39 lines
1.2 KiB
Go
39 lines
1.2 KiB
Go
package smithy
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import (
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"sync/atomic"
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"unsafe"
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)
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// ExtensionID identifies a schema extension slot. Each codec family
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// (JSON, CBOR, etc.) uses a distinct slot to cache precomputed data.
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type ExtensionID int
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const numExtensionSlots = 5
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const (
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ExtJSON ExtensionID = iota // transport/http/protocol/internal/json
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ExtCBOR // transport/http/protocol/internal/cbor
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ExtXML // transport/http/protocol/internal/xml
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ExtQuery // transport/http/protocol/internal/query
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ExtHTTPBinding // transport/http/protocol/internal/httpbinding
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)
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// SchemaExtension retrieves or lazily computes the extension for the given
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// slot. build is called on first access for a schema and the result is cached.
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// The build function must return a pointer to an immutable value.
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func SchemaExtension[T any](s *Schema, id ExtensionID, build func(*Schema) *T) *T {
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p := atomic.LoadPointer(&s.ext[id])
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if p != nil {
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return (*T)(p)
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}
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return computeSchemaExtension(s, id, build)
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}
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//go:noinline
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func computeSchemaExtension[T any](s *Schema, id ExtensionID, build func(*Schema) *T) *T {
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v := build(s)
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atomic.StorePointer(&s.ext[id], unsafe.Pointer(v))
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return v
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}
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