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Merge pull request #17 from jarxorg/feature/improve-multireader
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Change public interfaces to create multi readers and added some funct…
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@mojatter
mojatter authored Aug 4, 2022
2 parents 05983ed + 49407d2 commit ba6db99
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Showing 3 changed files with 214 additions and 97 deletions.
2 changes: 1 addition & 1 deletion example_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ func ExampleNewWriteSeekBuffer() {
}

func ExampleMultiReadSeeker() {
r, _ := io2.MultiReadSeeker(
r, _ := io2.NewMultiReadSeeker(
strings.NewReader("Hello !"),
strings.NewReader(" World"),
)
Expand Down
141 changes: 96 additions & 45 deletions multireader.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,50 +7,84 @@ import (
"strings"
)

// MultiReader represents a multiple reader.
type MultiReader interface {
io.Reader
// Current returns a current index of multiple readers. The current starts 0.
Current() int
}

// MultiReadCloser is the interface that groups the MultiReader and Close methods.
type MultiReadCloser interface {
MultiReader
io.Closer
}

// MultiReadCloser is the interface that groups the MultiReader, Seek and SeekReader methods.
type MultiReadSeeker interface {
MultiReader
io.Seeker
// SeekReader sets the offset of multiple readers.
SeekReader(current int) (int64, error)
}

// MultiReadSeekCloser is the interface that groups the MultiReadSeeker and Close methods.
type MultiReadSeekCloser interface {
MultiReadSeeker
io.Closer
}

var errSkip = errors.New("skip")

type reader struct {
type singleReader struct {
io.ReadSeekCloser
off int64
length int64
}

type multiReader struct {
rs []*reader
off int
length int64
rs []*singleReader
current int
length int64
}

var _ io.ReadSeekCloser = (*multiReader)(nil)

// MultiReadCloser returns a ReaderCloser that's the logical concatenation
// NewMultiReader creates a Reader that's the logical concatenation
// of the provided input readers.
func MultiReadCloser(rs ...io.ReadCloser) io.ReadCloser {
ds := make([]*reader, len(rs))
func NewMultiReader(rs ...io.Reader) MultiReader {
ds := make([]*singleReader, len(rs))
for i, r := range rs {
ds[i] = &reader{
ReadSeekCloser: Delegate(r),
}
ds[i] = &singleReader{ReadSeekCloser: Delegate(r)}
}
io.MultiReader()
return &multiReader{rs: ds}
}

// MultiReadSeeker returns a ReadSeeker that's the logical concatenation
// NewMultiReadCloser create a ReaderCloser that's the logical concatenation
// of the provided input readers.
func MultiReadSeeker(rs ...io.ReadSeeker) (io.ReadSeeker, error) {
func NewMultiReadCloser(rs ...io.ReadCloser) MultiReadCloser {
ds := make([]*singleReader, len(rs))
for i, r := range rs {
ds[i] = &singleReader{ReadSeekCloser: Delegate(r)}
}
return &multiReader{rs: ds}
}

// NewMultiReadSeeker creates a ReadSeeker that's the logical concatenation
// of the provided input readers.
func NewMultiReadSeeker(rs ...io.ReadSeeker) (MultiReadSeeker, error) {
ds := make([]io.ReadSeekCloser, len(rs))
for i, r := range rs {
ds[i] = NopReadSeekCloser(r)
}
return MultiReadSeekCloser(ds...)
return NewMultiReadSeekCloser(ds...)
}

// MultiReadSeekCloser returns a ReadSeekCloser that's the logical concatenation
// of the provided input readers.
func MultiReadSeekCloser(rs ...io.ReadSeekCloser) (io.ReadSeekCloser, error) {
// NewMultiReadSeekCloser creates a ReadSeekCloser that's the logical
// concatenation of the provided input readers.
func NewMultiReadSeekCloser(rs ...io.ReadSeekCloser) (MultiReadSeekCloser, error) {
length := int64(0)
ds := make([]*reader, len(rs))
ds := make([]*singleReader, len(rs))
for i, r := range rs {
n, err := r.Seek(0, io.SeekEnd)
if err != nil {
Expand All @@ -59,7 +93,7 @@ func MultiReadSeekCloser(rs ...io.ReadSeekCloser) (io.ReadSeekCloser, error) {
if _, err = r.Seek(0, io.SeekStart); err != nil {
return nil, err
}
ds[i] = &reader{
ds[i] = &singleReader{
ReadSeekCloser: Delegate(r),
length: n,
}
Expand All @@ -68,43 +102,48 @@ func MultiReadSeekCloser(rs ...io.ReadSeekCloser) (io.ReadSeekCloser, error) {
return &multiReader{rs: ds, length: length}, nil
}

func (mr *multiReader) each(i int, offset int64, fn func(r *reader) error) error {
mr.off = i
// Current returns a current index of multiple readers.
func (mr *multiReader) Current() int {
return mr.current
}

func (mr *multiReader) each(i int, offset int64, fn func(r *singleReader) error) error {
mr.current = i
if offset >= 0 {
for ; mr.off < len(mr.rs); mr.off++ {
if err := fn(mr.rs[mr.off]); err != nil {
for ; mr.current < len(mr.rs); mr.current++ {
if err := fn(mr.rs[mr.current]); err != nil {
if err == errSkip {
err = nil
}
return err
}
}
if mr.off >= len(mr.rs) {
mr.off = len(mr.rs) - 1
if mr.current >= len(mr.rs) {
mr.current = len(mr.rs) - 1
}
return nil
}
for ; mr.off >= 0; mr.off-- {
if err := fn(mr.rs[mr.off]); err != nil {
for ; mr.current >= 0; mr.current-- {
if err := fn(mr.rs[mr.current]); err != nil {
if err == errSkip {
err = nil
}
return err
}
}
if mr.off < 0 {
mr.off = 0
if mr.current < 0 {
mr.current = 0
}
return nil
}

func (mr *multiReader) Read(p []byte) (n int, err error) {
if mr.off >= len(mr.rs) {
if mr.current >= len(mr.rs) {
return 0, io.EOF
}
off := 0
for ; mr.off < len(mr.rs); mr.off++ {
r := mr.rs[mr.off]
for ; mr.current < len(mr.rs); mr.current++ {
r := mr.rs[mr.current]
n, err = r.Read(p[off:])
if err != nil {
return 0, err
Expand All @@ -130,8 +169,20 @@ func (mr *multiReader) Seek(offset int64, whence int) (int64, error) {
return 0, errors.New("invalid whence")
}

// SeekReader sets the offset of multiple readers. The current starts 0.
func (mr *multiReader) SeekReader(current int) (int64, error) {
var offset int64
for i, r := range mr.rs {
if i >= current {
break
}
offset += r.length
}
return mr.Seek(offset, io.SeekStart)
}

func (mr *multiReader) resetTails() error {
for i := mr.off + 1; i < len(mr.rs); i++ {
for i := mr.current + 1; i < len(mr.rs); i++ {
r := mr.rs[i]
if _, err := r.Seek(0, io.SeekStart); err != nil {
return err
Expand All @@ -146,9 +197,9 @@ func (mr *multiReader) seekStart(offset int64, start int) (int64, error) {
for i := 0; i < start; i++ {
off += mr.rs[i].length
}
err := mr.each(start, offset, func(r *reader) error {
err := mr.each(start, offset, func(r *singleReader) error {
safeOffset := offset
if mr.off != len(mr.rs)-1 && safeOffset > (r.length-r.off) {
if mr.current != len(mr.rs)-1 && safeOffset > (r.length-r.off) {
safeOffset = (r.length - r.off)
}
n, err := r.Seek(safeOffset, io.SeekStart)
Expand All @@ -175,18 +226,18 @@ func (mr *multiReader) seekStart(offset int64, start int) (int64, error) {

func (mr *multiReader) seekCurrent(offset int64) (int64, error) {
off := int64(0)
for i := 0; i < mr.off; i++ {
for i := 0; i < mr.current; i++ {
off += mr.rs[i].length
}

r := mr.rs[mr.off]
r := mr.rs[mr.current]
safeOffset := offset
if offset >= 0 {
if mr.off != len(mr.rs)-1 && safeOffset > (r.length-r.off) {
if mr.current != len(mr.rs)-1 && safeOffset > (r.length-r.off) {
safeOffset = (r.length - r.off)
}
} else {
if mr.off != 0 && -safeOffset > r.off {
if mr.current != 0 && -safeOffset > r.off {
safeOffset = -r.off
}
}
Expand All @@ -197,9 +248,9 @@ func (mr *multiReader) seekCurrent(offset int64) (int64, error) {
r.off = n
if diffset := offset - safeOffset; diffset != 0 {
if offset >= 0 {
return mr.seekStart(diffset, mr.off+1)
return mr.seekStart(diffset, mr.current+1)
}
return mr.seekEnd(diffset, mr.off-1)
return mr.seekEnd(diffset, mr.current-1)
}
if err := mr.resetTails(); err != nil {
return 0, err
Expand All @@ -212,9 +263,9 @@ func (mr *multiReader) seekEnd(offset int64, end int) (int64, error) {
for i := end + 1; i < len(mr.rs); i++ {
off -= mr.rs[i].length
}
err := mr.each(end, offset, func(r *reader) error {
err := mr.each(end, offset, func(r *singleReader) error {
safeOffset := offset
if mr.off != 0 && -safeOffset > r.length {
if mr.current != 0 && -safeOffset > r.length {
safeOffset = -r.length
}
n, err := r.Seek(safeOffset, io.SeekEnd)
Expand All @@ -238,7 +289,7 @@ func (mr *multiReader) seekEnd(offset int64, end int) (int64, error) {

func (mr *multiReader) Close() error {
var errs []string
mr.each(0, 1, func(r *reader) error {
mr.each(0, 1, func(r *singleReader) error {
if err := r.Close(); err != nil {
errs = append(errs, err.Error())
}
Expand All @@ -248,7 +299,7 @@ func (mr *multiReader) Close() error {
return fmt.Errorf("failed to close: %s", strings.Join(errs, "; "))
}
mr.rs = nil
mr.off = 0
mr.current = 0
mr.length = 0
return nil
}
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