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