A variable-length unsigned integer using base128 encoding. 1-byte groups consist of 1-bit flag of continuation and 7-bit value chunk, and are ordered "most significant group first", i.e. in "big-endian" manner.
This particular encoding is specified and used in:
More information on this encoding is available at https://en.wikipedia.org/wiki/Variable-length_quantity
This particular implementation supports serialized values to up 8 bytes long.
This page hosts a formal specification of Variable length quantity, unsigned integer, base128, big-endian 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 = VlqBase128Be.FromFile("path/to/local/file.bin");
Or parse structure from a byte array:
byte[] someArray = new byte[] { ... };
var data = new VlqBase128Be(new KaitaiStream(someArray));
After that, one can get various attributes from the structure by accessing properties like:
data.Value // => Resulting value as normal integer
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
using System.Collections.Generic;
namespace Kaitai
{
/// <summary>
/// A variable-length unsigned integer using base128 encoding. 1-byte groups
/// consist of 1-bit flag of continuation and 7-bit value chunk, and are ordered
/// "most significant group first", i.e. in "big-endian" manner.
///
/// This particular encoding is specified and used in:
///
/// * Standard MIDI file format
/// * ASN.1 BER encoding
/// * RAR 5.0 file format
///
/// More information on this encoding is available at
/// <https://en.wikipedia.org/wiki/Variable-length_quantity>
///
/// This particular implementation supports serialized values to up 8 bytes long.
/// </summary>
public partial class VlqBase128Be : KaitaiStruct
{
public static VlqBase128Be FromFile(string fileName)
{
return new VlqBase128Be(new KaitaiStream(fileName));
}
public VlqBase128Be(KaitaiStream p__io, KaitaiStruct p__parent = null, VlqBase128Be p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root ?? this;
f_last = false;
f_value = false;
_read();
}
private void _read()
{
_groups = new List<Group>();
{
var i = 0;
Group M_;
do {
M_ = new Group(m_io, this, m_root);
_groups.Add(M_);
i++;
} while (!(!(M_.HasNext)));
}
}
/// <summary>
/// One byte group, clearly divided into 7-bit "value" chunk and 1-bit "continuation" flag.
/// </summary>
public partial class Group : KaitaiStruct
{
public static Group FromFile(string fileName)
{
return new Group(new KaitaiStream(fileName));
}
public Group(KaitaiStream p__io, VlqBase128Be p__parent = null, VlqBase128Be p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root;
_read();
}
private void _read()
{
_hasNext = m_io.ReadBitsIntBe(1) != 0;
_value = m_io.ReadBitsIntBe(7);
}
private bool _hasNext;
private ulong _value;
private VlqBase128Be m_root;
private VlqBase128Be m_parent;
/// <summary>
/// If true, then we have more bytes to read
/// </summary>
public bool HasNext { get { return _hasNext; } }
/// <summary>
/// The 7-bit (base128) numeric value chunk of this group
/// </summary>
public ulong Value { get { return _value; } }
public VlqBase128Be M_Root { get { return m_root; } }
public VlqBase128Be M_Parent { get { return m_parent; } }
}
private bool f_last;
private int _last;
public int Last
{
get
{
if (f_last)
return _last;
_last = (int) ((Groups.Count - 1));
f_last = true;
return _last;
}
}
private bool f_value;
private ulong _value;
/// <summary>
/// Resulting value as normal integer
/// </summary>
public ulong Value
{
get
{
if (f_value)
return _value;
_value = (ulong) (((ulong) ((((((((Groups[Last].Value + (Last >= 1 ? (Groups[(Last - 1)].Value << 7) : 0)) + (Last >= 2 ? (Groups[(Last - 2)].Value << 14) : 0)) + (Last >= 3 ? (Groups[(Last - 3)].Value << 21) : 0)) + (Last >= 4 ? (Groups[(Last - 4)].Value << 28) : 0)) + (Last >= 5 ? (Groups[(Last - 5)].Value << 35) : 0)) + (Last >= 6 ? (Groups[(Last - 6)].Value << 42) : 0)) + (Last >= 7 ? (Groups[(Last - 7)].Value << 49) : 0)))));
f_value = true;
return _value;
}
}
private List<Group> _groups;
private VlqBase128Be m_root;
private KaitaiStruct m_parent;
public List<Group> Groups { get { return _groups; } }
public VlqBase128Be M_Root { get { return m_root; } }
public KaitaiStruct M_Parent { get { return m_parent; } }
}
}