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// Copyright 2019 the u-root Authors. All rights reserved
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package uio
import (
"io"
)
// AlignReader keeps track of how many bytes were read so the reader can be
// aligned at a future time.
type AlignReader struct {
R io.Reader
N int
}
// Read reads from the underlying io.Reader.
func (r *AlignReader) Read(b []byte) (int, error) {
n, err := r.R.Read(b)
r.N += n
return n, err
}
// ReadByte reads one byte from the underlying io.Reader.
func (r *AlignReader) ReadByte() (byte, error) {
b := make([]byte, 1)
_, err := io.ReadFull(r, b)
return b[0], err
}
// Align aligns the reader to the given number of bytes and returns the
// bytes read to pad it.
func (r *AlignReader) Align(n int) ([]byte, error) {
if r.N%n == 0 {
return []byte{}, nil
}
pad := make([]byte, n-r.N%n)
m, err := io.ReadFull(r, pad)
return pad[:m], err
}
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