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