infra/proxyd/reader.go

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package proxyd
import (
"errors"
"io"
)
var ErrLimitReaderOverLimit = errors.New("over read limit")
func LimitReader(r io.Reader, n int64) io.Reader { return &LimitedReader{r, n} }
// A LimitedReader reads from R but limits the amount of
// data returned to just N bytes. Each call to Read
// updates N to reflect the new amount remaining.
// Unlike the standard library version, Read returns
// ErrLimitReaderOverLimit when N <= 0.
type LimitedReader struct {
R io.Reader // underlying reader
N int64 // max bytes remaining
}
func (l *LimitedReader) Read(p []byte) (int, error) {
if l.N <= 0 {
return 0, ErrLimitReaderOverLimit
}
if int64(len(p)) > l.N {
p = p[0:l.N]
}
n, err := l.R.Read(p)
l.N -= int64(n)
return n, err
}