Add a few functions to calculate Blob buffer len

src/restic/archiver/archive_reader_test.go

@@ -5,7 +5,6 @@ import (
 	"io"
 	"math/rand"
 	"restic"
-	"restic/crypto"
 	"restic/repository"
 	"testing"
 )
@@ -45,7 +44,7 @@ func checkSavedFile(t *testing.T, repo restic.Repository, treeID restic.ID, name
 			t.Fatal(err)
 		}
 
-		buf := make([]byte, int(size), int(size)+crypto.Extension)
+		buf := restic.NewBlobBuffer(int(size))
 		n := loadBlob(t, repo, id, buf)
 		if n != len(buf) {
 			t.Errorf("wrong number of bytes read, want %d, got %d", len(buf), n)

src/restic/buffer.go

@@ -0,0 +1,21 @@
+package restic
+
+import "restic/crypto"
+
+// NewBlobBuffer returns a buffer that is large enough to hold a blob of size
+// plaintext bytes, including the crypto overhead.
+func NewBlobBuffer(size int) []byte {
+	return make([]byte, size, size+crypto.Extension)
+}
+
+// PlaintextLength returns the plaintext length of a blob with ciphertextSize
+// bytes.
+func PlaintextLength(ciphertextSize int) int {
+	return ciphertextSize - crypto.Extension
+}
+
+// CiphertextLength returns the encrypted length of a blob with plaintextSize
+// bytes.
+func CiphertextLength(plaintextSize int) int {
+	return plaintextSize + crypto.Extension
+}

src/restic/node.go

@@ -10,7 +10,6 @@ import (
 	"syscall"
 	"time"
 
-	"restic/crypto"
 	"restic/errors"
 
 	"runtime"
@@ -209,7 +208,7 @@ func (node Node) createFileAt(path string, repo Repository) error {
 
 		buf = buf[:cap(buf)]
 		if uint(len(buf)) < size {
-			buf = make([]byte, size, size+crypto.Extension)
+			buf = NewBlobBuffer(int(size))
 		}
 
 		n, err := repo.LoadBlob(DataBlob, id, buf)

src/restic/pack/pack.go

@@ -85,15 +85,15 @@ func (p *Packer) Finalize() (uint, error) {
 		return 0, errors.Wrap(err, "Write")
 	}
 
-	hdrBytes := bytesHeader + crypto.Extension
-	if uint(n) != hdrBytes {
+	hdrBytes := restic.CiphertextLength(int(bytesHeader))
+	if n != hdrBytes {
 		return 0, errors.New("wrong number of bytes written")
 	}
 
-	bytesWritten += hdrBytes
+	bytesWritten += uint(hdrBytes)
 
 	// write length
-	err = binary.Write(p.wr, binary.LittleEndian, uint32(uint(len(p.blobs))*entrySize+crypto.Extension))
+	err = binary.Write(p.wr, binary.LittleEndian, uint32(restic.CiphertextLength(len(p.blobs)*int(entrySize))))
 	if err != nil {
 		return 0, errors.Wrap(err, "binary.Write")
 	}

src/restic/pack/pack_test.go

@@ -54,10 +54,9 @@ func verifyBlobs(t testing.TB, bufs []Buf, k *crypto.Key, rd io.ReaderAt, packSi
 	}
 	// header length
 	written += binary.Size(uint32(0))
-	// header
-	written += len(bufs) * (binary.Size(restic.BlobType(0)) + binary.Size(uint32(0)) + len(restic.ID{}))
-	// header crypto
-	written += crypto.Extension
+	// header + header crypto
+	headerSize := len(bufs) * (binary.Size(restic.BlobType(0)) + binary.Size(uint32(0)) + len(restic.ID{}))
+	written += restic.CiphertextLength(headerSize)
 
 	// check length
 	Equals(t, uint(written), packSize)

src/restic/repository/index.go

@@ -10,7 +10,6 @@ import (
 
 	"restic/errors"
 
-	"restic/crypto"
 	"restic/debug"
 )
 
@@ -177,15 +176,15 @@ func (idx *Index) Has(id restic.ID, tpe restic.BlobType) bool {
 	return false
 }
 
-// LookupSize returns the length of the cleartext content behind the
-// given id
-func (idx *Index) LookupSize(id restic.ID, tpe restic.BlobType) (cleartextLength uint, err error) {
+// LookupSize returns the length of the plaintext content of the blob with the
+// given id.
+func (idx *Index) LookupSize(id restic.ID, tpe restic.BlobType) (plaintextLength uint, err error) {
 	blobs, err := idx.Lookup(id, tpe)
 	if err != nil {
 		return 0, err
 	}
 
-	return blobs[0].Length - crypto.Extension, nil
+	return uint(restic.PlaintextLength(int(blobs[0].Length))), nil
 }
 
 // Supersedes returns the list of indexes this index supersedes, if any.

src/restic/repository/repository.go

@@ -213,7 +213,7 @@ func (r *Repository) SaveJSONUnpacked(t restic.FileType, item interface{}) (rest
 // SaveUnpacked encrypts data and stores it in the backend. Returned is the
 // storage hash.
 func (r *Repository) SaveUnpacked(t restic.FileType, p []byte) (id restic.ID, err error) {
-	ciphertext := make([]byte, len(p)+crypto.Extension)
+	ciphertext := restic.NewBlobBuffer(len(p))
 	ciphertext, err = r.Encrypt(ciphertext, p)
 	if err != nil {
 		return restic.ID{}, err
@@ -528,8 +528,8 @@ func (r *Repository) LoadBlob(t restic.BlobType, id restic.ID, buf []byte) (int,
 	}
 
 	buf = buf[:cap(buf)]
-	if len(buf) < int(size)+crypto.Extension {
-		return 0, errors.Errorf("buffer is too small for data blob (%d < %d)", len(buf), size+crypto.Extension)
+	if len(buf) < restic.CiphertextLength(int(size)) {
+		return 0, errors.Errorf("buffer is too small for data blob (%d < %d)", len(buf), restic.CiphertextLength(int(size)))
 	}
 
 	n, err := r.loadBlob(id, t, buf)
@@ -563,7 +563,7 @@ func (r *Repository) LoadTree(id restic.ID) (*restic.Tree, error) {
 	}
 
 	debug.Log("size is %d, create buffer", size)
-	buf := make([]byte, size+crypto.Extension)
+	buf := restic.NewBlobBuffer(int(size))
 
 	n, err := r.loadBlob(id, restic.TreeBlob, buf)
 	if err != nil {

src/restic/repository/repository_test.go

@@ -11,7 +11,6 @@ import (
 
 	"restic"
 	"restic/archiver"
-	"restic/crypto"
 	"restic/repository"
 	. "restic/test"
 )
@@ -41,7 +40,7 @@ func TestSave(t *testing.T) {
 		// OK(t, repo.SaveIndex())
 
 		// read back
-		buf := make([]byte, size, size+crypto.Extension)
+		buf := restic.NewBlobBuffer(size)
 		n, err := repo.LoadBlob(restic.DataBlob, id, buf)
 		OK(t, err)
 		Equals(t, len(buf), n)
@@ -75,7 +74,7 @@ func TestSaveFrom(t *testing.T) {
 		OK(t, repo.Flush())
 
 		// read back
-		buf := make([]byte, size, size+crypto.Extension)
+		buf := restic.NewBlobBuffer(size)
 		n, err := repo.LoadBlob(restic.DataBlob, id, buf)
 		OK(t, err)
 		Equals(t, len(buf), n)
@@ -153,7 +152,7 @@ func BenchmarkLoadBlob(b *testing.B) {
 	defer cleanup()
 
 	length := 1000000
-	buf := make([]byte, length, length+crypto.Extension)
+	buf := restic.NewBlobBuffer(length)
 	_, err := io.ReadFull(rnd, buf)
 	OK(b, err)