YTSFlix_Go/vendor/github.com/anacrolix/missinggo/section_read_seeker.go

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2018-11-04 14:58:15 +00:00
package missinggo
import (
"context"
"fmt"
"io"
)
type sectionReadSeeker struct {
base io.ReadSeeker
off, size int64
}
type ReadSeekContexter interface {
io.ReadSeeker
ReadContexter
}
// Returns a ReadSeeker on a section of another ReadSeeker.
func NewSectionReadSeeker(base io.ReadSeeker, off, size int64) (ret ReadSeekContexter) {
ret = &sectionReadSeeker{
base: base,
off: off,
size: size,
}
seekOff, err := ret.Seek(0, io.SeekStart)
if err != nil {
panic(err)
}
if seekOff != 0 {
panic(seekOff)
}
return
}
func (me *sectionReadSeeker) Seek(off int64, whence int) (ret int64, err error) {
switch whence {
case io.SeekStart:
off += me.off
case io.SeekCurrent:
case io.SeekEnd:
off += me.off + me.size
whence = io.SeekStart
default:
err = fmt.Errorf("unhandled whence: %d", whence)
return
}
ret, err = me.base.Seek(off, whence)
ret -= me.off
return
}
func (me *sectionReadSeeker) ReadContext(ctx context.Context, b []byte) (int, error) {
off, err := me.Seek(0, io.SeekCurrent)
if err != nil {
return 0, err
}
left := me.size - off
if left <= 0 {
return 0, io.EOF
}
b = LimitLen(b, left)
if rc, ok := me.base.(ReadContexter); ok {
return rc.ReadContext(ctx, b)
}
if ctx != context.Background() {
// Can't handle cancellation.
panic(ctx)
}
return me.base.Read(b)
}
func (me *sectionReadSeeker) Read(b []byte) (int, error) {
return me.ReadContext(context.Background(), b)
}