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package loose
import (
"fmt"
"os"
"path/filepath"
"lindenii.org/go/furgit/object/id"
"lindenii.org/go/furgit/object/store"
)
// Loose reads loose Git objects from an objects directory root.
//
// Loose objects are zlib streams whose trailer uses Adler-32.
// Which reads consume enough of the stream
// to reach and verify that trailer
// is documented on the individual methods.
//
// Labels: Close-Caller.
type Loose struct {
// root is the objects directory capability used for all object file access.
// Object files are opened by relative paths like "<first2>/<rest>".
// Loose borrows this root.
root *os.Root
// objectFormat is the expected object format for lookups.
objectFormat id.ObjectFormat
}
var (
_ store.ObjectReader = (*Loose)(nil)
_ store.ObjectWriter = (*Loose)(nil)
)
// New creates a loose-object store rooted at an objects directory for objectFormat.
//
// Labels: Deps-Borrowed, Life-Parent.
func New(root *os.Root, objectFormat id.ObjectFormat) (*Loose, error) {
if objectFormat.Size() == 0 {
return nil, id.ErrInvalidObjectFormat
}
return &Loose{
root: root,
objectFormat: objectFormat,
}, nil
}
// Close releases resources associated with the backend.
//
// Labels: MT-Unsafe.
func (loose *Loose) Close() error { return nil }
// objectPath returns the loose object path for objectID relative to the objects root.
func (loose *Loose) objectPath(objectID id.ObjectID) (string, error) {
if objectID.ObjectFormat() != loose.objectFormat {
return "", fmt.Errorf("%w: got %s want %s", id.ErrInvalidObjectFormat, objectID.ObjectFormat(), loose.objectFormat)
}
hex := objectID.String()
return filepath.Join(hex[:2], hex[2:]), nil
}
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