fix: read the correct number of bytes for the piece

Author: rvagg

commp.go

@@ -14,7 +14,8 @@ import (
 // GeneratePieceCIDFromFile generates an a piece cid from an io.Reader
 func GeneratePieceCIDFromFile(proofType abi.RegisteredSealProof, piece io.Reader, pieceSize abi.UnpaddedPieceSize) (cid.Cid, error) {
 	var cc commphh.Calc
-	if _, err := io.Copy(&cc, piece); err != nil {
+	expectedBytes := int64(pieceSize)
+	if _, err := io.CopyN(&cc, piece, expectedBytes); err != nil {
 		return cid.Undef, err
 	}
 	p, _, err := cc.Digest()

commp_test.go

@@ -2,11 +2,13 @@ package commp_test
 
 import (
 	"bytes"
+	"io"
 	"testing"
 
 	"github.com/filecoin-project/go-commp-utils/v2"
 	"github.com/filecoin-project/go-state-types/abi"
 	"github.com/ipfs/go-cid"
+	"github.com/stretchr/testify/require"
 )
 
 func TestZeroPadding(t *testing.T) {
@@ -17,34 +19,27 @@ func TestZeroPadding(t *testing.T) {
 	copy(data, content)
 
 	pcid, err := commp.GeneratePieceCIDFromFile(abi.RegisteredSealProof_StackedDrg32GiBV1_1, bytes.NewReader(data), psize)
-	if err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, 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)
-	}
+	require.NoError(t, err)
+	require.Equal(t, expCid, pcid)
 
 	padded, err := commp.ZeroPadPieceCommitment(pcid, psize, psize*4)
-	if err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, err)
 
 	data2 := make([]byte, psize*4)
 	copy(data2, content)
 
 	padExpCid, err := commp.GeneratePieceCIDFromFile(abi.RegisteredSealProof_StackedDrg32GiBV1_1, bytes.NewReader(data2), psize*4)
-	if err != nil {
-		t.Fatal(err)
-	}
+	require.NoError(t, err)
+	require.Equal(t, padded, padExpCid)
+}
 
-	if padded != padExpCid {
-		t.Fatalf("wrong padding, expected %s, got %s", padExpCid, padded)
-	}
+func TestMismatchedPieceSize(t *testing.T) {
+	psize := abi.PaddedPieceSize(128).Unpadded()
+	data := []byte("i am the smallest cat") // less than psize
+	_, err := commp.GeneratePieceCIDFromFile(abi.RegisteredSealProof_StackedDrg32GiBV1_1, bytes.NewReader(data), psize)
+	require.ErrorIs(t, err, io.EOF)
 }

writer/writer.go

@@ -5,11 +5,10 @@ import (
 	"math/bits"
 	"runtime"
 
-	"github.com/ipfs/go-cid"
-	"golang.org/x/xerrors"
-
 	"github.com/filecoin-project/go-padreader"
 	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/ipfs/go-cid"
+	"golang.org/x/xerrors"
 
 	commp "github.com/filecoin-project/go-commp-utils/v2"
 	"github.com/filecoin-project/go-commp-utils/v2/zerocomm"