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|
package main
import (
"fmt"
"math/bits"
"strconv"
"strings"
)
type ReaderType struct {
data []byte // Reader data from a byte array
base int // Current reader byte location
index int // Current reader index
le bool // Little endian or big endian?
}
func Reader(data []byte, le bool) *ReaderType {
dataClone := data
if le {
for index, byteValue := range data {
dataClone[index] = bits.Reverse8(byteValue)
}
}
return &ReaderType{
data: dataClone,
base: 0,
index: 0,
le: le,
}
}
func (reader *ReaderType) SkipBits(bits int) error {
if bits <= 0 {
return fmt.Errorf("SkipBits Error: Bits value %d lower or equals than 0.", bits)
}
err := reader.checkAvailableBits(bits)
if err != nil {
return err
}
for reader.index+bits > 7 {
reader.base++
reader.index = 0
bits -= 8
}
reader.index += bits
return nil
}
func (reader *ReaderType) SkipBytes(bytes int) error {
err := reader.SkipBits(bytes * 8)
if err != nil {
return err
}
return nil
}
func (reader *ReaderType) ReadBits(bits int) (int, error) {
if bits <= 0 {
return -1, fmt.Errorf("ReadBits Error: Bits value %d lower or equals than 0.", bits)
}
if bits > 64 {
return -1, fmt.Errorf("ReadBits Error: Bits value %d higher than 64.", bits)
}
err := reader.checkAvailableBits(bits)
if err != nil {
return -1, err
}
if reader.le {
var output string
// Go to last bit and read backwards from there
reader.base += bits / 8
reader.index += bits % 8
if reader.index > 7 {
reader.index -= 8
reader.base++
}
for i := 0; i < bits; i++ {
reader.index--
if reader.index < 0 {
reader.base--
reader.index = 7
}
binary := fmt.Sprintf("%08b", reader.data[reader.base])
binaryArr := strings.Split(binary, "")
output += binaryArr[reader.index]
}
// Return to last bit after reading
reader.base += bits / 8
reader.index += bits % 8
if reader.index > 7 {
reader.index -= 8
}
// Conversion of string binary to int
value, err := strconv.ParseUint(output, 2, 64)
if err != nil {
return -1, fmt.Errorf("%s", err)
}
return int(value), nil
} else {
var output string
for i := 0; i < bits; i++ {
binary := fmt.Sprintf("%08b", reader.data[reader.base])
binaryArr := strings.Split(binary, "")
output += binaryArr[reader.index]
reader.index++
if reader.index > 7 {
reader.base++
reader.index = 0
}
}
// Conversion of string binary to int
value, err := strconv.ParseUint(output, 2, 64)
if err != nil {
return -1, fmt.Errorf("%s", err)
}
return int(value), nil
}
}
func (reader *ReaderType) ReadBit() (bool, error) {
value, err := reader.ReadBits(1)
if err != nil {
return false, fmt.Errorf("ReadBit Error: %s", err)
}
return value != 0, nil
}
func (reader *ReaderType) checkAvailableBits(bits int) error {
availableBits := (len(reader.data)-reader.base)*8 - reader.index
if availableBits < bits {
return fmt.Errorf("BitReaderOutOfBounds: Wanted to read/skip %d bit(s) but only %d bit(s) is/are available.", bits, availableBits)
}
return nil
}
|