From 3a02ef24e09a6ead82d73ff52eaf0854312a8e5b Mon Sep 17 00:00:00 2001
From: Jarek Kowalski <jaak@jkowalski.net>
Date: Sat, 5 May 2018 10:34:39 -0700
Subject: [PATCH] retire block.ContentID and replace with string

---
 block/block_manager.go                    | 53 ++++++++++-------------
 block/block_manager_test.go               | 16 +++----
 block/committed_block_index.go            |  6 +--
 block/inmemory_committed_block_index.go   |  6 +--
 block/simple_committed_block_index.go     |  4 +-
 cli/command_block_list.go                 |  2 +-
 cli/command_block_rm.go                   |  5 +--
 cli/command_block_show.go                 |  5 +--
 cli/command_object_ls.go                  |  3 +-
 internal/packindex/builder.go             |  8 ++--
 internal/packindex/content_id_to_bytes.go | 10 ++---
 internal/packindex/index.go               | 16 +++----
 internal/packindex/info.go                |  5 +--
 internal/packindex/merged.go              |  6 +--
 internal/packindex/merged_test.go         |  4 +-
 internal/packindex/packindex_test.go      |  8 ++--
 manifest/manifest_manager.go              | 12 ++---
 object/object_manager.go                  | 10 ++---
 object/object_manager_test.go             | 16 +++----
 object/object_writer.go                   | 11 +++--
 object/objectid.go                        |  8 ++--
 tests/stress_test/stress_test.go          |  2 +-
 22 files changed, 102 insertions(+), 114 deletions(-)

diff --git a/block/block_manager.go b/block/block_manager.go
index 799b1fdd1..d4217edfb 100644
--- a/block/block_manager.go
+++ b/block/block_manager.go
@@ -43,11 +43,6 @@ const (
 // Info is an information about a single block managed by Manager.
 type Info = packindex.Info
 
-// ContentID uniquely identifies a block of content stored in repository.
-// It consists of optional one-character prefix (which can't be 0..9 or a..f) followed by hexa-decimal
-// digits representing hash of the content.
-type ContentID = packindex.ContentID
-
 // PhysicalBlockID identifies physical storage block.
 type PhysicalBlockID = packindex.PhysicalBlockID
 
@@ -69,9 +64,9 @@ type Manager struct {
 	locked                  bool
 	checkInvariantsOnUnlock bool
 
-	currentPackItems      map[ContentID]Info // blocks that are in the pack block currently being built (all inline)
-	currentPackDataLength int                // total length of all items in the current pack block
-	packIndexBuilder      packindex.Builder  // blocks that are in index currently being built (current pack and all packs saved but not committed)
+	currentPackItems      map[string]Info   // blocks that are in the pack block currently being built (all inline)
+	currentPackDataLength int               // total length of all items in the current pack block
+	packIndexBuilder      packindex.Builder // blocks that are in index currently being built (current pack and all packs saved but not committed)
 	committedBlocks       committedBlockIndex
 
 	flushPackIndexesAfter time.Time // time when those indexes should be flushed
@@ -93,7 +88,7 @@ type Manager struct {
 // NOTE: To avoid race conditions only blocks that cannot be possibly re-created
 // should ever be deleted. That means that contents of such blocks should include some element
 // of randomness or a contemporaneous timestamp that will never reappear.
-func (bm *Manager) DeleteBlock(blockID ContentID) error {
+func (bm *Manager) DeleteBlock(blockID string) error {
 	bm.lock()
 	defer bm.unlock()
 
@@ -121,7 +116,7 @@ func (bm *Manager) setPendingBlock(i Info) {
 	bm.currentPackItems[i.BlockID] = i
 }
 
-func (bm *Manager) addToPackLocked(ctx context.Context, blockID ContentID, data []byte) error {
+func (bm *Manager) addToPackLocked(ctx context.Context, blockID string, data []byte) error {
 	bm.assertLocked()
 
 	bm.currentPackDataLength += len(data)
@@ -234,7 +229,7 @@ func (bm *Manager) invariantViolated(msg string, arg ...interface{}) {
 }
 
 func (bm *Manager) startPackIndexLocked() {
-	bm.currentPackItems = make(map[ContentID]Info)
+	bm.currentPackItems = make(map[string]Info)
 	bm.currentPackDataLength = 0
 }
 
@@ -306,13 +301,13 @@ func (bm *Manager) writePackBlockLocked(ctx context.Context) error {
 	return nil
 }
 
-func (bm *Manager) preparePackDataBlock() ([]byte, map[ContentID]Info, error) {
+func (bm *Manager) preparePackDataBlock() ([]byte, map[string]Info, error) {
 	blockData, err := appendRandomBytes(nil, rand.Intn(bm.maxPreambleLength-bm.minPreambleLength+1)+bm.minPreambleLength)
 	if err != nil {
 		return nil, nil, fmt.Errorf("unable to prepare block preamble: %v", err)
 	}
 
-	pending := map[ContentID]Info{}
+	pending := map[string]Info{}
 	for blockID, info := range bm.currentPackItems {
 		if info.Deleted {
 			continue
@@ -351,7 +346,7 @@ func (bm *Manager) preparePackDataBlock() ([]byte, map[ContentID]Info, error) {
 
 }
 
-func (bm *Manager) maybeEncryptBlockDataForPacking(data []byte, blockID ContentID) ([]byte, error) {
+func (bm *Manager) maybeEncryptBlockDataForPacking(data []byte, blockID string) ([]byte, error) {
 	if bm.writeFormatVersion == 0 {
 		// in v0 the entire block is encrypted together later on
 		return data, nil
@@ -510,14 +505,14 @@ func (bm *Manager) CompactIndexes(ctx context.Context) error {
 }
 
 // ListBlocks returns the metadata about blocks with a given prefix and kind.
-func (bm *Manager) ListBlocks(prefix ContentID) ([]Info, error) {
+func (bm *Manager) ListBlocks(prefix string) ([]Info, error) {
 	bm.lock()
 	defer bm.unlock()
 
 	var result []Info
 
 	appendToResult := func(i Info) error {
-		if i.Deleted || !strings.HasPrefix(string(i.BlockID), string(prefix)) {
+		if i.Deleted || !strings.HasPrefix(i.BlockID, prefix) {
 			return nil
 		}
 		if bi, ok := bm.packIndexBuilder[i.BlockID]; ok && bi.Deleted {
@@ -587,11 +582,11 @@ func (bm *Manager) Flush(ctx context.Context) error {
 
 // WriteBlock saves a given block of data to a pack group with a provided name and returns a blockID
 // that's based on the contents of data written.
-func (bm *Manager) WriteBlock(ctx context.Context, data []byte, prefix ContentID) (ContentID, error) {
+func (bm *Manager) WriteBlock(ctx context.Context, data []byte, prefix string) (string, error) {
 	if err := validatePrefix(prefix); err != nil {
 		return "", err
 	}
-	blockID := prefix + ContentID(hex.EncodeToString(bm.hashData(data)))
+	blockID := prefix + hex.EncodeToString(bm.hashData(data))
 
 	bm.lock()
 	defer bm.unlock()
@@ -609,7 +604,7 @@ func (bm *Manager) WriteBlock(ctx context.Context, data []byte, prefix ContentID
 	return blockID, err
 }
 
-func validatePrefix(prefix ContentID) error {
+func validatePrefix(prefix string) error {
 	switch len(prefix) {
 	case 0:
 		return nil
@@ -672,7 +667,7 @@ func (bm *Manager) hashData(data []byte) []byte {
 	return blockID
 }
 
-func (bm *Manager) getPendingBlockLocked(blockID ContentID) ([]byte, error) {
+func (bm *Manager) getPendingBlockLocked(blockID string) ([]byte, error) {
 	bm.assertLocked()
 
 	bi, ok := bm.currentPackItems[blockID]
@@ -684,7 +679,7 @@ func (bm *Manager) getPendingBlockLocked(blockID ContentID) ([]byte, error) {
 }
 
 // GetBlock gets the contents of a given block. If the block is not found returns blob.ErrBlockNotFound.
-func (bm *Manager) GetBlock(ctx context.Context, blockID ContentID) ([]byte, error) {
+func (bm *Manager) GetBlock(ctx context.Context, blockID string) ([]byte, error) {
 	bm.lock()
 	defer bm.unlock()
 
@@ -704,14 +699,14 @@ func (bm *Manager) GetIndexBlock(ctx context.Context, blockID PhysicalBlockID) (
 }
 
 // BlockInfo returns information about a single block.
-func (bm *Manager) BlockInfo(ctx context.Context, blockID ContentID) (Info, error) {
+func (bm *Manager) BlockInfo(ctx context.Context, blockID string) (Info, error) {
 	bm.lock()
 	defer bm.unlock()
 
 	return bm.packedBlockInfoLocked(blockID)
 }
 
-func (bm *Manager) packedBlockInfoLocked(blockID ContentID) (Info, error) {
+func (bm *Manager) packedBlockInfoLocked(blockID string) (Info, error) {
 	bm.assertLocked()
 
 	if bi, ok := bm.packIndexBuilder[blockID]; ok {
@@ -725,7 +720,7 @@ func (bm *Manager) packedBlockInfoLocked(blockID ContentID) (Info, error) {
 	return bm.committedBlocks.getBlock(blockID)
 }
 
-func (bm *Manager) getPackedBlockInternalLocked(ctx context.Context, blockID ContentID) ([]byte, error) {
+func (bm *Manager) getPackedBlockInternalLocked(ctx context.Context, blockID string) ([]byte, error) {
 	bm.assertLocked()
 
 	bi, err := bm.packedBlockInfoLocked(blockID)
@@ -739,7 +734,7 @@ func (bm *Manager) getPackedBlockInternalLocked(ctx context.Context, blockID Con
 	}
 
 	packBlockID := bi.PackBlockID
-	payload, err := bm.cache.getBlock(ctx, string(blockID), packBlockID, int64(bi.PackOffset), int64(bi.Length))
+	payload, err := bm.cache.getBlock(ctx, blockID, packBlockID, int64(bi.PackOffset), int64(bi.Length))
 	if err != nil {
 		return nil, err
 	}
@@ -747,7 +742,7 @@ func (bm *Manager) getPackedBlockInternalLocked(ctx context.Context, blockID Con
 	return bm.decryptAndVerifyPayload(bi.FormatVersion, payload, int(bi.PackOffset), blockID, packBlockID)
 }
 
-func (bm *Manager) decryptAndVerifyPayload(formatVersion byte, payload []byte, offset int, blockID ContentID, packBlockID PhysicalBlockID) ([]byte, error) {
+func (bm *Manager) decryptAndVerifyPayload(formatVersion byte, payload []byte, offset int, blockID string, packBlockID PhysicalBlockID) ([]byte, error) {
 	atomic.AddInt32(&bm.stats.ReadBlocks, 1)
 	atomic.AddInt64(&bm.stats.ReadBytes, int64(len(payload)))
 
@@ -818,8 +813,8 @@ func (bm *Manager) getPhysicalBlockInternal(ctx context.Context, blockID Physica
 	return payload, nil
 }
 
-func getPackedBlockIV(s ContentID) ([]byte, error) {
-	return hex.DecodeString(string(s[len(s)-(aes.BlockSize*2):]))
+func getPackedBlockIV(blockID string) ([]byte, error) {
+	return hex.DecodeString(blockID[len(blockID)-(aes.BlockSize*2):])
 }
 
 func getPhysicalBlockIV(b PhysicalBlockID) ([]byte, error) {
@@ -952,7 +947,7 @@ func newManagerWithOptions(ctx context.Context, st storage.Storage, f Formatting
 		flushPackIndexesAfter: timeNow().Add(flushPackIndexTimeout),
 		maxPackSize:           f.MaxPackSize,
 		formatter:             formatter,
-		currentPackItems:      make(map[ContentID]Info),
+		currentPackItems:      make(map[string]Info),
 		packIndexBuilder:      packindex.NewBuilder(),
 		committedBlocks:       cbi,
 		minPreambleLength:     defaultMinPreambleLength,
diff --git a/block/block_manager_test.go b/block/block_manager_test.go
index ec4302947..971260ba8 100644
--- a/block/block_manager_test.go
+++ b/block/block_manager_test.go
@@ -146,7 +146,7 @@ func TestBlockManagerEmpty(t *testing.T) {
 	keyTime := map[string]time.Time{}
 	bm := newTestBlockManager(data, keyTime, nil)
 
-	noSuchBlockID := ContentID(md5hash([]byte("foo")))
+	noSuchBlockID := string(md5hash([]byte("foo")))
 
 	b, err := bm.GetBlock(ctx, noSuchBlockID)
 	if err != storage.ErrBlockNotFound {
@@ -220,7 +220,7 @@ func TestBlockManagerWriteMultiple(t *testing.T) {
 	keyTime := map[string]time.Time{}
 	bm := newTestBlockManager(data, keyTime, nil)
 
-	var blockIDs []ContentID
+	var blockIDs []string
 
 	for i := 0; i < 5000; i++ {
 		//t.Logf("i=%v", i)
@@ -439,7 +439,7 @@ func verifyVersionCompat(t *testing.T, writeVersion int) {
 	mgr := newTestBlockManager(data, keyTime, nil)
 	mgr.writeFormatVersion = int32(writeVersion)
 
-	dataSet := map[ContentID][]byte{}
+	dataSet := map[string][]byte{}
 
 	for i := 0; i < 3000000; i = (i + 1) * 2 {
 		data := make([]byte, i)
@@ -487,7 +487,7 @@ func verifyVersionCompat(t *testing.T, writeVersion int) {
 	verifyBlockManagerDataSet(ctx, t, mgr, dataSet)
 }
 
-func verifyBlockManagerDataSet(ctx context.Context, t *testing.T, mgr *Manager, dataSet map[ContentID][]byte) {
+func verifyBlockManagerDataSet(ctx context.Context, t *testing.T, mgr *Manager, dataSet map[string][]byte) {
 	for blockID, originalPayload := range dataSet {
 		v, err := mgr.GetBlock(ctx, blockID)
 		if err != nil {
@@ -546,7 +546,7 @@ func fakeTimeNowWithAutoAdvance(t time.Time, dt time.Duration) func() time.Time
 	}
 }
 
-func verifyBlockNotFound(ctx context.Context, t *testing.T, bm *Manager, blockID ContentID) {
+func verifyBlockNotFound(ctx context.Context, t *testing.T, bm *Manager, blockID string) {
 	t.Helper()
 
 	b, err := bm.GetBlock(ctx, blockID)
@@ -555,7 +555,7 @@ func verifyBlockNotFound(ctx context.Context, t *testing.T, bm *Manager, blockID
 	}
 }
 
-func verifyBlock(ctx context.Context, t *testing.T, bm *Manager, blockID ContentID, b []byte) {
+func verifyBlock(ctx context.Context, t *testing.T, bm *Manager, blockID string, b []byte) {
 	t.Helper()
 
 	b2, err := bm.GetBlock(ctx, blockID)
@@ -578,7 +578,7 @@ func verifyBlock(ctx context.Context, t *testing.T, bm *Manager, blockID Content
 	}
 
 }
-func writeBlockAndVerify(ctx context.Context, t *testing.T, bm *Manager, b []byte) ContentID {
+func writeBlockAndVerify(ctx context.Context, t *testing.T, bm *Manager, b []byte) string {
 	t.Helper()
 
 	blockID, err := bm.WriteBlock(ctx, b, "")
@@ -586,7 +586,7 @@ func writeBlockAndVerify(ctx context.Context, t *testing.T, bm *Manager, b []byt
 		t.Errorf("err: %v", err)
 	}
 
-	if got, want := blockID, ContentID(md5hash(b)); got != want {
+	if got, want := blockID, string(md5hash(b)); got != want {
 		t.Errorf("invalid block ID for %x, got %v, want %v", b, got, want)
 	}
 
diff --git a/block/committed_block_index.go b/block/committed_block_index.go
index dff258e19..af7cf1885 100644
--- a/block/committed_block_index.go
+++ b/block/committed_block_index.go
@@ -5,16 +5,16 @@ import (
 )
 
 type committedBlockIndex interface {
-	getBlock(blockID ContentID) (Info, error)
+	getBlock(blockID string) (Info, error)
 	commit(indexBlockID PhysicalBlockID, pendingBlocks packindex.Builder) error
 	load(indexBlockID PhysicalBlockID, data []byte) (int, error)
-	listBlocks(prefix ContentID, cb func(i Info) error) error
+	listBlocks(prefix string, cb func(i Info) error) error
 	hasIndexBlockID(indexBlockID PhysicalBlockID) (bool, error)
 }
 
 func newCommittedBlockIndex() committedBlockIndex {
 	return &inMemoryCommittedBlockIndex{
-		blocks:         make(map[ContentID]Info),
+		blocks:         make(map[string]Info),
 		physicalBlocks: make(map[PhysicalBlockID]bool),
 	}
 }
diff --git a/block/inmemory_committed_block_index.go b/block/inmemory_committed_block_index.go
index 93170d806..7e864b02a 100644
--- a/block/inmemory_committed_block_index.go
+++ b/block/inmemory_committed_block_index.go
@@ -11,11 +11,11 @@ import (
 
 type inMemoryCommittedBlockIndex struct {
 	mu             sync.Mutex
-	blocks         map[ContentID]Info
+	blocks         map[string]Info
 	physicalBlocks map[PhysicalBlockID]bool
 }
 
-func (b *inMemoryCommittedBlockIndex) getBlock(blockID ContentID) (Info, error) {
+func (b *inMemoryCommittedBlockIndex) getBlock(blockID string) (Info, error) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
@@ -66,7 +66,7 @@ func (b *inMemoryCommittedBlockIndex) load(indexBlockID PhysicalBlockID, data []
 	return updated, nil
 }
 
-func (b *inMemoryCommittedBlockIndex) listBlocks(prefix ContentID, cb func(i Info) error) error {
+func (b *inMemoryCommittedBlockIndex) listBlocks(prefix string, cb func(i Info) error) error {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
diff --git a/block/simple_committed_block_index.go b/block/simple_committed_block_index.go
index 713a05893..ebcac4d96 100644
--- a/block/simple_committed_block_index.go
+++ b/block/simple_committed_block_index.go
@@ -23,7 +23,7 @@ type simpleCommittedBlockIndex struct {
 	merged       packindex.Merged
 }
 
-func (b *simpleCommittedBlockIndex) getBlock(blockID ContentID) (Info, error) {
+func (b *simpleCommittedBlockIndex) getBlock(blockID string) (Info, error) {
 	info, err := b.merged.GetInfo(blockID)
 	if info != nil {
 		return *info, nil
@@ -89,7 +89,7 @@ func (b *simpleCommittedBlockIndex) load(indexBlockID PhysicalBlockID, data []by
 	return 0, nil
 }
 
-func (b *simpleCommittedBlockIndex) listBlocks(prefix ContentID, cb func(i Info) error) error {
+func (b *simpleCommittedBlockIndex) listBlocks(prefix string, cb func(i Info) error) error {
 	return b.merged.Iterate(prefix, cb)
 }
 
diff --git a/cli/command_block_list.go b/cli/command_block_list.go
index 449d7395b..b80aeb34b 100644
--- a/cli/command_block_list.go
+++ b/cli/command_block_list.go
@@ -19,7 +19,7 @@ var (
 )
 
 func runListBlocksAction(ctx context.Context, rep *repo.Repository) error {
-	blocks, err := rep.Blocks.ListBlocks(block.ContentID(*blockListPrefix))
+	blocks, err := rep.Blocks.ListBlocks(*blockListPrefix)
 	if err != nil {
 		return err
 	}
diff --git a/cli/command_block_rm.go b/cli/command_block_rm.go
index 695847051..5e4d6835f 100644
--- a/cli/command_block_rm.go
+++ b/cli/command_block_rm.go
@@ -3,7 +3,6 @@ package cli
 import (
 	"context"
 
-	"github.com/kopia/kopia/block"
 	"github.com/kopia/kopia/repo"
 )
 
@@ -15,7 +14,7 @@ var (
 
 func runRemoveBlockCommand(ctx context.Context, rep *repo.Repository) error {
 	for _, blockID := range *removeBlockIDs {
-		if err := removeBlock(rep, block.ContentID(blockID)); err != nil {
+		if err := removeBlock(rep, blockID); err != nil {
 			return err
 		}
 	}
@@ -23,7 +22,7 @@ func runRemoveBlockCommand(ctx context.Context, rep *repo.Repository) error {
 	return nil
 }
 
-func removeBlock(r *repo.Repository, blockID block.ContentID) error {
+func removeBlock(r *repo.Repository, blockID string) error {
 	return r.Blocks.DeleteBlock(blockID)
 }
 
diff --git a/cli/command_block_show.go b/cli/command_block_show.go
index 9d4352809..019dc4def 100644
--- a/cli/command_block_show.go
+++ b/cli/command_block_show.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 
-	"github.com/kopia/kopia/block"
 	"github.com/kopia/kopia/repo"
 )
 
@@ -16,7 +15,7 @@ var (
 
 func runShowBlockCommand(ctx context.Context, rep *repo.Repository) error {
 	for _, blockID := range *showBlockIDs {
-		if err := showBlock(ctx, rep, block.ContentID(blockID)); err != nil {
+		if err := showBlock(ctx, rep, blockID); err != nil {
 			return err
 		}
 	}
@@ -24,7 +23,7 @@ func runShowBlockCommand(ctx context.Context, rep *repo.Repository) error {
 	return nil
 }
 
-func showBlock(ctx context.Context, r *repo.Repository, blockID block.ContentID) error {
+func showBlock(ctx context.Context, r *repo.Repository, blockID string) error {
 	data, err := r.Blocks.GetBlock(ctx, blockID)
 	if err != nil {
 		return err
diff --git a/cli/command_object_ls.go b/cli/command_object_ls.go
index 66ddba92f..99b9009ea 100644
--- a/cli/command_object_ls.go
+++ b/cli/command_object_ls.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 
-	"github.com/kopia/kopia/block"
 	"github.com/kopia/kopia/repo"
 )
 
@@ -14,7 +13,7 @@ var (
 )
 
 func runListObjectsAction(ctx context.Context, rep *repo.Repository) error {
-	info, err := rep.Blocks.ListBlocks(block.ContentID(*objectListPrefix))
+	info, err := rep.Blocks.ListBlocks(*objectListPrefix)
 	if err != nil {
 		return err
 	}
diff --git a/internal/packindex/builder.go b/internal/packindex/builder.go
index 50fa2f4ce..30e5df7e7 100644
--- a/internal/packindex/builder.go
+++ b/internal/packindex/builder.go
@@ -9,7 +9,7 @@ import (
 )
 
 // Builder prepares and writes block index for writing.
-type Builder map[ContentID]*Info
+type Builder map[string]*Info
 
 // Add adds a new entry to the builder or conditionally replaces it if the timestamp is greater.
 func (b Builder) Add(i Info) {
@@ -35,7 +35,7 @@ func (b Builder) sortedBlocks() []*Info {
 
 type indexLayout struct {
 	packBlockIDOffsets map[PhysicalBlockID]uint32
-	payloadOffsets     map[ContentID]uint32
+	payloadOffsets     map[string]uint32
 	entryCount         int
 	keyLength          int
 	entryLength        int
@@ -47,7 +47,7 @@ func (b Builder) Build(output io.Writer) error {
 	allBlocks := b.sortedBlocks()
 	layout := &indexLayout{
 		packBlockIDOffsets: map[PhysicalBlockID]uint32{},
-		payloadOffsets:     map[ContentID]uint32{},
+		payloadOffsets:     map[string]uint32{},
 		keyLength:          -1,
 		entryLength:        20,
 		entryCount:         len(allBlocks),
@@ -159,5 +159,5 @@ func formatEntry(entry []byte, it *Info, layout *indexLayout) error {
 
 // NewBuilder creates a new Builder.
 func NewBuilder() Builder {
-	return make(map[ContentID]*Info)
+	return make(map[string]*Info)
 }
diff --git a/internal/packindex/content_id_to_bytes.go b/internal/packindex/content_id_to_bytes.go
index bc82787d2..bc123a2a6 100644
--- a/internal/packindex/content_id_to_bytes.go
+++ b/internal/packindex/content_id_to_bytes.go
@@ -4,22 +4,22 @@ import (
 	"encoding/hex"
 )
 
-func bytesToContentID(b []byte) ContentID {
+func bytesToContentID(b []byte) string {
 	if len(b) == 0 {
 		return ""
 	}
 	if b[0] == 0xff {
-		return ContentID(b[1:])
+		return string(b[1:])
 	}
 	prefix := ""
 	if b[0] != 0 {
 		prefix = string(b[0:1])
 	}
 
-	return ContentID(prefix + hex.EncodeToString(b[1:]))
+	return prefix + hex.EncodeToString(b[1:])
 }
 
-func contentIDToBytes(c ContentID) []byte {
+func contentIDToBytes(c string) []byte {
 	var prefix []byte
 	if len(c)%2 == 1 {
 		prefix = []byte(c[0:1])
@@ -28,7 +28,7 @@ func contentIDToBytes(c ContentID) []byte {
 		prefix = []byte{0}
 	}
 
-	b, err := hex.DecodeString(string(c))
+	b, err := hex.DecodeString(c)
 	if err != nil {
 		return append([]byte{0xff}, []byte(c)...)
 	}
diff --git a/internal/packindex/index.go b/internal/packindex/index.go
index 90e3c33d2..de3a2778e 100644
--- a/internal/packindex/index.go
+++ b/internal/packindex/index.go
@@ -15,8 +15,8 @@ type Index interface {
 	io.Closer
 
 	EntryCount() int
-	GetInfo(blockID ContentID) (*Info, error)
-	Iterate(prefix ContentID, cb func(Info) error) error
+	GetInfo(blockID string) (*Info, error)
+	Iterate(prefix string, cb func(Info) error) error
 }
 
 type index struct {
@@ -57,7 +57,7 @@ func (b *index) EntryCount() int {
 // Iterate invokes the provided callback function for all blocks in the index, sorted alphabetically.
 // The iteration ends when the callback returns an error, which is propagated to the caller or when
 // all blocks have been visited.
-func (b *index) Iterate(prefix ContentID, cb func(Info) error) error {
+func (b *index) Iterate(prefix string, cb func(Info) error) error {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
@@ -80,7 +80,7 @@ func (b *index) Iterate(prefix ContentID, cb func(Info) error) error {
 		if err != nil {
 			return fmt.Errorf("invalid index data: %v", err)
 		}
-		if !strings.HasPrefix(string(i.BlockID), string(prefix)) {
+		if !strings.HasPrefix(i.BlockID, prefix) {
 			break
 		}
 		if err := cb(i); err != nil {
@@ -90,7 +90,7 @@ func (b *index) Iterate(prefix ContentID, cb func(Info) error) error {
 	return nil
 }
 
-func (b *index) findEntryPosition(blockID ContentID) (int, error) {
+func (b *index) findEntryPosition(blockID string) (int, error) {
 	stride := b.hdr.keySize + b.hdr.valueSize
 	entryBuf := make([]byte, stride)
 	var readErr error
@@ -110,7 +110,7 @@ func (b *index) findEntryPosition(blockID ContentID) (int, error) {
 	return pos, readErr
 }
 
-func (b *index) findEntry(blockID ContentID) ([]byte, error) {
+func (b *index) findEntry(blockID string) ([]byte, error) {
 	key := contentIDToBytes(blockID)
 	if len(key) != b.hdr.keySize {
 		return nil, fmt.Errorf("invalid block ID: %q", blockID)
@@ -138,7 +138,7 @@ func (b *index) findEntry(blockID ContentID) ([]byte, error) {
 }
 
 // GetInfo returns information about a given block. If a block is not found, nil is returned.
-func (b *index) GetInfo(blockID ContentID) (*Info, error) {
+func (b *index) GetInfo(blockID string) (*Info, error) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
@@ -158,7 +158,7 @@ func (b *index) GetInfo(blockID ContentID) (*Info, error) {
 	return &i, err
 }
 
-func (b *index) entryToInfo(blockID ContentID, entryData []byte) (Info, error) {
+func (b *index) entryToInfo(blockID string, entryData []byte) (Info, error) {
 	if len(entryData) < 20 {
 		return Info{}, fmt.Errorf("invalid entry length: %v", len(entryData))
 	}
diff --git a/internal/packindex/info.go b/internal/packindex/info.go
index a58ab9043..8e126b9ca 100644
--- a/internal/packindex/info.go
+++ b/internal/packindex/info.go
@@ -5,13 +5,12 @@ import (
 	"time"
 )
 
-type ContentID string
-
+// PhysicalBlockID is the name of a physical block in storage.
 type PhysicalBlockID string
 
 // Info is an information about a single block managed by Manager.
 type Info struct {
-	BlockID          ContentID       `json:"blockID"`
+	BlockID          string          `json:"blockID"`
 	Length           uint32          `json:"length"`
 	TimestampSeconds int64           `json:"time"`
 	PackBlockID      PhysicalBlockID `json:"packBlockID,omitempty"`
diff --git a/internal/packindex/merged.go b/internal/packindex/merged.go
index 74d40be36..d54b739d1 100644
--- a/internal/packindex/merged.go
+++ b/internal/packindex/merged.go
@@ -29,7 +29,7 @@ func (m Merged) EntryCount() int {
 }
 
 // GetInfo returns information about a single block. If a block is not found, returns (nil,nil)
-func (m Merged) GetInfo(contentID ContentID) (*Info, error) {
+func (m Merged) GetInfo(contentID string) (*Info, error) {
 	var best *Info
 
 	for _, ndx := range m {
@@ -67,7 +67,7 @@ func (h *nextInfoHeap) Pop() interface{} {
 	return x
 }
 
-func iterateChan(prefix ContentID, ndx Index, done chan bool) <-chan Info {
+func iterateChan(prefix string, ndx Index, done chan bool) <-chan Info {
 	ch := make(chan Info)
 	go func() {
 		defer close(ch)
@@ -86,7 +86,7 @@ func iterateChan(prefix ContentID, ndx Index, done chan bool) <-chan Info {
 
 // Iterate invokes the provided callback for all unique block IDs in the underlying sources until either
 // all blocks have been visited or until an error is returned by the callback.
-func (m Merged) Iterate(prefix ContentID, cb func(i Info) error) error {
+func (m Merged) Iterate(prefix string, cb func(i Info) error) error {
 	var minHeap nextInfoHeap
 	done := make(chan bool)
 	defer close(done)
diff --git a/internal/packindex/merged_test.go b/internal/packindex/merged_test.go
index e4d2fa2f3..0b05e72ff 100644
--- a/internal/packindex/merged_test.go
+++ b/internal/packindex/merged_test.go
@@ -44,13 +44,13 @@ func TestMerged(t *testing.T) {
 		t.Errorf("invalid pack offset %v, wanted %v", got, want)
 	}
 
-	var inOrder []packindex.ContentID
+	var inOrder []string
 	m.Iterate("", func(i packindex.Info) error {
 		inOrder = append(inOrder, i.BlockID)
 		return nil
 	})
 
-	expectedInOrder := []packindex.ContentID{
+	expectedInOrder := []string{
 		"aabbcc",
 		"ddeeff",
 		"k010203",
diff --git a/internal/packindex/packindex_test.go b/internal/packindex/packindex_test.go
index 583192446..7f3b8ea69 100644
--- a/internal/packindex/packindex_test.go
+++ b/internal/packindex/packindex_test.go
@@ -17,7 +17,7 @@ func TestPackIndex(t *testing.T) {
 
 	blockNumber := 0
 
-	deterministicBlockID := func(prefix string, id int) packindex.ContentID {
+	deterministicBlockID := func(prefix string, id int) string {
 		h := sha1.New()
 		fmt.Fprintf(h, "%v%v", prefix, id)
 		blockNumber++
@@ -32,7 +32,7 @@ func TestPackIndex(t *testing.T) {
 		if id%5 == 0 {
 			prefix2 = "m"
 		}
-		return packindex.ContentID(fmt.Sprintf("%v%x", prefix2, h.Sum(nil)))
+		return string(fmt.Sprintf("%v%x", prefix2, h.Sum(nil)))
 	}
 	deterministicPackBlockID := func(id int) packindex.PhysicalBlockID {
 		h := sha1.New()
@@ -95,7 +95,7 @@ func TestPackIndex(t *testing.T) {
 		})
 	}
 
-	infoMap := map[packindex.ContentID]packindex.Info{}
+	infoMap := map[string]packindex.Info{}
 
 	for _, info := range infos {
 		infoMap[info.BlockID] = info
@@ -151,7 +151,7 @@ func TestPackIndex(t *testing.T) {
 
 	for _, prefix := range prefixes {
 		cnt2 := 0
-		ndx.Iterate(packindex.ContentID(prefix), func(info2 packindex.Info) error {
+		ndx.Iterate(string(prefix), func(info2 packindex.Info) error {
 			cnt2++
 			if !strings.HasPrefix(string(info2.BlockID), string(prefix)) {
 				t.Errorf("unexpected item %v when iterating prefix %v", info2.BlockID, prefix)
diff --git a/manifest/manifest_manager.go b/manifest/manifest_manager.go
index eab419648..a81944ab9 100644
--- a/manifest/manifest_manager.go
+++ b/manifest/manifest_manager.go
@@ -28,7 +28,7 @@ type Manager struct {
 	mu             sync.Mutex
 	b              *block.Manager
 	entries        map[string]*manifestEntry
-	blockIDs       []block.ContentID
+	blockIDs       []string
 	pendingEntries []*manifestEntry
 }
 
@@ -165,7 +165,7 @@ func (m *Manager) Flush(ctx context.Context) error {
 	return nil
 }
 
-func (m *Manager) flushPendingEntriesLocked(ctx context.Context) (block.ContentID, error) {
+func (m *Manager) flushPendingEntriesLocked(ctx context.Context) (string, error) {
 	if len(m.pendingEntries) == 0 {
 		return "", nil
 	}
@@ -279,7 +279,7 @@ func (m *Manager) loadManifestBlocks(ctx context.Context, blocks []block.Info) e
 func (m *Manager) loadBlocksInParallel(ctx context.Context, blocks []block.Info) ([]manifest, error) {
 	errors := make(chan error, len(blocks))
 	manifests := make(chan manifest, len(blocks))
-	blockIDs := make(chan block.ContentID, len(blocks))
+	blockIDs := make(chan string, len(blocks))
 	var wg sync.WaitGroup
 
 	for i := 0; i < 8; i++ {
@@ -290,7 +290,7 @@ func (m *Manager) loadBlocksInParallel(ctx context.Context, blocks []block.Info)
 			for blk := range blockIDs {
 				t1 := time.Now()
 				man, err := m.loadManifestBlock(ctx, blk)
-				log.Debug().Dur("duration", time.Since(t1)).Str("blk", string(blk)).Int("worker", workerID).Err(err).Msg("manifest block loaded")
+				log.Debug().Dur("duration", time.Since(t1)).Str("blk", blk).Int("worker", workerID).Err(err).Msg("manifest block loaded")
 				if err != nil {
 					errors <- err
 				} else {
@@ -324,7 +324,7 @@ func (m *Manager) loadBlocksInParallel(ctx context.Context, blocks []block.Info)
 	return man, nil
 }
 
-func (m *Manager) loadManifestBlock(ctx context.Context, blockID block.ContentID) (manifest, error) {
+func (m *Manager) loadManifestBlock(ctx context.Context, blockID string) (manifest, error) {
 	man := manifest{}
 	blk, err := m.b.GetBlock(ctx, blockID)
 	if err != nil {
@@ -388,7 +388,7 @@ func (m *Manager) compactLocked(ctx context.Context) error {
 	}
 
 	// all previous blocks were deleted, now we have a new block
-	m.blockIDs = []block.ContentID{blockID}
+	m.blockIDs = []string{blockID}
 	return nil
 }
 
diff --git a/object/object_manager.go b/object/object_manager.go
index 1d05b0e20..035603419 100644
--- a/object/object_manager.go
+++ b/object/object_manager.go
@@ -24,9 +24,9 @@ type Reader interface {
 }
 
 type blockManager interface {
-	BlockInfo(ctx context.Context, blockID block.ContentID) (block.Info, error)
-	GetBlock(ctx context.Context, blockID block.ContentID) ([]byte, error)
-	WriteBlock(ctx context.Context, data []byte, prefix block.ContentID) (block.ContentID, error)
+	BlockInfo(ctx context.Context, blockID string) (block.Info, error)
+	GetBlock(ctx context.Context, blockID string) ([]byte, error)
+	WriteBlock(ctx context.Context, data []byte, prefix string) (string, error)
 	Flush(ctx context.Context) error
 }
 
@@ -102,7 +102,7 @@ func (om *Manager) Open(ctx context.Context, objectID ID) (Reader, error) {
 
 // VerifyObject ensures that all objects backing ObjectID are present in the repository
 // and returns the total length of the object and storage blocks of which it is composed.
-func (om *Manager) VerifyObject(ctx context.Context, oid ID) (int64, []block.ContentID, error) {
+func (om *Manager) VerifyObject(ctx context.Context, oid ID) (int64, []string, error) {
 	// Flush any pending writes.
 	om.writeBackWG.Wait()
 
@@ -157,7 +157,7 @@ func (om *Manager) verifyObjectInternal(ctx context.Context, oid ID, blocks *blo
 	blocks.addBlock(oid.ContentBlockID)
 
 	if p.PackBlockID != "" {
-		l, err := om.verifyObjectInternal(ctx, ID{ContentBlockID: block.ContentID(p.PackBlockID)}, blocks)
+		l, err := om.verifyObjectInternal(ctx, ID{ContentBlockID: string(p.PackBlockID)}, blocks)
 		if err != nil {
 			return 0, err
 		}
diff --git a/object/object_manager_test.go b/object/object_manager_test.go
index ef3188000..6337e9a70 100644
--- a/object/object_manager_test.go
+++ b/object/object_manager_test.go
@@ -24,10 +24,10 @@ import (
 
 type fakeBlockManager struct {
 	mu   sync.Mutex
-	data map[block.ContentID][]byte
+	data map[string][]byte
 }
 
-func (f *fakeBlockManager) GetBlock(ctx context.Context, blockID block.ContentID) ([]byte, error) {
+func (f *fakeBlockManager) GetBlock(ctx context.Context, blockID string) ([]byte, error) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 
@@ -38,10 +38,10 @@ func (f *fakeBlockManager) GetBlock(ctx context.Context, blockID block.ContentID
 	return nil, storage.ErrBlockNotFound
 }
 
-func (f *fakeBlockManager) WriteBlock(ctx context.Context, data []byte, prefix block.ContentID) (block.ContentID, error) {
+func (f *fakeBlockManager) WriteBlock(ctx context.Context, data []byte, prefix string) (string, error) {
 	h := md5.New()
 	h.Write(data)
-	blockID := prefix + block.ContentID(hex.EncodeToString(h.Sum(nil)))
+	blockID := prefix + string(hex.EncodeToString(h.Sum(nil)))
 
 	f.mu.Lock()
 	defer f.mu.Unlock()
@@ -50,7 +50,7 @@ func (f *fakeBlockManager) WriteBlock(ctx context.Context, data []byte, prefix b
 	return blockID, nil
 }
 
-func (f *fakeBlockManager) BlockInfo(ctx context.Context, blockID block.ContentID) (block.Info, error) {
+func (f *fakeBlockManager) BlockInfo(ctx context.Context, blockID string) (block.Info, error) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 
@@ -65,11 +65,11 @@ func (f *fakeBlockManager) Flush(ctx context.Context) error {
 	return nil
 }
 
-func setupTest(t *testing.T) (map[block.ContentID][]byte, *Manager) {
-	return setupTestWithData(t, map[block.ContentID][]byte{}, ManagerOptions{})
+func setupTest(t *testing.T) (map[string][]byte, *Manager) {
+	return setupTestWithData(t, map[string][]byte{}, ManagerOptions{})
 }
 
-func setupTestWithData(t *testing.T, data map[block.ContentID][]byte, opts ManagerOptions) (map[block.ContentID][]byte, *Manager) {
+func setupTestWithData(t *testing.T, data map[string][]byte, opts ManagerOptions) (map[string][]byte, *Manager) {
 	r, err := NewObjectManager(context.Background(), &fakeBlockManager{data: data}, config.RepositoryObjectFormat{
 		FormattingOptions: block.FormattingOptions{
 			Version: 1,
diff --git a/object/object_writer.go b/object/object_writer.go
index 7df528187..ed4ef6a84 100644
--- a/object/object_writer.go
+++ b/object/object_writer.go
@@ -7,7 +7,6 @@ import (
 	"io"
 	"sync"
 
-	"github.com/kopia/kopia/block"
 	"github.com/kopia/kopia/internal/jsonstream"
 )
 
@@ -21,24 +20,24 @@ type Writer interface {
 
 type blockTracker struct {
 	mu     sync.Mutex
-	blocks map[block.ContentID]bool
+	blocks map[string]bool
 }
 
-func (t *blockTracker) addBlock(blockID block.ContentID) {
+func (t *blockTracker) addBlock(blockID string) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
 	if t.blocks == nil {
-		t.blocks = make(map[block.ContentID]bool)
+		t.blocks = make(map[string]bool)
 	}
 	t.blocks[blockID] = true
 }
 
-func (t *blockTracker) blockIDs() []block.ContentID {
+func (t *blockTracker) blockIDs() []string {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
-	result := make([]block.ContentID, 0, len(t.blocks))
+	result := make([]string, 0, len(t.blocks))
 	for k := range t.blocks {
 		result = append(result, k)
 	}
diff --git a/object/objectid.go b/object/objectid.go
index 665d667e2..c8e5cedab 100644
--- a/object/objectid.go
+++ b/object/objectid.go
@@ -4,8 +4,6 @@ import (
 	"encoding/json"
 
 	"fmt"
-
-	"github.com/kopia/kopia/block"
 )
 
 // ID is an identifier of a repository object. Repository objects can be stored:
@@ -14,7 +12,7 @@ import (
 // 2. In a series of content blocks with an indirect block pointing at them (multiple indirections are allowed). This is used for larger files.
 //
 type ID struct {
-	ContentBlockID block.ContentID
+	ContentBlockID string
 	Indirect       *ID
 }
 
@@ -53,7 +51,7 @@ func (oid ID) String() string {
 	}
 
 	if oid.ContentBlockID != "" {
-		return "D" + string(oid.ContentBlockID)
+		return "D" + oid.ContentBlockID
 	}
 
 	return "B"
@@ -98,7 +96,7 @@ func ParseID(s string) (ID, error) {
 				return ID{Indirect: &base}, nil
 			}
 
-			return ID{ContentBlockID: block.ContentID(content)}, nil
+			return ID{ContentBlockID: content}, nil
 		}
 	}
 
diff --git a/tests/stress_test/stress_test.go b/tests/stress_test/stress_test.go
index 45eed7bc6..4f1048c0e 100644
--- a/tests/stress_test/stress_test.go
+++ b/tests/stress_test/stress_test.go
@@ -72,7 +72,7 @@ func stressWorker(ctx context.Context, t *testing.T, workerID int, openMgr func(
 	}
 
 	type writtenBlock struct {
-		contentID block.ContentID
+		contentID string
 		data      []byte
 	}