86 lines
2.0 KiB
Rust
86 lines
2.0 KiB
Rust
//! vector util functions
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use std::ptr;
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pub trait InsertSlice<T> {
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fn insert_slice(&mut self, index: usize, elements: &[T]);
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}
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/// based on `insert` function implementation from standard library
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impl<T> InsertSlice<T> for Vec<T> {
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fn insert_slice(&mut self, index: usize, elements: &[T]) {
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let e_len = elements.len();
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if e_len == 0 {
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return;
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}
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let len = self.len();
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assert!(index <= len);
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// space for the new element
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self.reserve(e_len);
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unsafe {
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{
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let p = self.as_mut_ptr().offset(index as isize);
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let ep = elements.as_ptr().offset(0);
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// shift everything by e_len, to make space
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ptr::copy(p, p.offset(e_len as isize), len - index);
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// write new element
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ptr::copy(ep, p, e_len);
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}
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self.set_len(len + e_len);
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}
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}
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}
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/// Returns len of prefix shared with elem
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///
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/// ```rust
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/// extern crate ethcore_util as util;
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/// use util::vector::SharedPrefix;
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///
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/// fn main () {
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/// let a = vec![1,2,3,3,5];
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/// let b = vec![1,2,3];
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/// assert_eq!(a.shared_prefix_len(&b), 3);
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/// }
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/// ```
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pub trait SharedPrefix <T> {
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fn shared_prefix_len(&self, elem: &[T]) -> usize;
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}
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impl <T> SharedPrefix<T> for Vec<T> where T: Eq {
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fn shared_prefix_len(&self, elem: &[T]) -> usize {
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use std::cmp;
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let len = cmp::min(self.len(), elem.len());
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(0..len).take_while(|&i| self[i] == elem[i]).count()
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}
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}
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#[cfg(test)]
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mod test {
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use vector::SharedPrefix;
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#[test]
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fn test_shared_prefix() {
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let a = vec![1,2,3,4,5,6];
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let b = vec![4,2,3,4,5,6];
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assert_eq!(a.shared_prefix_len(&b), 0);
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}
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#[test]
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fn test_shared_prefix2() {
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let a = vec![1,2,3,3,5];
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let b = vec![1,2,3];
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assert_eq!(a.shared_prefix_len(&b), 3);
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}
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#[test]
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fn test_shared_prefix3() {
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let a = vec![1,2,3,4,5,6];
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let b = vec![1,2,3,4,5,6];
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assert_eq!(a.shared_prefix_len(&b), 6);
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}
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}
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