Struct diem_proptest_helpers::RepeatVec

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pub struct RepeatVec<T> { /* private fields */ }

Expand description

An efficient representation of a vector with repeated elements inserted.

Internally, this data structure stores one copy of each inserted element, along with data about how many times each element is repeated.

This data structure does not do any sort of deduplication, so it isn’t any sort of set (or multiset).

This is useful for presenting a large logical vector for picking proptest indexes from.

Examples

use diem_proptest_helpers::RepeatVec;

let mut repeat_vec = RepeatVec::new();
repeat_vec.extend("a", 10); // logically, insert "a" 10 times
repeat_vec.extend("b", 20); // logically, insert "b" 20 times
assert_eq!(repeat_vec.get(0), Some((&"a", 0))); // returns the "a" at logical position 0
assert_eq!(repeat_vec.get(5), Some((&"a", 5))); // returns the "a" at logical position 5
assert_eq!(repeat_vec.get(10), Some((&"b", 0))); // returns the "b" (offset 0) at logical position 10
assert_eq!(repeat_vec.get(20), Some((&"b", 10))); // returns the "b" (offset 10) at logical position 20
assert_eq!(repeat_vec.get(30), None); // past the end of the logical array

The data structure doesn’t care about whether the inserted items are equal or not.

use diem_proptest_helpers::RepeatVec;

let mut repeat_vec = RepeatVec::new();
repeat_vec.extend("a", 10); // logically, insert "a" 10 times
repeat_vec.extend("a", 20); // logically, insert "a" 20 times
assert_eq!(repeat_vec.get(0), Some((&"a", 0)));
assert_eq!(repeat_vec.get(5), Some((&"a", 5)));
assert_eq!(repeat_vec.get(10), Some((&"a", 0))); // This refers to the second "a".

Implementations§

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impl<T> RepeatVec<T>

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pub fn new() -> Self

Creates a new, empty RepeatVec.

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pub fn with_capacity(capacity: usize) -> Self

Creates a new, empty RepeatVec with the specified capacity to store physical elements.

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pub fn len(&self) -> usize

Returns the logical number of elements in this RepeatVec.

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pub fn is_empty(&self) -> bool

Returns true if this RepeatVec has no logical elements.

Examples

use diem_proptest_helpers::RepeatVec;

let mut repeat_vec = RepeatVec::new();

// There are no elements in this RepeatVec.
assert!(repeat_vec.is_empty());

// Adding 0 logical copies of an element still means it's empty.
repeat_vec.extend("a", 0);
assert!(repeat_vec.is_empty());

// Adding non-zero logical copies makes this vector not empty.
repeat_vec.extend("b", 1);
assert!(!repeat_vec.is_empty());

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pub fn extend(&mut self, item: T, size: usize)

Extends this RepeatVec by logically adding size copies of item to the end of it.

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pub fn remove(&mut self, index: usize)

Removes the item specified by the given logical index, shifting all elements after it to the left by updating start positions.

Out of bounds indexes have no effect.

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pub fn remove_all(&mut self, logical_indexes: impl IntoIterator<Item = usize>)

Removes the items specified by the given logical indexes, shifting all elements after them to the left by updating start positions.

Ignores any out of bounds indexes.

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pub fn get(&self, at: usize) -> Option<(&T, usize)>

Returns the item at location at. The return value is a reference to the stored item, plus the offset from the start (logically, which copy of the item is being returned).

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