cleanup: remove syncmap impl, comments, add NewDiffMetadata constructor

Author: ValentaTomas

packages/orchestrator/pkg/sandbox/block/cache.go

@@ -116,11 +116,7 @@ func (c *Cache) ExportToDiff(ctx context.Context, out *os.File) (*header.DiffMet
 	}
 
 	if c.mmap == nil {
-		return &header.DiffMetadata{
-			Dirty:     bitset.New(0),
-			Empty:     bitset.New(0),
-			BlockSize: c.blockSize,
-		}, nil
+		return header.NewDiffMetadata(c.blockSize, bitset.New(0)), nil
 	}
 
 	f, err := os.Open(c.filePath)
@@ -140,9 +136,7 @@ func (c *Cache) ExportToDiff(ctx context.Context, out *os.File) (*header.DiffMet
 	}
 
 	buildStart := time.Now()
-	builder := header.NewDiffMetadataBuilderFromDirty(c.blockSize, c.dirty.BitSet())
-
-	diffMetadata := builder.Build()
+	diffMetadata := header.NewDiffMetadata(c.blockSize, c.dirty.BitSet())
 	telemetry.SetAttributes(ctx, attribute.Int64("build_metadata_ms", time.Since(buildStart).Milliseconds()))
 
 	dst := int(out.Fd())

packages/shared/pkg/atomicbitset/bab.go

@@ -6,7 +6,8 @@ import (
 	"github.com/bits-and-blooms/bitset"
 )
 
-// BitsAndBlooms wraps a bits-and-blooms/bitset.BitSet with an internal RWMutex.
+var _ Bitset = (*BitsAndBlooms)(nil)
+
 type BitsAndBlooms struct {
 	mu sync.RWMutex
 	bs *bitset.BitSet

packages/shared/pkg/atomicbitset/bitset.go

@@ -1,5 +1,3 @@
-// Package atomicbitset provides fixed-size bitset implementations.
-// All implementations are safe for concurrent HasRange and SetRange.
 package atomicbitset
 
 import (

packages/shared/pkg/atomicbitset/bitset_test.go

@@ -20,7 +20,6 @@ var impls = []implFactory{
 	{"BitsAndBlooms", func(n uint) Bitset { return NewBitsAndBlooms(n) }},
 	{"Sharded", func(n uint) Bitset { return NewSharded(n, DefaultShardBits) }},
 	{"Sharded/small", func(n uint) Bitset { return NewSharded(n, 64) }},
-	{"SyncMap", func(n uint) Bitset { return NewSyncMap(n) }},
 }
 
 func TestHasRange(t *testing.T) {

packages/shared/pkg/atomicbitset/flat.go

@@ -7,6 +7,8 @@ import (
 	"github.com/bits-and-blooms/bitset"
 )
 
+var _ Bitset = (*Flat)(nil)
+
 type Flat struct {
 	words []atomic.Uint64
 	n     uint

packages/shared/pkg/atomicbitset/roaring.go

@@ -7,7 +7,8 @@ import (
 	"github.com/bits-and-blooms/bitset"
 )
 
-// Roaring wraps a roaring bitmap (32-bit) with an internal RWMutex.
+var _ Bitset = (*Roaring)(nil)
+
 type Roaring struct {
 	mu sync.RWMutex
 	bm *roaring.Bitmap

packages/shared/pkg/atomicbitset/roaring64.go

@@ -7,7 +7,8 @@ import (
 	"github.com/bits-and-blooms/bitset"
 )
 
-// Roaring64 wraps a roaring64 bitmap (64-bit keys) with an internal RWMutex.
+var _ Bitset = (*Roaring64)(nil)
+
 type Roaring64 struct {
 	mu sync.RWMutex
 	bm *roaring64.Bitmap

packages/shared/pkg/atomicbitset/sharded.go

@@ -6,7 +6,6 @@ import (
 	"github.com/bits-and-blooms/bitset"
 )
 
-// DefaultShardBits is 128 MB / 4 KB = 32768 bits per shard (4 KB bitmap, one OS page).
 const DefaultShardBits uint = 32768
 
 type shard struct {
@@ -19,7 +18,6 @@ func newShard(bitsPerShard uint) *shard {
 	}
 }
 
-// Sharded is a two-level lock-free bitset with lazily allocated shard bitmaps.
 type Sharded struct {
 	shards       []atomic.Pointer[shard]
 	n            uint
@@ -173,10 +171,4 @@ func shardSetRange(sh *shard, lo, hi uint) {
 	}
 }
 
-var (
-	_ Bitset = (*Flat)(nil)
-	_ Bitset = (*Roaring)(nil)
-	_ Bitset = (*Roaring64)(nil)
-	_ Bitset = (*Sharded)(nil)
-	_ Bitset = (*SyncMap)(nil)
-)
+var _ Bitset = (*Sharded)(nil)

packages/shared/pkg/atomicbitset/syncmap.go

@@ -24,6 +24,14 @@ type DiffMetadata struct {
 	BlockSize int64
 }
 
+func NewDiffMetadata(blockSize int64, dirty *bitset.BitSet) *DiffMetadata {
+	return &DiffMetadata{
+		Dirty:     dirty,
+		Empty:     bitset.New(0),
+		BlockSize: blockSize,
+	}
+}
+
 func (d *DiffMetadata) toDiffMapping(
 	ctx context.Context,
 	buildID uuid.UUID,
@@ -122,14 +130,6 @@ func NewDiffMetadataBuilder(size, blockSize int64) *DiffMetadataBuilder {
 	}
 }
 
-func NewDiffMetadataBuilderFromDirty(blockSize int64, dirty *bitset.BitSet) *DiffMetadataBuilder {
-	return &DiffMetadataBuilder{
-		dirty:     dirty,
-		empty:     bitset.New(0),
-		blockSize: blockSize,
-	}
-}
-
 func (b *DiffMetadataBuilder) Process(ctx context.Context, block []byte, out io.Writer, offset int64) error {
 	blockIdx := BlockIdx(offset, b.blockSize)