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Implement remove for RingBuf

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This commit is contained in:
Piotr Czarnecki 2014-12-17 00:37:55 +01:00
parent 93c0610096
commit 59d4153457
1 changed files with 250 additions and 50 deletions
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300
src/libcollections/ring_buf.rs
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@ -102,17 +102,15 @@ impl<T> RingBuf<T> {
/// Copies a contiguous block of memory len long from src to dst
#[inline]
fn copy(&self, dst: uint, src: uint, len: uint) {
unsafe {
debug_assert!(dst + len <= self.cap, "dst={} src={} len={} cap={}", dst, src, len,
self.cap);
debug_assert!(src + len <= self.cap, "dst={} src={} len={} cap={}", dst, src, len,
self.cap);
ptr::copy_memory(
self.ptr.offset(dst as int),
self.ptr.offset(src as int) as *const T,
len);
}
unsafe fn copy(&self, dst: uint, src: uint, len: uint) {
debug_assert!(dst + len <= self.cap, "dst={} src={} len={} cap={}", dst, src, len,
self.cap);
debug_assert!(src + len <= self.cap, "dst={} src={} len={} cap={}", dst, src, len,
self.cap);
ptr::copy_memory(
self.ptr.offset(dst as int),
self.ptr.offset(src as int) as *const T,
len);
}
}
@ -732,7 +730,7 @@ impl<T> RingBuf<T> {
self.tail = self.wrap_index(self.tail - 1);
},
(true, true, _) => {
(true, true, _) => unsafe {
// contiguous, insert closer to tail:
//
// T I H
@ -752,13 +750,15 @@ impl<T> RingBuf<T> {
// [o I A o o o o o . . . . . . . o]
// M M
let old_tail = self.tail;
self.tail = self.wrap_index(self.tail - 1);
let new_tail = self.wrap_index(self.tail - 1);
self.copy(self.tail, old_tail, 1);
self.copy(old_tail, old_tail + 1, i);
self.copy(new_tail, self.tail, 1);
// Already moved the tail, so we only copy `i - 1` elements.
self.copy(self.tail, self.tail + 1, i - 1);
self.tail = new_tail;
},
(true, false, _) => {
(true, false, _) => unsafe {
// contiguous, insert closer to head:
//
// T I H
@ -768,12 +768,11 @@ impl<T> RingBuf<T> {
// [. . . o o o o I A o o . . . . .]
// M M M
let old_head = self.head;
self.copy(idx + 1, idx, self.head - idx);
self.head = self.wrap_index(self.head + 1);
self.copy(idx + 1, idx, old_head - idx);
},
(false, true, true) => {
// discontiguous, tail section, insert closer to tail:
(false, true, true) => unsafe {
// discontiguous, insert closer to tail, tail section:
//
// H T I
// [o o o o o o . . . . . o o A o o]
@ -782,12 +781,11 @@ impl<T> RingBuf<T> {
// [o o o o o o . . . . o o I A o o]
// M M
let old_tail = self.tail;
self.tail = self.tail - 1;
self.copy(self.tail, old_tail, i);
self.copy(self.tail - 1, self.tail, i);
self.tail -= 1;
},
(false, false, true) => {
// discontiguous, tail section, insert closer to head:
(false, false, true) => unsafe {
// discontiguous, insert closer to head, tail section:
//
// H T I
// [o o . . . . . . . o o o o o A o]
@ -796,20 +794,19 @@ impl<T> RingBuf<T> {
// [o o o . . . . . . o o o o o I A]
// M M M M
let old_head = self.head;
self.head = self.head + 1;
// copy elements up to new head
self.copy(1, 0, old_head);
self.copy(1, 0, self.head);
// copy last element into empty spot at bottom of buffer
self.copy(0, self.cap - 1, 1);
// move elements from idx to end forward not including ^ element
self.copy(idx + 1, idx, self.cap - 1 - idx);
self.head += 1;
},
(false, true, false) if idx == 0 => {
// discontiguous, head section, insert is closer to tail,
(false, true, false) if idx == 0 => unsafe {
// discontiguous, insert is closer to tail, head section,
// and is at index zero in the internal buffer:
//
// I H T
@ -819,16 +816,16 @@ impl<T> RingBuf<T> {
// [A o o o o o o o o o . . o o o I]
// M M M
let old_tail = self.tail;
self.tail = self.tail - 1;
// copy elements up to new tail
self.copy(old_tail - 1, old_tail, i);
self.copy(self.tail - 1, self.tail, self.cap - self.tail);
// copy last element into empty spot at bottom of buffer
self.copy(self.cap - 1, 0, 1);
self.tail -= 1;
},
(false, true, false) => {
// discontiguous, head section, insert closer to tail:
(false, true, false) => unsafe {
// discontiguous, insert closer to tail, head section:
//
// I H T
// [o o o A o o o o o o . . . o o o]
@ -837,19 +834,19 @@ impl<T> RingBuf<T> {
// [o o I A o o o o o o . . o o o o]
// M M M M M M
let old_tail = self.tail;
self.tail = self.tail - 1;
// copy elements up to new tail
self.copy(old_tail - 1, old_tail, i);
self.copy(self.tail - 1, self.tail, self.cap - self.tail);
// copy last element into empty spot at bottom of buffer
self.copy(self.cap - 1, 0, 1);
// move elements from idx-1 to end forward not including ^ element
self.copy(0, 1, idx - 1);
}
(false, false, false) => {
// discontiguous, head section, insert closer to head:
self.tail -= 1;
},
(false, false, false) => unsafe {
// discontiguous, insert closer to head, head section:
//
// I H T
// [o o o o A o o . . . . . . o o o]
@ -858,9 +855,8 @@ impl<T> RingBuf<T> {
// [o o o o I A o o . . . . . o o o]
// M M M
let old_head = self.head;
self.head = self.head + 1;
self.copy(idx + 1, idx, old_head - idx);
self.copy(idx + 1, idx, self.head - idx);
self.head += 1;
}
}
@ -870,6 +866,170 @@ impl<T> RingBuf<T> {
self.buffer_write(new_idx, t);
}
}
/// Removes and returns the element at position `i` from the ringbuf.
/// Whichever end is closer to the removal point will be moved to make
/// room, and all the affected elements will be moved to new positions.
/// Returns `None` if `i` is out of bounds.
///
/// # Example
/// ```rust
/// use std::collections::RingBuf;
///
/// let mut buf = RingBuf::new();
/// buf.push_back(5i);
/// buf.push_back(10i);
/// buf.push_back(12i);
/// buf.push_back(15);
/// buf.remove(2);
/// assert_eq!(Some(&15), buf.get(2));
/// ```
#[unstable = "matches collection reform specification; waiting on panic semantics"]
pub fn remove(&mut self, i: uint) -> Option<T> {
if self.is_empty() || self.len() <= i {
return None;
}
// There are three main cases:
// Elements are contiguous
// Elements are discontiguous and the removal is in the tail section
// Elements are discontiguous and the removal is in the head section
// - special case when elements are technically contiguous,
// but self.head = 0
//
// For each of those there are two more cases:
// Insert is closer to tail
// Insert is closer to head
//
// Key: H - self.head
// T - self.tail
// o - Valid element
// x - Element marked for removal
// R - Indicates element that is being removed
// M - Indicates element was moved
let idx = self.wrap_index(self.tail + i);
let elem = unsafe {
Some(self.buffer_read(idx))
};
let distance_to_tail = i;
let distance_to_head = self.len() - i;
let contiguous = self.tail <= self.head;
match (contiguous, distance_to_tail <= distance_to_head, idx >= self.tail) {
(true, true, _) => unsafe {
// contiguous, remove closer to tail:
//
// T R H
// [. . . o o x o o o o . . . . . .]
//
// T H
// [. . . . o o o o o o . . . . . .]
// M M
self.copy(self.tail + 1, self.tail, i);
self.tail += 1;
},
(true, false, _) => unsafe {
// contiguous, remove closer to head:
//
// T R H
// [. . . o o o o x o o . . . . . .]
//
// T H
// [. . . o o o o o o . . . . . . .]
// M M
self.copy(idx, idx + 1, self.head - idx - 1);
self.head -= 1;
},
(false, true, true) => unsafe {
// discontiguous, remove closer to tail, tail section:
//
// H T R
// [o o o o o o . . . . . o o x o o]
//
// H T
// [o o o o o o . . . . . . o o o o]
// M M
self.copy(self.tail + 1, self.tail, i);
self.tail = self.wrap_index(self.tail + 1);
},
(false, false, false) => unsafe {
// discontiguous, remove closer to head, head section:
//
// R H T
// [o o o o x o o . . . . . . o o o]
//
// H T
// [o o o o o o . . . . . . . o o o]
// M M
self.copy(idx, idx + 1, self.head - idx - 1);
self.head -= 1;
},
(false, false, true) => unsafe {
// discontiguous, remove closer to head, tail section:
//
// H T R
// [o o o . . . . . . o o o o o x o]
//
// H T
// [o o . . . . . . . o o o o o o o]
// M M M M
//
// or quasi-discontiguous, remove next to head, tail section:
//
// H T R
// [. . . . . . . . . o o o o o x o]
//
// T H
// [. . . . . . . . . o o o o o o .]
// M
// draw in elements in the tail section
self.copy(idx, idx + 1, self.cap - idx - 1);
// Prevents underflow.
if self.head != 0 {
// copy first element into empty spot
self.copy(self.cap - 1, 0, 1);
// move elements in the head section backwards
self.copy(0, 1, self.head - 1);
}
self.head = self.wrap_index(self.head - 1);
},
(false, true, false) => unsafe {
// discontiguous, remove closer to tail, head section:
//
// R H T
// [o o x o o o o o o o . . . o o o]
//
// H T
// [o o o o o o o o o o . . . . o o]
// M M M M M
// draw in elements up to idx
self.copy(1, 0, idx);
// copy last element into empty spot
self.copy(0, self.cap - 1, 1);
// move elements from tail to end forward, excluding the last one
self.copy(self.tail + 1, self.tail, self.cap - self.tail - 1);
self.tail = self.wrap_index(self.tail + 1);
}
}
return elem;
}
}
/// Returns the index in the underlying buffer for a given logical element index.
@ -1103,6 +1263,7 @@ mod tests {
use core::iter;
use self::Taggy::*;
use self::Taggypar::*;
use std::cmp;
use std::fmt::Show;
use std::prelude::*;
use std::hash;
@ -1892,11 +2053,11 @@ mod tests {
#[test]
fn test_insert() {
// This test checks that every single combination of tail position, length, and
// insertion position is tested. Capacity 7 should be large enough to cover every case.
// insertion position is tested. Capacity 15 should be large enough to cover every case.
let mut tester = RingBuf::with_capacity(7);
// can't guarantee we got 7, so have to get what we got.
// 7 would be great, but we will definitely get 2^k - 1, for k >= 3, or else
let mut tester = RingBuf::with_capacity(15);
// can't guarantee we got 15, so have to get what we got.
// 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else
// this test isn't covering what it wants to
let cap = tester.capacity();
@ -1915,6 +2076,45 @@ mod tests {
}
}
tester.insert(to_insert, to_insert);
assert!(tester.tail < tester.cap);
assert!(tester.head < tester.cap);
assert_eq!(tester, expected);
}
}
}
}
#[test]
fn test_remove() {
// This test checks that every single combination of tail position, length, and
// removal position is tested. Capacity 15 should be large enough to cover every case.
let mut tester = RingBuf::with_capacity(15);
// can't guarantee we got 15, so have to get what we got.
// 15 would be great, but we will definitely get 2^k - 1, for k >= 4, or else
// this test isn't covering what it wants to
let cap = tester.capacity();
// len is the length *after* removal
for len in range(0, cap - 1) {
// 0, 1, 2, .., len - 1
let expected = iter::count(0, 1).take(len).collect();
for tail_pos in range(0, cap) {
for to_remove in range(0, len + 1) {
tester.tail = tail_pos;
tester.head = tail_pos;
for i in range(0, len) {
if i == to_remove {
tester.push_back(1234);
}
tester.push_back(i);
}
if to_remove == len {
tester.push_back(1234);
}
tester.remove(to_remove);
assert!(tester.tail < tester.cap);
assert!(tester.head < tester.cap);
assert_eq!(tester, expected);
}
}