maddy

 1/*
 2Maddy Mail Server - Composable all-in-one email server.
 3Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
 4
 5This program is free software: you can redistribute it and/or modify
 6it under the terms of the GNU General Public License as published by
 7the Free Software Foundation, either version 3 of the License, or
 8(at your option) any later version.
 9
10This program is distributed in the hope that it will be useful,
11but WITHOUT ANY WARRANTY; without even the implied warranty of
12MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13GNU General Public License for more details.
14
15You should have received a copy of the GNU General Public License
16along with this program.  If not, see <https://www.gnu.org/licenses/>.
17*/
18
19package buffer
20
21import (
22	"bytes"
23)
24
25// BytesReader is a wrapper for bytes.Reader that stores the original []byte
26// value and allows to retrieve it.
27//
28// It is meant for passing to libraries that expect a io.Reader
29// but apply certain optimizations when the Reader implements
30// Bytes() interface.
31type BytesReader struct {
32	*bytes.Reader
33	value []byte
34}
35
36// Bytes returns the unread portion of underlying slice used to construct
37// BytesReader.
38func (br BytesReader) Bytes() []byte {
39	return br.value[int(br.Size())-br.Len():]
40}
41
42// Copy returns the BytesReader reading from the same slice as br at the same
43// position.
44func (br BytesReader) Copy() BytesReader {
45	return NewBytesReader(br.Bytes())
46}
47
48// Close is a dummy method for implementation of io.Closer so BytesReader can
49// be used in MemoryBuffer directly.
50func (br BytesReader) Close() error {
51	return nil
52}
53
54func NewBytesReader(b []byte) BytesReader {
55	// BytesReader and not *BytesReader because BytesReader already wraps two
56	// pointers and double indirection would be pointless.
57	return BytesReader{
58		Reader: bytes.NewReader(b),
59		value:  b,
60	}
61}