Changed GetDimensions to handle a stream at the end and one exit

Shared/Models/Stateless/Methods/Dimensions.cs

@@ -0,0 +1,149 @@
+using System.Drawing;
+
+namespace View_by_Distance.Shared.Models.Stateless.Methods;
+
+internal static class Dimensions
+{
+
+#pragma warning disable IDE0230
+    private static readonly Dictionary<byte[], Func<BinaryReader, Size?>> _ImageFormatDecoders = new()
+    {
+        { new byte[] { 0xff, 0xd8 }, DecodeJfif },
+        { new byte[] { 0x42, 0x4D }, DecodeBitmap },
+        { new byte[] { 0x52, 0x49, 0x46, 0x46 }, DecodeWebP },
+        { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x37, 0x61 }, DecodeGif },
+        { new byte[] { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61 }, DecodeGif },
+        { new byte[] { 0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A }, DecodePng },
+    };
+#pragma warning restore IDE0230
+
+    private static bool StartsWith(List<byte> thisBytes, byte[] thatBytes)
+    {
+        for (int i = 0; i < thatBytes.Length; i += 1)
+        {
+            if (thisBytes[i] == thatBytes[i])
+                continue;
+            return false;
+        }
+        return true;
+    }
+
+    private static short ReadLittleEndianInt16(BinaryReader binaryReader)
+    {
+        byte[] bytes = new byte[sizeof(short)];
+        for (int i = 0; i < sizeof(short); i += 1)
+            bytes[sizeof(short) - 1 - i] = binaryReader.ReadByte();
+        return BitConverter.ToInt16(bytes, 0);
+    }
+
+    private static int ReadLittleEndianInt32(BinaryReader binaryReader)
+    {
+        byte[] bytes = new byte[sizeof(int)];
+        for (int i = 0; i < sizeof(int); i += 1)
+            bytes[sizeof(int) - 1 - i] = binaryReader.ReadByte();
+        return BitConverter.ToInt32(bytes, 0);
+    }
+
+    private static Size? DecodeBitmap(BinaryReader binaryReader)
+    {
+        _ = binaryReader.ReadBytes(16);
+        int width = binaryReader.ReadInt32();
+        int height = binaryReader.ReadInt32();
+        return new Size(width, height);
+    }
+
+    private static Size? DecodeGif(BinaryReader binaryReader)
+    {
+        int width = binaryReader.ReadInt16();
+        int height = binaryReader.ReadInt16();
+        return new Size(width, height);
+    }
+
+    private static Size? DecodePng(BinaryReader binaryReader)
+    {
+        _ = binaryReader.ReadBytes(8);
+        int width = ReadLittleEndianInt32(binaryReader);
+        int height = ReadLittleEndianInt32(binaryReader);
+        return new Size(width, height);
+    }
+
+    private static Size? DecodeJfif(BinaryReader binaryReader)
+    {
+        while (binaryReader.ReadByte() == 0xff)
+        {
+            byte marker = binaryReader.ReadByte();
+            short chunkLength = ReadLittleEndianInt16(binaryReader);
+            if (marker == 0xc0)
+            {
+                _ = binaryReader.ReadByte();
+                int height = ReadLittleEndianInt16(binaryReader);
+                int width = ReadLittleEndianInt16(binaryReader);
+                return new Size(width, height);
+            }
+            if (chunkLength >= 0)
+                _ = binaryReader.ReadBytes(chunkLength - 2);
+            else
+            {
+                ushort uChunkLength = (ushort)chunkLength;
+                _ = binaryReader.ReadBytes(uChunkLength - 2);
+            }
+        }
+        return null;
+    }
+
+    private static Size? DecodeWebP(BinaryReader binaryReader)
+    {
+        _ = binaryReader.ReadUInt32(); // Size
+        _ = binaryReader.ReadBytes(15); // WEBP, VP8 + more
+        _ = binaryReader.ReadBytes(3); // SYNC
+        int width = binaryReader.ReadUInt16() & 0b00_11111111111111; // 14 bits width
+        int height = binaryReader.ReadUInt16() & 0b00_11111111111111; // 14 bits height
+        return new Size(width, height);
+    }
+
+    internal static Size GetDimensions(BinaryReader binaryReader, int? faceRight, int? faceBottom)
+    {
+        Size? result;
+        List<byte> magicBytes = [];
+        int[] magicBytesLengths = (from l in _ImageFormatDecoders.Keys where l.Length <= binaryReader.BaseStream.Length orderby l.Length descending select l.Length).ToArray();
+        if (magicBytesLengths.Length == 0)
+            result = null;
+        else
+        {
+            result = null;
+            if (binaryReader.BaseStream.Length == binaryReader.BaseStream.Position)
+                _ = binaryReader.BaseStream.Seek(0, SeekOrigin.Begin);
+            for (int i = 0; i < magicBytesLengths[0]; i++)
+            {
+                magicBytes.Add(binaryReader.ReadByte());
+                foreach (KeyValuePair<byte[], Func<BinaryReader, Size?>> kvPair in _ImageFormatDecoders)
+                {
+                    if (StartsWith(magicBytes, kvPair.Key))
+                    {
+                        result = kvPair.Value(binaryReader);
+                        break;
+                    }
+                }
+                if (result is not null)
+                    break;
+            }
+        }        
+        if (result is null)
+        {
+            if (faceRight is null || faceBottom is null)
+                throw new Exception("face is null!");
+            result = new(faceRight.Value, faceBottom.Value);
+        }
+        return result.Value;
+    }
+
+    internal static Size GetDimensions(string path, int? faceRight, int? faceBottom)
+    {
+        Size result;
+        using FileStream fileStream = File.OpenRead(path);
+        using BinaryReader binaryReader = new(fileStream);
+        result = GetDimensions(binaryReader, faceRight, faceBottom);
+        return result;
+    }
+
+}