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// package hash provides a way for managing the
// underlying hash implementations used across go-git.
package hash
import (
"crypto"
"fmt"
"hash"
"github.com/pjbgf/sha1cd/cgo"
)
// algos is a map of hash algorithms.
var algos = map[crypto.Hash]func() hash.Hash{}
func init() {
reset()
}
// reset resets the default algos value. Can be used after running tests
// that registers new algorithms to avoid side effects.
func reset() {
// For performance reasons the cgo version of the collision
// detection algorithm is being used.
algos[crypto.SHA1] = cgo.New
}
// RegisterHash allows for the hash algorithm used to be overriden.
// This ensures the hash selection for go-git must be explicit, when
// overriding the default value.
func RegisterHash(h crypto.Hash, f func() hash.Hash) error {
if f == nil {
return fmt.Errorf("cannot register hash: f is nil")
}
switch h {
case crypto.SHA1:
algos[h] = f
default:
return fmt.Errorf("unsupported hash function: %v", h)
}
return nil
}
// Hash is the same as hash.Hash. This allows consumers
// to not having to import this package alongside "hash".
type Hash interface {
hash.Hash
}
// New returns a new Hash for the given hash function.
// It panics if the hash function is not registered.
func New(h crypto.Hash) Hash {
hh, ok := algos[h]
if !ok {
panic(fmt.Sprintf("hash algorithm not registered: %v", h))
}
return hh()
}
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