1  package codec
 2  
 3  import (
 4  	"encoding/binary"
 5  )
 6  
 7  type Encoder struct {
 8  	buf []byte
 9  }
10  
11  func Encode(size_hint int) *Encoder {
12  	return &Encoder{buf: make([]byte, 0, size_hint)}
13  }
14  
15  // Get the encoded array of bytes
16  func (e *Encoder) Result() []byte {
17  	return e.buf
18  }
19  
20  func (e *Encoder) Bytes(b []byte) {
21  	e.buf = append(e.buf, b...)
22  }
23  
24  func (e *Encoder) Bool(b bool) {
25  	var v byte = 0
26  	if b {
27  		v = 1
28  	}
29  	e.buf = append(e.buf, v)
30  }
31  
32  func (e *Encoder) UInt8(v uint8) {
33  	e.buf = append(e.buf, v)
34  }
35  
36  func (e *Encoder) UInt16le(v uint16) {
37  	e.buf = binary.LittleEndian.AppendUint16(e.buf, v)
38  }
39  
40  func (e *Encoder) UInt16be(v uint16) {
41  	e.buf = binary.BigEndian.AppendUint16(e.buf, v)
42  }
43  
44  func (e *Encoder) UInt32le(v uint32) {
45  	e.buf = binary.LittleEndian.AppendUint32(e.buf, v)
46  }
47  
48  func (e *Encoder) UInt32be(v uint32) {
49  	e.buf = binary.BigEndian.AppendUint32(e.buf, v)
50  }
51  
52  func (e *Encoder) UInt64le(v uint64) {
53  	e.buf = binary.LittleEndian.AppendUint64(e.buf, v)
54  }
55  
56  func (e *Encoder) Int64le(v int64) {
57  	e.buf = binary.LittleEndian.AppendUint64(e.buf, uint64(v))
58  }
59  
60  func (e *Encoder) VarUInt(val uint64) {
61  	if val < 0xFD {
62  		e.buf = append(e.buf, byte(val))
63  	} else if val <= 0xFFFF {
64  		e.buf = append(e.buf, 0xFD)
65  		e.buf = binary.LittleEndian.AppendUint16(e.buf, uint16(val))
66  	} else if val <= 0xFFFFFFFF {
67  		e.buf = append(e.buf, 0xFE)
68  		e.buf = binary.LittleEndian.AppendUint32(e.buf, uint32(val))
69  	} else {
70  		e.buf = append(e.buf, 0xFF)
71  		e.buf = binary.LittleEndian.AppendUint64(e.buf, val)
72  	}
73  }
74  
75  func (e *Encoder) VarString(v string) {
76  	b := []byte(v)
77  	e.VarUInt(uint64(len(b)))
78  	e.buf = append(e.buf, b...)
79  }
80  
81  func (e *Encoder) PadString(size uint64, v string) {
82  	bytes := []byte(v)
83  	e.buf = append(e.buf, bytes[0:size]...)
84  	used := uint64(len(v))
85  	for used < size {
86  		e.buf = append(e.buf, 0)
87  	}
88  }