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restic/internal/backend/utils.go
greatroar 190d8e2f51 Flatten backend.LimitedReadCloser structure
This inlines the io.LimitedReader into the LimitedReadCloser body to
achieve fewer allocations. Results on linux/amd64:

name                                      old time/op    new time/op    delta
Backend/BenchmarkLoadPartialFile-8           412µs ± 4%     413µs ± 4%    ~     (p=0.634 n=17+17)
Backend/BenchmarkLoadPartialFileOffset-8     455µs ±13%     441µs ±10%    ~     (p=0.072 n=20+18)

name                                      old speed      new speed      delta
Backend/BenchmarkLoadPartialFile-8        10.2GB/s ± 3%  10.2GB/s ± 4%    ~     (p=0.817 n=16+17)
Backend/BenchmarkLoadPartialFileOffset-8  9.25GB/s ±12%  9.54GB/s ± 9%    ~     (p=0.072 n=20+18)

name                                      old alloc/op   new alloc/op   delta
Backend/BenchmarkLoadPartialFile-8            888B ± 0%      872B ± 0%  -1.80%  (p=0.000 n=15+15)
Backend/BenchmarkLoadPartialFileOffset-8      888B ± 0%      872B ± 0%  -1.80%  (p=0.000 n=15+15)

name                                      old allocs/op  new allocs/op  delta
Backend/BenchmarkLoadPartialFile-8            18.0 ± 0%      17.0 ± 0%  -5.56%  (p=0.000 n=15+15)
Backend/BenchmarkLoadPartialFileOffset-8      18.0 ± 0%      17.0 ± 0%  -5.56%  (p=0.000 n=15+15)
2020-06-17 13:11:45 +02:00

59 lines
1.6 KiB
Go

package backend
import (
"bytes"
"context"
"io"
"github.com/restic/restic/internal/restic"
)
// LoadAll reads all data stored in the backend for the handle into the given
// buffer, which is truncated. If the buffer is not large enough or nil, a new
// one is allocated.
func LoadAll(ctx context.Context, buf []byte, be restic.Backend, h restic.Handle) ([]byte, error) {
err := be.Load(ctx, h, 0, 0, func(rd io.Reader) error {
// make sure this is idempotent, in case an error occurs this function may be called multiple times!
wr := bytes.NewBuffer(buf[:0])
_, cerr := io.Copy(wr, rd)
if cerr != nil {
return cerr
}
buf = wr.Bytes()
return nil
})
if err != nil {
return nil, err
}
return buf, nil
}
// LimitedReadCloser wraps io.LimitedReader and exposes the Close() method.
type LimitedReadCloser struct {
io.Closer
io.LimitedReader
}
// LimitReadCloser returns a new reader wraps r in an io.LimitedReader, but also
// exposes the Close() method.
func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser {
return &LimitedReadCloser{Closer: r, LimitedReader: io.LimitedReader{R: r, N: n}}
}
// DefaultLoad implements Backend.Load using lower-level openReader func
func DefaultLoad(ctx context.Context, h restic.Handle, length int, offset int64,
openReader func(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error),
fn func(rd io.Reader) error) error {
rd, err := openReader(ctx, h, length, offset)
if err != nil {
return err
}
err = fn(rd)
if err != nil {
rd.Close() // ignore secondary errors closing the reader
return err
}
return rd.Close()
}