57 lines
1.4 KiB
Go
57 lines
1.4 KiB
Go
|
// Copyright 2018 Klaus Post. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
// Based on work Copyright (c) 2013, Yann Collet, released under BSD License.
|
||
|
|
|
||
|
|
package fse
|
||
|
|
|
||
|
|
// byteReader provides a byte reader that reads
|
||
|
|
// little endian values from a byte stream.
|
||
|
|
// The input stream is manually advanced.
|
||
|
|
// The reader performs no bounds checks.
|
||
|
|
type byteReader struct {
|
||
|
|
b []byte
|
||
|
|
off int
|
||
|
|
}
|
||
|
|
|
||
|
|
// init will initialize the reader and set the input.
|
||
|
|
func (b *byteReader) init(in []byte) {
|
||
|
|
b.b = in
|
||
|
|
b.off = 0
|
||
|
|
}
|
||
|
|
|
||
|
|
// advance the stream b n bytes.
|
||
|
|
func (b *byteReader) advance(n uint) {
|
||
|
|
b.off += int(n)
|
||
|
|
}
|
||
|
|
|
||
|
|
// Int32 returns a little endian int32 starting at current offset.
|
||
|
|
func (b byteReader) Int32() int32 {
|
||
|
|
b2 := b.b[b.off : b.off+4 : b.off+4]
|
||
|
|
v3 := int32(b2[3])
|
||
|
|
v2 := int32(b2[2])
|
||
|
|
v1 := int32(b2[1])
|
||
|
|
v0 := int32(b2[0])
|
||
|
|
return v0 | (v1 << 8) | (v2 << 16) | (v3 << 24)
|
||
|
|
}
|
||
|
|
|
||
|
|
// Uint32 returns a little endian uint32 starting at current offset.
|
||
|
|
func (b byteReader) Uint32() uint32 {
|
||
|
|
b2 := b.b[b.off : b.off+4 : b.off+4]
|
||
|
|
v3 := uint32(b2[3])
|
||
|
|
v2 := uint32(b2[2])
|
||
|
|
v1 := uint32(b2[1])
|
||
|
|
v0 := uint32(b2[0])
|
||
|
|
return v0 | (v1 << 8) | (v2 << 16) | (v3 << 24)
|
||
|
|
}
|
||
|
|
|
||
|
|
// unread returns the unread portion of the input.
|
||
|
|
func (b byteReader) unread() []byte {
|
||
|
|
return b.b[b.off:]
|
||
|
|
}
|
||
|
|
|
||
|
|
// remain will return the number of bytes remaining.
|
||
|
|
func (b byteReader) remain() int {
|
||
|
|
return len(b.b) - b.off
|
||
|
|
}
|