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Add insert method #23

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8792433
Add count_ones, count_zeros methods
canndrew Nov 17, 2019
ce792b0
Add insert method
canndrew Nov 17, 2019
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89 changes: 89 additions & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -334,6 +334,43 @@ impl SmallBitVec {
}
}

/// Insert a bit at the given index, shifting all following values toward the back.
pub fn insert(&mut self, idx: usize, val: bool) {
let len = self.len();
assert!(idx <= len, "range out of bounds");
self.reserve(1);
if self.is_inline() {
let mask = inline_ones(idx);
let new_vals = (self.data & !mask) >> 1;
self.data = (self.data & mask) | new_vals;
if val {
self.data |= inline_index(idx);
}
} else {
let first = idx / bits_per_storage();
let offset = idx % bits_per_storage();
let count = buffer_len(len + 1);
for i in ((first + 1)..count).rev() {
self.buffer_mut()[i] <<= 1;
let bit_idx = i * bits_per_storage();
unsafe {
let first_bit = self.get_unchecked(bit_idx - 1);
self.set_unchecked(bit_idx, first_bit);
}
}
let buf = self.buffer_mut();
let mask = !0 << offset;
let new_vals = (buf[first] & mask) << 1;
buf[first] = (buf[first] & !mask) | new_vals;
if val {
buf[first] |= 1 << offset;
}
unsafe {
self.set_len(len + 1);
}
}
}

/// Append a bit to the end of the vector.
///
/// ```
Expand Down Expand Up @@ -551,6 +588,58 @@ impl SmallBitVec {
}
}

/// Counts the number of bits in the vector that are set to one/true
pub fn count_ones(&self) -> usize {
let mut len = self.len();
if len == 0 {
return 0;
}

if self.is_inline() {
let mask = inline_ones(len);
(self.data & mask).count_ones() as usize
} else {
let mut count = 0;
for &storage in self.buffer() {
if len >= bits_per_storage() {
count += storage.count_ones() as usize;
len -= bits_per_storage();
} else {
let mask = (1 << len) - 1;
count += (storage & mask).count_ones() as usize;
break;
}
}
count
}
}

/// Counts the number of bits in the vector that are set to zero/false
pub fn count_zeros(&self) -> usize {
let mut len = self.len();
if len == 0 {
return 0;
}

if self.is_inline() {
let mask = inline_ones(len);
(!self.data & mask).count_ones() as usize
} else {
let mut count = 0;
for &storage in self.buffer() {
if len >= bits_per_storage() {
count += storage.count_zeros() as usize;
len -= bits_per_storage();
} else {
let mask = (1 << len) - 1;
count += (!storage & mask).count_ones() as usize;
break;
}
}
count
}
}

/// Shorten the vector, keeping the first `len` elements and dropping the rest.
///
/// If `len` is greater than or equal to the vector's current length, this has no
Expand Down
65 changes: 65 additions & 0 deletions src/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -365,3 +365,68 @@ fn resize() {
assert_eq!(v.get(98).unwrap(), false);
assert_eq!(v.get(99).unwrap(), false);
}

#[test]
fn count_ones_zeros() {
let random_bits = &[
false, true, true, true, true, false, true, false,
true, true, false, false, false, false, true, false,
false, true, true, false, false, false, false, false,
false, true, false, false, false, false, false, true,
false, true, true, true, false, true, false, true,
true, true, false, false, true, false, false, false,
true, false, true, false, true, false, false, false,
false, true, false, true, false, false, true, true,
true, true, false, true, true, true, false, false,
false, false, true, false, true, true, false, false,
];
let mut v = SmallBitVec::new();
for start in 0..random_bits.len() {
for i in 0..random_bits.len() {
let index = (start + i) % random_bits.len();
let bit = random_bits[index];
v.push(bit);
assert_eq!(v.iter().filter(|&b| b).count(), v.count_ones());
assert_eq!(v.iter().filter(|&b| !b).count(), v.count_zeros());
}
v.clear();
}
}

#[test]
fn insert() {
let random_bits = &[
false, true, true, true, true, false, true, false,
true, true, false, false, false, false, true, false,
false, true, true, false, false, false, false, false,
false, true, false, false, false, false, false, true,
false, true, true, true, false, true, false, true,
true, true, false, false, true, false, false, false,
true, false, true, false, true, false, false, false,
false, true, false, true, false, false, true, true,
true, true, false, true, true, true, false, false,
false, false, true, false, true, true, false, false,
];
let mut seed = 0xaaaaaaaau32;
let mut v0 = SmallBitVec::new();
let mut v1 = SmallBitVec::new();
for start in 0..random_bits.len() {
for i in 0..random_bits.len() {
seed ^= seed << 13;
seed ^= seed >> 17;
seed ^= seed << 5;
let bit = random_bits[(start + i) % random_bits.len()];
let index = (seed as usize) % (i + 1);
v0.insert(index, bit);
v1.push(false);
for j in (index..i).rev() {
let bit = v1.get(j).unwrap();
v1.set(j + 1, bit);
}
v1.set(index, bit);
assert_eq!(v0, v1);
}
v0.clear();
v1.clear();
}
}