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