Revert "Merge fix/restore-cache-readat"

This reverts commit 44c9008e7e, reversing
changes made to b55d5763ad.

internal/vaultik/restore.go

@@ -569,22 +569,14 @@ func (v *Vaultik) restoreRegularFile(
 			return fmt.Errorf("getting blob %s: %w", blobChunk.BlobID, err)
 		}
 
-		// If the blob isn't on disk yet, download it (one full readout
+		// Download and decrypt blob if not cached
-		// of the plaintext into memory), write it to the cache, and
-		// satisfy THIS chunk from the in-memory copy. Subsequent files
-		// needing chunks from the same blob hit the ReadAt branch and
-		// read only the bytes they actually want — never the whole
-		// blob — which is the difference between sub-millisecond chunk
-		// extraction and ~1 s per cache hit on a 10 GB blob.
 		blobHashStr := blob.Hash.String()
-		var chunkData []byte
 		t0 = time.Now()
-		blobInCache := blobCache.Has(blobHashStr)
+		blobData, ok := blobCache.Get(blobHashStr)
 		cacheGetDur += time.Since(t0)
-
+		if !ok {
-		if !blobInCache {
 			t0 = time.Now()
-			blobData, err := v.downloadBlob(ctx, blobHashStr, blob.CompressedSize, identity)
+			blobData, err = v.downloadBlob(ctx, blobHashStr, blob.CompressedSize, identity)
 			downloadDur += time.Since(t0)
 			if err != nil {
 				return fmt.Errorf("downloading blob %s: %w", blobHashStr[:16], err)
@@ -597,22 +589,17 @@ func (v *Vaultik) restoreRegularFile(
 			downloadCount++
 			result.BlobsDownloaded++
 			result.BytesDownloaded += blob.CompressedSize
-
-			if blobChunk.Offset+blobChunk.Length > int64(len(blobData)) {
-				return fmt.Errorf("chunk %s extends beyond blob data (offset=%d, length=%d, blob_size=%d)",
-					fc.ChunkHash[:16], blobChunk.Offset, blobChunk.Length, len(blobData))
-			}
-			chunkData = blobData[blobChunk.Offset : blobChunk.Offset+blobChunk.Length]
 		} else {
 			cacheHitCount++
-			t0 = time.Now()
-			chunkData, err = blobCache.ReadAt(blobHashStr, blobChunk.Offset, blobChunk.Length)
-			cacheGetDur += time.Since(t0)
-			if err != nil {
-				return fmt.Errorf("reading chunk %s from cached blob %s: %w", fc.ChunkHash[:16], blobHashStr[:16], err)
-			}
 		}
 
+		// Extract chunk from blob
+		if blobChunk.Offset+blobChunk.Length > int64(len(blobData)) {
+			return fmt.Errorf("chunk %s extends beyond blob data (offset=%d, length=%d, blob_size=%d)",
+				fc.ChunkHash[:16], blobChunk.Offset, blobChunk.Length, len(blobData))
+		}
+		chunkData := blobData[blobChunk.Offset : blobChunk.Offset+blobChunk.Length]
+
 		// Write chunk to output file
 		t0 = time.Now()
 		n, err := outFile.Write(chunkData)