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|
package bits
import (
"bufio"
"fmt"
"io"
)
type Bits struct {
Version byte
TypeID byte
Value int
Operators []*Bits
Len int
}
// Scanner represents a lexical scanner.
type Scanner struct {
r *bufio.Reader
buff byte
readBits byte
parsingDepth int
}
// NewScanner returns a new instance of Scanner.
func NewScanner(r io.Reader) *Scanner {
return &Scanner{r: bufio.NewReader(r)}
}
// read reads the next bits from the bufferred reader.
// Returns the rune(0) if an error occurs (or io.EOF is returned).
func (s *Scanner) readBit() (bool, error) {
var ret bool
s.readBits++
switch s.readBits {
case 2:
ret = s.buff&0b0100 != 0
case 3:
ret = s.buff&0b0010 != 0
case 4:
ret = s.buff&0b0001 != 0
default:
var err error
s.buff, err = s.r.ReadByte()
if err != nil || s.buff == '\n' {
return false, err
}
if s.buff <= '9' {
s.buff -= '0'
} else {
s.buff = s.buff - 'A' + 10
}
if err != nil {
return false, err
}
s.readBits = 1
ret = s.buff&0b1000 != 0
}
if ret {
fmt.Print("1")
} else {
fmt.Print("0")
}
return ret, nil
}
// Scan returns the next Bits packet
func (s *Scanner) Scan() *Bits {
var bits Bits
for i := 0; i < 3; i++ {
bits.Version <<= 1
b, err := s.readBit()
if err != nil {
return nil
}
if b {
bits.Version++
}
}
fmt.Println("Version:", bits.Version)
for i := 0; i < 3; i++ {
bits.TypeID <<= 1
b, err := s.readBit()
if err != nil {
return nil
}
if b {
bits.TypeID++
}
}
bits.Len += 6
fmt.Println("TypeID:", bits.TypeID)
if bits.TypeID == 4 {
for {
keepGoing, err := s.readBit()
if err != nil {
return nil
}
var buff byte
for i := 0; i < 4; i++ {
buff <<= 1
b, err := s.readBit()
if err != nil {
return nil
}
if b {
buff++
}
}
bits.Len += 5
bits.Value = bits.Value<<4 + int(buff)
if !keepGoing {
break
}
}
fmt.Println("Value:", bits.Value)
} else { // operator
b, err := s.readBit()
if err != nil {
return nil
}
bits.Len++
if b {
var buff int
for i := 0; i < 11; i++ {
buff <<= 1
b, err := s.readBit()
if err != nil {
return nil
}
if b {
buff++
}
}
bits.Len += 11
fmt.Println("SubPackets type 1, nb of subpackets:", buff)
s.parsingDepth++
for i := 0; i < buff; i++ {
subBits := s.Scan()
if subBits == nil {
return nil
}
bits.Operators = append(bits.Operators, subBits)
bits.Len += subBits.Len
}
s.parsingDepth--
} else {
var buff int
for i := 0; i < 15; i++ {
buff <<= 1
b, err := s.readBit()
if err != nil {
return nil
}
if b {
buff++
}
}
bits.Len += 15
fmt.Println("SubPackets type 0 of len:", buff)
s.parsingDepth++
for buff > 0 {
subBits := s.Scan()
if subBits == nil {
return nil
}
bits.Operators = append(bits.Operators, subBits)
bits.Len += subBits.Len
buff -= subBits.Len
fmt.Println("remaining bits:", buff)
}
s.parsingDepth--
}
}
if s.parsingDepth == 0 {
bits.Len += 4 - int(s.readBits)
s.readBits = 0
}
switch bits.TypeID {
case 0:
for _, sub := range bits.Operators {
bits.Value += sub.Value
}
case 1:
bits.Value = 1
for _, sub := range bits.Operators {
bits.Value *= sub.Value
}
case 2:
bits.Value = bits.Operators[0].Value
for _, sub := range bits.Operators {
if bits.Value > sub.Value {
bits.Value = sub.Value
}
}
case 3:
bits.Value = bits.Operators[0].Value
for _, sub := range bits.Operators {
if bits.Value < sub.Value {
bits.Value = sub.Value
}
}
case 5:
if bits.Operators[0].Value > bits.Operators[1].Value {
bits.Value = 1
}
case 6:
if bits.Operators[0].Value < bits.Operators[1].Value {
bits.Value = 1
}
case 7:
if bits.Operators[0].Value == bits.Operators[1].Value {
bits.Value = 1
}
}
return &bits
}
|
