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|
package storage
import (
"context"
"errors"
"io"
"io/ioutil"
"github.com/docker/distribution/registry/storage/driver"
)
const (
maxBlobGetSize = 4 << 20
)
func getContent(ctx context.Context, driver driver.StorageDriver, p string) ([]byte, error) {
r, err := driver.Reader(ctx, p, 0)
if err != nil {
return nil, err
}
defer r.Close()
return readAllLimited(r, maxBlobGetSize)
}
func readAllLimited(r io.Reader, limit int64) ([]byte, error) {
r = limitReader(r, limit)
return ioutil.ReadAll(r)
}
// limitReader returns a new reader limited to n bytes. Unlike io.LimitReader,
// this returns an error when the limit reached.
func limitReader(r io.Reader, n int64) io.Reader {
return &limitedReader{r: r, n: n}
}
// limitedReader implements a reader that errors when the limit is reached.
//
// Partially cribbed from net/http.MaxBytesReader.
type limitedReader struct {
r io.Reader // underlying reader
n int64 // max bytes remaining
err error // sticky error
}
func (l *limitedReader) Read(p []byte) (n int, err error) {
if l.err != nil {
return 0, l.err
}
if len(p) == 0 {
return 0, nil
}
// If they asked for a 32KB byte read but only 5 bytes are
// remaining, no need to read 32KB. 6 bytes will answer the
// question of the whether we hit the limit or go past it.
if int64(len(p)) > l.n+1 {
p = p[:l.n+1]
}
n, err = l.r.Read(p)
if int64(n) <= l.n {
l.n -= int64(n)
l.err = err
return n, err
}
n = int(l.n)
l.n = 0
l.err = errors.New("storage: read exceeds limit")
return n, l.err
}
|
