tusd/pkg/handler/composer.mgo

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package handler
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#define USE_FUNC(TYPE) \
func (store *StoreComposer) Use ## TYPE(ext TYPE ## DataStore) { \
store.Uses ## TYPE = ext != nil; \
store.TYPE = ext; \
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}
#define USE_FIELD(TYPE) Uses ## TYPE bool; \
TYPE TYPE ## DataStore
#define USE_FROM(TYPE) if mod, ok := store.(TYPE ## DataStore); ok { \
composer.Use ## TYPE (mod) \
}
#define USE_CAP(TYPE) str += ` TYPE: `; \
if store.Uses ## TYPE { \
str += "✓" \
} else { \
str += "✗" \
}
// StoreComposer represents a composable data store. It consists of the core
// data store and optional extensions. Please consult the package's overview
// for a more detailed introduction in how to use this structure.
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type StoreComposer struct {
Core DataStore
USE_FIELD(Terminater)
USE_FIELD(Finisher)
USE_FIELD(Locker)
USE_FIELD(GetReader)
USE_FIELD(Concater)
USE_FIELD(LengthDeferrer)
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}
// NewStoreComposer creates a new and empty store composer.
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func NewStoreComposer() *StoreComposer {
return &StoreComposer{}
}
// newStoreComposerFromDataStore creates a new store composer and attempts to
// extract the extensions for the provided store. This is intended to be used
// for transitioning from data stores to composers.
func newStoreComposerFromDataStore(store DataStore) *StoreComposer {
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composer := NewStoreComposer()
composer.UseCore(store)
USE_FROM(Terminater)
USE_FROM(Finisher)
USE_FROM(Locker)
USE_FROM(GetReader)
USE_FROM(Concater)
USE_FROM(LengthDeferrer)
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return composer
}
// Capabilities returns a string representing the provided extensions in a
// human-readable format meant for debugging.
func (store *StoreComposer) Capabilities() string {
str := "Core: "
if store.Core != nil {
str += "✓"
} else {
str += "✗"
}
USE_CAP(Terminater)
USE_CAP(Finisher)
USE_CAP(Locker)
USE_CAP(GetReader)
USE_CAP(Concater)
USE_CAP(LengthDeferrer)
return str
}
// UseCore will set the used core data store. If the argument is nil, the
// property will be unset.
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func (store *StoreComposer) UseCore(core DataStore) {
store.Core = core
}
USE_FUNC(Terminater)
USE_FUNC(Finisher)
USE_FUNC(Locker)
USE_FUNC(GetReader)
USE_FUNC(Concater)
USE_FUNC(LengthDeferrer)