From ab5e27004b154d4f52c199c8ec8e68a9eeef87c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miloslav=20Trma=C4=8D?= <mitr@redhat.com>
Date: Mon, 22 Apr 2024 22:43:27 +0200
Subject: [PATCH] Shorten readZstdChunkedManifest a bit further
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

We have the ImageSourceChunk data type, and we already
construct these values, so scan into them directly instead
of having three separate variables for the two bits of data.

Should not change behavior.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>
---
 pkg/chunked/compression_linux.go | 39 ++++++++++++--------------------
 1 file changed, 15 insertions(+), 24 deletions(-)

diff --git a/pkg/chunked/compression_linux.go b/pkg/chunked/compression_linux.go
index 8fe21a90f8..3499acbd18 100644
--- a/pkg/chunked/compression_linux.go
+++ b/pkg/chunked/compression_linux.go
@@ -138,15 +138,17 @@ func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Di
 	if offsetMetadata == "" {
 		return nil, nil, 0, fmt.Errorf("%q annotation missing", internal.ManifestInfoKey)
 	}
-	var manifestOffset, manifestLengthCompressed, manifestLengthUncompressed, manifestType uint64
-	if _, err := fmt.Sscanf(offsetMetadata, "%d:%d:%d:%d", &manifestOffset, &manifestLengthCompressed, &manifestLengthUncompressed, &manifestType); err != nil {
+	var manifestChunk ImageSourceChunk
+	var manifestLengthUncompressed, manifestType uint64
+	if _, err := fmt.Sscanf(offsetMetadata, "%d:%d:%d:%d", &manifestChunk.Offset, &manifestChunk.Length, &manifestLengthUncompressed, &manifestType); err != nil {
 		return nil, nil, 0, err
 	}
-	// The tarSplit… values are valid if tarSplitOffset > 0
-	var tarSplitOffset, tarSplitLengthCompressed, tarSplitLengthUncompressed uint64
+	// The tarSplit… values are valid if tarSplitChunk.Offset > 0
+	var tarSplitChunk ImageSourceChunk
+	var tarSplitLengthUncompressed uint64
 	var tarSplitChecksum string
 	if tarSplitInfoKeyAnnotation, found := annotations[internal.TarSplitInfoKey]; found {
-		if _, err := fmt.Sscanf(tarSplitInfoKeyAnnotation, "%d:%d:%d", &tarSplitOffset, &tarSplitLengthCompressed, &tarSplitLengthUncompressed); err != nil {
+		if _, err := fmt.Sscanf(tarSplitInfoKeyAnnotation, "%d:%d:%d", &tarSplitChunk.Offset, &tarSplitChunk.Length, &tarSplitLengthUncompressed); err != nil {
 			return nil, nil, 0, err
 		}
 		tarSplitChecksum = annotations[internal.TarSplitChecksumKey]
@@ -157,28 +159,17 @@ func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Di
 	}
 
 	// set a reasonable limit
-	if manifestLengthCompressed > (1<<20)*50 {
+	if manifestChunk.Length > (1<<20)*50 {
 		return nil, nil, 0, errors.New("manifest too big")
 	}
 	if manifestLengthUncompressed > (1<<20)*50 {
 		return nil, nil, 0, errors.New("manifest too big")
 	}
 
-	chunk := ImageSourceChunk{
-		Offset: manifestOffset,
-		Length: manifestLengthCompressed,
-	}
-
-	chunks := []ImageSourceChunk{chunk}
-
-	if tarSplitOffset > 0 {
-		chunkTarSplit := ImageSourceChunk{
-			Offset: tarSplitOffset,
-			Length: tarSplitLengthCompressed,
-		}
-		chunks = append(chunks, chunkTarSplit)
+	chunks := []ImageSourceChunk{manifestChunk}
+	if tarSplitChunk.Offset > 0 {
+		chunks = append(chunks, tarSplitChunk)
 	}
-
 	parts, errs, err := blobStream.GetBlobAt(chunks)
 	if err != nil {
 		return nil, nil, 0, err
@@ -204,7 +195,7 @@ func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Di
 		return blob, nil
 	}
 
-	manifest, err := readBlob(manifestLengthCompressed)
+	manifest, err := readBlob(manifestChunk.Length)
 	if err != nil {
 		return nil, nil, 0, err
 	}
@@ -214,8 +205,8 @@ func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Di
 		return nil, nil, 0, err
 	}
 	decodedTarSplit := []byte{}
-	if tarSplitOffset > 0 {
-		tarSplit, err := readBlob(tarSplitLengthCompressed)
+	if tarSplitChunk.Offset > 0 {
+		tarSplit, err := readBlob(tarSplitChunk.Length)
 		if err != nil {
 			return nil, nil, 0, err
 		}
@@ -225,7 +216,7 @@ func readZstdChunkedManifest(blobStream ImageSourceSeekable, tocDigest digest.Di
 			return nil, nil, 0, err
 		}
 	}
-	return decodedBlob, decodedTarSplit, int64(manifestOffset), err
+	return decodedBlob, decodedTarSplit, int64(manifestChunk.Offset), err
 }
 
 func decodeAndValidateBlob(blob []byte, lengthUncompressed uint64, expectedCompressedChecksum string) ([]byte, error) {