Try adding equalfile package

drive-demuxer.go

@@ -1,10 +1,9 @@
 package main
 
 import (
-	"bytes"
 	"flag"
 	"github.com/cheggaaa/pb/v3"
-	"io"
+	"github.com/udhos/equalfile"
 	"log"
 	"os"
 	"path"
@@ -18,6 +17,7 @@ type TopLevel struct {
 	RightOutput    string
 	DryRun         bool
 	Bar            *pb.ProgressBar
+	Comparer       *equalfile.Cmp
 }
 
 type Step struct {
@@ -214,67 +214,12 @@ func (s *Step) ListChildren() []string {
 func (s *Step) AreFilesIdentical(child string) bool {
 	leftInPath := s.InputPath(child, LEFT)
 	rightInPath := s.InputPath(child, RIGHT)
-	leftInfo, err := os.Stat(leftInPath)
+	equal, err := s.Comparer.CompareFile(leftInPath, rightInPath)
 	if err != nil {
-		log.Printf("Error statting path %s: %s\n", leftInPath, err)
+		log.Printf("Error comparing path %s and %s: %s\n", leftInPath, rightInPath, err)
 		return false
 	}
-	rightInfo, err := os.Stat(rightInPath)
-	if err != nil {
-		log.Printf("Error statting path %s: %s\n", rightInPath, err)
-		return false
-	}
-	if leftInfo.Size() != rightInfo.Size() {
-		return false
-	}
-
-	leftFile, err := os.OpenFile(leftInPath, os.O_RDONLY, 0)
-	if err != nil {
-		log.Printf("Error opening path %s: %s\n", leftInPath, err)
-		return false
-	}
-	defer func() {
-		err := leftFile.Close()
-		if err != nil {
-			log.Printf("Error closing %s: %s\n", leftInPath, err)
-		}
-	}()
-	rightFile, err := os.OpenFile(rightInPath, os.O_RDONLY, 0)
-	if err != nil {
-		log.Printf("Error opening path %s: %s\n", rightInPath, err)
-		return false
-	}
-	defer func() {
-		err := rightFile.Close()
-		if err != nil {
-			log.Printf("Error closing %s: %s\n", rightInPath, err)
-		}
-	}()
-
-	// 4 MB buffers
-	var leftData [4194304]byte
-	var rightData [4194304]byte
-	for {
-		leftRead, err := leftFile.Read(leftData[:])
-		if err != nil && err != io.EOF {
-			log.Printf("Error reading %s: %s\n", leftInPath, err)
-			return false
-		}
-		rightRead, err := rightFile.Read(rightData[:])
-		if err != nil && err != io.EOF {
-			log.Printf("Error reading %s: %s\n", rightInPath, err)
-			return false
-		}
-		if leftRead != rightRead {
-			return false
-		}
-		if !bytes.Equal(leftData[:leftRead], rightData[:rightRead]) {
-			return false
-		}
-		if err == io.EOF {
-			return true
-		}
-	}
+	return equal
 }
 
 func (s *Step) Walk() {
@@ -349,7 +294,8 @@ func (s *Step) Walk() {
 
 func main() {
 	settings := TopLevel{
-		Bar: pb.StartNew(1),
+		Bar:      pb.StartNew(1),
+		Comparer: equalfile.New(nil, equalfile.Options{}),
 	}
 	flag.StringVar(&settings.LeftInput,
 		"left-input", "./input/left", "The name of the left side of the input.")