7 files changed, 33 insertions, 26 deletions

diff --git a/plumbing/format/idxfile/decoder.go b/plumbing/format/idxfile/decoder.go
index 51a3904..9afdce3 100644
--- a/plumbing/format/idxfile/decoder.go
+++ b/plumbing/format/idxfile/decoder.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"io"
 
+	"github.com/go-git/go-git/v5/plumbing/hash"
 	"github.com/go-git/go-git/v5/utils/binary"
 )
 
@@ -19,7 +20,7 @@ var (
 
 const (
 	fanout         = 256
-	objectIDLength = 20
+	objectIDLength = hash.Size
 )
 
 // Decoder reads and decodes idx files from an input stream.
diff --git a/plumbing/format/idxfile/decoder_test.go b/plumbing/format/idxfile/decoder_test.go
index 94059cc..2c4a801 100644
--- a/plumbing/format/idxfile/decoder_test.go
+++ b/plumbing/format/idxfile/decoder_test.go
@@ -5,7 +5,6 @@ import (
 	"encoding/base64"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"testing"
 
 	"github.com/go-git/go-git/v5/plumbing"
@@ -119,7 +118,7 @@ ch2xUA==
 
 func BenchmarkDecode(b *testing.B) {
 	f := fixtures.Basic().One()
-	fixture, err := ioutil.ReadAll(f.Idx())
+	fixture, err := io.ReadAll(f.Idx())
 	if err != nil {
 		b.Errorf("unexpected error reading idx file: %s", err)
 	}
diff --git a/plumbing/format/idxfile/encoder.go b/plumbing/format/idxfile/encoder.go
index 26b2e4d..7514737 100644
--- a/plumbing/format/idxfile/encoder.go
+++ b/plumbing/format/idxfile/encoder.go
@@ -1,10 +1,9 @@
 package idxfile
 
 import (
-	"crypto/sha1"
-	"hash"
 	"io"
 
+	"github.com/go-git/go-git/v5/plumbing/hash"
 	"github.com/go-git/go-git/v5/utils/binary"
 )
 
@@ -16,7 +15,7 @@ type Encoder struct {
 
 // NewEncoder returns a new stream encoder that writes to w.
 func NewEncoder(w io.Writer) *Encoder {
-	h := sha1.New()
+	h := hash.New(hash.CryptoType)
 	mw := io.MultiWriter(w, h)
 	return &Encoder{mw, h}
 }
@@ -133,10 +132,10 @@ func (e *Encoder) encodeChecksums(idx *MemoryIndex) (int, error) {
 		return 0, err
 	}
 
-	copy(idx.IdxChecksum[:], e.hash.Sum(nil)[:20])
+	copy(idx.IdxChecksum[:], e.hash.Sum(nil)[:hash.Size])
 	if _, err := e.Write(idx.IdxChecksum[:]); err != nil {
 		return 0, err
 	}
 
-	return 40, nil
+	return hash.HexSize, nil
 }
diff --git a/plumbing/format/idxfile/encoder_test.go b/plumbing/format/idxfile/encoder_test.go
index 32b60f9..b8ece83 100644
--- a/plumbing/format/idxfile/encoder_test.go
+++ b/plumbing/format/idxfile/encoder_test.go
@@ -2,7 +2,7 @@ package idxfile_test
 
 import (
 	"bytes"
-	"io/ioutil"
+	"io"
 
 	. "github.com/go-git/go-git/v5/plumbing/format/idxfile"
 
@@ -12,7 +12,7 @@ import (
 
 func (s *IdxfileSuite) TestDecodeEncode(c *C) {
 	fixtures.ByTag("packfile").Test(c, func(f *fixtures.Fixture) {
-		expected, err := ioutil.ReadAll(f.Idx())
+		expected, err := io.ReadAll(f.Idx())
 		c.Assert(err, IsNil)
 
 		idx := new(MemoryIndex)
diff --git a/plumbing/format/idxfile/idxfile.go b/plumbing/format/idxfile/idxfile.go
index 64dd8dc..9237a74 100644
--- a/plumbing/format/idxfile/idxfile.go
+++ b/plumbing/format/idxfile/idxfile.go
@@ -8,6 +8,7 @@ import (
 	encbin "encoding/binary"
 
 	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/hash"
 )
 
 const (
@@ -53,8 +54,8 @@ type MemoryIndex struct {
 	Offset32         [][]byte
 	CRC32            [][]byte
 	Offset64         []byte
-	PackfileChecksum [20]byte
-	IdxChecksum      [20]byte
+	PackfileChecksum [hash.Size]byte
+	IdxChecksum      [hash.Size]byte
 
 	offsetHash       map[int64]plumbing.Hash
 	offsetHashIsFull bool
diff --git a/plumbing/format/idxfile/writer.go b/plumbing/format/idxfile/writer.go
index daa1605..c4c21e1 100644
--- a/plumbing/format/idxfile/writer.go
+++ b/plumbing/format/idxfile/writer.go
@@ -84,11 +84,8 @@ func (w *Writer) OnFooter(h plumbing.Hash) error {
 	w.checksum = h
 	w.finished = true
 	_, err := w.createIndex()
-	if err != nil {
-		return err
-	}
 
-	return nil
+	return err
 }
 
 // creatIndex returns a filled MemoryIndex with the information filled by
@@ -139,15 +136,23 @@ func (w *Writer) createIndex() (*MemoryIndex, error) {
 
 		offset := o.Offset
 		if offset > math.MaxInt32 {
-			offset = w.addOffset64(offset)
+			var err error
+			offset, err = w.addOffset64(offset)
+			if err != nil {
+				return nil, err
+			}
 		}
 
 		buf.Truncate(0)
-		binary.WriteUint32(buf, uint32(offset))
+		if err := binary.WriteUint32(buf, uint32(offset)); err != nil {
+			return nil, err
+		}
 		idx.Offset32[bucket] = append(idx.Offset32[bucket], buf.Bytes()...)
 
 		buf.Truncate(0)
-		binary.WriteUint32(buf, o.CRC32)
+		if err := binary.WriteUint32(buf, o.CRC32); err != nil {
+			return nil, err
+		}
 		idx.CRC32[bucket] = append(idx.CRC32[bucket], buf.Bytes()...)
 	}
 
@@ -161,15 +166,17 @@ func (w *Writer) createIndex() (*MemoryIndex, error) {
 	return idx, nil
 }
 
-func (w *Writer) addOffset64(pos uint64) uint64 {
+func (w *Writer) addOffset64(pos uint64) (uint64, error) {
 	buf := new(bytes.Buffer)
-	binary.WriteUint64(buf, pos)
-	w.index.Offset64 = append(w.index.Offset64, buf.Bytes()...)
+	if err := binary.WriteUint64(buf, pos); err != nil {
+		return 0, err
+	}
 
+	w.index.Offset64 = append(w.index.Offset64, buf.Bytes()...)
 	index := uint64(w.offset64 | (1 << 31))
 	w.offset64++
 
-	return index
+	return index, nil
 }
 
 func (o objects) Len() int {
diff --git a/plumbing/format/idxfile/writer_test.go b/plumbing/format/idxfile/writer_test.go
index fba3e42..eaa8605 100644
--- a/plumbing/format/idxfile/writer_test.go
+++ b/plumbing/format/idxfile/writer_test.go
@@ -3,7 +3,7 @@ package idxfile_test
 import (
 	"bytes"
 	"encoding/base64"
-	"io/ioutil"
+	"io"
 
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/go-git/go-git/v5/plumbing/format/idxfile"
@@ -34,7 +34,7 @@ func (s *WriterSuite) TestWriter(c *C) {
 	c.Assert(err, IsNil)
 
 	idxFile := f.Idx()
-	expected, err := ioutil.ReadAll(idxFile)
+	expected, err := io.ReadAll(idxFile)
 	c.Assert(err, IsNil)
 	idxFile.Close()
 
@@ -65,7 +65,7 @@ func (s *WriterSuite) TestWriterLarge(c *C) {
 
 	// load fixture index
 	f := bytes.NewBufferString(fixtureLarge4GB)
-	expected, err := ioutil.ReadAll(base64.NewDecoder(base64.StdEncoding, f))
+	expected, err := io.ReadAll(base64.NewDecoder(base64.StdEncoding, f))
 	c.Assert(err, IsNil)
 
 	buf := new(bytes.Buffer)