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 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. 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 b2 := b.b[b.off : b.off+4 : b.off+4] 31 v3 := int32(b2[3]) 32 v2 := int32(b2[2]) 33 v1 := int32(b2[1]) 34 v0 := int32(b2[0]) 35 return v0 | (v1 << 8) | (v2 << 16) | (v3 << 24) 36} 37 38// Uint32 returns a little endian uint32 starting at current offset. 39func (b byteReader) Uint32() uint32 { 40 b2 := b.b[b.off : b.off+4 : b.off+4] 41 v3 := uint32(b2[3]) 42 v2 := uint32(b2[2]) 43 v1 := uint32(b2[1]) 44 v0 := uint32(b2[0]) 45 return v0 | (v1 << 8) | (v2 << 16) | (v3 << 24) 46} 47 48// unread returns the unread portion of the input. 49func (b byteReader) unread() []byte { 50 return b.b[b.off:] 51} 52 53// remain will return the number of bytes remaining. 54func (b byteReader) remain() int { 55 return len(b.b) - b.off 56} 57