HUDManager/HudSwap/HUD.cs

using Dalamud.Plugin;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Runtime.InteropServices;

namespace HudSwap {
    public class HUD {
        private const int LAYOUT_SIZE = 0xb40; // 5.4
        private const int SLOT_OFFSET = 0x59e8; // 5.4

        private delegate IntPtr GetFilePointerDelegate(byte index);

        private delegate uint SetHudLayoutDelegate(IntPtr filePtr, uint hudLayout, byte unk0, byte unk1);

        private readonly GetFilePointerDelegate _getFilePointer;
        private readonly SetHudLayoutDelegate _setHudLayout;

        private readonly DalamudPluginInterface pi;

        public HUD(DalamudPluginInterface pi) {
            this.pi = pi ?? throw new ArgumentNullException(nameof(pi), "DalamudPluginInterface cannot be null");
            IntPtr getFilePointerPtr = this.pi.TargetModuleScanner.ScanText("E8 ?? ?? ?? ?? 48 85 C0 74 14 83 7B 44 00");
            IntPtr setHudLayoutPtr = this.pi.TargetModuleScanner.ScanText("E8 ?? ?? ?? ?? 33 C0 EB 15");
            if (getFilePointerPtr != IntPtr.Zero) {
                this._getFilePointer = Marshal.GetDelegateForFunctionPointer<GetFilePointerDelegate>(getFilePointerPtr);
            }

            if (setHudLayoutPtr != IntPtr.Zero) {
                this._setHudLayout = Marshal.GetDelegateForFunctionPointer<SetHudLayoutDelegate>(setHudLayoutPtr);
            }
        }

        private IntPtr GetFilePointer(byte index) {
            return this._getFilePointer.Invoke(index);
        }

        public uint SelectSlot(HudSlot slot, bool force = false) {
            IntPtr file = this.GetFilePointer(0);
            // change the current slot so the game lets us pick one that's currently in use
            if (!force) {
                goto Return;
            }

            IntPtr currentSlotPtr = this.GetDataPointer() + SLOT_OFFSET;
            // read the current slot
            uint currentSlot = (uint)Marshal.ReadInt32(currentSlotPtr);
            // change it to a different slot
            if (currentSlot == (uint)slot) {
                if (currentSlot < 3) {
                    currentSlot += 1;
                } else {
                    currentSlot = 0;
                }

                // back up this different slot
                byte[] backup = this.ReadLayout((HudSlot)currentSlot);
                // change the current slot in memory
                Marshal.WriteInt32(currentSlotPtr, (int)currentSlot);
                // ask the game to change slot to our desired slot
                // for some reason, this overwrites the current slot, so this is why we back up
                uint res = this._setHudLayout.Invoke(file, (uint)slot, 0, 1);
                // restore the backup
                this.WriteLayout((HudSlot)currentSlot, backup);
                return res;
            }

            Return:
            return this._setHudLayout.Invoke(file, (uint)slot, 0, 1);
        }

        private IntPtr GetDataPointer() {
            IntPtr dataPtr = this.GetFilePointer(0) + 0x50;
            return Marshal.ReadIntPtr(dataPtr);
        }

        private IntPtr GetLayoutPointer(HudSlot slot) {
            int slotNum = (int)slot;
            return this.GetDataPointer() + 0x2c58 + (slotNum * LAYOUT_SIZE);
        }

        public HudSlot GetActiveHudSlot() {
            int slotVal = Marshal.ReadInt32(this.GetDataPointer() + SLOT_OFFSET);

            if (!Enum.IsDefined(typeof(HudSlot), slotVal)) {
                throw new IOException($"invalid hud slot in FFXIV memory of ${slotVal}");
            }

            return (HudSlot)slotVal;
        }

        public byte[] ReadLayout(HudSlot slot) {
            IntPtr slotPtr = this.GetLayoutPointer(slot);
            byte[] bytes = new byte[LAYOUT_SIZE];
            Marshal.Copy(slotPtr, bytes, 0, LAYOUT_SIZE);
            return bytes;
        }

        public void WriteLayout(HudSlot slot, byte[] layout) {
            if (layout == null) {
                throw new ArgumentNullException(nameof(layout), "layout cannot be null");
            }

            if (layout.Length != LAYOUT_SIZE) {
                throw new ArgumentException($"layout must be {LAYOUT_SIZE} bytes", nameof(layout));
            }

            IntPtr slotPtr = this.GetLayoutPointer(slot);
            Marshal.Copy(layout, 0, slotPtr, LAYOUT_SIZE);

            var currentSlot = this.GetActiveHudSlot();
            if (currentSlot == slot) {
                this.SelectSlot(currentSlot, true);
            }
        }

        public void WriteLayout(byte[] layout) => WriteLayout(this.GetActiveHudSlot(), layout);
    }

    public enum HudSlot {
        One = 0,
        Two = 1,
        Three = 2,
        Four = 3,
    }

    public class Vector2<T> {
        public T X { get; private set; }
        public T Y { get; private set; }

        public Vector2(T x, T y) {
            this.X = x;
            this.Y = y;
        }
    }

    [Serializable]
    public class SharedLayout {
        [JsonProperty]
        private readonly byte[] compressed;

        [NonSerialized]
        private byte[] uncompressed = null;

        public Dictionary<string, Vector2<short>> Positions { get; private set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Design", "CA1031:Do not catch general exception types", Justification = "nah")]
        public byte[] Layout() {
            if (this.uncompressed != null) {
                return this.uncompressed;
            }

            try {
                using (MemoryStream compressed = new MemoryStream(this.compressed)) {
                    using (GZipStream gzip = new GZipStream(compressed, CompressionMode.Decompress)) {
                        using (MemoryStream uncompressed = new MemoryStream()) {
                            gzip.CopyTo(uncompressed);
                            this.uncompressed = uncompressed.ToArray();
                        }
                    }
                }
            } catch (Exception) {
                return null;
            }

            return this.uncompressed;
        }

        [JsonConstructor]
        private SharedLayout() {
            // For JSON
        }

        public SharedLayout(Layout layout) {
            if (layout == null) {
                throw new ArgumentNullException(nameof(layout), "Layout cannot be null");
            }

            using (MemoryStream compressed = new MemoryStream()) {
                using (GZipStream gzip = new GZipStream(compressed, CompressionLevel.Optimal)) {
                    using (MemoryStream uncompressed = new MemoryStream(layout.Hud)) {
                        uncompressed.CopyTo(gzip);
                    }
                }

                this.compressed = compressed.ToArray();
            }

            this.Positions = layout.Positions;
        }
    }
}