Merge pull request #3 from filecoin-project/feat/add-padding-helper

add a padding helper function

Author: magik6k

ffiwrapper/ffiwrapper.go

@@ -6,6 +6,7 @@ import (
 	"sync"
 
 	ffi "github.com/filecoin-project/filecoin-ffi"
+	"github.com/filecoin-project/go-commp-utils/zerocomm"
 	"github.com/filecoin-project/go-state-types/abi"
 	"github.com/ipfs/go-cid"
 	logging "github.com/ipfs/go-log/v2"
@@ -73,3 +74,30 @@ func GeneratePieceCIDFromFile(proofType abi.RegisteredSealProof, piece io.Reader
 
 	return pieceCID, werr()
 }
+
+func ZeroPadPieceCommitment(c cid.Cid, curSize abi.UnpaddedPieceSize, toSize abi.UnpaddedPieceSize) (cid.Cid, error) {
+	cur := c
+	for curSize < toSize {
+
+		zc := zerocomm.ZeroPieceCommitment(curSize)
+
+		p, err := ffi.GenerateUnsealedCID(abi.RegisteredSealProof_StackedDrg32GiBV1, []abi.PieceInfo{
+			abi.PieceInfo{
+				Size:     curSize.Padded(),
+				PieceCID: cur,
+			},
+			abi.PieceInfo{
+				Size:     curSize.Padded(),
+				PieceCID: zc,
+			},
+		})
+		if err != nil {
+			return cid.Undef, err
+		}
+
+		cur = p
+		curSize = curSize * 2
+	}
+
+	return cur, nil
+}

ffiwrapper/ffiwrapper_test.go

@@ -0,0 +1,49 @@
+package ffiwrapper
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/ipfs/go-cid"
+)
+
+func TestZeroPadding(t *testing.T) {
+	psize := abi.PaddedPieceSize(128).Unpadded()
+	data := make([]byte, psize)
+
+	content := []byte("i am the biggest cat, what do you think about that")
+	copy(data, content)
+
+	pcid, err := GeneratePieceCIDFromFile(abi.RegisteredSealProof_StackedDrg32GiBV1_1, bytes.NewReader(data), psize)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// value calculated using separate tooling
+	expCid, err := cid.Decode("baga6ea4seaqozp3abki6vgdf7ztbipcycmxfyt2o64cpuyvdkczsjxsg7bqmioi")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if pcid != expCid {
+		t.Fatalf("expected %s, got %s", expCid, pcid)
+	}
+
+	padded, err := ZeroPadPieceCommitment(pcid, psize, psize*4)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data2 := make([]byte, psize*4)
+	copy(data2, content)
+
+	padExpCid, err := GeneratePieceCIDFromFile(abi.RegisteredSealProof_StackedDrg32GiBV1_1, bytes.NewReader(data2), psize*4)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if padded != padExpCid {
+		t.Fatalf("wrong padding, expected %s, got %s", padExpCid, padded)
+	}
+}