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| 1 | +use std::cmp::Ordering; |
| 2 | + |
| 3 | +use hyperlight_common::mem::{PAGE_SIZE_USIZE, PAGES_IN_BLOCK}; |
| 4 | + |
| 5 | +use crate::{Result, log_then_return}; |
| 6 | + |
| 7 | +// Contains various helper functions for dealing with bitmaps. |
| 8 | + |
| 9 | +/// Returns a new bitmap of pages. If `init_dirty` is true, all pages are marked as dirty, otherwise all pages are clean. |
| 10 | +/// Will return an error if given size is 0. |
| 11 | +pub fn new_page_bitmap(size_in_bytes: usize, init_dirty: bool) -> Result<Vec<u64>> { |
| 12 | + if size_in_bytes == 0 { |
| 13 | + log_then_return!("Tried to create a bitmap with size 0."); |
| 14 | + } |
| 15 | + let num_pages = size_in_bytes.div_ceil(PAGE_SIZE_USIZE); |
| 16 | + let num_blocks = num_pages.div_ceil(PAGES_IN_BLOCK); |
| 17 | + match init_dirty { |
| 18 | + false => Ok(vec![0; num_blocks]), |
| 19 | + true => { |
| 20 | + let mut bitmap = vec![!0u64; num_blocks]; // all pages are dirty |
| 21 | + let num_unused_bits = num_blocks * PAGES_IN_BLOCK - num_pages; |
| 22 | + // set the unused bits to 0, could cause problems otherwise |
| 23 | + let last_block = bitmap.last_mut().unwrap(); // unwrap is safe since size_in_bytes>0 |
| 24 | + *last_block >>= num_unused_bits; |
| 25 | + Ok(bitmap) |
| 26 | + } |
| 27 | + } |
| 28 | +} |
| 29 | + |
| 30 | +/// Returns the union (bitwise OR) of two bitmaps. The resulting bitmap will have the same length |
| 31 | +/// as the longer of the two input bitmaps. |
| 32 | +pub(crate) fn bitmap_union(bitmap: &[u64], other_bitmap: &[u64]) -> Vec<u64> { |
| 33 | + let min_len = bitmap.len().min(other_bitmap.len()); |
| 34 | + let max_len = bitmap.len().max(other_bitmap.len()); |
| 35 | + |
| 36 | + let mut result = vec![0; max_len]; |
| 37 | + |
| 38 | + for i in 0..min_len { |
| 39 | + result[i] = bitmap[i] | other_bitmap[i]; |
| 40 | + } |
| 41 | + |
| 42 | + match bitmap.len().cmp(&other_bitmap.len()) { |
| 43 | + Ordering::Greater => { |
| 44 | + result[min_len..].copy_from_slice(&bitmap[min_len..]); |
| 45 | + } |
| 46 | + Ordering::Less => { |
| 47 | + result[min_len..].copy_from_slice(&other_bitmap[min_len..]); |
| 48 | + } |
| 49 | + Ordering::Equal => {} |
| 50 | + } |
| 51 | + |
| 52 | + result |
| 53 | +} |
| 54 | + |
| 55 | +// Used as a helper struct to implement an iterator on. |
| 56 | +struct SetBitIndices<'a> { |
| 57 | + bitmap: &'a [u64], |
| 58 | + block_index: usize, // one block is 1 u64, which is 64 pages |
| 59 | + current: u64, // the current block we are iterating over, or 0 if first iteration |
| 60 | +} |
| 61 | + |
| 62 | +/// Iterates over the zero-based indices of the set bits in the given bitmap. |
| 63 | +pub(crate) fn bit_index_iterator(bitmap: &[u64]) -> impl Iterator<Item = usize> + '_ { |
| 64 | + SetBitIndices { |
| 65 | + bitmap, |
| 66 | + block_index: 0, |
| 67 | + current: 0, |
| 68 | + } |
| 69 | +} |
| 70 | + |
| 71 | +impl Iterator for SetBitIndices<'_> { |
| 72 | + type Item = usize; |
| 73 | + |
| 74 | + fn next(&mut self) -> Option<Self::Item> { |
| 75 | + while self.current == 0 { |
| 76 | + // will always enter this on first iteration because current is initialized to 0 |
| 77 | + if self.block_index >= self.bitmap.len() { |
| 78 | + // no more blocks to iterate over |
| 79 | + return None; |
| 80 | + } |
| 81 | + self.current = self.bitmap[self.block_index]; |
| 82 | + self.block_index += 1; |
| 83 | + } |
| 84 | + let trailing_zeros = self.current.trailing_zeros(); |
| 85 | + self.current &= self.current - 1; // Clear the least significant set bit |
| 86 | + Some((self.block_index - 1) * 64 + trailing_zeros as usize) // block_index guaranteed to be > 0 at this point |
| 87 | + } |
| 88 | +} |
| 89 | + |
| 90 | +#[cfg(test)] |
| 91 | +mod tests { |
| 92 | + use hyperlight_common::mem::PAGE_SIZE_USIZE; |
| 93 | + |
| 94 | + use crate::Result; |
| 95 | + use crate::mem::bitmap::{bit_index_iterator, bitmap_union, new_page_bitmap}; |
| 96 | + |
| 97 | + #[test] |
| 98 | + fn new_page_bitmap_test() -> Result<()> { |
| 99 | + let bitmap = new_page_bitmap(1, false)?; |
| 100 | + assert_eq!(bitmap.len(), 1); |
| 101 | + assert_eq!(bitmap[0], 0); |
| 102 | + |
| 103 | + let bitmap = new_page_bitmap(1, true)?; |
| 104 | + assert_eq!(bitmap.len(), 1); |
| 105 | + assert_eq!(bitmap[0], 1); |
| 106 | + |
| 107 | + let bitmap = new_page_bitmap(32 * PAGE_SIZE_USIZE, false)?; |
| 108 | + assert_eq!(bitmap.len(), 1); |
| 109 | + assert_eq!(bitmap[0], 0); |
| 110 | + |
| 111 | + let bitmap = new_page_bitmap(32 * PAGE_SIZE_USIZE, true)?; |
| 112 | + assert_eq!(bitmap.len(), 1); |
| 113 | + assert_eq!(bitmap[0], 0x0000_0000_FFFF_FFFF); |
| 114 | + Ok(()) |
| 115 | + } |
| 116 | + |
| 117 | + #[test] |
| 118 | + fn page_iterator() { |
| 119 | + let data = vec![0b1000010100, 0b01, 0b100000000000000011]; |
| 120 | + let mut iter = bit_index_iterator(&data); |
| 121 | + assert_eq!(iter.next(), Some(2)); |
| 122 | + assert_eq!(iter.next(), Some(4)); |
| 123 | + assert_eq!(iter.next(), Some(9)); |
| 124 | + assert_eq!(iter.next(), Some(64)); |
| 125 | + assert_eq!(iter.next(), Some(128)); |
| 126 | + assert_eq!(iter.next(), Some(129)); |
| 127 | + assert_eq!(iter.next(), Some(145)); |
| 128 | + assert_eq!(iter.next(), None); |
| 129 | + |
| 130 | + let data_2 = vec![0, 0, 0]; |
| 131 | + let mut iter_2 = bit_index_iterator(&data_2); |
| 132 | + assert_eq!(iter_2.next(), None); |
| 133 | + |
| 134 | + let data_3 = vec![0, 0, 0b1, 1 << 63]; |
| 135 | + let mut iter_3 = bit_index_iterator(&data_3); |
| 136 | + assert_eq!(iter_3.next(), Some(128)); |
| 137 | + assert_eq!(iter_3.next(), Some(255)); |
| 138 | + assert_eq!(iter_3.next(), None); |
| 139 | + |
| 140 | + let data_4 = vec![]; |
| 141 | + let mut iter_4 = bit_index_iterator(&data_4); |
| 142 | + assert_eq!(iter_4.next(), None); |
| 143 | + } |
| 144 | + |
| 145 | + #[test] |
| 146 | + fn union() -> Result<()> { |
| 147 | + let a = 0b1000010100; |
| 148 | + let b = 0b01; |
| 149 | + let c = 0b100000000000000011; |
| 150 | + let d = 0b101010100000011000000011; |
| 151 | + let e = 0b000000000000001000000000000000000000; |
| 152 | + let f = 0b100000000000000001010000000001010100000000000; |
| 153 | + let bitmap = vec![a, b, c]; |
| 154 | + let other_bitmap = vec![d, e, f]; |
| 155 | + let union = bitmap_union(&bitmap, &other_bitmap); |
| 156 | + assert_eq!(union, vec![a | d, b | e, c | f]); |
| 157 | + |
| 158 | + // different length |
| 159 | + let union = bitmap_union(&[a], &[d, e, f]); |
| 160 | + assert_eq!(union, vec![a | d, e, f]); |
| 161 | + |
| 162 | + let union = bitmap_union(&[a, b, c], &[d]); |
| 163 | + assert_eq!(union, vec![a | d, b, c]); |
| 164 | + |
| 165 | + let union = bitmap_union(&[], &[d, e]); |
| 166 | + assert_eq!(union, vec![d, e]); |
| 167 | + |
| 168 | + let union = bitmap_union(&[a, b, c], &[]); |
| 169 | + assert_eq!(union, vec![a, b, c]); |
| 170 | + |
| 171 | + let union = bitmap_union(&[], &[]); |
| 172 | + let empty: Vec<u64> = vec![]; |
| 173 | + assert_eq!(union, empty); |
| 174 | + |
| 175 | + Ok(()) |
| 176 | + } |
| 177 | +} |
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