mfbt/RollingMean.h@97036ab72558 (annotated)
mfbt/RollingMean.h
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | /* -*- Mode: C++; tab-w idth: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ |
| michael@0 | 2 | /* This Source Code Form is subject to the terms of the Mozilla Public |
| michael@0 | 3 | * License, v. 2.0. If a copy of the MPL was not distributed with this |
| michael@0 | 4 | * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| michael@0 | 5 | |
| michael@0 | 6 | /* A set abstraction for enumeration values. */ |
| michael@0 | 7 | |
| michael@0 | 8 | #ifndef mozilla_RollingMean_h_ |
| michael@0 | 9 | #define mozilla_RollingMean_h_ |
| michael@0 | 10 | |
| michael@0 | 11 | #include "mozilla/Assertions.h" |
| michael@0 | 12 | #include "mozilla/TypeTraits.h" |
| michael@0 | 13 | #include "mozilla/Vector.h" |
| michael@0 | 14 | |
| michael@0 | 15 | #include <algorithm> |
| michael@0 | 16 | #include <stddef.h> |
| michael@0 | 17 | #include <stdint.h> |
| michael@0 | 18 | |
| michael@0 | 19 | namespace mozilla { |
| michael@0 | 20 | |
| michael@0 | 21 | /** |
| michael@0 | 22 | * RollingMean<T> calculates a rolling mean of the values it is given. It |
| michael@0 | 23 | * accumulates the total as values are added and removed. The second type |
| michael@0 | 24 | * argument S specifies the type of the total. This may need to be a bigger |
| michael@0 | 25 | * type in order to maintain that the sum of all values in the average doesn't |
| michael@0 | 26 | * exceed the maximum input value. |
| michael@0 | 27 | * |
| michael@0 | 28 | * WARNING: Float types are not supported due to rounding errors. |
| michael@0 | 29 | */ |
| michael@0 | 30 | template<typename T, typename S> |
| michael@0 | 31 | class RollingMean |
| michael@0 | 32 | { |
| michael@0 | 33 | private: |
| michael@0 | 34 | size_t mInsertIndex; |
| michael@0 | 35 | size_t mMaxValues; |
| michael@0 | 36 | Vector<T> mValues; |
| michael@0 | 37 | S mTotal; |
| michael@0 | 38 | |
| michael@0 | 39 | public: |
| michael@0 | 40 | static_assert(!IsFloatingPoint<T>::value, |
| michael@0 | 41 | "floating-point types are unsupported due to rounding " |
| michael@0 | 42 | "errors"); |
| michael@0 | 43 | |
| michael@0 | 44 | RollingMean(size_t aMaxValues) |
| michael@0 | 45 | : mInsertIndex(0), |
| michael@0 | 46 | mMaxValues(aMaxValues), |
| michael@0 | 47 | mTotal(0) |
| michael@0 | 48 | { |
| michael@0 | 49 | MOZ_ASSERT(aMaxValues > 0); |
| michael@0 | 50 | } |
| michael@0 | 51 | |
| michael@0 | 52 | RollingMean& operator=(RollingMean&& aOther) { |
| michael@0 | 53 | MOZ_ASSERT(this != &aOther, "self-assignment is forbidden"); |
| michael@0 | 54 | this->~RollingMean(); |
| michael@0 | 55 | new(this) RollingMean(aOther.mMaxValues); |
| michael@0 | 56 | mInsertIndex = aOther.mInsertIndex; |
| michael@0 | 57 | mTotal = aOther.mTotal; |
| michael@0 | 58 | mValues.swap(aOther.mValues); |
| michael@0 | 59 | return *this; |
| michael@0 | 60 | } |
| michael@0 | 61 | |
| michael@0 | 62 | /** |
| michael@0 | 63 | * Insert a value into the rolling mean. |
| michael@0 | 64 | */ |
| michael@0 | 65 | bool insert(T aValue) { |
| michael@0 | 66 | MOZ_ASSERT(mValues.length() <= mMaxValues); |
| michael@0 | 67 | |
| michael@0 | 68 | if (mValues.length() == mMaxValues) { |
| michael@0 | 69 | mTotal = mTotal - mValues[mInsertIndex] + aValue; |
| michael@0 | 70 | mValues[mInsertIndex] = aValue; |
| michael@0 | 71 | } else { |
| michael@0 | 72 | if (!mValues.append(aValue)) |
| michael@0 | 73 | return false; |
| michael@0 | 74 | mTotal = mTotal + aValue; |
| michael@0 | 75 | } |
| michael@0 | 76 | |
| michael@0 | 77 | mInsertIndex = (mInsertIndex + 1) % mMaxValues; |
| michael@0 | 78 | return true; |
| michael@0 | 79 | } |
| michael@0 | 80 | |
| michael@0 | 81 | /** |
| michael@0 | 82 | * Calculate the rolling mean. |
| michael@0 | 83 | */ |
| michael@0 | 84 | T mean() { |
| michael@0 | 85 | MOZ_ASSERT(!empty()); |
| michael@0 | 86 | return T(mTotal / mValues.length()); |
| michael@0 | 87 | } |
| michael@0 | 88 | |
| michael@0 | 89 | bool empty() { |
| michael@0 | 90 | return mValues.empty(); |
| michael@0 | 91 | } |
| michael@0 | 92 | |
| michael@0 | 93 | /** |
| michael@0 | 94 | * Remove all values from the rolling mean. |
| michael@0 | 95 | */ |
| michael@0 | 96 | void clear() { |
| michael@0 | 97 | mValues.clear(); |
| michael@0 | 98 | mInsertIndex = 0; |
| michael@0 | 99 | mTotal = T(0); |
| michael@0 | 100 | } |
| michael@0 | 101 | |
| michael@0 | 102 | size_t maxValues() { |
| michael@0 | 103 | return mMaxValues; |
| michael@0 | 104 | } |
| michael@0 | 105 | }; |
| michael@0 | 106 | |
| michael@0 | 107 | } // namespace mozilla |
| michael@0 | 108 | |
| michael@0 | 109 | #endif // mozilla_RollingMean_h_ |
