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distribution.go
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distribution.go
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// Copyright 2016 The rkt Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package distribution
import (
"fmt"
"net/url"
)
// Type represents the Distribution type
type Type string
const (
// Scheme represents the Distribution URI scheme
Scheme = "cimd"
)
// Distribution is the interface that represents a distribution point.
type Distribution interface {
// URI returns a copy of the Distribution CIMD URI.
CIMD() *url.URL
// String returns a user friendly representation of the distribution point.
String() string
// Equals returns true if this distribution equals the given distribution, else false.
Equals(Distribution) bool
}
type newDistribution func(*url.URL) (Distribution, error)
var distributions = make(map[Type]newDistribution)
// Register registers a function that returns a new instance of the given
// distribution. This is intended to be called from the init function in
// packages that implement distribution functions.
func Register(distType Type, f newDistribution) {
if _, ok := distributions[distType]; ok {
panic(fmt.Errorf("distribution %q already registered", distType))
}
distributions[distType] = f
}
// Get returns a Distribution from the input URI.
// It returns an error if the uri string is wrong or referencing an unknown
// distribution type.
func Get(u *url.URL) (Distribution, error) {
c, err := parseCIMD(u)
if err != nil {
return nil, fmt.Errorf("malformed distribution uri %q: %v", u.String(), err)
}
if u.Scheme != Scheme {
return nil, fmt.Errorf("malformed distribution uri %q", u.String())
}
if _, ok := distributions[c.Type]; !ok {
return nil, fmt.Errorf("unknown distribution type: %q", c.Type)
}
return distributions[c.Type](u)
}
// Parse parses the provided distribution URI string and returns a
// Distribution.
func Parse(rawuri string) (Distribution, error) {
u, err := url.Parse(rawuri)
if err != nil {
return nil, fmt.Errorf("cannot parse uri: %q: %v", rawuri, err)
}
return Get(u)
}