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package storer
import (
"errors"
"io"
"gopkg.in/src-d/go-git.v4/plumbing"
)
const MaxResolveRecursion = 1024
// ErrMaxResolveRecursion is returned by ResolveReference is MaxResolveRecursion
// is exceeded
var ErrMaxResolveRecursion = errors.New("max. recursion level reached")
// ReferenceStorer is a generic storage of references.
type ReferenceStorer interface {
SetReference(*plumbing.Reference) error
Reference(plumbing.ReferenceName) (*plumbing.Reference, error)
IterReferences() (ReferenceIter, error)
RemoveReference(plumbing.ReferenceName) error
}
// ReferenceIter is a generic closable interface for iterating over references.
type ReferenceIter interface {
Next() (*plumbing.Reference, error)
ForEach(func(*plumbing.Reference) error) error
Close()
}
// ReferenceSliceIter implements ReferenceIter. It iterates over a series of
// references stored in a slice and yields each one in turn when Next() is
// called.
//
// The ReferenceSliceIter must be closed with a call to Close() when it is no
// longer needed.
type ReferenceSliceIter struct {
series []*plumbing.Reference
pos int
}
// NewReferenceSliceIter returns a reference iterator for the given slice of
// objects.
func NewReferenceSliceIter(series []*plumbing.Reference) *ReferenceSliceIter {
return &ReferenceSliceIter{
series: series,
}
}
// Next returns the next reference from the iterator. If the iterator has
// reached the end it will return io.EOF as an error.
func (iter *ReferenceSliceIter) Next() (*plumbing.Reference, error) {
if iter.pos >= len(iter.series) {
return nil, io.EOF
}
obj := iter.series[iter.pos]
iter.pos++
return obj, nil
}
// ForEach call the cb function for each reference contained on this iter until
// an error happends or the end of the iter is reached. If ErrStop is sent
// the iteration is stop but no error is returned. The iterator is closed.
func (iter *ReferenceSliceIter) ForEach(cb func(*plumbing.Reference) error) error {
defer iter.Close()
for _, r := range iter.series {
if err := cb(r); err != nil {
if err == ErrStop {
return nil
}
return err
}
}
return nil
}
// Close releases any resources used by the iterator.
func (iter *ReferenceSliceIter) Close() {
iter.pos = len(iter.series)
}
// ResolveReference resolves a SymbolicReference to a HashReference.
func ResolveReference(s ReferenceStorer, n plumbing.ReferenceName) (*plumbing.Reference, error) {
r, err := s.Reference(n)
if err != nil || r == nil {
return r, err
}
return resolveReference(s, r, 0)
}
func resolveReference(s ReferenceStorer, r *plumbing.Reference, recursion int) (*plumbing.Reference, error) {
if r.Type() != plumbing.SymbolicReference {
return r, nil
}
if recursion > MaxResolveRecursion {
return nil, ErrMaxResolveRecursion
}
t, err := s.Reference(r.Target())
if err != nil {
return nil, err
}
recursion++
return resolveReference(s, t, recursion)
}
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