mirror of https://github.com/restic/restic.git
129 lines
2.3 KiB
Go
129 lines
2.3 KiB
Go
package backend
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import (
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"bytes"
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"crypto/sha256"
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"encoding/hex"
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"errors"
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"sort"
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)
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const (
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MinPrefixLength = 4
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)
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var (
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ErrNoIDPrefixFound = errors.New("no ID found")
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ErrMultipleIDMatches = errors.New("multiple IDs with prefix found")
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)
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var (
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newHash = sha256.New
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hashData = sha256.Sum256
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)
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const hashSize = sha256.Size
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// Each lists all entries of type t in the backend and calls function f() with
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// the id.
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func EachID(be Lister, t Type, f func(ID)) error {
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ids, err := be.List(t)
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if err != nil {
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return err
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}
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for _, id := range ids {
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f(id)
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}
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return nil
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}
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// Hash returns the ID for data.
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func Hash(data []byte) ID {
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h := hashData(data)
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id := idPool.Get().(ID)
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copy(id, h[:])
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return id
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}
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// Find loads the list of all blobs of type t and searches for IDs which start
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// with prefix. If none is found, nil and ErrNoIDPrefixFound is returned. If
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// more than one is found, nil and ErrMultipleIDMatches is returned.
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func Find(be Lister, t Type, prefix string) (ID, error) {
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p, err := hex.DecodeString(prefix)
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if err != nil {
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return nil, err
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}
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list, err := be.List(t)
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if err != nil {
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return nil, err
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}
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match := ID(nil)
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// TODO: optimize by sorting list etc.
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for _, id := range list {
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if bytes.Equal(p, id[:len(p)]) {
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if match == nil {
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match = id
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} else {
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return nil, ErrMultipleIDMatches
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}
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}
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}
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if match != nil {
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return match, nil
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}
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return nil, ErrNoIDPrefixFound
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}
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// FindSnapshot takes a string and tries to find a snapshot whose ID matches
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// the string as closely as possible.
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func FindSnapshot(be Lister, s string) (ID, error) {
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// parse ID directly
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if id, err := ParseID(s); err == nil {
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return id, nil
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}
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// find snapshot id with prefix
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id, err := Find(be, Snapshot, s)
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if err != nil {
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return nil, err
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}
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return id, nil
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}
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// PrefixLength returns the number of bytes required so that all prefixes of
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// all IDs of type t are unique.
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func PrefixLength(be Lister, t Type) (int, error) {
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// load all IDs of the given type
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list, err := be.List(t)
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if err != nil {
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return 0, err
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}
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sort.Sort(list)
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// select prefixes of length l, test if the last one is the same as the current one
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outer:
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for l := MinPrefixLength; l < IDSize; l++ {
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var last ID
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for _, id := range list {
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if bytes.Equal(last, id[:l]) {
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continue outer
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}
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last = id[:l]
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}
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return l, nil
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}
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return IDSize, nil
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}
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