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66 lines
1.8 KiB
66 lines
1.8 KiB
package middleware
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// MetadataReader provides an interface for reading metadata from the
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// underlying metadata container.
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type MetadataReader interface {
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Get(key interface{}) interface{}
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}
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// Metadata provides storing and reading metadata values. Keys may be any
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// comparable value type. Get and set will panic if key is not a comparable
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// value type.
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//
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// Metadata uses lazy initialization, and Set method must be called as an
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// addressable value, or pointer. Not doing so may cause key/value pair to not
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// be set.
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type Metadata struct {
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values map[interface{}]interface{}
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}
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// Get attempts to retrieve the value the key points to. Returns nil if the
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// key was not found.
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//
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// Panics if key type is not comparable.
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func (m Metadata) Get(key interface{}) interface{} {
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return m.values[key]
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}
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// Clone creates a shallow copy of Metadata entries, returning a new Metadata
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// value with the original entries copied into it.
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func (m Metadata) Clone() Metadata {
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vs := make(map[interface{}]interface{}, len(m.values))
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for k, v := range m.values {
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vs[k] = v
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}
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return Metadata{
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values: vs,
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}
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}
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// Set stores the value pointed to by the key. If a value already exists at
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// that key it will be replaced with the new value.
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//
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// Set method must be called as an addressable value, or pointer. If Set is not
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// called as an addressable value or pointer, the key value pair being set may
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// be lost.
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//
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// Panics if the key type is not comparable.
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func (m *Metadata) Set(key, value interface{}) {
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if m.values == nil {
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m.values = map[interface{}]interface{}{}
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}
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m.values[key] = value
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}
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// Has returns whether the key exists in the metadata.
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//
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// Panics if the key type is not comparable.
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func (m Metadata) Has(key interface{}) bool {
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if m.values == nil {
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return false
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}
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_, ok := m.values[key]
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return ok
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}
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