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Create a
SpanSearchValue class that allows tree-searching without e…
…xtra intermediate `if null/missing` checks. (#36754) * Start adding the fluent tree object * Start adding unit tests * Add test file * more testing * update sizes hint and make use of things into CodegenDataModelProvider * Restyle * Fix some commments * More merge fixes * Remove some odd copy&paste comments * Update src/lib/support/FluentTreeObject.h Co-authored-by: Boris Zbarsky <[email protected]> * Update src/lib/support/FluentTreeObject.h Co-authored-by: Boris Zbarsky <[email protected]> * Fix up comments a bit * Simplify FluentTreeObject a bit * Extra wrapper not needed * Cleaned up comments * Restyled by clang-format * Sed rename FluentTreeObject to SpanSearchValue * Also rename files * Restyle * Very slight reduction in complexity that reduces extra flash usage by a few bytes * Another minor source code size decrease * Even slightly smaller code * Restyle * Fix comment typo * make cc32xx compile optimized for size by default, so we can treak flash usage as such * Restyled by gn * Update src/data-model-providers/codegen/CodegenDataModelProvider.cpp Co-authored-by: Boris Zbarsky <[email protected]> * Update src/lib/support/SpanSearchValue.h Co-authored-by: Boris Zbarsky <[email protected]> * Update src/lib/support/SpanSearchValue.h Co-authored-by: Boris Zbarsky <[email protected]> * Update src/lib/support/SpanSearchValue.h Co-authored-by: Boris Zbarsky <[email protected]> * Rename tree to searchable * Fix comment * Restyled by clang-format --------- Co-authored-by: Andrei Litvin <[email protected]> Co-authored-by: Boris Zbarsky <[email protected]> Co-authored-by: Restyled.io <[email protected]>
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| /* | ||
| * Copyright (c) 2024 Project CHIP Authors | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| #pragma once | ||
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| #include <cstddef> | ||
| #include <lib/support/Span.h> | ||
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| #include <optional> | ||
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| namespace chip { | ||
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| /// represents a wrapper around a type `T` that contains internal | ||
| /// `Span<...>` values of other sub-types. It allows searching within the container sub-spans | ||
| /// to create new containers. | ||
| /// | ||
| /// The use case is that we very often search within nested containers, like "find-endpoint" + "find-cluster" + "find-attribute" | ||
| /// and we generally only care about "does the last element exist or not" | ||
| /// | ||
| /// A typical example of the way this class is used looks like this: | ||
| /// | ||
| /// SpanSearchValue container(somePointer); | ||
| /// | ||
| /// const AcceptedCommandData * value = | ||
| /// container | ||
| /// .Find<ByEndpoint>(path.mEndpointId, mEndpointIndexHint) | ||
| /// .Find<ByServerCluster>(path.mClusterId, mServerClusterHint) | ||
| /// .Find<ByAcceptedCommand>(path.mCommandId, mAcceptedCommandHint) | ||
| /// .Value(); | ||
| /// | ||
| /// Where a `ByFoo` structure looks like: | ||
| /// | ||
| /// struct ByFoo { | ||
| /// using Key = int; // the KEY inside a type | ||
| /// using Type = SomeValueType; // The type that is indexed by `Key` | ||
| /// | ||
| /// /// Allows getting the "Span of Type" from an underlying structure. | ||
| /// /// A `SpanSearchValue<Foo>` will require a `GetSpan(Foo&)` | ||
| /// static Span<Type> GetSpan(ContainerType & data) { /* return ... */ } | ||
| /// | ||
| /// /// Checks that the `Type` value has the given `Key` or not | ||
| /// static bool HasKey(const Key & id, const Type & instance) { /* return "instance has key id" */ } | ||
| /// } | ||
| /// | ||
| /// Where we define: | ||
| /// - how to get a "span of sub-elements" for an object (`GetSpan`) | ||
| /// - how to determine if a given sub-element has the "correct key" | ||
| template <typename T> | ||
| class SpanSearchValue | ||
| { | ||
| public: | ||
| SpanSearchValue() : mValue(nullptr) {} | ||
| SpanSearchValue(std::nullptr_t) : mValue(nullptr) {} | ||
| explicit SpanSearchValue(T * value) : mValue(value) {} | ||
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| /// Returns nullptr if such an element does not exist or non-null valid value if the element exists | ||
| T * Value() const { return mValue; } | ||
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| /// Gets the first element of `TYPE::Type` | ||
| template <typename TYPE> | ||
| SpanSearchValue<typename TYPE::Type> First(unsigned & indexHint) | ||
| { | ||
| // if no value, searching more also yields no value | ||
| VerifyOrReturnValue(mValue != nullptr, nullptr); | ||
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| Span<typename TYPE::Type> value_span = TYPE::GetSpan(*mValue); | ||
| VerifyOrReturnValue(!value_span.empty(), nullptr); | ||
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| // found it, save the hint | ||
| indexHint = 0; | ||
| return SpanSearchValue<typename TYPE::Type>(&value_span[0]); | ||
| } | ||
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| /// Find the value corresponding to `key` | ||
| template <typename TYPE> | ||
| SpanSearchValue<typename TYPE::Type> Find(typename TYPE::Key key, unsigned & indexHint) | ||
| { | ||
| VerifyOrReturnValue(mValue != nullptr, nullptr); | ||
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| Span<typename TYPE::Type> value_span = TYPE::GetSpan(*mValue); | ||
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| if (!FindIndexUsingHint(key, value_span, indexHint, TYPE::HasKey)) | ||
| { | ||
| return nullptr; | ||
| } | ||
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| return SpanSearchValue<typename TYPE::Type>(&value_span[indexHint]); | ||
| } | ||
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| /// Finds the value that occurs after `key` in the underlying collection. | ||
| template <typename TYPE> | ||
| SpanSearchValue<typename TYPE::Type> Next(typename TYPE::Key key, unsigned & indexHint) | ||
| { | ||
| VerifyOrReturnValue(mValue != nullptr, nullptr); | ||
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| Span<typename TYPE::Type> value_span = TYPE::GetSpan(*mValue); | ||
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| if (!FindIndexUsingHint(key, value_span, indexHint, TYPE::HasKey)) | ||
| { | ||
| return nullptr; | ||
| } | ||
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| VerifyOrReturnValue((indexHint + 1) < value_span.size(), nullptr); | ||
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| indexHint++; | ||
| return SpanSearchValue<typename TYPE::Type>(&value_span[indexHint]); | ||
| } | ||
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| private: | ||
| T * mValue = nullptr; // underlying value, NULL if such a value does not exist | ||
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| /// Search for the index where `needle` is located inside `haystack` | ||
| /// | ||
| /// using `haystackValueMatchesNeedle` to find if a given haystack value matches the given needle | ||
| /// | ||
| /// `in_out_hint` contains a start search point at the start and will contain the found index | ||
| /// location (if found) at the end. | ||
| /// | ||
| /// Returns true on success (index found) false on failure (index not found). If returning | ||
| /// false, the value of `in_out_hint` is unchanged | ||
| template <typename N, typename H> | ||
| static bool FindIndexUsingHint(const N & needle, Span<H> haystack, unsigned & in_out_hint, | ||
| bool (*haystackValueMatchesNeedle)(const N &, const typename std::remove_const<H>::type &)) | ||
| { | ||
| // search starts at `hint` rather than 0 | ||
| const unsigned haystackSize = static_cast<unsigned>(haystack.size()); | ||
| unsigned checkIndex = (in_out_hint < haystackSize) ? in_out_hint : 0; | ||
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| for (unsigned i = 0; i < haystackSize; i++, checkIndex++) | ||
| { | ||
| if (haystackValueMatchesNeedle(needle, haystack[checkIndex % haystackSize])) | ||
| { | ||
| in_out_hint = checkIndex % haystackSize; | ||
| return true; | ||
| } | ||
| } | ||
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| return false; | ||
| } | ||
| }; | ||
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| } // namespace chip |
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