clean up lazy union reader

Signed-off-by: Will Murphy <will.murphy@anchore.com>

syft/internal/unionreader/lazy_union_reader.go

@@ -9,8 +9,6 @@ import (
 	"sync"
 )
 
-const readSize int64 = 1024 * 1024
-
 // lazyUnionReader must implement UnionReader
 var _ UnionReader = (*lazyUnionReader)(nil)
 
@@ -21,7 +19,6 @@ var _ UnionReader = (*lazyUnionReader)(nil)
 type lazyUnionReader struct {
 	buf    []byte        // the bytes that have been read so far
 	cursor int64         // the current position where Read() will take place
-	done   bool          // whether we have seen EOF from rc
 	rc     io.ReadCloser // the underlying reader
 	mu     sync.Mutex    // exported methods must acquire this lock before changing any field. Unexported methods assume their caller acquired the lock
 }
@@ -35,7 +32,8 @@ func (c *lazyUnionReader) Read(p []byte) (n int, err error) {
 	if err != nil && !errors.Is(err, io.EOF) {
 		return 0, err
 	}
-	// stop reading either at cursor + length p, or the end of the buffer, whichever is sooner
+	// stop reading either at cursor + length p, or the end of the underlying reader,
+	// whichever is sooner
 	end := min(c.cursor+int64(len(p)), int64(len(c.buf)))
 	copy(p, c.buf[c.cursor:end])
 	n = int(end - c.cursor)
@@ -97,7 +95,6 @@ func (c *lazyUnionReader) readAll() error {
 	case err != nil:
 		return err
 	}
-	//c.maxRead = c.maxRead() + int64(len(buf))
 	c.buf = append(c.buf, buf...)
 	return nil
 }
@@ -120,16 +117,6 @@ func (c *lazyUnionReader) maxRead() int64 {
 	return int64(len(c.buf))
 }
 
-func max(ints ...int64) int64 {
-	var maxSeen int64
-	for _, in := range ints {
-		if in > maxSeen {
-			maxSeen = in
-		}
-	}
-	return maxSeen
-}
-
 func min(ints ...int64) int64 {
 	minSeeen := int64(math.MaxInt64) // really? math.MaxInt64 has type int?
 	for _, n := range ints {

syft/internal/unionreader/lazy_union_reader_test.go

@@ -2,13 +2,12 @@ package unionreader
 
 import (
 	"bytes"
-	"fmt"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 	"io"
 	"strings"
-	"sync"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 type spyingCloser struct {
@@ -38,9 +37,9 @@ func Test_lazyUnionReader_ReadAll(t *testing.T) {
 	subject, err := newLazyUnionReader(rc)
 	require.NoError(t, err)
 
-	bytes, err := io.ReadAll(subject)
+	b, err := io.ReadAll(subject)
 	require.NoError(t, err)
-	assert.Equal(t, "some data", string(bytes))
+	assert.Equal(t, "some data", string(b))
 }
 
 func Test_lazyUnionReader_RepeatedlyRead(t *testing.T) {
@@ -183,6 +182,15 @@ func Test_lazyUnionReader_Seek(t *testing.T) {
 			},
 			wantBytes: []byte("harehare"),
 		},
+		{
+			name: "read 4, skip 4, read 4",
+			commands: []command{
+				{readDst: make([]byte, 4)},
+				{seekOffset: 4, seekWhence: io.SeekCurrent},
+				{readDst: make([]byte, 4)},
+			},
+			wantBytes: []byte("thisa st"),
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -207,90 +215,3 @@ func Test_lazyUnionReader_Seek(t *testing.T) {
 		})
 	}
 }
-
-func Test_lazyUnionReader_ensureReadUntil(t *testing.T) {
-	type fields struct {
-		buf     []byte
-		cursor  int64
-		maxRead int64
-		done    bool
-		rc      io.ReadCloser
-		mu      sync.Mutex
-	}
-	type args struct {
-		offset int64
-	}
-	tests := []struct {
-		name    string
-		fields  fields
-		args    args
-		wantErr assert.ErrorAssertionFunc
-	}{
-		// TODO: Add test cases.
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			c := &lazyUnionReader{
-				buf:    tt.fields.buf,
-				cursor: tt.fields.cursor,
-				done:   tt.fields.done,
-				rc:     tt.fields.rc,
-				mu:     tt.fields.mu,
-			}
-			tt.wantErr(t, c.ensureReadUntil(tt.args.offset), fmt.Sprintf("ensureReadUntil(%v)", tt.args.offset))
-		})
-	}
-}
-
-func Test_lazyUnionReader_readAll(t *testing.T) {
-	type fields struct {
-		buf     []byte
-		cursor  int64
-		maxRead int64
-		done    bool
-		rc      io.ReadCloser
-		mu      sync.Mutex
-	}
-	tests := []struct {
-		name    string
-		fields  fields
-		wantErr assert.ErrorAssertionFunc
-	}{
-		// TODO: Add test cases.
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			c := &lazyUnionReader{
-				buf:    tt.fields.buf,
-				cursor: tt.fields.cursor,
-				done:   tt.fields.done,
-				rc:     tt.fields.rc,
-				mu:     tt.fields.mu,
-			}
-			tt.wantErr(t, c.readAll(), fmt.Sprintf("readAll()"))
-		})
-	}
-}
-
-func Test_newLazyUnionReader(t *testing.T) {
-	type args struct {
-		readCloser io.ReadCloser
-	}
-	tests := []struct {
-		name    string
-		args    args
-		want    UnionReader
-		wantErr assert.ErrorAssertionFunc
-	}{
-		// TODO: Add test cases.
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got, err := newLazyUnionReader(tt.args.readCloser)
-			if !tt.wantErr(t, err, fmt.Sprintf("newLazyUnionReader(%v)", tt.args.readCloser)) {
-				return
-			}
-			assert.Equalf(t, tt.want, got, "newLazyUnionReader(%v)", tt.args.readCloser)
-		})
-	}
-}

syft/internal/unionreader/union_reader.go

@@ -1,9 +1,10 @@
 package unionreader
 
 import (
+	"io"
+
 	macho "github.com/anchore/go-macholibre"
 	"github.com/anchore/syft/internal/log"
-	"io"
 )
 
 // UnionReader is a single interface with all reading functions needed by multi-arch binary catalogers
@@ -41,23 +42,4 @@ func GetUnionReader(readerCloser io.ReadCloser) (UnionReader, error) {
 		return reader, nil
 	}
 	return newLazyUnionReader(readerCloser)
-	//
-	//b, err := io.ReadAll(readerCloser)
-	//if err != nil {
-	//	return nil, fmt.Errorf("unable to read contents from binary: %w", err)
-	//}
-	//
-	//bytesReader := bytes.NewReader(b)
-	//
-	//reader = struct {
-	//	io.ReadCloser
-	//	io.ReaderAt
-	//	io.Seeker
-	//}{
-	//	ReadCloser: io.NopCloser(bytesReader),
-	//	ReaderAt:   bytesReader,
-	//	Seeker:     bytesReader,
-	//}
-	//
-	//return reader, nil
 }