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 6package huff0 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. 12type byteReader struct { 13 b []byte 14 off int 15} 16 17// init will initialize the reader and set the input. 18func (b *byteReader) init(in []byte) { 19 b.b = in 20 b.off = 0 21} 22 23// advance the stream b n bytes. 24func (b *byteReader) advance(n uint) { 25 b.off += int(n) 26} 27 28// Int32 returns a little endian int32 starting at current offset. 29func (b byteReader) Int32() int32 { 30 v3 := int32(b.b[b.off+3]) 31 v2 := int32(b.b[b.off+2]) 32 v1 := int32(b.b[b.off+1]) 33 v0 := int32(b.b[b.off]) 34 return (v3 << 24) | (v2 << 16) | (v1 << 8) | v0 35} 36 37// Uint32 returns a little endian uint32 starting at current offset. 38func (b byteReader) Uint32() uint32 { 39 v3 := uint32(b.b[b.off+3]) 40 v2 := uint32(b.b[b.off+2]) 41 v1 := uint32(b.b[b.off+1]) 42 v0 := uint32(b.b[b.off]) 43 return (v3 << 24) | (v2 << 16) | (v1 << 8) | v0 44} 45 46// unread returns the unread portion of the input. 47func (b byteReader) unread() []byte { 48 return b.b[b.off:] 49} 50 51// remain will return the number of bytes remaining. 52func (b byteReader) remain() int { 53 return len(b.b) - b.off 54} 55