Introduced repository.DownloadAndHash helper

Signed-off-by: Igor Fedorenko <igor@ifedorenko.com>

internal/checker/checker.go

@@ -2,15 +2,12 @@ package checker
 
 import (
 	"context"
-	"crypto/sha256"
 	"fmt"
 	"io"
 	"os"
 	"sync"
 
 	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/fs"
-	"github.com/restic/restic/internal/hashing"
 	"github.com/restic/restic/internal/restic"
 	"golang.org/x/sync/errgroup"
 
@@ -630,9 +627,9 @@ func checkPack(ctx context.Context, r restic.Repository, id restic.ID) error {
 	debug.Log("checking pack %v", id)
 	h := restic.Handle{Type: restic.DataFile, Name: id.String()}
 
-	packfile, err := fs.TempFile("", "restic-temp-check-")
+	packfile, hash, size, err := repository.DownloadAndHash(ctx, r, h)
 	if err != nil {
-		return errors.Wrap(err, "TempFile")
+		return errors.Wrap(err, "checkPack")
 	}
 
 	defer func() {
@@ -640,25 +637,6 @@ func checkPack(ctx context.Context, r restic.Repository, id restic.ID) error {
 		_ = os.Remove(packfile.Name())
 	}()
 
-	var hash restic.ID
-	var size int64
-	err = r.Backend().Load(ctx, h, 0, 0, func(rd io.Reader) (ierr error) {
-		_, ierr = packfile.Seek(0, io.SeekStart)
-		if ierr == nil {
-			ierr = packfile.Truncate(0)
-		}
-		if ierr != nil {
-			return ierr
-		}
-		hrd := hashing.NewReader(rd, sha256.New())
-		size, ierr = io.Copy(packfile, hrd)
-		hash = restic.IDFromHash(hrd.Sum(nil))
-		return ierr
-	})
-	if err != nil {
-		return errors.Wrap(err, "checkPack")
-	}
-
 	debug.Log("hash for pack %v is %v", id, hash)
 
 	if !hash.Equal(id) {

internal/repository/repack.go

@@ -2,14 +2,11 @@ package repository
 
 import (
 	"context"
-	"crypto/sha256"
 	"fmt"
-	"io"
 	"os"
 
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/fs"
-	"github.com/restic/restic/internal/hashing"
 	"github.com/restic/restic/internal/pack"
 	"github.com/restic/restic/internal/restic"
 
@@ -27,27 +24,7 @@ func Repack(ctx context.Context, repo restic.Repository, packs restic.IDSet, kee
 		// load the complete pack into a temp file
 		h := restic.Handle{Type: restic.DataFile, Name: packID.String()}
 
-		tempfile, err := fs.TempFile("", "restic-temp-repack-")
-		if err != nil {
-			return nil, errors.Wrap(err, "TempFile")
-		}
-
-		// TODO very similar code in checker, consider moving to utils.go
-		var hash restic.ID
-		var packLength int64
-		err = repo.Backend().Load(ctx, h, 0, 0, func(rd io.Reader) (ierr error) {
-			_, ierr = tempfile.Seek(0, io.SeekStart)
-			if ierr == nil {
-				ierr = tempfile.Truncate(0)
-			}
-			if ierr != nil {
-				return ierr
-			}
-			hrd := hashing.NewReader(rd, sha256.New())
-			packLength, ierr = io.Copy(tempfile, hrd)
-			hash = restic.IDFromHash(hrd.Sum(nil))
-			return ierr
-		})
+		tempfile, hash, packLength, err := DownloadAndHash(ctx, repo, h)
 		if err != nil {
 			return nil, errors.Wrap(err, "Repack")
 		}

internal/repository/repository.go

@@ -3,12 +3,16 @@ package repository
 import (
 	"bytes"
 	"context"
+	"crypto/sha256"
 	"encoding/json"
 	"fmt"
+	"io"
 	"os"
 
 	"github.com/restic/restic/internal/cache"
 	"github.com/restic/restic/internal/errors"
+	"github.com/restic/restic/internal/fs"
+	"github.com/restic/restic/internal/hashing"
 	"github.com/restic/restic/internal/restic"
 
 	"github.com/restic/restic/internal/backend"
@@ -654,3 +658,36 @@ func (r *Repository) SaveTree(ctx context.Context, t *restic.Tree) (restic.ID, e
 	_, err = r.SaveBlob(ctx, restic.TreeBlob, buf, id)
 	return id, err
 }
+
+// DownloadAndHash is all-in-one helper to download content of the file at h to a temporary filesystem location
+// and calculate ID of the contents. Returned (temporary) file is positioned at the beginning of the file;
+// it is reponsibility of the caller to close and delete the file.
+func DownloadAndHash(ctx context.Context, repo restic.Repository, h restic.Handle) (tmpfile *os.File, hash restic.ID, size int64, err error) {
+	tmpfile, err = fs.TempFile("", "restic-temp-")
+	if err != nil {
+		return nil, restic.ID{}, -1, errors.Wrap(err, "TempFile")
+	}
+
+	err = repo.Backend().Load(ctx, h, 0, 0, func(rd io.Reader) (ierr error) {
+		_, ierr = tmpfile.Seek(0, io.SeekStart)
+		if ierr == nil {
+			ierr = tmpfile.Truncate(0)
+		}
+		if ierr != nil {
+			return ierr
+		}
+		hrd := hashing.NewReader(rd, sha256.New())
+		size, ierr = io.Copy(tmpfile, hrd)
+		hash = restic.IDFromHash(hrd.Sum(nil))
+		return ierr
+	})
+
+	_, err = tmpfile.Seek(0, io.SeekStart)
+	if err != nil {
+		tmpfile.Close()
+		os.Remove(tmpfile.Name())
+		return nil, restic.ID{}, -1, errors.Wrap(err, "Seek")
+	}
+
+	return tmpfile, hash, size, err
+}