swarm: clean up unused private types and functions (#17989)

* swarm: clean up unused private types and functions

Those that were identified by code inspection tool.

* swarm/storage: move/add Proximity GoDoc from deleted private function

The mentioned proximity() private function was deleted in:
1ca8fc1e6fa0ab4ab1aaca06d6fb32e173cd5f2f

4 files changed, 13 insertions, 44 deletions

diff --git a/swarm/storage/common_test.go b/swarm/storage/common_test.go
index 33133edd7..600be164a 100644
--- a/swarm/storage/common_test.go
+++ b/swarm/storage/common_test.go
@@ -88,17 +88,6 @@ func mputRandomChunks(store ChunkStore, n int, chunksize int64) ([]Chunk, error)
 	return mput(store, n, GenerateRandomChunk)
 }
 
-func mputChunks(store ChunkStore, chunks ...Chunk) error {
-	i := 0
-	f := func(n int64) Chunk {
-		chunk := chunks[i]
-		i++
-		return chunk
-	}
-	_, err := mput(store, len(chunks), f)
-	return err
-}
-
 func mput(store ChunkStore, n int, f func(i int64) Chunk) (hs []Chunk, err error) {
 	// put to localstore and wait for stored channel
 	// does not check delivery error state
diff --git a/swarm/storage/feed/handler_test.go b/swarm/storage/feed/handler_test.go
index cf95bc1f5..fb2ef3a6b 100644
--- a/swarm/storage/feed/handler_test.go
+++ b/swarm/storage/feed/handler_test.go
@@ -27,7 +27,6 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/crypto"
-
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/swarm/chunk"
 	"github.com/ethereum/go-ethereum/swarm/storage"
@@ -506,15 +505,3 @@ func newCharlieSigner() *GenericSigner {
 	privKey, _ := crypto.HexToECDSA("facadefacadefacadefacadefacadefacadefacadefacadefacadefacadefaca")
 	return NewGenericSigner(privKey)
 }
-
-func getUpdateDirect(rh *Handler, addr storage.Address) ([]byte, error) {
-	chunk, err := rh.chunkStore.Get(context.TODO(), addr)
-	if err != nil {
-		return nil, err
-	}
-	var r Request
-	if err := r.fromChunk(addr, chunk.Data()); err != nil {
-		return nil, err
-	}
-	return r.data, nil
-}
diff --git a/swarm/storage/ldbstore.go b/swarm/storage/ldbstore.go
index 49508911f..9feb68741 100644
--- a/swarm/storage/ldbstore.go
+++ b/swarm/storage/ldbstore.go
@@ -39,7 +39,6 @@ import (
 	"github.com/ethereum/go-ethereum/swarm/log"
 	"github.com/ethereum/go-ethereum/swarm/storage/mock"
 	"github.com/syndtr/goleveldb/leveldb"
-	"github.com/syndtr/goleveldb/leveldb/opt"
 )
 
 const (
@@ -72,13 +71,6 @@ var (
 	ErrDBClosed = errors.New("LDBStore closed")
 )
 
-type gcItem struct {
-	idx    *dpaDBIndex
-	value  uint64
-	idxKey []byte
-	po     uint8
-}
-
 type LDBStoreParams struct {
 	*StoreParams
 	Path string
@@ -961,15 +953,3 @@ func (s *LDBStore) SyncIterator(since uint64, until uint64, po uint8, f func(Add
 	}
 	return it.Error()
 }
-
-func databaseExists(path string) bool {
-	o := &opt.Options{
-		ErrorIfMissing: true,
-	}
-	tdb, err := leveldb.OpenFile(path, o)
-	if err != nil {
-		return false
-	}
-	defer tdb.Close()
-	return true
-}
diff --git a/swarm/storage/types.go b/swarm/storage/types.go
index 8c70f4584..ada86831f 100644
--- a/swarm/storage/types.go
+++ b/swarm/storage/types.go
@@ -80,6 +80,19 @@ func (a Address) bits(i, j uint) uint {
 	return res
 }
 
+// Proximity(x, y) returns the proximity order of the MSB distance between x and y
+//
+// The distance metric MSB(x, y) of two equal length byte sequences x an y is the
+// value of the binary integer cast of the x^y, ie., x and y bitwise xor-ed.
+// the binary cast is big endian: most significant bit first (=MSB).
+//
+// Proximity(x, y) is a discrete logarithmic scaling of the MSB distance.
+// It is defined as the reverse rank of the integer part of the base 2
+// logarithm of the distance.
+// It is calculated by counting the number of common leading zeros in the (MSB)
+// binary representation of the x^y.
+//
+// (0 farthest, 255 closest, 256 self)
 func Proximity(one, other []byte) (ret int) {
 	b := (MaxPO-1)/8 + 1
 	if b > len(one) {