forked from TrueCloudLab/restic
86 lines
1.9 KiB
Go
86 lines
1.9 KiB
Go
package limiter
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import (
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"context"
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"io"
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"github.com/restic/restic/internal/restic"
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)
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// LimitBackend wraps a Backend and applies rate limiting to Load() and Save()
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// calls on the backend.
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func LimitBackend(be restic.Backend, l Limiter) restic.Backend {
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return rateLimitedBackend{
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Backend: be,
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limiter: l,
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}
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}
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type rateLimitedBackend struct {
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restic.Backend
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limiter Limiter
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}
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func (r rateLimitedBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
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limited := limitedRewindReader{
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RewindReader: rd,
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limited: r.limiter.Upstream(rd),
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}
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return r.Backend.Save(ctx, h, limited)
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}
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type limitedRewindReader struct {
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restic.RewindReader
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limited io.Reader
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}
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func (l limitedRewindReader) Read(b []byte) (int, error) {
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return l.limited.Read(b)
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}
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func (r rateLimitedBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64, consumer func(rd io.Reader) error) error {
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return r.Backend.Load(ctx, h, length, offset, func(rd io.Reader) error {
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return consumer(newDownstreamLimitedReadCloser(rd, r.limiter, nil))
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})
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}
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type limitedReadCloser struct {
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io.Reader
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original io.ReadCloser
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}
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type limitedReadWriteToCloser struct {
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limitedReadCloser
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writerTo io.WriterTo
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limiter Limiter
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}
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func newDownstreamLimitedReadCloser(rd io.Reader, limiter Limiter, original io.ReadCloser) io.ReadCloser {
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lrd := limitedReadCloser{
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Reader: limiter.Downstream(rd),
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original: original,
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}
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if _, ok := rd.(io.WriterTo); ok {
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return &limitedReadWriteToCloser{
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limitedReadCloser: lrd,
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writerTo: rd.(io.WriterTo),
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limiter: limiter,
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}
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}
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return &lrd
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}
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func (l limitedReadCloser) Close() error {
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if l.original == nil {
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return nil
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}
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return l.original.Close()
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}
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func (l limitedReadWriteToCloser) WriteTo(w io.Writer) (int64, error) {
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return l.writerTo.WriteTo(l.limiter.DownstreamWriter(w))
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}
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var _ restic.Backend = (*rateLimitedBackend)(nil)
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