35 lines
925 B
Rust
35 lines
925 B
Rust
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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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