1 // Copyright 2018 Klaus Post. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 // Based on work Copyright (c) 2013, Yann Collet, released under BSD License.
5 6 package fse
7 8 // byteReader provides a byte reader that reads
9 // little endian values from a byte stream.
10 // The input stream is manually advanced.
11 // The reader performs no bounds checks.
12 type byteReader struct {
13 b []byte
14 off int
15 }
16 17 // init will initialize the reader and set the input.
18 func (b *byteReader) init(in []byte) {
19 b.b = in
20 b.off = 0
21 }
22 23 // advance the stream b n bytes.
24 func (b *byteReader) advance(n uint) {
25 b.off += int(n)
26 }
27 28 // Uint32 returns a little endian uint32 starting at current offset.
29 func (b byteReader) Uint32() uint32 {
30 b2 := b.b[b.off:]
31 b2 = b2[:4]
32 v3 := uint32(b2[3])
33 v2 := uint32(b2[2])
34 v1 := uint32(b2[1])
35 v0 := uint32(b2[0])
36 return v0 | (v1 << 8) | (v2 << 16) | (v3 << 24)
37 }
38 39 // unread returns the unread portion of the input.
40 func (b byteReader) unread() []byte {
41 return b.b[b.off:]
42 }
43 44 // remain will return the number of bytes remaining.
45 func (b byteReader) remain() int {
46 return len(b.b) - b.off
47 }
48