terraform/diff/lazy_resource_map.go

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2014-06-18 04:06:13 +02:00
package diff
import (
"sync"
)
// LazyResourceMap is a way to lazy-load resource builders.
//
// By lazy loading resource builders, a considerable amount of compute
// effort for building the builders can be avoided. This is especially
// helpful in Terraform providers that support many resource types.
type LazyResourceMap struct {
Resources map[string]ResourceBuilderFactory
l sync.Mutex
memoized map[string]*ResourceBuilder
}
// ResourceBuilderFactory is a factory function for creating a resource
// builder that is used for lazy loading resource builders in the Builder
// struct.
type ResourceBuilderFactory func() *ResourceBuilder
// Get gets the ResourceBuilder for the given resource type, and returns
// nil if the resource builder cannot be found.
//
// This will memoize the result, returning the same result for the same
// type if called again.
func (m *LazyResourceMap) Get(r string) *ResourceBuilder {
m.l.Lock()
defer m.l.Unlock()
// If we have it saved, return that
if rb, ok := m.memoized[r]; ok {
return rb
}
// Get the factory function
f, ok := m.Resources[r]
if !ok {
return nil
}
// Save it so that we don't rebuild
if m.memoized == nil {
m.memoized = make(map[string]*ResourceBuilder)
}
m.memoized[r] = f()
return m.memoized[r]
}