restic/internal/backend/readerat.go

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package backend
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import (
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"context"
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"io"
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"github.com/restic/restic/internal/debug"
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"github.com/restic/restic/internal/errors"
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)
type backendReaderAt struct {
ctx context.Context
be Backend
h Handle
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}
func (brd backendReaderAt) ReadAt(p []byte, offset int64) (n int, err error) {
return ReadAt(brd.ctx, brd.be, brd.h, offset, p)
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}
// ReaderAt returns an io.ReaderAt for a file in the backend. The returned reader
// should not escape the caller function to avoid unexpected interactions with the
// embedded context
func ReaderAt(ctx context.Context, be Backend, h Handle) io.ReaderAt {
return backendReaderAt{ctx: ctx, be: be, h: h}
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}
// ReadAt reads from the backend handle h at the given position.
func ReadAt(ctx context.Context, be Backend, h Handle, offset int64, p []byte) (n int, err error) {
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debug.Log("ReadAt(%v) at %v, len %v", h, offset, len(p))
err = be.Load(ctx, h, len(p), offset, func(rd io.Reader) (ierr error) {
n, ierr = io.ReadFull(rd, p)
return ierr
})
if err != nil {
return 0, errors.Wrapf(err, "ReadFull(%v)", h)
}
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debug.Log("ReadAt(%v) ReadFull returned %v bytes", h, n)
return n, nil
}