HW7 is completed

hw07_file_copying/copy.go

@@ -2,14 +2,98 @@ package main
 
 import (
 	"errors"
+	"io"
+	"os"
+
+	"github.com/cheggaaa/pb/v3"
 )
 
 var (
+	ErrFileNotExist          = errors.New("file doesn't exist")
 	ErrUnsupportedFile       = errors.New("unsupported file")
 	ErrOffsetExceedsFileSize = errors.New("offset exceeds file size")
 )
 
 func Copy(fromPath string, toPath string, offset, limit int64) error {
-	// Place your code here
+	err := fileErrors(fromPath, offset)
+	if err != nil {
+		return err
+	}
+
+	// use limited reader instead default reader
+	limit = changeZeroLimit(fromPath, limit)
+	limitedReader, err := openLimitedReader(fromPath, offset, limit)
+	if err != nil {
+		return err
+	}
+
+	// define bar reader
+	bar := pb.Full.Start64(limit)
+	defer bar.Finish()
+	barReader := bar.NewProxyReader(limitedReader)
+	defer barReader.Close()
+
+	// define default writer
+	writer, err := os.Create(toPath)
+	if err != nil {
+		return err
+	}
+	defer writer.Close()
+
+	_, err = io.Copy(writer, barReader)
+	if err != nil {
+		return err
+	}
+
 	return nil
 }
+
+func fileErrors(fromPath string, offset int64) error {
+	fileSt, err := os.Stat(fromPath)
+	if os.IsNotExist(err) {
+		return ErrFileNotExist
+	}
+	// check other errors
+	if err != nil {
+		return err
+	}
+
+	fileSize := fileSt.Size()
+	if fileSize < 0 {
+		return ErrUnsupportedFile
+	}
+	if offset > fileSize {
+		return ErrOffsetExceedsFileSize
+	}
+
+	return nil
+}
+
+func changeZeroLimit(fromPath string, limit int64) int64 {
+	fileSt, err := os.Stat(fromPath)
+	// stay limit unchanged if stat caught error
+	if err != nil {
+		return limit
+	}
+
+	if limit < 1 {
+		limit = fileSt.Size()
+	}
+
+	return limit
+}
+
+func openLimitedReader(fromPath string, offset, limit int64) (io.Reader, error) {
+	reader, err := os.Open(fromPath)
+	if err != nil {
+		return reader, err
+	}
+
+	_, err = reader.Seek(offset, io.SeekStart)
+	if err != nil {
+		return reader, err
+	}
+	limitedReader := io.LimitReader(reader, limit)
+
+	return limitedReader, nil
+}

hw07_file_copying/copy_test.go

@@ -1,7 +1,20 @@
 package main
 
-import "testing"
+import (
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
 
 func TestCopy(t *testing.T) {
-	// Place your code here
+	t.Run("Check not exists file", func(t *testing.T) {
+		err := Copy("not-exist-file", "", 0, 0)
+		require.Equal(t, err, ErrFileNotExist)
+	})
+
+	t.Run("Too long offset", func(t *testing.T) {
+		err := Copy("testdata/input.txt", "", int64(math.Exp2(20)), 0)
+		require.Equal(t, err, ErrOffsetExceedsFileSize)
+	})
 }

hw07_file_copying/go.mod

@@ -1,3 +1,8 @@
-module github.com/fixme_my_friend/hw07_file_copying
+module github.com/ezhk/golang-learning/hw07_file_copying
 
 go 1.14
+
+require (
+	github.com/cheggaaa/pb/v3 v3.0.4
+	github.com/stretchr/testify v1.6.1
+)

hw07_file_copying/go.sum

@@ -0,0 +1,28 @@
+github.com/VividCortex/ewma v1.1.1 h1:MnEK4VOv6n0RSY4vtRe3h11qjxL3+t0B8yOL8iMXdcM=
+github.com/VividCortex/ewma v1.1.1/go.mod h1:2Tkkvm3sRDVXaiyucHiACn4cqf7DpdyLvmxzcbUokwA=
+github.com/cheggaaa/pb v1.0.28 h1:kWGpdAcSp3MxMU9CCHOwz/8V0kCHN4+9yQm2MzWuI98=
+github.com/cheggaaa/pb v2.0.7+incompatible h1:gLKifR1UkZ/kLkda5gC0K6c8g+jU2sINPtBeOiNlMhU=
+github.com/cheggaaa/pb/v3 v3.0.4 h1:QZEPYOj2ix6d5oEg63fbHmpolrnNiwjUsk+h74Yt4bM=
+github.com/cheggaaa/pb/v3 v3.0.4/go.mod h1:7rgWxLrAUcFMkvJuv09+DYi7mMUYi8nO9iOWcvGJPfw=
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fatih/color v1.7.0 h1:DkWD4oS2D8LGGgTQ6IvwJJXSL5Vp2ffcQg58nFV38Ys=
+github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
+github.com/mattn/go-colorable v0.1.2 h1:/bC9yWikZXAL9uJdulbSfyVNIR3n3trXl+v8+1sx8mU=
+github.com/mattn/go-colorable v0.1.2/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
+github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
+github.com/mattn/go-isatty v0.0.10 h1:qxFzApOv4WsAL965uUPIsXzAKCZxN2p9UqdhFS4ZW10=
+github.com/mattn/go-isatty v0.0.10/go.mod h1:qgIWMr58cqv1PHHyhnkY9lrL7etaEgOFcMEpPG5Rm84=
+github.com/mattn/go-runewidth v0.0.7 h1:Ei8KR0497xHyKJPAv59M1dkC+rOZCMBJ+t3fZ+twI54=
+github.com/mattn/go-runewidth v0.0.7/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191128015809-6d18c012aee9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

hw07_file_copying/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"log"
 )
 
 var (
@@ -18,5 +19,9 @@ func init() {
 
 func main() {
 	flag.Parse()
-	// Place your code here
+
+	err := Copy(from, to, offset, limit)
+	if err != nil {
+		log.Fatal(err)
+	}
 }