Hash check, and S3 pulled in parallel

Signed-off-by: Jimmy Moore <[email protected]>

pkg/storage/device/device.go

@@ -1,7 +1,9 @@
 package device
 
 import (
+	"bytes"
 	"context"
+	"crypto/sha256"
 	"encoding/binary"
 	"errors"
 	"fmt"
@@ -308,20 +310,32 @@ func NewDevice(ds *config.DeviceSchema) (storage.StorageProvider, storage.Expose
 			if data != nil {
 				alternateSources := data.([]packets.AlternateSource)
 
-				// TODO: Pull these in parallel
+				var wg sync.WaitGroup
+
+				// Pull these blocks in parallel
 				for _, as := range alternateSources {
-					buffer := make([]byte, as.Length)
-					n, err := s3dest.ReadAt(buffer, as.Offset)
-					if err != nil || n != int(as.Length) {
-						panic(err)
-					}
+					wg.Add(1)
+					go func(a packets.AlternateSource) {
+						buffer := make([]byte, a.Length)
+						n, err := s3dest.ReadAt(buffer, a.Offset)
+						if err != nil || n != int(a.Length) {
+							panic(fmt.Sprintf("sync.start unable to read from S3. %v", err))
+						}
 
-					// TODO: We should probably check the hash here, though if it's incorrect there's nothing we can do.
-					n, err = prov.WriteAt(buffer, as.Offset)
-					if err != nil || n != int(as.Length) {
-						panic(err)
-					}
+						// Check the data in S3 hasn't changed.
+						hash := sha256.Sum256(buffer)
+						if !bytes.Equal(hash[:], a.Hash[:]) {
+							panic("The data in S3 is corrupt.")
+						}
+
+						n, err = prov.WriteAt(buffer, a.Offset)
+						if err != nil || n != int(a.Length) {
+							panic(fmt.Sprintf("sync.start unable to write data to device from S3. %v", err))
+						}
+						wg.Done()
+					}(as)
 				}
+				wg.Wait() // Wait for all S3 requests to complete
 			}
 
 			sync_lock.Lock()