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+// Copyright (c) 2022 Shivaram Lingamneni
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+// released under the MIT license
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+
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+package utils
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+
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+import (
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+ "sync/atomic"
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+ "unsafe"
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+)
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+
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+/*
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+This can be used to implement the following pattern:
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+
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+1. Prepare a config object (this can be arbitrarily expensive)
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+2. Take a pointer to the config object and use Set() to install it
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+3. Use Get() to access the config from any goroutine
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+4. To update the config, call Set() again with a new prepared config object
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+5. As long as any individual config object is not modified (by any goroutine)
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+ after it is installed with Set(), this is free of data races, and Get()
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+ is extremely cheap (on amd64 it compiles down to plain MOV instructions).
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+*/
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+
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+type ConfigStore[Config any] struct {
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+ ptr unsafe.Pointer
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+}
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+
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+func (c *ConfigStore[Config]) Get() *Config {
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+ return (*Config)(atomic.LoadPointer(&c.ptr))
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+}
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+
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+func (c *ConfigStore[Config]) Set(ptr *Config) {
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+ atomic.StorePointer(&c.ptr, unsafe.Pointer(ptr))
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+}
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