A variable-length unsigned integer using base128 encoding. 1-byte groups consists of 1-bit flag of continuation and 7-bit value, and are ordered "least significant group first", i.e. in "little-endian" manner.
This particular encoding is specified and used in:
More information on this encoding is available at https://en.wikipedia.org/wiki/LEB128
This particular implementation supports serialized values to up 8 bytes long.
This page hosts a formal specification of Variable length quantity, unsigned integer, base128, little-endian using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
Parse a local file and get structure in memory:
var data = VlqBase128Le.FromFile("path/to/local/file.vlq_base128_le");Or parse structure from a byte array:
byte[] someArray = new byte[] { ... };
var data = new VlqBase128Le(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
/// consists of 1-bit flag of continuation and 7-bit value, and are ordered
/// "least significant group first", i.e. in "little-endian" manner.
///
/// This particular encoding is specified and used in:
///
/// * DWARF debug file format, where it's dubbed "unsigned LEB128" or "ULEB128".
/// http://dwarfstd.org/doc/dwarf-2.0.0.pdf - page 139
/// * Google Protocol Buffers, where it's called "Base 128 Varints".
/// https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints
/// * Apache Lucene, where it's called "VInt"
/// http://lucene.apache.org/core/3_5_0/fileformats.html#VInt
/// * Apache Avro uses this as a basis for integer encoding, adding ZigZag on
/// top of it for signed ints
/// http://avro.apache.org/docs/current/spec.html#binary_encode_primitive
///
/// More information on this encoding is available at https://en.wikipedia.org/wiki/LEB128
///
/// This particular implementation supports serialized values to up 8 bytes long.
/// </summary>
public partial class VlqBase128Le : KaitaiStruct
{
public static VlqBase128Le FromFile(string fileName)
{
return new VlqBase128Le(new KaitaiStream(fileName));
}
public VlqBase128Le(KaitaiStream p__io, KaitaiStruct p__parent = null, VlqBase128Le p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root ?? this;
f_len = 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" and 1-bit "has continuation
/// in the next byte" flag.
/// </summary>
public partial class Group : KaitaiStruct
{
public static Group FromFile(string fileName)
{
return new Group(new KaitaiStream(fileName));
}
public Group(KaitaiStream p__io, VlqBase128Le p__parent = null, VlqBase128Le p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root;
f_hasNext = false;
f_value = false;
_read();
}
private void _read()
{
_b = m_io.ReadU1();
}
private bool f_hasNext;
private bool _hasNext;
/// <summary>
/// If true, then we have more bytes to read
/// </summary>
public bool HasNext
{
get
{
if (f_hasNext)
return _hasNext;
_hasNext = (bool) ((B & 128) != 0);
f_hasNext = true;
return _hasNext;
}
}
private bool f_value;
private int _value;
/// <summary>
/// The 7-bit (base128) numeric value of this group
/// </summary>
public int Value
{
get
{
if (f_value)
return _value;
_value = (int) ((B & 127));
f_value = true;
return _value;
}
}
private byte _b;
private VlqBase128Le m_root;
private VlqBase128Le m_parent;
public byte B { get { return _b; } }
public VlqBase128Le M_Root { get { return m_root; } }
public VlqBase128Le M_Parent { get { return m_parent; } }
}
private bool f_len;
private int _len;
public int Len
{
get
{
if (f_len)
return _len;
_len = (int) (Groups.Count);
f_len = true;
return _len;
}
}
private bool f_value;
private int _value;
/// <summary>
/// Resulting value as normal integer
/// </summary>
public int Value
{
get
{
if (f_value)
return _value;
_value = (int) ((((((((Groups[0].Value + (Len >= 2 ? (Groups[1].Value << 7) : 0)) + (Len >= 3 ? (Groups[2].Value << 14) : 0)) + (Len >= 4 ? (Groups[3].Value << 21) : 0)) + (Len >= 5 ? (Groups[4].Value << 28) : 0)) + (Len >= 6 ? (Groups[5].Value << 35) : 0)) + (Len >= 7 ? (Groups[6].Value << 42) : 0)) + (Len >= 8 ? (Groups[7].Value << 49) : 0)));
f_value = true;
return _value;
}
}
private List<Group> _groups;
private VlqBase128Le m_root;
private KaitaiStruct m_parent;
public List<Group> Groups { get { return _groups; } }
public VlqBase128Le M_Root { get { return m_root; } }
public KaitaiStruct M_Parent { get { return m_parent; } }
}
}