59 lines
2 KiB
Go
59 lines
2 KiB
Go
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// Copyright 2023 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package optional
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// ShallowOptional is an optional type that can be constructed from a pointer.
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// It will not copy the pointer, and its size is the same size as a single pointer.
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// It can be used to prevent a downstream consumer from modifying the value through
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// the pointer, but is not suitable for an Optional type with stronger value semantics
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// like you would expect from C++ or Rust Optionals.
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type ShallowOptional[T any] struct {
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inner *T
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}
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// NewShallowOptional creates a new ShallowOptional from a pointer.
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// The pointer will not be copied, the object could be changed by the calling
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// code after the optional was created.
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func NewShallowOptional[T any](inner *T) ShallowOptional[T] {
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return ShallowOptional[T]{inner: inner}
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}
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// IsPresent returns true if the optional contains a value
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func (o *ShallowOptional[T]) IsPresent() bool {
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return o.inner != nil
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}
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// IsEmpty returns true if the optional does not have a value
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func (o *ShallowOptional[T]) IsEmpty() bool {
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return o.inner == nil
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}
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// Get() returns the value inside the optional. It panics if IsEmpty() returns true
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func (o *ShallowOptional[T]) Get() T {
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if o.inner == nil {
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panic("tried to get an empty optional")
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}
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return *o.inner
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}
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// GetOrDefault() returns the value inside the optional if IsPresent() returns true,
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// or the provided value otherwise.
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func (o *ShallowOptional[T]) GetOrDefault(other T) T {
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if o.inner == nil {
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return other
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}
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return *o.inner
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}
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