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serenity/AK/BinarySearch.h

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Meta: Add license header to source files As suggested by Joshua, this commit adds the 2-clause BSD license as a comment block to the top of every source file. For the first pass, I've just added myself for simplicity. I encourage everyone to add themselves as copyright holders of any file they've added or modified in some significant way. If I've added myself in error somewhere, feel free to replace it with the appropriate copyright holder instead. Going forward, all new source files should include a license header.
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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
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#pragma once
Refactor: Change the AK::binary_search signature to use AK::Span.
2020-07-26 09:22:05 +00:00
#include <AK/Span.h>
Kernel: Optimize VM range deallocation a bit Previously, when deallocating a range of VM, we would sort and merge the range list. This was quite slow for large processes. This patch optimizes VM deallocation in the following ways: - Use binary search instead of linear scan to find the place to insert the deallocated range. - Insert at the right place immediately, removing the need to sort. - Merge the inserted range with any adjacent range(s) in-line instead of doing a separate merge pass into a list copy. - Add Traits<Range> to inform Vector that Range objects are trivial and can be moved using memmove(). I've also added an assertion that deallocated ranges are actually part of the RangeAllocator's initial address range. I've benchmarked this using g++ to compile Kernel/Process.cpp. With these changes, compilation goes from ~41 sec to ~35 sec.
2020-01-19 12:18:27 +00:00
#include <AK/StdLibExtras.h>
Shell: Cache PATH for faster tab completion This patch reduces the O(n) tab completion to something like O(log(n)). The cache is just a sorted vector of strings and we binary search it to get a string matching our input, and then check the surrounding strings to see if we need to remove any characters. Also we no longer stat each file every time. Also added an #include in BinarySearch since it was using size_t. Oops. If `export` is called, we recache. Need to implement the `hash` builtin for when an executable has been added to a directory in PATH.
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#include <AK/Types.h>
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
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namespace AK {
template<typename T>
BinarySearch: constexpr support Problem: - It is not possible to perform a binary search at compile-time because `binary_search` is not `constexpr`-aware. Solution: - Add `constexpr` support.
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constexpr int integral_compare(const typename RemoveConst<T>::Type& a, const typename RemoveConst<T>::Type& b)
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
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{
return a - b;
}
template<typename T, typename Compare>
BinarySearch: constexpr support Problem: - It is not possible to perform a binary search at compile-time because `binary_search` is not `constexpr`-aware. Solution: - Add `constexpr` support.
2020-10-13 22:30:35 +00:00
constexpr T* binary_search(Span<T> haystack, const typename RemoveConst<T>::Type& needle, Compare compare = integral_compare, size_t* nearby_index = nullptr)
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
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{
AK: Fix overflow and mixed-signedness issues in binary_search() (#2961)
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if (haystack.size() == 0) {
if (nearby_index)
*nearby_index = 0;
return nullptr;
}
size_t low = 0;
size_t high = haystack.size() - 1;
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
2019-12-02 04:19:57 +00:00
while (low <= high) {
AK: Fix overflow and mixed-signedness issues in binary_search() (#2961)
2020-08-02 19:10:35 +00:00
size_t middle = low + ((high - low) / 2);
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
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int comparison = compare(needle, haystack[middle]);
if (comparison < 0)
AK: Fix overflow and mixed-signedness issues in binary_search() (#2961)
2020-08-02 19:10:35 +00:00
if (middle != 0)
high = middle - 1;
else
break;
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
2019-12-02 04:19:57 +00:00
else if (comparison > 0)
low = middle + 1;
Kernel: Optimize VM range deallocation a bit Previously, when deallocating a range of VM, we would sort and merge the range list. This was quite slow for large processes. This patch optimizes VM deallocation in the following ways: - Use binary search instead of linear scan to find the place to insert the deallocated range. - Insert at the right place immediately, removing the need to sort. - Merge the inserted range with any adjacent range(s) in-line instead of doing a separate merge pass into a list copy. - Add Traits<Range> to inform Vector that Range objects are trivial and can be moved using memmove(). I've also added an assertion that deallocated ranges are actually part of the RangeAllocator's initial address range. I've benchmarked this using g++ to compile Kernel/Process.cpp. With these changes, compilation goes from ~41 sec to ~35 sec.
2020-01-19 12:18:27 +00:00
else {
if (nearby_index)
*nearby_index = middle;
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
2019-12-02 04:19:57 +00:00
return &haystack[middle];
Kernel: Optimize VM range deallocation a bit Previously, when deallocating a range of VM, we would sort and merge the range list. This was quite slow for large processes. This patch optimizes VM deallocation in the following ways: - Use binary search instead of linear scan to find the place to insert the deallocated range. - Insert at the right place immediately, removing the need to sort. - Merge the inserted range with any adjacent range(s) in-line instead of doing a separate merge pass into a list copy. - Add Traits<Range> to inform Vector that Range objects are trivial and can be moved using memmove(). I've also added an assertion that deallocated ranges are actually part of the RangeAllocator's initial address range. I've benchmarked this using g++ to compile Kernel/Process.cpp. With these changes, compilation goes from ~41 sec to ~35 sec.
2020-01-19 12:18:27 +00:00
}
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
2019-12-02 04:19:57 +00:00
}
Kernel: Optimize VM range deallocation a bit Previously, when deallocating a range of VM, we would sort and merge the range list. This was quite slow for large processes. This patch optimizes VM deallocation in the following ways: - Use binary search instead of linear scan to find the place to insert the deallocated range. - Insert at the right place immediately, removing the need to sort. - Merge the inserted range with any adjacent range(s) in-line instead of doing a separate merge pass into a list copy. - Add Traits<Range> to inform Vector that Range objects are trivial and can be moved using memmove(). I've also added an assertion that deallocated ranges are actually part of the RangeAllocator's initial address range. I've benchmarked this using g++ to compile Kernel/Process.cpp. With these changes, compilation goes from ~41 sec to ~35 sec.
2020-01-19 12:18:27 +00:00
if (nearby_index)
AK: Fix overflow and mixed-signedness issues in binary_search() (#2961)
2020-08-02 19:10:35 +00:00
*nearby_index = min(low, high);
Kernel: Optimize VM range deallocation a bit Previously, when deallocating a range of VM, we would sort and merge the range list. This was quite slow for large processes. This patch optimizes VM deallocation in the following ways: - Use binary search instead of linear scan to find the place to insert the deallocated range. - Insert at the right place immediately, removing the need to sort. - Merge the inserted range with any adjacent range(s) in-line instead of doing a separate merge pass into a list copy. - Add Traits<Range> to inform Vector that Range objects are trivial and can be moved using memmove(). I've also added an assertion that deallocated ranges are actually part of the RangeAllocator's initial address range. I've benchmarked this using g++ to compile Kernel/Process.cpp. With these changes, compilation goes from ~41 sec to ~35 sec.
2020-01-19 12:18:27 +00:00
AK: Add a BinarySearch template implementation binary_search takes a haystack, a size, a needle and a compare function. The compare function should return negative if a < b, positive if a > b and 0 if a == b. The "sane default" compare function is integral_compare which implements this with subtraction a - b. binary_search returns a pointer to a matching element, NOT necessarily the FIRST matching element. It returns a nullptr if the element was not found. This patch includes tests for binary_search.
2019-12-02 04:19:57 +00:00
return nullptr;
}
}
using AK::binary_search;
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