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package objectid
import (
"crypto/sha1" //#nosec gosec
"crypto/sha256"
"hash"
)
// maxObjectIDSize MUST be >= the largest supported algorithm size.
const maxObjectIDSize = sha256.Size
// Algorithm identifies the hash algorithm used for Git object IDs.
type Algorithm uint8
const (
AlgorithmUnknown Algorithm = iota
AlgorithmSHA1
AlgorithmSHA256
)
type algorithmDetails struct {
name string
size int
packHashID uint32
sum func([]byte) ObjectID
new func() hash.Hash
emptyTree ObjectID
}
//nolint:gochecknoglobals
var algorithmTable = [...]algorithmDetails{
AlgorithmUnknown: {},
AlgorithmSHA1: {
name: "sha1",
size: sha1.Size,
packHashID: 1,
sum: func(data []byte) ObjectID {
sum := sha1.Sum(data) //#nosec G401
var id ObjectID
copy(id.data[:], sum[:])
id.algo = AlgorithmSHA1
return id
},
new: sha1.New,
},
AlgorithmSHA256: {
name: "sha256",
size: sha256.Size,
packHashID: 2,
sum: func(data []byte) ObjectID {
sum := sha256.Sum256(data)
var id ObjectID
copy(id.data[:], sum[:])
id.algo = AlgorithmSHA256
return id
},
new: sha256.New,
},
}
var (
//nolint:gochecknoglobals
algorithmByName = map[string]Algorithm{}
//nolint:gochecknoglobals
supportedAlgorithms []Algorithm
)
func init() { //nolint:gochecknoinits
emptyTreeInput := []byte("tree 0\x00")
for algo := Algorithm(0); int(algo) < len(algorithmTable); algo++ {
info := &algorithmTable[algo]
if info.name == "" {
continue
}
info.emptyTree = info.sum(emptyTreeInput)
algorithmByName[info.name] = algo
supportedAlgorithms = append(supportedAlgorithms, algo)
}
}
// SupportedAlgorithms returns all object ID algorithms supported by furgit.
// Do not mutate.
func SupportedAlgorithms() []Algorithm {
return supportedAlgorithms
}
// ParseAlgorithm parses a canonical algorithm name (e.g. "sha1", "sha256").
func ParseAlgorithm(s string) (Algorithm, bool) {
algo, ok := algorithmByName[s]
return algo, ok
}
// Size returns the hash size in bytes.
func (algo Algorithm) Size() int {
return algo.info().size
}
// String returns the canonical algorithm name.
func (algo Algorithm) String() string {
inf := algo.info()
if inf.name == "" {
return "unknown"
}
return inf.name
}
// HexLen returns the encoded hexadecimal length.
func (algo Algorithm) HexLen() int {
return algo.Size() * 2
}
// PackHashID returns the Git pack/rev hash-id encoding for this algorithm.
//
// Unknown algorithms return 0.
func (algo Algorithm) PackHashID() uint32 {
return algo.info().packHashID
}
// Sum computes an object ID from raw data using the selected algorithm.
func (algo Algorithm) Sum(data []byte) ObjectID {
return algo.info().sum(data)
}
// New returns a new hash.Hash for this algorithm.
func (algo Algorithm) New() (hash.Hash, error) {
newFn := algo.info().new
if newFn == nil {
return nil, ErrInvalidAlgorithm
}
return newFn(), nil
}
// EmptyTree returns the object ID of an empty tree ("tree 0\x00") for this
// algorithm.
func (algo Algorithm) EmptyTree() ObjectID {
return algo.info().emptyTree
}
func (algo Algorithm) info() algorithmDetails {
return algorithmTable[algo]
}
|
