Remove old serialization format code (#4410)

Remove the now unused serialization format
code that lived in the kopia package

---

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* closes #4328

#### Test Plan

- [x] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

src/internal/kopia/upload.go

@@ -1,13 +1,9 @@
 package kopia
 
 import (
-	"bytes"
 	"context"
 	"encoding/base64"
-	"encoding/binary"
 	"errors"
-	"io"
-	"os"
 	"runtime/trace"
 	"strings"
 	"sync"
@@ -23,7 +19,6 @@ import (
 
 	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/common/ptr"
-	"github.com/alcionai/corso/src/internal/common/readers"
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/diagnostics"
 	"github.com/alcionai/corso/src/internal/m365/graph"
@@ -37,101 +32,6 @@ import (
 
 const maxInflateTraversalDepth = 500
 
-var versionSize = readers.VersionFormatSize
-
-func newBackupStreamReader(version uint32, reader io.ReadCloser) *backupStreamReader {
-	buf := make([]byte, versionSize)
-	binary.BigEndian.PutUint32(buf, version)
-	bufReader := io.NopCloser(bytes.NewReader(buf))
-
-	return &backupStreamReader{
-		readers:  []io.ReadCloser{bufReader, reader},
-		combined: io.NopCloser(io.MultiReader(bufReader, reader)),
-	}
-}
-
-// backupStreamReader is a wrapper around the io.Reader that other Corso
-// components return when backing up information. It injects a version number at
-// the start of the data stream. Future versions of Corso may not need this if
-// they use more complex serialization logic as serialization/version injection
-// will be handled by other components.
-type backupStreamReader struct {
-	readers  []io.ReadCloser
-	combined io.ReadCloser
-}
-
-func (rw *backupStreamReader) Read(p []byte) (n int, err error) {
-	if rw.combined == nil {
-		return 0, os.ErrClosed
-	}
-
-	return rw.combined.Read(p)
-}
-
-func (rw *backupStreamReader) Close() error {
-	if rw.combined == nil {
-		return nil
-	}
-
-	rw.combined = nil
-
-	var errs *clues.Err
-
-	for _, r := range rw.readers {
-		err := r.Close()
-		if err != nil {
-			errs = clues.Stack(clues.Wrap(err, "closing reader"), errs)
-		}
-	}
-
-	return errs.OrNil()
-}
-
-// restoreStreamReader is a wrapper around the io.Reader that kopia returns when
-// reading data from an item. It examines and strips off the version number of
-// the restored data. Future versions of Corso may not need this if they use
-// more complex serialization logic as version checking/deserialization will be
-// handled by other components. A reader that returns a version error is no
-// longer valid and should not be used once the version error is returned.
-type restoreStreamReader struct {
-	io.ReadCloser
-	expectedVersion uint32
-	readVersion     bool
-}
-
-func (rw *restoreStreamReader) checkVersion() error {
-	versionBuf := make([]byte, versionSize)
-
-	for newlyRead := 0; newlyRead < versionSize; {
-		n, err := rw.ReadCloser.Read(versionBuf[newlyRead:])
-		if err != nil {
-			return clues.Wrap(err, "reading data format version")
-		}
-
-		newlyRead += n
-	}
-
-	version := binary.BigEndian.Uint32(versionBuf)
-
-	if version != rw.expectedVersion {
-		return clues.New("unexpected data format").With("read_version", version)
-	}
-
-	return nil
-}
-
-func (rw *restoreStreamReader) Read(p []byte) (n int, err error) {
-	if !rw.readVersion {
-		rw.readVersion = true
-
-		if err := rw.checkVersion(); err != nil {
-			return 0, err
-		}
-	}
-
-	return rw.ReadCloser.Read(p)
-}
-
 type itemDetails struct {
 	infoer       data.ItemInfo
 	repoPath     path.Path

src/internal/kopia/upload_test.go

@@ -14,7 +14,6 @@ import (
 	"github.com/kopia/kopia/repo/manifest"
 	"github.com/kopia/kopia/snapshot"
 	"github.com/kopia/kopia/snapshot/snapshotfs"
-	"github.com/pkg/errors"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
@@ -220,135 +219,6 @@ func getDirEntriesForEntry(
 // ---------------
 // unit tests
 // ---------------
-type limitedRangeReader struct {
-	readLen int
-	io.ReadCloser
-}
-
-func (lrr *limitedRangeReader) Read(p []byte) (int, error) {
-	if len(p) == 0 {
-		// Not well specified behavior, defer to underlying reader.
-		return lrr.ReadCloser.Read(p)
-	}
-
-	toRead := lrr.readLen
-	if len(p) < toRead {
-		toRead = len(p)
-	}
-
-	return lrr.ReadCloser.Read(p[:toRead])
-}
-
-type VersionReadersUnitSuite struct {
-	tester.Suite
-}
-
-func TestVersionReadersUnitSuite(t *testing.T) {
-	suite.Run(t, &VersionReadersUnitSuite{Suite: tester.NewUnitSuite(t)})
-}
-
-func (suite *VersionReadersUnitSuite) TestWriteAndRead() {
-	inputData := []byte("This is some data for the reader to test with")
-	table := []struct {
-		name         string
-		readVersion  uint32
-		writeVersion uint32
-		check        assert.ErrorAssertionFunc
-	}{
-		{
-			name:         "SameVersionSucceeds",
-			readVersion:  42,
-			writeVersion: 42,
-			check:        assert.NoError,
-		},
-		{
-			name:         "DifferentVersionsFail",
-			readVersion:  7,
-			writeVersion: 42,
-			check:        assert.Error,
-		},
-	}
-
-	for _, test := range table {
-		suite.Run(test.name, func() {
-			t := suite.T()
-
-			baseReader := bytes.NewReader(inputData)
-
-			reversible := &restoreStreamReader{
-				expectedVersion: test.readVersion,
-				ReadCloser: newBackupStreamReader(
-					test.writeVersion,
-					io.NopCloser(baseReader)),
-			}
-
-			defer reversible.Close()
-
-			allData, err := io.ReadAll(reversible)
-			test.check(t, err, clues.ToCore(err))
-
-			if err != nil {
-				return
-			}
-
-			assert.Equal(t, inputData, allData)
-		})
-	}
-}
-
-func readAllInParts(
-	t *testing.T,
-	partLen int,
-	reader io.ReadCloser,
-) ([]byte, int) {
-	res := []byte{}
-	read := 0
-	tmp := make([]byte, partLen)
-
-	for {
-		n, err := reader.Read(tmp)
-		if errors.Is(err, io.EOF) {
-			break
-		}
-
-		require.NoError(t, err, clues.ToCore(err))
-
-		read += n
-		res = append(res, tmp[:n]...)
-	}
-
-	return res, read
-}
-
-func (suite *VersionReadersUnitSuite) TestWriteHandlesShortReads() {
-	t := suite.T()
-	inputData := []byte("This is some data for the reader to test with")
-	version := uint32(42)
-	baseReader := bytes.NewReader(inputData)
-	versioner := newBackupStreamReader(version, io.NopCloser(baseReader))
-	expectedToWrite := len(inputData) + int(versionSize)
-
-	// "Write" all the data.
-	versionedData, writtenLen := readAllInParts(t, 1, versioner)
-	assert.Equal(t, expectedToWrite, writtenLen)
-
-	// Read all of the data back.
-	baseReader = bytes.NewReader(versionedData)
-	reader := &restoreStreamReader{
-		expectedVersion: version,
-		// Be adversarial and only allow reads of length 1 from the byte reader.
-		ReadCloser: &limitedRangeReader{
-			readLen:    1,
-			ReadCloser: io.NopCloser(baseReader),
-		},
-	}
-	readData, readLen := readAllInParts(t, 1, reader)
-	// This reports the bytes read and returned to the user, excluding the version
-	// that is stripped off at the start.
-	assert.Equal(t, len(inputData), readLen)
-	assert.Equal(t, inputData, readData)
-}
-
 type CorsoProgressUnitSuite struct {
 	tester.Suite
 	targetFilePath path.Path