Merge pull request #1348 from versity/ben/crc-mp-complete

feat: calculate full object crc for multi-part uploads for compatible checksums

backend/posix/posix.go

@@ -1352,6 +1352,8 @@ func getPartChecksum(algo types.ChecksumAlgorithm, part types.CompletedPart) str
 		return backend.GetStringFromPtr(part.ChecksumSHA1)
 	case types.ChecksumAlgorithmSha256:
 		return backend.GetStringFromPtr(part.ChecksumSHA256)
+	case types.ChecksumAlgorithmCrc64nvme:
+		return backend.GetStringFromPtr(part.ChecksumCRC64NVME)
 	default:
 		return ""
 	}
@@ -1418,6 +1420,12 @@ func (p *Posix) CompleteMultipartUpload(ctx context.Context, input *s3.CompleteM
 	last := len(parts) - 1
 	var totalsize int64
 
+	var composableCRC bool
+	switch checksums.Type {
+	case types.ChecksumTypeFullObject:
+		composableCRC = utils.IsChecksumComposable(checksumAlgorithm)
+	}
+
 	// The initialie values is the lower limit of partNumber: 0
 	var partNumber int32
 	for i, part := range parts {
@@ -1441,7 +1449,7 @@ func (p *Posix) CompleteMultipartUpload(ctx context.Context, input *s3.CompleteM
 		}
 
 		totalsize += fi.Size()
-		// all parts except the last need to be greater, thena
+		// all parts except the last need to be greater, than or equal to
 		// the minimum allowed size (5 Mib)
 		if i < last && fi.Size() < backend.MinPartSize {
 			return res, "", s3err.GetAPIError(s3err.ErrEntityTooSmall)
@@ -1476,9 +1484,11 @@ func (p *Posix) CompleteMultipartUpload(ctx context.Context, input *s3.CompleteM
 	var compositeChecksumRdr *utils.CompositeChecksumReader
 	switch checksums.Type {
 	case types.ChecksumTypeFullObject:
-		hashRdr, err = utils.NewHashReader(nil, "", utils.HashType(strings.ToLower(string(checksumAlgorithm))))
-		if err != nil {
-			return res, "", fmt.Errorf("initialize hash reader: %w", err)
+		if !composableCRC {
+			hashRdr, err = utils.NewHashReader(nil, "", utils.HashType(strings.ToLower(string(checksumAlgorithm))))
+			if err != nil {
+				return res, "", fmt.Errorf("initialize hash reader: %w", err)
+			}
 		}
 	case types.ChecksumTypeComposite:
 		compositeChecksumRdr, err = utils.NewCompositeChecksumReader(utils.HashType(strings.ToLower(string(checksumAlgorithm))))
@@ -1497,22 +1507,46 @@ func (p *Posix) CompleteMultipartUpload(ctx context.Context, input *s3.CompleteM
 	}
 	defer f.cleanup()
 
-	for _, part := range parts {
+	var composableCsum string
+	for i, part := range parts {
 		partObjPath := filepath.Join(objdir, uploadID, fmt.Sprintf("%v", *part.PartNumber))
 		fullPartPath := filepath.Join(bucket, partObjPath)
 		pf, err := os.Open(fullPartPath)
 		if err != nil {
 			return res, "", fmt.Errorf("open part %v: %v", *part.PartNumber, err)
 		}
+		pfi, err := pf.Stat()
+		if err != nil {
+			pf.Close()
+			return res, "", fmt.Errorf("stat part %v: %v", *part.PartNumber, err)
+		}
 
 		var rdr io.Reader = pf
-		if checksums.Type == types.ChecksumTypeFullObject {
+		switch checksums.Type {
+		case types.ChecksumTypeFullObject:
+			if composableCRC {
+				if i == 0 {
+					composableCsum = getPartChecksum(checksumAlgorithm, part)
+					break
+				}
+				composableCsum, err = utils.AddCRCChecksum(checksumAlgorithm,
+					composableCsum, getPartChecksum(checksumAlgorithm, part),
+					pfi.Size())
+				if err != nil {
+					pf.Close()
+					return res, "", fmt.Errorf("add part %v checksum: %w",
+						*part.PartNumber, err)
+				}
+				break
+			}
 			hashRdr.SetReader(rdr)
 			rdr = hashRdr
-		} else if checksums.Type == types.ChecksumTypeComposite {
+		case types.ChecksumTypeComposite:
 			err := compositeChecksumRdr.Process(getPartChecksum(checksumAlgorithm, part))
 			if err != nil {
-				return res, "", fmt.Errorf("process %v part checksum: %w", *part.PartNumber, err)
+				pf.Close()
+				return res, "", fmt.Errorf("process %v part checksum: %w",
+					*part.PartNumber, err)
 			}
 		}
 
@@ -1621,7 +1655,11 @@ func (p *Posix) CompleteMultipartUpload(ctx context.Context, input *s3.CompleteM
 		case types.ChecksumTypeComposite:
 			sum = compositeChecksumRdr.Sum()
 		case types.ChecksumTypeFullObject:
-			sum = hashRdr.Sum()
+			if !composableCRC {
+				sum = hashRdr.Sum()
+			} else {
+				sum = composableCsum
+			}
 		}
 
 		switch checksumAlgorithm {

s3api/utils/crc.go

@@ -0,0 +1,180 @@
+// Copyright (C) 1995-2017 Jean-loup Gailly and Mark Adler
+//
+// This software is provided 'as-is', without any express or implied
+// warranty.  In no event will the authors be held liable for any damages
+// arising from the use of this software.
+//
+// Permission is granted to anyone to use this software for any purpose,
+// including commercial applications, and to alter it and redistribute it
+// freely, subject to the following restrictions:
+//
+// 1. The origin of this software must not be misrepresented; you must not
+//    claim that you wrote the original software. If you use this software
+//    in a product, an acknowledgment in the product documentation would be
+//    appreciated but is not required.
+// 2. Altered source versions must be plainly marked as such, and must not be
+//    misrepresented as being the original software.
+// 3. This notice may not be removed or altered from any source distribution.
+//
+// Jean-loup Gailly        Mark Adler
+// jloup@gzip.org          madler@alumni.caltech.edu
+
+// Original implementation is from
+// https://github.com/vimeo/go-util/blob/8cd4c737f091d9317f72b25df78ce6cf869f7d30/crc32combine/crc32combine.go
+// extended for crc64 support.
+
+// Following is ported from C to Go in 2016 by Justin Ruggles, with minimal alteration.
+// Used uint for unsigned long. Used uint32 for input arguments in order to match
+// the Go hash/crc32 package. zlib CRC32 combine (https://github.com/madler/zlib)
+
+package utils
+
+import (
+	"hash/crc64"
+)
+
+const crc64NVME = 0x9a6c_9329_ac4b_c9b5
+
+var crc64NVMETable = crc64.MakeTable(crc64NVME)
+
+func gf2MatrixTimes(mat []uint64, vec uint64) uint64 {
+	var sum uint64
+
+	for vec != 0 {
+		if vec&1 != 0 {
+			sum ^= mat[0]
+		}
+		vec >>= 1
+		mat = mat[1:]
+	}
+	return sum
+}
+
+func gf2MatrixSquare(square, mat []uint64) {
+	if len(square) != len(mat) {
+		panic("square matrix size mismatch")
+	}
+	for n := range mat {
+		square[n] = gf2MatrixTimes(mat, mat[n])
+	}
+}
+
+// crc32Combine returns the combined CRC-32 hash value of the two passed CRC-32
+// hash values crc1 and crc2. poly represents the generator polynomial
+// and len2 specifies the byte length that the crc2 hash covers.
+func crc32Combine(poly uint32, crc1, crc2 uint32, len2 int64) uint32 {
+	// degenerate case (also disallow negative lengths)
+	if len2 <= 0 {
+		return crc1
+	}
+
+	even := make([]uint64, 32) // even-power-of-two zeros operator
+	odd := make([]uint64, 32)  // odd-power-of-two zeros operator
+
+	// put operator for one zero bit in odd
+	odd[0] = uint64(poly) // CRC-32 polynomial
+	row := uint64(1)
+	for n := 1; n < 32; n++ {
+		odd[n] = row
+		row <<= 1
+	}
+
+	// put operator for two zero bits in even
+	gf2MatrixSquare(even, odd)
+
+	// put operator for four zero bits in odd
+	gf2MatrixSquare(odd, even)
+
+	// apply len2 zeros to crc1 (first square will put the operator for one
+	// zero byte, eight zero bits, in even)
+	crc1n := uint64(crc1)
+	for {
+		// apply zeros operator for this bit of len2
+		gf2MatrixSquare(even, odd)
+		if len2&1 != 0 {
+			crc1n = gf2MatrixTimes(even, crc1n)
+		}
+		len2 >>= 1
+
+		// if no more bits set, then done
+		if len2 == 0 {
+			break
+		}
+
+		// another iteration of the loop with odd and even swapped
+		gf2MatrixSquare(odd, even)
+		if len2&1 != 0 {
+			crc1n = gf2MatrixTimes(odd, crc1n)
+		}
+		len2 >>= 1
+
+		// if no more bits set, then done
+		if len2 == 0 {
+			break
+		}
+	}
+
+	// return combined crc
+	crc1n ^= uint64(crc2)
+	return uint32(crc1n)
+}
+
+// crc64Combine returns the combined CRC-64 hash value of the two passed CRC-64
+// hash values crc1 and crc2. poly represents the generator polynomial
+// and len2 specifies the byte length that the crc2 hash covers.
+func crc64Combine(poly uint64, crc1, crc2 uint64, len2 int64) uint64 {
+	// degenerate case (also disallow negative lengths)
+	if len2 <= 0 {
+		return crc1
+	}
+
+	even := make([]uint64, 64) // even-power-of-two zeros operator
+	odd := make([]uint64, 64)  // odd-power-of-two zeros operator
+
+	// put operator for one zero bit in odd
+	odd[0] = poly // CRC-64 polynomial
+	row := uint64(1)
+	for n := 1; n < 64; n++ {
+		odd[n] = row
+		row <<= 1
+	}
+
+	// put operator for two zero bits in even
+	gf2MatrixSquare(even, odd)
+
+	// put operator for four zero bits in odd
+	gf2MatrixSquare(odd, even)
+
+	// apply len2 zeros to crc1 (first square will put the operator for one
+	// zero byte, eight zero bits, in even)
+	crc1n := crc1
+	for {
+		// apply zeros operator for this bit of len2
+		gf2MatrixSquare(even, odd)
+		if len2&1 != 0 {
+			crc1n = gf2MatrixTimes(even, crc1n)
+		}
+		len2 >>= 1
+
+		// if no more bits set, then done
+		if len2 == 0 {
+			break
+		}
+
+		// another iteration of the loop with odd and even swapped
+		gf2MatrixSquare(odd, even)
+		if len2&1 != 0 {
+			crc1n = gf2MatrixTimes(odd, crc1n)
+		}
+		len2 >>= 1
+
+		// if no more bits set, then done
+		if len2 == 0 {
+			break
+		}
+	}
+
+	// return combined crc
+	crc1n ^= crc2
+	return crc1n
+}

s3api/utils/crc_test.go

@@ -0,0 +1,57 @@
+// Copyright 2025 Versity Software
+// This file is licensed under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package utils
+
+import (
+	"hash/crc32"
+	"hash/crc64"
+	"testing"
+)
+
+func TestCRC32Combine(t *testing.T) {
+	data := []byte("The quick brown fox jumps over the lazy dog")
+	mid := len(data) / 2
+	part1 := data[:mid]
+	part2 := data[mid:]
+
+	var poly uint32 = crc32.IEEE
+	tab := crc32.MakeTable(poly)
+	crc1 := crc32.Checksum(part1, tab)
+	crc2 := crc32.Checksum(part2, tab)
+	combined := crc32Combine(poly, crc1, crc2, int64(len(part2)))
+	full := crc32.Checksum(data, tab)
+
+	if combined != full {
+		t.Errorf("crc32Combine failed: got %08x, want %08x", combined, full)
+	}
+}
+
+func TestCRC64Combine(t *testing.T) {
+	data := []byte("The quick brown fox jumps over the lazy dog")
+	mid := len(data) / 2
+	part1 := data[:mid]
+	part2 := data[mid:]
+
+	var poly uint64 = crc64NVME
+	tab := crc64NVMETable
+	crc1 := crc64.Checksum(part1, tab)
+	crc2 := crc64.Checksum(part2, tab)
+	combined := crc64Combine(poly, crc1, crc2, int64(len(part2)))
+	full := crc64.Checksum(data, tab)
+
+	if combined != full {
+		t.Errorf("crc64Combine failed: got %016x, want %016x", combined, full)
+	}
+}

s3api/utils/csum-reader.go

@@ -26,7 +26,6 @@ import (
 	"hash/crc32"
 	"hash/crc64"
 	"io"
-	"math/bits"
 
 	"github.com/aws/aws-sdk-go-v2/service/s3/types"
 	"github.com/versity/versitygw/s3err"
@@ -89,7 +88,7 @@ func NewHashReader(r io.Reader, expectedSum string, ht HashType) (*HashReader, e
 	case HashTypeCRC32C:
 		hash = crc32.New(crc32.MakeTable(crc32.Castagnoli))
 	case HashTypeCRC64NVME:
-		hash = crc64.New(crc64.MakeTable(bits.Reverse64(0xad93d23594c93659)))
+		hash = crc64.New(crc64NVMETable)
 	case HashTypeNone:
 		hash = noop{}
 	default:
@@ -185,7 +184,7 @@ func (hr *HashReader) Type() HashType {
 	return hr.hashType
 }
 
-// Md5SumString converts the hash bytes to the string checksum value
+// Base64SumString converts the hash bytes to the b64 encoded string checksum value
 func Base64SumString(b []byte) string {
 	return base64.StdEncoding.EncodeToString(b)
 }
@@ -198,6 +197,108 @@ func (n noop) Reset()                      {}
 func (n noop) Size() int                   { return 0 }
 func (n noop) BlockSize() int              { return 1 }
 
+// IsChecksumComposable tests if the final foll object crc can be calculated
+// based on the part crc values.
+func IsChecksumComposable(algo types.ChecksumAlgorithm) bool {
+	switch algo {
+	case types.ChecksumAlgorithmCrc32, types.ChecksumAlgorithmCrc32c, types.ChecksumAlgorithmCrc64nvme:
+		return true
+	default:
+		return false
+	}
+}
+
+// AddCRCChecksum calculates the composite CRC checksum after adding the part crc.
+// Only CRC32, CRC32C, and CRC64NVME are supported. The input checksums must be base64-encoded strings.
+func AddCRCChecksum(algo types.ChecksumAlgorithm, crc, partCrc string, partLen int64) (string, error) {
+	switch algo {
+	case types.ChecksumAlgorithmCrc32:
+		data, err := base64.StdEncoding.DecodeString(partCrc)
+		if err != nil {
+			return "", fmt.Errorf("base64 decode partCrc: %w", err)
+		}
+		if len(data) != 4 {
+			return "", fmt.Errorf("invalid crc32 part checksum length: %d", len(data))
+		}
+		currentCRC, err := base64.StdEncoding.DecodeString(crc)
+		if err != nil {
+			return "", fmt.Errorf("base64 decode crc: %w", err)
+		}
+		if len(currentCRC) != 4 {
+			return "", fmt.Errorf("invalid crc32 checksum length: %d", len(currentCRC))
+		}
+
+		currentVal := uint32(currentCRC[0])<<24 | uint32(currentCRC[1])<<16 | uint32(currentCRC[2])<<8 | uint32(currentCRC[3])
+		val := uint32(data[0])<<24 | uint32(data[1])<<16 | uint32(data[2])<<8 | uint32(data[3])
+		composite := crc32Combine(crc32.IEEE, currentVal, val, partLen)
+
+		out := []byte{
+			byte(composite >> 24),
+			byte(composite >> 16),
+			byte(composite >> 8),
+			byte(composite),
+		}
+		return base64.StdEncoding.EncodeToString(out), nil
+	case types.ChecksumAlgorithmCrc32c:
+		data, err := base64.StdEncoding.DecodeString(partCrc)
+		if err != nil {
+			return "", fmt.Errorf("base64 decode partCrc: %w", err)
+		}
+		if len(data) != 4 {
+			return "", fmt.Errorf("invalid crc32 part checksum length: %d", len(data))
+		}
+		currentCRC, err := base64.StdEncoding.DecodeString(crc)
+		if err != nil {
+			return "", fmt.Errorf("base64 decode crc: %w", err)
+		}
+		if len(currentCRC) != 4 {
+			return "", fmt.Errorf("invalid crc32 checksum length: %d", len(currentCRC))
+		}
+
+		currentVal := uint32(currentCRC[0])<<24 | uint32(currentCRC[1])<<16 | uint32(currentCRC[2])<<8 | uint32(currentCRC[3])
+		val := uint32(data[0])<<24 | uint32(data[1])<<16 | uint32(data[2])<<8 | uint32(data[3])
+		composite := crc32Combine(crc32.Castagnoli, currentVal, val, partLen)
+
+		// Convert composite to big-endian bytes
+		out := []byte{
+			byte(composite >> 24),
+			byte(composite >> 16),
+			byte(composite >> 8),
+			byte(composite),
+		}
+		return base64.StdEncoding.EncodeToString(out), nil
+	case types.ChecksumAlgorithmCrc64nvme:
+		data, err := base64.StdEncoding.DecodeString(partCrc)
+		if err != nil {
+			return "", fmt.Errorf("base64 decode partCrc: %w", err)
+		}
+		if len(data) != 8 {
+			return "", fmt.Errorf("invalid crc64 part checksum length: %d", len(data))
+		}
+		currentCRC, err := base64.StdEncoding.DecodeString(crc)
+		if err != nil {
+			return "", fmt.Errorf("base64 decode crc: %w", err)
+		}
+		if len(currentCRC) != 8 {
+			return "", fmt.Errorf("invalid crc64 checksum length: %d", len(currentCRC))
+		}
+
+		currentVal := uint64(currentCRC[0])<<56 | uint64(currentCRC[1])<<48 | uint64(currentCRC[2])<<40 | uint64(currentCRC[3])<<32 |
+			uint64(currentCRC[4])<<24 | uint64(currentCRC[5])<<16 | uint64(currentCRC[6])<<8 | uint64(currentCRC[7])
+		val := uint64(data[0])<<56 | uint64(data[1])<<48 | uint64(data[2])<<40 | uint64(data[3])<<32 |
+			uint64(data[4])<<24 | uint64(data[5])<<16 | uint64(data[6])<<8 | uint64(data[7])
+		composite := crc64Combine(crc64NVME, currentVal, val, partLen)
+
+		out := []byte{
+			byte(composite >> 56), byte(composite >> 48), byte(composite >> 40), byte(composite >> 32),
+			byte(composite >> 24), byte(composite >> 16), byte(composite >> 8), byte(composite),
+		}
+		return base64.StdEncoding.EncodeToString(out), nil
+	default:
+		return "", fmt.Errorf("composite checksum not supported for algorithm: %v", algo)
+	}
+}
+
 // NewCompositeChecksumReader initializes a composite checksum
 // processor, which decodes and validates the provided
 // checksums and returns the final checksum based on

s3api/utils/csum-reader_test.go

@@ -0,0 +1,120 @@
+// Copyright 2025 Versity Software
+// This file is licensed under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package utils
+
+import (
+	"encoding/base64"
+	"hash/crc32"
+	"hash/crc64"
+	"testing"
+
+	"github.com/aws/aws-sdk-go-v2/service/s3/types"
+)
+
+func TestAddCRCChecksum_CRC32(t *testing.T) {
+	data := []byte("this is a test buffer for crc32")
+	mid := len(data) / 2
+	part1 := data[:mid]
+	part2 := data[mid:]
+
+	crc1 := crc32.Checksum(part1, crc32.IEEETable)
+	crc2 := crc32.Checksum(part2, crc32.IEEETable)
+	crcFull := crc32.Checksum(data, crc32.IEEETable)
+
+	crc1b := []byte{byte(crc1 >> 24), byte(crc1 >> 16), byte(crc1 >> 8), byte(crc1)}
+	crc2b := []byte{byte(crc2 >> 24), byte(crc2 >> 16), byte(crc2 >> 8), byte(crc2)}
+	crc1b64 := base64.StdEncoding.EncodeToString(crc1b)
+	crc2b64 := base64.StdEncoding.EncodeToString(crc2b)
+
+	combined, err := AddCRCChecksum(types.ChecksumAlgorithmCrc32, crc1b64, crc2b64, int64(len(part2)))
+	if err != nil {
+		t.Fatalf("AddCRCChecksum failed: %v", err)
+	}
+	combinedBytes, err := base64.StdEncoding.DecodeString(combined)
+	if err != nil {
+		t.Fatalf("base64 decode failed: %v", err)
+	}
+	combinedVal := uint32(combinedBytes[0])<<24 | uint32(combinedBytes[1])<<16 | uint32(combinedBytes[2])<<8 | uint32(combinedBytes[3])
+	if combinedVal != crcFull {
+		t.Errorf("CRC32 combine mismatch: got %x, want %x", combinedVal, crcFull)
+	}
+}
+
+func TestAddCRCChecksum_CRC32c(t *testing.T) {
+	data := []byte("this is a test buffer for crc32c")
+	mid := len(data) / 2
+	part1 := data[:mid]
+	part2 := data[mid:]
+
+	castagnoli := crc32.MakeTable(crc32.Castagnoli)
+	crc1 := crc32.Checksum(part1, castagnoli)
+	crc2 := crc32.Checksum(part2, castagnoli)
+	crcFull := crc32.Checksum(data, castagnoli)
+
+	crc1b := []byte{byte(crc1 >> 24), byte(crc1 >> 16), byte(crc1 >> 8), byte(crc1)}
+	crc2b := []byte{byte(crc2 >> 24), byte(crc2 >> 16), byte(crc2 >> 8), byte(crc2)}
+	crc1b64 := base64.StdEncoding.EncodeToString(crc1b)
+	crc2b64 := base64.StdEncoding.EncodeToString(crc2b)
+
+	combined, err := AddCRCChecksum(types.ChecksumAlgorithmCrc32c, crc1b64, crc2b64, int64(len(part2)))
+	if err != nil {
+		t.Fatalf("AddCRCChecksum failed: %v", err)
+	}
+	combinedBytes, err := base64.StdEncoding.DecodeString(combined)
+	if err != nil {
+		t.Fatalf("base64 decode failed: %v", err)
+	}
+	combinedVal := uint32(combinedBytes[0])<<24 | uint32(combinedBytes[1])<<16 | uint32(combinedBytes[2])<<8 | uint32(combinedBytes[3])
+	if combinedVal != crcFull {
+		t.Errorf("CRC32c combine mismatch: got %x, want %x", combinedVal, crcFull)
+	}
+}
+
+func TestAddCRCChecksum_CRC64NVME(t *testing.T) {
+	data := []byte("this is a test buffer for crc64nvme")
+	mid := len(data) / 2
+	part1 := data[:mid]
+	part2 := data[mid:]
+
+	table := crc64NVMETable
+	crc1 := crc64.Checksum(part1, table)
+	crc2 := crc64.Checksum(part2, table)
+	crcFull := crc64.Checksum(data, table)
+
+	crc1b := []byte{
+		byte(crc1 >> 56), byte(crc1 >> 48), byte(crc1 >> 40), byte(crc1 >> 32),
+		byte(crc1 >> 24), byte(crc1 >> 16), byte(crc1 >> 8), byte(crc1),
+	}
+	crc2b := []byte{
+		byte(crc2 >> 56), byte(crc2 >> 48), byte(crc2 >> 40), byte(crc2 >> 32),
+		byte(crc2 >> 24), byte(crc2 >> 16), byte(crc2 >> 8), byte(crc2),
+	}
+	crc1b64 := base64.StdEncoding.EncodeToString(crc1b)
+	crc2b64 := base64.StdEncoding.EncodeToString(crc2b)
+
+	combined, err := AddCRCChecksum(types.ChecksumAlgorithmCrc64nvme, crc1b64, crc2b64, int64(len(part2)))
+	if err != nil {
+		t.Fatalf("AddCRCChecksum failed: %v", err)
+	}
+	combinedBytes, err := base64.StdEncoding.DecodeString(combined)
+	if err != nil {
+		t.Fatalf("base64 decode failed: %v", err)
+	}
+	combinedVal := uint64(combinedBytes[0])<<56 | uint64(combinedBytes[1])<<48 | uint64(combinedBytes[2])<<40 | uint64(combinedBytes[3])<<32 |
+		uint64(combinedBytes[4])<<24 | uint64(combinedBytes[5])<<16 | uint64(combinedBytes[6])<<8 | uint64(combinedBytes[7])
+	if combinedVal != crcFull {
+		t.Errorf("CRC64NVME combine mismatch: got %x, want %x", combinedVal, crcFull)
+	}
+}