DockerCLI/cli/context/store/io_utils.go

30 lines
602 B
Go

package store
import (
"errors"
"io"
)
// LimitedReader is a fork of io.LimitedReader to override Read.
type LimitedReader struct {
R io.Reader
N int64 // max bytes remaining
}
// Read is a fork of io.LimitedReader.Read that returns an error when limit exceeded.
func (l *LimitedReader) Read(p []byte) (n int, err error) {
if l.N < 0 {
return 0, errors.New("read exceeds the defined limit")
}
if l.N == 0 {
return 0, io.EOF
}
// have to cap N + 1 otherwise we won't hit limit err
if int64(len(p)) > l.N+1 {
p = p[0 : l.N+1]
}
n, err = l.R.Read(p)
l.N -= int64(n)
return n, err
}