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Add ArrayEncodedMap #2750
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Add ArrayEncodedMap #2750
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Original file line number | Diff line number | Diff line change | ||||
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@@ -0,0 +1,226 @@ | ||||||
package encoding | ||||||
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import ( | ||||||
"encoding/json" | ||||||
"fmt" | ||||||
"sort" | ||||||
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"gopkg.in/yaml.v3" | ||||||
) | ||||||
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// MapElement is the in-memory representation of the item when stored in a map. | ||||||
type MapElement interface { | ||||||
// ToArrayEntry converts to the representation of the item when stored in an | ||||||
// array. | ||||||
ToArrayEntry(key string) ArrayElement | ||||||
} | ||||||
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// ArrayElement is the representation of the item when stored in an array, and | ||||||
// includes the key under which the element was stored in the original map. | ||||||
type ArrayElement interface { | ||||||
// GetKey returns the unique item key. | ||||||
GetKey() string | ||||||
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// ToMapEntry converts to the representation of the item when stored in a map. | ||||||
ToMapEntry() MapElement | ||||||
} | ||||||
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// ArrayEncodedMap is a map that is represented as an array when marshaled to json/yaml. | ||||||
// MapElement is the type of the elements when stored in a map and ArrayElement is the type of the elements when stored in an array. | ||||||
type ArrayEncodedMap[T MapElement, K ArrayElement] struct { | ||||||
items map[string]T | ||||||
} | ||||||
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// NewArrayEncodedMap initializes an empty ArrayEncodedMap. | ||||||
func NewArrayEncodedMap[T MapElement, K ArrayElement]() ArrayEncodedMap[T, K] { | ||||||
return MakeArrayEncodedMap[T, K](0) | ||||||
} | ||||||
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// MakeArrayEncodedMap allocates memory for the specified number of elements. | ||||||
func MakeArrayEncodedMap[T MapElement, K ArrayElement](len int) ArrayEncodedMap[T, K] { | ||||||
return ArrayEncodedMap[T, K]{ | ||||||
items: make(map[string]T, len), | ||||||
} | ||||||
} | ||||||
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// Len returns the number of items. | ||||||
func (m *ArrayEncodedMap[T, K]) Len() int { | ||||||
if m == nil { | ||||||
return 0 | ||||||
} | ||||||
return len(m.items) | ||||||
} | ||||||
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// Items returns a copy of the items, and is intended for use with the range | ||||||
// operator. | ||||||
// Use ItemsUnsafe() to directly manipulate the backing items map. | ||||||
func (m *ArrayEncodedMap[T, K]) Items() map[string]T { | ||||||
if m == nil { | ||||||
return nil | ||||||
} | ||||||
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result := make(map[string]T, len(m.items)) | ||||||
for k, v := range m.items { | ||||||
result[k] = v | ||||||
} | ||||||
return result | ||||||
} | ||||||
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// ItemsSorted returns a copy of the items, in a sorted array, and is intended | ||||||
// for using with serialization and consistently ranging over the items, in tests | ||||||
// or printing output to the console. | ||||||
func (m *ArrayEncodedMap[T, K]) ItemsSorted() []K { | ||||||
if m == nil { | ||||||
return nil | ||||||
} | ||||||
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result := make([]K, len(m.items)) | ||||||
i := 0 | ||||||
for k, v := range m.items { | ||||||
// I can't figure out how to constrain T such that ToArrayEntry returns K, so I'm doing a cast | ||||||
result[i] = v.ToArrayEntry(k).(K) | ||||||
i++ | ||||||
} | ||||||
sort.SliceStable(result, func(i, j int) bool { | ||||||
return result[i].GetKey() < result[j].GetKey() | ||||||
}) | ||||||
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return result | ||||||
} | ||||||
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// ItemsUnsafe returns the backing items map. It is intended for optimizing | ||||||
// memory usage when iterating over the items to convert them into alternative | ||||||
// representations. | ||||||
func (m *ArrayEncodedMap[T, K]) ItemsUnsafe() *map[string]T { | ||||||
if m == nil { | ||||||
return nil | ||||||
} | ||||||
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if m.items == nil { | ||||||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. is it ever possible to have |
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m.items = make(map[string]T) | ||||||
} | ||||||
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return &m.items | ||||||
} | ||||||
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// Get returns the specified element by its key. | ||||||
func (m *ArrayEncodedMap[T, K]) Get(key string) (T, bool) { | ||||||
if m == nil { | ||||||
return *new(T), false | ||||||
} | ||||||
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entry, ok := m.items[key] | ||||||
return entry, ok | ||||||
} | ||||||
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// Set the specified element by its key, overwriting previous values. | ||||||
func (m *ArrayEncodedMap[T, K]) Set(key string, entry T) { | ||||||
if m.items == nil { | ||||||
m.items = make(map[string]T, 1) | ||||||
} | ||||||
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m.items[key] = entry | ||||||
} | ||||||
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// Remove the specified element by its key. | ||||||
func (m *ArrayEncodedMap[T, K]) Remove(key string) { | ||||||
if m == nil { | ||||||
return | ||||||
} | ||||||
delete(m.items, key) | ||||||
} | ||||||
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// MarshalRaw is the common Marshal implementation between YAML and JSON. | ||||||
func (m *ArrayEncodedMap[T, K]) MarshalRaw() interface{} { | ||||||
if m == nil { | ||||||
return nil | ||||||
} | ||||||
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var raw []ArrayElement | ||||||
if m.items == nil { | ||||||
return raw | ||||||
} | ||||||
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raw = make([]ArrayElement, 0, len(m.items)) | ||||||
for k, v := range m.items { | ||||||
raw = append(raw, v.ToArrayEntry(k)) | ||||||
} | ||||||
sort.SliceStable(raw, func(i, j int) bool { | ||||||
return raw[i].GetKey() < raw[j].GetKey() | ||||||
}) | ||||||
return raw | ||||||
} | ||||||
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// UnmarshalRaw is the common Marshal implementation between YAML and JSON. | ||||||
func (m *ArrayEncodedMap[T, K]) UnmarshalRaw(raw []K) error { | ||||||
if m == nil { | ||||||
*m = ArrayEncodedMap[T, K]{} | ||||||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. won't this panic? seems like you'd need to set the value of the pointer to valid memory
Suggested change
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} | ||||||
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m.items = make(map[string]T, len(raw)) | ||||||
for _, rawItem := range raw { | ||||||
if _, hasKey := m.items[rawItem.GetKey()]; hasKey { | ||||||
return fmt.Errorf("cannot unmarshal source map: duplicate key found '%s'", rawItem.GetKey()) | ||||||
} | ||||||
item := rawItem.ToMapEntry() | ||||||
typedItem, ok := item.(T) | ||||||
if !ok { | ||||||
return fmt.Errorf("invalid ArrayEncodedMap generic types, ArrayElement %T returned a %T from ToMapEntry(), when it should return %T", rawItem, item, *new(T)) | ||||||
} | ||||||
m.items[rawItem.GetKey()] = typedItem | ||||||
} | ||||||
return nil | ||||||
} | ||||||
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// MarshalJSON marshals the items to JSON. | ||||||
func (m *ArrayEncodedMap[T, K]) MarshalJSON() ([]byte, error) { | ||||||
raw := m.MarshalRaw() | ||||||
return json.Marshal(raw) | ||||||
} | ||||||
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// UnmarshalJSON unmarshals the items in the specified JSON. | ||||||
func (m *ArrayEncodedMap[T, K]) UnmarshalJSON(data []byte) error { | ||||||
var raw []K | ||||||
err := json.Unmarshal(data, &raw) | ||||||
if err != nil { | ||||||
return err | ||||||
} | ||||||
return m.UnmarshalRaw(raw) | ||||||
} | ||||||
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// MarshalYAML marshals the items to YAML. | ||||||
func (m *ArrayEncodedMap[T, K]) MarshalYAML() (interface{}, error) { | ||||||
if m == nil { | ||||||
return nil, nil | ||||||
} | ||||||
return m.MarshalRaw(), nil | ||||||
} | ||||||
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// UnmarshalYAML unmarshals the items in the specified YAML. | ||||||
func (m *ArrayEncodedMap[T, K]) UnmarshalYAML(value *yaml.Node) error { | ||||||
var raw []K | ||||||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. same here RE checking |
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if err := value.Decode(&raw); err != nil { | ||||||
return err | ||||||
} | ||||||
return m.UnmarshalRaw(raw) | ||||||
} | ||||||
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// Merge applies the specified values on top of a base set of values. When a | ||||||
// key exists in both sets, use the value from the overrides. | ||||||
func (m *ArrayEncodedMap[T, K]) Merge(overrides *ArrayEncodedMap[T, K]) *ArrayEncodedMap[T, K] { | ||||||
result := make(map[string]T, m.Len()) | ||||||
if m != nil { | ||||||
for k, v := range m.items { | ||||||
result[k] = v | ||||||
} | ||||||
} | ||||||
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if overrides != nil { | ||||||
// If the name is in the base, overwrite its value with the override provided | ||||||
for k, v := range overrides.items { | ||||||
result[k] = v | ||||||
} | ||||||
} | ||||||
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return &ArrayEncodedMap[T, K]{items: result} | ||||||
} |
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return an empty
map
here, so callers don't blow up?There was a problem hiding this comment.
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Is this even reachable? If the object is nil then referencing any method on the object should result in a panic before it hits the implementation correct?
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Never mind just clarified my own question. Go can call methods on nil structs :)