fix: augment PieceAggregateCommP to return the resulting aggregate size (#18)

Author: ribasushi

Diff for: commd.go

@@ -25,13 +25,13 @@ type stackFrame struct {
 // This function makes no assumptions, other than maximum size, about the pieces that you include.
 // To create a correctly formed UnsealedCID (CommD) for a sector using this method, you should first
 // ensure that the pieces add up to the required size.
-func PieceAggregateCommP(proofType abi.RegisteredSealProof, pieceInfos []abi.PieceInfo) (cid.Cid, error) {
+func PieceAggregateCommP(proofType abi.RegisteredSealProof, pieceInfos []abi.PieceInfo) (cid.Cid, abi.PaddedPieceSize, error) {
 	spi, found := abi.SealProofInfos[proofType]
 	if !found {
-		return cid.Undef, fmt.Errorf("unknown seal proof type %d", proofType)
+		return cid.Undef, 0, fmt.Errorf("unknown seal proof type %d", proofType)
 	}
 	if len(pieceInfos) == 0 {
-		return cid.Undef, errors.New("no pieces provided")
+		return cid.Undef, 0, errors.New("no pieces provided")
 	}
 
 	maxSize := uint64(spi.SectorSize)
@@ -41,18 +41,18 @@ func PieceAggregateCommP(proofType abi.RegisteredSealProof, pieceInfos []abi.Pie
 	// sancheck everything
 	for i, p := range pieceInfos {
 		if p.Size < 128 {
-			return cid.Undef, fmt.Errorf("invalid Size of PieceInfo %d: value %d is too small", i, p.Size)
+			return cid.Undef, 0, fmt.Errorf("invalid Size of PieceInfo %d: value %d is too small", i, p.Size)
 		}
 		if uint64(p.Size) > maxSize {
-			return cid.Undef, fmt.Errorf("invalid Size of PieceInfo %d: value %d is larger than sector size of SealProofType %d", i, p.Size, proofType)
+			return cid.Undef, 0, fmt.Errorf("invalid Size of PieceInfo %d: value %d is larger than sector size of SealProofType %d", i, p.Size, proofType)
 		}
 		if bits.OnesCount64(uint64(p.Size)) != 1 {
-			return cid.Undef, fmt.Errorf("invalid Size of PieceInfo %d: value %d is not a power of 2", i, p.Size)
+			return cid.Undef, 0, fmt.Errorf("invalid Size of PieceInfo %d: value %d is not a power of 2", i, p.Size)
 		}
 
 		cp, err := commcid.CIDToPieceCommitmentV1(p.PieceCID)
 		if err != nil {
-			return cid.Undef, fmt.Errorf("invalid PieceCid for PieceInfo %d: %w", i, err)
+			return cid.Undef, 0, fmt.Errorf("invalid PieceCid for PieceInfo %d: %w", i, err)
 		}
 		todo[i] = stackFrame{size: uint64(p.Size), commP: cp}
 	}
@@ -106,10 +106,12 @@ func PieceAggregateCommP(proofType abi.RegisteredSealProof, pieceInfos []abi.Pie
 	}
 
 	if stack[0].size > maxSize {
-		return cid.Undef, fmt.Errorf("provided pieces sum up to %d bytes, which is larger than sector size of SealProofType %d", stack[0].size, proofType)
+		return cid.Undef, 0, fmt.Errorf("provided pieces sum up to %d bytes, which is larger than sector size of SealProofType %d", stack[0].size, proofType)
 	}
 
-	return commcid.PieceCommitmentV1ToCID(stack[0].commP)
+	fincid, err := commcid.PieceCommitmentV1ToCID(stack[0].commP)
+
+	return fincid, abi.PaddedPieceSize(stack[0].size), err
 }
 
 var s256pool = sync.Pool{New: func() any { return sha256simd.New() }}

Diff for: commd_test.go

@@ -26,7 +26,7 @@ func TestGenerateUnsealedCID(t *testing.T) {
 
 	expCommD := cidMustParse("baga6ea4seaqiw3gbmstmexb7sqwkc5r23o3i7zcyx5kr76pfobpykes3af62kca")
 
-	commD, _ := commp.PieceAggregateCommP(
+	commD, sizeD, _ := commp.PieceAggregateCommP(
 		abi.RegisteredSealProof_StackedDrg32GiBV1_1, // 32G sector SP
 		[]abi.PieceInfo{
 			{PieceCID: cidMustParse("baga6ea4seaqknzm22isnhsxt2s4dnw45kfywmhenngqq3nc7jvecakoca6ksyhy"), Size: 256 << 20},  // https://filfox.info/en/deal/3755444
@@ -49,6 +49,10 @@ func TestGenerateUnsealedCID(t *testing.T) {
 	if commD != expCommD {
 		t.Fatalf("calculated commd for sector f01392893:139074 as %s, expected %s", commD, expCommD)
 	}
+
+	if sizeD != 32<<30 {
+		t.Fatalf("calculated size for sector f01392893:139074 as %d, expected 32GiB", sizeD)
+	}
 }
 
 // Delete below when this ships in a stable release https://github.com/ipfs/go-cid/pull/139

Diff for: writer/writer.go

@@ -143,14 +143,14 @@ func (w *Writer) Sum() (DataCIDSize, error) {
 		}
 	}
 
-	p, err := commp.PieceAggregateCommP(abi.RegisteredSealProof_StackedDrg64GiBV1, pieces)
+	p, sz, err := commp.PieceAggregateCommP(abi.RegisteredSealProof_StackedDrg64GiBV1, pieces)
 	if err != nil {
 		return DataCIDSize{}, xerrors.Errorf("generating unsealed CID: %w", err)
 	}
 
 	return DataCIDSize{
 		PayloadSize: rawLen,
-		PieceSize:   abi.PaddedPieceSize(len(leaves)) * commPBufPad,
+		PieceSize:   sz,
 		PieceCID:    p,
 	}, nil
 }