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package s3
import (
"io"
)
type ReaderAtCloser interface {
io.ReaderAt
io.Closer
}
type readerAtCloser struct {
offset int64
rc io.ReadCloser
ra io.ReaderAt
open func(offset int64) (io.ReadCloser, error)
closed bool
}
func toReaderAtCloser(open func(offset int64) (io.ReadCloser, error)) ReaderAtCloser {
return &readerAtCloser{
open: open,
}
}
func (hrs *readerAtCloser) ReadAt(p []byte, off int64) (n int, err error) {
if hrs.closed {
return 0, io.EOF
}
if hrs.ra != nil {
return hrs.ra.ReadAt(p, off)
}
if hrs.rc == nil || off != hrs.offset {
if hrs.rc != nil {
hrs.rc.Close()
hrs.rc = nil
}
rc, err := hrs.open(off)
if err != nil {
return 0, err
}
hrs.rc = rc
}
if ra, ok := hrs.rc.(io.ReaderAt); ok {
hrs.ra = ra
n, err = ra.ReadAt(p, off)
} else {
for {
var nn int
nn, err = hrs.rc.Read(p)
n += nn
p = p[nn:]
if nn == len(p) || err != nil {
break
}
}
}
hrs.offset += int64(n)
return
}
func (hrs *readerAtCloser) Close() error {
if hrs.closed {
return nil
}
hrs.closed = true
if hrs.rc != nil {
return hrs.rc.Close()
}
return nil
}
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