Don't compute file hashes when DUPLICACY_SKIP_FILE_HASH is set; handle vertical backup-style hashes in restore

src/duplicacy_backupmanager.go

@@ -1233,7 +1233,7 @@ func (manager *BackupManager) RestoreFile(chunkDownloader *ChunkDownloader, chun
 
         // Verify the download by hash
         hash := hex.EncodeToString(hasher.Sum(nil))
-        if hash != entry.Hash {
+        if hash != entry.Hash && hash != "" && entry.Hash != "" && !strings.HasPrefix(entry.Hash, "#") {
             LOG_ERROR("DOWNLOAD_HASH", "File %s has a mismatched hash: %s instead of %s (in-place)",
                       fullPath, "", entry.Hash)
             return false
@@ -1306,7 +1306,7 @@ func (manager *BackupManager) RestoreFile(chunkDownloader *ChunkDownloader, chun
         }
 
         hash := hex.EncodeToString(hasher.Sum(nil))
-        if hash != entry.Hash {
+        if hash != entry.Hash && hash != "" && entry.Hash != "" && !strings.HasPrefix(entry.Hash, "#") {
             LOG_ERROR("DOWNLOAD_HASH", "File %s has a mismatched hash: %s instead of %s",
                       entry.Path, hash, entry.Hash)
             return false

src/duplicacy_config.go

@@ -225,8 +225,41 @@ func (config *Config) NewKeyedHasher(key []byte) hash.Hash {
     }
 }
 
+var SkipFileHash = false
+
+func init() {
+    if value, found := os.LookupEnv("DUPLICACY_SKIP_FILE_HASH"); found && value != "" && value != "0" {
+        SkipFileHash = true
+    }
+}
+
+// Implement a dummy hasher to be used when SkipFileHash is true.
+type DummyHasher struct {
+}
+
+func (hasher *DummyHasher) Write(p []byte) (int, error) {
+    return len(p), nil
+}
+
+func (hasher *DummyHasher) Sum(b []byte) []byte {
+    return []byte("")
+}
+
+func (hasher *DummyHasher) Reset() {
+}
+
+func (hasher *DummyHasher) Size() int {
+    return 0
+}
+
+func (hasher *DummyHasher) BlockSize() int {
+    return 0
+}
+
 func (config *Config) NewFileHasher() hash.Hash {
-    if config.CompressionLevel == DEFAULT_COMPRESSION_LEVEL {
+    if SkipFileHash {
+        return &DummyHasher {}
+    } else if config.CompressionLevel == DEFAULT_COMPRESSION_LEVEL {
         hasher, _ := blake2.New(&blake2.Config{ Size: 32 })
         return hasher
     } else {

src/duplicacy_snapshotmanager.go

@@ -1084,7 +1084,7 @@ func (manager *SnapshotManager) RetrieveFile(snapshot *Snapshot, file *Entry, ou
     if alternateHash {
         fileHash = "#" + fileHash
     }
-    if strings.ToLower(fileHash) != strings.ToLower(file.Hash) {
+    if strings.ToLower(fileHash) != strings.ToLower(file.Hash) && !SkipFileHash {
         LOG_WARN("SNAPSHOT_HASH", "File %s has mismatched hashes: %s vs %s", file.Path, file.Hash, fileHash)
         return false
     }