BCD (Binary Coded Decimals) is a common way to encode integer numbers in a way that makes human-readable output somewhat simpler. In this encoding scheme, every decimal digit is encoded as either a single byte (8 bits), or a nibble (half of a byte, 4 bits). This obviously wastes a lot of bits, but it makes translation into human-readable string much easier than traditional binary-to-decimal conversion process, which includes lots of divisions by 10.
For example, encoding integer 31337 in 8-digit, 8 bits per digit, big endian order of digits BCD format yields
00 00 00 03 01 03 03 07
Encoding the same integer as 8-digit, 4 bits per digit, little endian order BCD format would yield:
73 31 30 00
Using this type of encoding in Kaitai Struct is pretty
straightforward: one calls for this type, specifying desired
encoding parameters, and gets result using either as_int or
as_str attributes.
This page hosts a formal specification of BCD (Binary Coded Decimals) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for C# generated by Kaitai Struct depends on the C# runtime library. You have to install it before you can parse data.
The C# runtime library is available in the NuGet Gallery. Installation instructions can also be found there.
Parse a local file and get structure in memory:
var data = Bcd.FromFile("path/to/local/file.bin");
Or parse structure from a byte array:
byte[] someArray = new byte[] { ... };
var data = new Bcd(new KaitaiStream(someArray));
After that, one can get various attributes from the structure by accessing properties like:
data.AsInt // => Value of this BCD number as integer. Endianness would be selected based on `is_le` parameter given.
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
using System.Collections.Generic;
namespace Kaitai
{
/// <summary>
/// BCD (Binary Coded Decimals) is a common way to encode integer
/// numbers in a way that makes human-readable output somewhat
/// simpler. In this encoding scheme, every decimal digit is encoded as
/// either a single byte (8 bits), or a nibble (half of a byte, 4
/// bits). This obviously wastes a lot of bits, but it makes translation
/// into human-readable string much easier than traditional
/// binary-to-decimal conversion process, which includes lots of
/// divisions by 10.
///
/// For example, encoding integer 31337 in 8-digit, 8 bits per digit,
/// big endian order of digits BCD format yields
///
/// ```
/// 00 00 00 03 01 03 03 07
/// ```
///
/// Encoding the same integer as 8-digit, 4 bits per digit, little
/// endian order BCD format would yield:
///
/// ```
/// 73 31 30 00
/// ```
///
/// Using this type of encoding in Kaitai Struct is pretty
/// straightforward: one calls for this type, specifying desired
/// encoding parameters, and gets result using either `as_int` or
/// `as_str` attributes.
/// </summary>
public partial class Bcd : KaitaiStruct
{
public Bcd(byte p_numDigits, byte p_bitsPerDigit, bool p_isLe, KaitaiStream p__io, KaitaiStruct p__parent = null, Bcd p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root ?? this;
_numDigits = p_numDigits;
_bitsPerDigit = p_bitsPerDigit;
_isLe = p_isLe;
f_asInt = false;
f_asIntLe = false;
f_lastIdx = false;
f_asIntBe = false;
_read();
}
private void _read()
{
_digits = new List<int>();
for (var i = 0; i < NumDigits; i++)
{
switch (BitsPerDigit) {
case 4: {
_digits.Add(m_io.ReadBitsIntBe(4));
break;
}
case 8: {
_digits.Add(m_io.ReadU1());
break;
}
}
}
}
private bool f_asInt;
private int _asInt;
/// <summary>
/// Value of this BCD number as integer. Endianness would be selected based on `is_le` parameter given.
/// </summary>
public int AsInt
{
get
{
if (f_asInt)
return _asInt;
_asInt = (int) ((IsLe ? AsIntLe : AsIntBe));
f_asInt = true;
return _asInt;
}
}
private bool f_asIntLe;
private int _asIntLe;
/// <summary>
/// Value of this BCD number as integer (treating digit order as little-endian).
/// </summary>
public int AsIntLe
{
get
{
if (f_asIntLe)
return _asIntLe;
_asIntLe = (int) ((Digits[0] + (NumDigits < 2 ? 0 : ((Digits[1] * 10) + (NumDigits < 3 ? 0 : ((Digits[2] * 100) + (NumDigits < 4 ? 0 : ((Digits[3] * 1000) + (NumDigits < 5 ? 0 : ((Digits[4] * 10000) + (NumDigits < 6 ? 0 : ((Digits[5] * 100000) + (NumDigits < 7 ? 0 : ((Digits[6] * 1000000) + (NumDigits < 8 ? 0 : (Digits[7] * 10000000))))))))))))))));
f_asIntLe = true;
return _asIntLe;
}
}
private bool f_lastIdx;
private int _lastIdx;
/// <summary>
/// Index of last digit (0-based).
/// </summary>
public int LastIdx
{
get
{
if (f_lastIdx)
return _lastIdx;
_lastIdx = (int) ((NumDigits - 1));
f_lastIdx = true;
return _lastIdx;
}
}
private bool f_asIntBe;
private int _asIntBe;
/// <summary>
/// Value of this BCD number as integer (treating digit order as big-endian).
/// </summary>
public int AsIntBe
{
get
{
if (f_asIntBe)
return _asIntBe;
_asIntBe = (int) ((Digits[LastIdx] + (NumDigits < 2 ? 0 : ((Digits[(LastIdx - 1)] * 10) + (NumDigits < 3 ? 0 : ((Digits[(LastIdx - 2)] * 100) + (NumDigits < 4 ? 0 : ((Digits[(LastIdx - 3)] * 1000) + (NumDigits < 5 ? 0 : ((Digits[(LastIdx - 4)] * 10000) + (NumDigits < 6 ? 0 : ((Digits[(LastIdx - 5)] * 100000) + (NumDigits < 7 ? 0 : ((Digits[(LastIdx - 6)] * 1000000) + (NumDigits < 8 ? 0 : (Digits[(LastIdx - 7)] * 10000000))))))))))))))));
f_asIntBe = true;
return _asIntBe;
}
}
private List<int> _digits;
private byte _numDigits;
private byte _bitsPerDigit;
private bool _isLe;
private Bcd m_root;
private KaitaiStruct m_parent;
public List<int> Digits { get { return _digits; } }
/// <summary>
/// Number of digits in this BCD representation. Only values from 1 to 8 inclusive are supported.
/// </summary>
public byte NumDigits { get { return _numDigits; } }
/// <summary>
/// Number of bits per digit. Only values of 4 and 8 are supported.
/// </summary>
public byte BitsPerDigit { get { return _bitsPerDigit; } }
/// <summary>
/// Endianness used by this BCD representation. True means little-endian, false is for big-endian.
/// </summary>
public bool IsLe { get { return _isLe; } }
public Bcd M_Root { get { return m_root; } }
public KaitaiStruct M_Parent { get { return m_parent; } }
}
}