i: usize) -> bool {
(*data.add(i >> 3) & BIT_MASK[i & 7]) != 0
(*data.add(i / 8) & (1 << (i % 8))) != 0
}

/// 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];
data[i / 8] |= 1 << (i % 8);
}

/// Sets bit at position `i` for `data`
Expand All @@ -75,13 +63,13 @@ pub fn set_bit(data: &mut [u8], i: usize) {
/// responsible to guarantee that `i` is within bounds.
#[inline]
pub unsafe fn set_bit_raw(data: *mut u8, i: usize) {
*data.add(i >> 3) |= BIT_MASK[i & 7];
*data.add(i / 8) |= 1 << (i % 8);
}

/// Sets bit at position `i` for `data` to 0
#[inline]
pub fn unset_bit(data: &mut [u8], i: usize) {
data[i >> 3] &= UNSET_BIT_MASK[i & 7];
data[i / 8] &= !(1 << (i % 8));
}

/// Sets bit at position `i` for `data` to 0
Expand All @@ -92,7 +80,7 @@ pub fn unset_bit(data: &mut [u8], i: usize) {
/// responsible to guarantee that `i` is within bounds.
#[inline]
pub unsafe fn unset_bit_raw(data: *mut u8, i: usize) {
*data.add(i >> 3) &= UNSET_BIT_MASK[i & 7];
*data.add(i / 8) &= !(1 << (i % 8));
}

/// Returns the ceil of `value`/`divisor`
Expand Down
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