From 04f6692aaf78809c041ba6145bde2dcbeec9725e Mon Sep 17 00:00:00 2001 From: Diggory Blake Date: Mon, 26 Mar 2018 23:24:31 +0100 Subject: [PATCH] Implement `shrink_to` method on collections --- src/liballoc/binary_heap.rs | 25 +++++++++++++++++++ src/liballoc/string.rs | 28 +++++++++++++++++++++ src/liballoc/vec.rs | 27 +++++++++++++++++++- src/liballoc/vec_deque.rs | 35 +++++++++++++++++++++++++- src/libstd/collections/hash/map.rs | 40 ++++++++++++++++++++++++++++++ src/libstd/collections/hash/set.rs | 28 +++++++++++++++++++++ src/libstd/ffi/os_str.rs | 30 ++++++++++++++++++++++ src/libstd/lib.rs | 1 + src/libstd/sys/redox/os_str.rs | 5 ++++ src/libstd/sys/unix/os_str.rs | 5 ++++ src/libstd/sys/wasm/os_str.rs | 5 ++++ src/libstd/sys/windows/os_str.rs | 5 ++++ src/libstd/sys_common/wtf8.rs | 5 ++++ 13 files changed, 237 insertions(+), 2 deletions(-) diff --git a/src/liballoc/binary_heap.rs b/src/liballoc/binary_heap.rs index 8aaac5d6e08a5..f6a666b599b09 100644 --- a/src/liballoc/binary_heap.rs +++ b/src/liballoc/binary_heap.rs @@ -509,6 +509,31 @@ impl BinaryHeap { self.data.shrink_to_fit(); } + /// Discards capacity with a lower bound. + /// + /// The capacity will remain at least as large as both the length + /// and the supplied value. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// use std::collections::BinaryHeap; + /// let mut heap: BinaryHeap = BinaryHeap::with_capacity(100); + /// + /// assert!(heap.capacity() >= 100); + /// heap.shrink_to(10); + /// assert!(heap.capacity() >= 10); + /// ``` + #[inline] + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.data.shrink_to(min_capacity) + } + /// Removes the greatest item from the binary heap and returns it, or `None` if it /// is empty. /// diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs index e253122ffd6b6..2bb60a50679e6 100644 --- a/src/liballoc/string.rs +++ b/src/liballoc/string.rs @@ -1015,6 +1015,34 @@ impl String { self.vec.shrink_to_fit() } + /// Shrinks the capacity of this `String` with a lower bound. + /// + /// The capacity will remain at least as large as both the length + /// and the supplied value. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// let mut s = String::from("foo"); + /// + /// s.reserve(100); + /// assert!(s.capacity() >= 100); + /// + /// s.shrink_to(10); + /// assert!(s.capacity() >= 10); + /// s.shrink_to(0); + /// assert!(s.capacity() >= 3); + /// ``` + #[inline] + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.vec.shrink_to(min_capacity) + } + /// Appends the given [`char`] to the end of this `String`. /// /// [`char`]: ../../std/primitive.char.html diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs index 953f95876be15..c9c6cf1cb6691 100644 --- a/src/liballoc/vec.rs +++ b/src/liballoc/vec.rs @@ -66,7 +66,7 @@ #![stable(feature = "rust1", since = "1.0.0")] -use core::cmp::Ordering; +use core::cmp::{self, Ordering}; use core::fmt; use core::hash::{self, Hash}; use core::intrinsics::{arith_offset, assume}; @@ -586,6 +586,31 @@ impl Vec { self.buf.shrink_to_fit(self.len); } + /// Shrinks the capacity of the vector with a lower bound. + /// + /// The capacity will remain at least as large as both the length + /// and the supplied value. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// let mut vec = Vec::with_capacity(10); + /// vec.extend([1, 2, 3].iter().cloned()); + /// assert_eq!(vec.capacity(), 10); + /// vec.shrink_to(4); + /// assert!(vec.capacity() >= 4); + /// vec.shrink_to(0); + /// assert!(vec.capacity() >= 3); + /// ``` + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.buf.shrink_to_fit(cmp::max(self.len, min_capacity)); + } + /// Converts the vector into [`Box<[T]>`][owned slice]. /// /// Note that this will drop any excess capacity. diff --git a/src/liballoc/vec_deque.rs b/src/liballoc/vec_deque.rs index 0658777f0a0e0..be6e8d0f22f07 100644 --- a/src/liballoc/vec_deque.rs +++ b/src/liballoc/vec_deque.rs @@ -676,9 +676,42 @@ impl VecDeque { /// ``` #[stable(feature = "deque_extras_15", since = "1.5.0")] pub fn shrink_to_fit(&mut self) { + self.shrink_to(0); + } + + /// Shrinks the capacity of the `VecDeque` with a lower bound. + /// + /// The capacity will remain at least as large as both the length + /// and the supplied value. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// use std::collections::VecDeque; + /// + /// let mut buf = VecDeque::with_capacity(15); + /// buf.extend(0..4); + /// assert_eq!(buf.capacity(), 15); + /// buf.shrink_to(6); + /// assert!(buf.capacity() >= 6); + /// buf.shrink_to(0); + /// assert!(buf.capacity() >= 4); + /// ``` + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity"); + // +1 since the ringbuffer always leaves one space empty // len + 1 can't overflow for an existing, well-formed ringbuffer. - let target_cap = cmp::max(self.len() + 1, MINIMUM_CAPACITY + 1).next_power_of_two(); + let target_cap = cmp::max( + cmp::max(min_capacity, self.len()) + 1, + MINIMUM_CAPACITY + 1 + ).next_power_of_two(); + if target_cap < self.cap() { // There are three cases of interest: // All elements are out of desired bounds diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs index b18b38ec30246..169d365c0ac50 100644 --- a/src/libstd/collections/hash/map.rs +++ b/src/libstd/collections/hash/map.rs @@ -910,6 +910,46 @@ impl HashMap } } + /// Shrinks the capacity of the map with a lower limit. It will drop + /// down no lower than the supplied limit while maintaining the internal rules + /// and possibly leaving some space in accordance with the resize policy. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// use std::collections::HashMap; + /// + /// let mut map: HashMap = HashMap::with_capacity(100); + /// map.insert(1, 2); + /// map.insert(3, 4); + /// assert!(map.capacity() >= 100); + /// map.shrink_to(10); + /// assert!(map.capacity() >= 10); + /// map.shrink_to(0); + /// assert!(map.capacity() >= 2); + /// ``` + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + assert!(self.capacity() >= min_capacity, "Tried to shrink to a larger capacity"); + + let new_raw_cap = self.resize_policy.raw_capacity(max(self.len(), min_capacity)); + if self.raw_capacity() != new_raw_cap { + let old_table = replace(&mut self.table, RawTable::new(new_raw_cap)); + let old_size = old_table.size(); + + // Shrink the table. Naive algorithm for resizing: + for (h, k, v) in old_table.into_iter() { + self.insert_hashed_nocheck(h, k, v); + } + + debug_assert_eq!(self.table.size(), old_size); + } + } + /// Insert a pre-hashed key-value pair, without first checking /// that there's enough room in the buckets. Returns a reference to the /// newly insert value. diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs index 9e63ba2717a6a..855563a5cb8db 100644 --- a/src/libstd/collections/hash/set.rs +++ b/src/libstd/collections/hash/set.rs @@ -292,6 +292,34 @@ impl HashSet self.map.shrink_to_fit() } + /// Shrinks the capacity of the set with a lower limit. It will drop + /// down no lower than the supplied limit while maintaining the internal rules + /// and possibly leaving some space in accordance with the resize policy. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// use std::collections::HashSet; + /// + /// let mut set = HashSet::with_capacity(100); + /// set.insert(1); + /// set.insert(2); + /// assert!(set.capacity() >= 100); + /// set.shrink_to(10); + /// assert!(set.capacity() >= 10); + /// set.shrink_to(0); + /// assert!(set.capacity() >= 2); + /// ``` + #[inline] + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.map.shrink_to(min_capacity) + } + /// An iterator visiting all elements in arbitrary order. /// The iterator element type is `&'a T`. /// diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs index 3959e8533be5f..7520121a8c290 100644 --- a/src/libstd/ffi/os_str.rs +++ b/src/libstd/ffi/os_str.rs @@ -295,6 +295,36 @@ impl OsString { self.inner.shrink_to_fit() } + /// Shrinks the capacity of the `OsString` with a lower bound. + /// + /// The capacity will remain at least as large as both the length + /// and the supplied value. + /// + /// Panics if the current capacity is smaller than the supplied + /// minimum capacity. + /// + /// # Examples + /// + /// ``` + /// #![feature(shrink_to)] + /// use std::ffi::OsString; + /// + /// let mut s = OsString::from("foo"); + /// + /// s.reserve(100); + /// assert!(s.capacity() >= 100); + /// + /// s.shrink_to(10); + /// assert!(s.capacity() >= 10); + /// s.shrink_to(0); + /// assert!(s.capacity() >= 3); + /// ``` + #[inline] + #[unstable(feature = "shrink_to", reason = "new API", issue="0")] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.inner.shrink_to(min_capacity) + } + /// Converts this `OsString` into a boxed [`OsStr`]. /// /// [`OsStr`]: struct.OsStr.html diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index 0b06c5d4d656e..edecf309d16f9 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -299,6 +299,7 @@ #![feature(raw)] #![feature(rustc_attrs)] #![feature(stdsimd)] +#![feature(shrink_to)] #![feature(slice_bytes)] #![feature(slice_concat_ext)] #![feature(slice_internals)] diff --git a/src/libstd/sys/redox/os_str.rs b/src/libstd/sys/redox/os_str.rs index 655bfdb916707..da27787babb97 100644 --- a/src/libstd/sys/redox/os_str.rs +++ b/src/libstd/sys/redox/os_str.rs @@ -104,6 +104,11 @@ impl Buf { self.inner.shrink_to_fit() } + #[inline] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.inner.shrink_to(min_capacity) + } + pub fn as_slice(&self) -> &Slice { unsafe { mem::transmute(&*self.inner) } } diff --git a/src/libstd/sys/unix/os_str.rs b/src/libstd/sys/unix/os_str.rs index e034938799866..e43bc6da5f1f8 100644 --- a/src/libstd/sys/unix/os_str.rs +++ b/src/libstd/sys/unix/os_str.rs @@ -104,6 +104,11 @@ impl Buf { self.inner.shrink_to_fit() } + #[inline] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.inner.shrink_to(min_capacity) + } + pub fn as_slice(&self) -> &Slice { unsafe { mem::transmute(&*self.inner) } } diff --git a/src/libstd/sys/wasm/os_str.rs b/src/libstd/sys/wasm/os_str.rs index 543c22ebe18a3..84f560af69bec 100644 --- a/src/libstd/sys/wasm/os_str.rs +++ b/src/libstd/sys/wasm/os_str.rs @@ -104,6 +104,11 @@ impl Buf { self.inner.shrink_to_fit() } + #[inline] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.inner.shrink_to(min_capacity) + } + pub fn as_slice(&self) -> &Slice { unsafe { mem::transmute(&*self.inner) } } diff --git a/src/libstd/sys/windows/os_str.rs b/src/libstd/sys/windows/os_str.rs index 414c9c5418e45..bcc66b9954b89 100644 --- a/src/libstd/sys/windows/os_str.rs +++ b/src/libstd/sys/windows/os_str.rs @@ -113,6 +113,11 @@ impl Buf { self.inner.shrink_to_fit() } + #[inline] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.inner.shrink_to(min_capacity) + } + #[inline] pub fn into_box(self) -> Box { unsafe { mem::transmute(self.inner.into_box()) } diff --git a/src/libstd/sys_common/wtf8.rs b/src/libstd/sys_common/wtf8.rs index 78b2bb5fe6e2f..dda4e1bab3b42 100644 --- a/src/libstd/sys_common/wtf8.rs +++ b/src/libstd/sys_common/wtf8.rs @@ -253,6 +253,11 @@ impl Wtf8Buf { self.bytes.shrink_to_fit() } + #[inline] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.bytes.shrink_to(min_capacity) + } + /// Returns the number of bytes that this string buffer can hold without reallocating. #[inline] pub fn capacity(&self) -> usize {