Calculate Field Offset Based On Members' Name

namespace WinDbg;

using System;

/// <summary>
/// represents a class for working with type dumps of <see href="https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/">WinDbg</see>
/// <see href="https://learn.microsoft.com/en-us/windows-hardware/drivers/debuggercmds/dt--display-type-">td</see> command.
/// </summary>
internal class DisplayTypeDump
{
    private readonly string[] dump;

    /// <summary>
    /// initializes a new instance of the <see cref="DisplayTypeDump"/> class.
    /// </summary>
    /// <param name="dump">an array of strings representing the type dump.</param>
    internal DisplayTypeDump(string[] dump) => this.dump = dump;

    /// <summary>
    /// initializes a new instance of the <see cref="DisplayTypeDump"/> class.
    /// </summary>
    /// <param name="dump">a string representing the type dump.</param>
    /// <param name="seperator">the separator used to split the dump string.</param>
    internal DisplayTypeDump(string dump, string seperator) =>
        this.dump = dump.Split(seperator);

    /// <summary>
    /// represents the 32nd character of the ASCII table.
    /// </summary>
    private const char BlankSpace = (char)ConsoleKey.Spacebar;

    /// <summary>
    /// gets the hexadecimal value from a given string.
    /// </summary>
    /// <param name="vessel">the input string containing the hexadecimal value.</param>
    /// <returns>the hexadecimal value as an integer.</returns>
    internal static int GetHexValue(string vessel)
    {
        const int HexBase = 16;
        var start = new Index(3);
        var end = new Index(vessel.IndexOf(BlankSpace, 6));
        var hexNumberString = vessel[start..end];
        var hexValue = Convert.ToInt32(hexNumberString, HexBase);
        return hexValue;
    }

    /// <summary>
    /// gets the field name from the input string.
    /// </summary>
    /// <param name="vessel">the input string containing the field name.</param>
    /// <returns>the extracted field name.</returns>
    internal static string GetFieldName(string vessel)
    {
        var start = new Index(7);
        var end = new Index(vessel.IndexOf(BlankSpace, start.Value));
        var fieldName = vessel[start..end];
        return fieldName;
    }

    /// <summary>
    /// gets the offset in bytes for a target field in the type dump.
    /// </summary>
    /// <param name="target">the target field whose offset is to be calculated.</param>
    /// <param name="startField">the optional starting field for offset calculation.</param>
    /// <returns>the offset in bytes.</returns>
    internal int GetOffsetInBytes(string target, string startField = null!)
    {
        var previousHex = 0;
        var startFieldProvided = !string.IsNullOrEmpty(startField);
        var offsetSum = 0;

        for (var i = 0; i < dump.Length; ++i)
        {
            var fieldName = GetFieldName(dump[i]);
            
            // target reached!
            if (fieldName.Equals(target)) break;
            
            var currentHex = GetHexValue(dump[i]);

            // skip duplicates of sequentially laid values,
            // only considering the first occurrence.
            // --------------------------------------------
            // potentially skipping the very first value
            // of the array since it's often 0.
            if (currentHex == previousHex) continue;
            
            if (startFieldProvided && !fieldName.Equals(startField))
            {
                offsetSum -= currentHex;
                continue;
            }

            offsetSum += currentHex;
            previousHex = currentHex;
        }
        
        return Math.Abs(offsetSum);
    }
}

namespace WinDbg;

using System;

/// <summary>
/// represents a class for working with type dumps of <see href="https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/">WinDbg</see>
/// <see href="https://learn.microsoft.com/en-us/windows-hardware/drivers/debuggercmds/dt--display-type-">td</see> command.
/// </summary>
internal class DisplayTypeDump
{
    private readonly string[] dump;

    /// <summary>
    /// initializes a new instance of the <see cref="DisplayTypeDump"/> class.
    /// </summary>
    /// <param name="dump">an array of strings representing the type dump.</param>
    internal DisplayTypeDump(string[] dump) => this.dump = dump;

    /// <summary>
    /// initializes a new instance of the <see cref="DisplayTypeDump"/> class.
    /// </summary>
    /// <param name="dump">a string representing the type dump.</param>
    /// <param name="seperator">the separator used to split the dump string.</param>
    internal DisplayTypeDump(string dump, string seperator) =>
        this.dump = dump.Split(seperator);

    /// <summary>
    /// represents the 32nd character of the ASCII table.
    /// </summary>
    private const char BlankSpace = (char)ConsoleKey.Spacebar;

    /// <summary>
    /// gets the hexadecimal value from a given string.
    /// </summary>
    /// <param name="vessel">the input string containing the hexadecimal value.</param>
    /// <returns>the hexadecimal value as an integer.</returns>
    internal static int GetHexValue(string vessel)
    {
        const int HexBase = 16;
        var start = new Index(3);
        var end = new Index(vessel.IndexOf(BlankSpace, 6));
        var hexNumberString = vessel[start..end];
        var hexValue = Convert.ToInt32(hexNumberString, HexBase);
        return hexValue;
    }

    /// <summary>
    /// gets the field name from the input string.
    /// </summary>
    /// <param name="vessel">the input string containing the field name.</param>
    /// <returns>the extracted field name.</returns>
    internal static string GetFieldName(string vessel)
    {
        var start = new Index(7);
        var end = new Index(vessel.IndexOf(BlankSpace, start.Value));
        var fieldName = vessel[start..end];
        return fieldName;
    }

    /// <summary>
    /// gets the offset in bytes for a target field in the type dump.
    /// </summary>
    /// <param name="target">the target field whose offset is to be calculated.</param>
    /// <param name="startField">the optional starting field for offset calculation.</param>
    /// <returns>the offset in bytes.</returns>
    internal int GetOffsetInBytes(string target, string startField = null!)
    {
        var previousHex = 0;
        var startFieldProvided = !string.IsNullOrEmpty(startField);
        var offsetSum = 0;

        for (var i = 0; i < dump.Length; ++i)
        {
            var fieldName = GetFieldName(dump[i]);
            
            // target reached!
            if (fieldName.Equals(target)) break;
            
            var currentHex = GetHexValue(dump[i]);

            // skip duplicates of sequentially laid values,
            // only considering the first occurrence.
            // --------------------------------------------
            // potentially skipping the very first value
            // of the array since it's often 0.
            if (currentHex == previousHex) continue;
            
            if (startFieldProvided && !fieldName.Equals(startField))
            {
                offsetSum -= currentHex;
                continue;
            }

            offsetSum += currentHex;
            previousHex = currentHex;
        }
        
        return Math.Abs(offsetSum);
    }
}

using System;
using WinDbg;

var dtd = new DisplayTypeDump(
    dump: DUMP,
    seperator: Environment.NewLine
);

var offset = dtd.GetOffsetInBytes(
    target: "ConsoleHandle",
    startField: "Length"
);

Console.WriteLine(offset); // NOTE: output is 16

using System;
using WinDbg;

var dtd = new DisplayTypeDump(
    dump: DUMP,
    seperator: Environment.NewLine
);

var offset = dtd.GetOffsetInBytes(
    target: "ConsoleHandle",
    startField: "Length"
);

Console.WriteLine(offset); // NOTE: output is 16

#define OFFSET_RESULT 16
typedef struct _placeholder_t {
    unsigned int MaximumLength;
    unsigned int Length; // this is the starting field.
    unsigned char /* aka: byte */ Padding[OFFSET_RESULT];
    void* ConsoleHandle; // this is the target.
} placeholder_t;

#define OFFSET_RESULT 16
typedef struct _placeholder_t {
    unsigned int MaximumLength;
    unsigned int Length; // this is the starting field.
    unsigned char /* aka: byte */ Padding[OFFSET_RESULT];
    void* ConsoleHandle; // this is the target.
} placeholder_t;

internal unsafe long GetOffsetOf<T>(string target, string startAtField = null!)
    where T : unmanaged
{
    var currentHex = GetHexValue(dump[1]);
    var previousHex = 0;
    var startFieldPresent = !string.IsNullOrEmpty(startAtField);
    var offsetSum = 0;
        
    for (var index = 2; index < dump.Length; index++)
    {
        var fieldName = GetFieldName(dump[index - 2]);
            
        // target reached!
        if (fieldName.Equals(target)) break;
            
        // skip duplicates of sequentially laid values,
        // only considering the first occurrence.
        if (currentHex != previousHex)
        {
            var fieldTypeSize = currentHex - previousHex;
            previousHex = currentHex;
                
            if (startFieldPresent)
            {
                if (fieldName.Equals(startAtField))
                    startFieldPresent = false;
                else
                    offsetSum -= fieldTypeSize;
            }
            else
            {
                offsetSum += fieldTypeSize;
                Console.WriteLine("{0}: {1}", fieldName, fieldTypeSize);
            }
        }
            
        currentHex = GetHexValue(dump[index]);
    }
        
    var offset = checked(Math.Abs(offsetSum)*((long)sizeof(T)));
    Console.WriteLine("{0} _[{1}];", typeof(T).Name.ToLower(), offset);
    return offset;
}

internal unsafe long GetOffsetOf<T>(string target, string startAtField = null!)
    where T : unmanaged
{
    var currentHex = GetHexValue(dump[1]);
    var previousHex = 0;
    var startFieldPresent = !string.IsNullOrEmpty(startAtField);
    var offsetSum = 0;
        
    for (var index = 2; index < dump.Length; index++)
    {
        var fieldName = GetFieldName(dump[index - 2]);
            
        // target reached!
        if (fieldName.Equals(target)) break;
            
        // skip duplicates of sequentially laid values,
        // only considering the first occurrence.
        if (currentHex != previousHex)
        {
            var fieldTypeSize = currentHex - previousHex;
            previousHex = currentHex;
                
            if (startFieldPresent)
            {
                if (fieldName.Equals(startAtField))
                    startFieldPresent = false;
                else
                    offsetSum -= fieldTypeSize;
            }
            else
            {
                offsetSum += fieldTypeSize;
                Console.WriteLine("{0}: {1}", fieldName, fieldTypeSize);
            }
        }
            
        currentHex = GetHexValue(dump[index]);
    }
        
    var offset = checked(Math.Abs(offsetSum)*((long)sizeof(T)));
    Console.WriteLine("{0} _[{1}];", typeof(T).Name.ToLower(), offset);
    return offset;
}