mirror of
https://github.com/restic/restic.git
synced 2024-12-27 18:28:30 +00:00
5cdcc99eba
Since backend.ID is always a slice of constant length, use an array
instead of a slice. Mostly, arrays behave as slices, except that an
array cannot be nil, so use `*backend.ID` insteaf of `backend.ID` in
places where the absence of an ID is possible (e.g. for the Subtree of a
Node, which may not present when the node is a file node).
This change allows to directly use backend.ID as the the key for a map,
so that arbitrary data structures (e.g. a Set implemented as a
map[backend.ID]struct{}) can easily be formed.
120 lines
2.3 KiB
Go
120 lines
2.3 KiB
Go
package backend
|
|
|
|
import (
|
|
"crypto/sha256"
|
|
"errors"
|
|
"io"
|
|
)
|
|
|
|
const (
|
|
MinPrefixLength = 8
|
|
)
|
|
|
|
var (
|
|
ErrNoIDPrefixFound = errors.New("no ID found")
|
|
ErrMultipleIDMatches = errors.New("multiple IDs with prefix found")
|
|
)
|
|
|
|
var (
|
|
hashData = sha256.Sum256
|
|
)
|
|
|
|
const hashSize = sha256.Size
|
|
|
|
// Hash returns the ID for data.
|
|
func Hash(data []byte) ID {
|
|
return hashData(data)
|
|
}
|
|
|
|
// 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)
|
|
|
|
match := ""
|
|
|
|
// TODO: optimize by sorting list etc.
|
|
for name := range be.List(t, done) {
|
|
if prefix == name[:len(prefix)] {
|
|
if match == "" {
|
|
match = name
|
|
} else {
|
|
return "", ErrMultipleIDMatches
|
|
}
|
|
}
|
|
}
|
|
|
|
if match != "" {
|
|
return match, nil
|
|
}
|
|
|
|
return "", ErrNoIDPrefixFound
|
|
}
|
|
|
|
// PrefixLength returns the number of bytes required so that all prefixes of
|
|
// all names of type t are unique.
|
|
func PrefixLength(be Lister, t Type) (int, error) {
|
|
done := make(chan struct{})
|
|
defer close(done)
|
|
|
|
// load all IDs of the given type
|
|
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:
|
|
for l := MinPrefixLength; l < IDSize; l++ {
|
|
var last string
|
|
|
|
for _, name := range list {
|
|
if last == name[:l] {
|
|
continue outer
|
|
}
|
|
last = name[:l]
|
|
}
|
|
|
|
return l, nil
|
|
}
|
|
|
|
return IDSize, nil
|
|
}
|
|
|
|
// wrap around io.LimitedReader that implements io.ReadCloser
|
|
type blobReader struct {
|
|
cl io.Closer
|
|
rd io.Reader
|
|
closed bool
|
|
}
|
|
|
|
func (l *blobReader) Read(p []byte) (int, error) {
|
|
n, err := l.rd.Read(p)
|
|
if err == io.EOF {
|
|
l.Close()
|
|
}
|
|
|
|
return n, err
|
|
}
|
|
|
|
func (l *blobReader) Close() error {
|
|
if l == nil {
|
|
return nil
|
|
}
|
|
|
|
if !l.closed {
|
|
err := l.cl.Close()
|
|
l.closed = true
|
|
return err
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// LimitReadCloser returns a new reader wraps r in an io.LimitReader, but also
|
|
// implements the Close() method.
|
|
func LimitReadCloser(r io.ReadCloser, n int64) *blobReader {
|
|
return &blobReader{cl: r, rd: io.LimitReader(r, n)}
|
|
}
|