restic/backend/generic.go

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package backend
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import "errors"
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// ErrNoIDPrefixFound is returned by Find() when no ID for the given prefix
// could be found.
var ErrNoIDPrefixFound = errors.New("no ID found")
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// ErrMultipleIDMatches is returned by Find() when multiple IDs with the given
// prefix are found.
var ErrMultipleIDMatches = errors.New("multiple IDs with prefix found")
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// Find loads the list of all blobs of type t and searches for names which
// start with prefix. If none is found, nil and ErrNoIDPrefixFound is returned.
// If more than one is found, nil and ErrMultipleIDMatches is returned.
func Find(be Lister, t Type, prefix string) (string, error) {
done := make(chan struct{})
defer close(done)
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match := ""
// TODO: optimize by sorting list etc.
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for name := range be.List(t, done) {
if prefix == name[:len(prefix)] {
if match == "" {
match = name
} else {
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return "", ErrMultipleIDMatches
}
}
}
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if match != "" {
return match, nil
}
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return "", ErrNoIDPrefixFound
}
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const minPrefixLength = 8
// PrefixLength returns the number of bytes required so that all prefixes of
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// all names of type t are unique.
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func PrefixLength(be Lister, t Type) (int, error) {
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done := make(chan struct{})
defer close(done)
// load all IDs of the given type
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list := make([]string, 0, 100)
for name := range be.List(t, done) {
list = append(list, name)
}
// select prefixes of length l, test if the last one is the same as the current one
outer:
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for l := minPrefixLength; l < IDSize; l++ {
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var last string
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for _, name := range list {
if last == name[:l] {
continue outer
}
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last = name[:l]
}
return l, nil
}
return IDSize, nil
}