102 lines
3.2 KiB
Go
102 lines
3.2 KiB
Go
/*
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Copyright 2018 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package loader
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import "fmt"
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// Loader interface exposes methods to read bytes in a scheme-agnostic manner.
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// The Loader encapsulating a root location to calculate where to read from.
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type Loader interface {
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// Root returns the scheme-specific string representing the root location for this Loader.
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Root() string
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// New returns Loader located at newRoot.
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New(newRoot string) (Loader, error)
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// Load returns the bytes read from the location or an error.
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Load(location string) ([]byte, error)
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}
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// Private implmentation of Loader interface.
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type loaderImpl struct {
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root string
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schemes []SchemeLoader
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}
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// Interface for different types of loaders (e.g. fileLoader, httpLoader, etc.)
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type SchemeLoader interface {
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// Does this location correspond to this scheme.
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IsScheme(root string, location string) bool
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// Combines the root and path into a full location string.
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FullLocation(root string, path string) (string, error)
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// Load bytes at scheme-specific location or an error.
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Load(location string) ([]byte, error)
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}
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const emptyRoot = ""
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// Init initializes the first loader with the supported schemes.
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// Example schemes: fileLoader, httpLoader, gitLoader.
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func Init(schemes []SchemeLoader) Loader {
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return &loaderImpl{root: emptyRoot, schemes: schemes}
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}
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// Root returns the scheme-specific root location for this Loader.
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func (l *loaderImpl) Root() string {
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return l.root
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}
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// Returns a new Loader rooted at newRoot. "newRoot" MUST be
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// a directory (not a file). The directory can have a trailing
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// slash or not.
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// Example: "/home/seans/project" or "/home/seans/project/"
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// NOT "/home/seans/project/file.yaml".
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func (l *loaderImpl) New(newRoot string) (Loader, error) {
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scheme, err := l.getSchemeLoader(newRoot)
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if err != nil {
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return nil, err
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}
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root, err := scheme.FullLocation(l.root, newRoot)
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if err != nil {
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return nil, err
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}
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return &loaderImpl{root: root, schemes: l.schemes}, nil
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}
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// Load returns all the bytes read from scheme-specific location or an error.
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// "location" can be an absolute path, or if relative, full location is
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// calculated from the Root().
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func (l *loaderImpl) Load(location string) ([]byte, error) {
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scheme, err := l.getSchemeLoader(location)
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if err != nil {
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return nil, err
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}
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fullLocation, err := scheme.FullLocation(l.root, location)
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if err != nil {
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return nil, err
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}
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return scheme.Load(fullLocation)
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}
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// Helper function to parse scheme from location parameter.
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func (l *loaderImpl) getSchemeLoader(location string) (SchemeLoader, error) {
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for _, scheme := range l.schemes {
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if scheme.IsScheme(l.root, location) {
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return scheme, nil
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}
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}
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return nil, fmt.Errorf("Unknown Scheme: %s, %s\n", l.root, location)
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}
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