From b6960a643850c6d72d2d3d385ff9a991dee47db8 Mon Sep 17 00:00:00 2001
From: Bezaleel Olakunori <bezaleeloci@gmail.com>
Date: Sun, 14 Jul 2024 10:21:36 +0200
Subject: [PATCH] Create a decoder with support for parsing the Draco header

---
 src/Draco/IO/DracoDecoder.cs | 46 ++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 src/Draco/IO/DracoDecoder.cs

diff --git a/src/Draco/IO/DracoDecoder.cs b/src/Draco/IO/DracoDecoder.cs
new file mode 100644
index 0000000..8b1ced1
--- /dev/null
+++ b/src/Draco/IO/DracoDecoder.cs
@@ -0,0 +1,46 @@
+namespace Draco.IO;
+
+public class DracoDecoder
+{
+    public DracoHeader? Header { get; private set; }
+
+    public void Decode(string path)
+    {
+        using var fs = new FileStream(path, FileMode.Open, FileAccess.Read);
+        Decode(new BinaryReader(fs));
+    }
+
+    public void Decode(Stream stream)
+    {
+        Decode(new BinaryReader(stream));
+    }
+
+    public void Decode(BinaryReader binaryReader)
+    {
+        using var buffer = new DecoderBuffer(binaryReader);
+        Header = ParseHeader(buffer);
+        buffer.BitStream_Version = Header.Version;
+    }
+
+    private static DracoHeader ParseHeader(DecoderBuffer buffer)
+    {
+        var dracoMagic = buffer.ReadASCIIBytes(Constants.DracoMagic.Length);
+        if (dracoMagic != Constants.DracoMagic)
+        {
+            throw new InvalidDataException("Invalid Draco file.");
+        }
+        var majorVersion = buffer.ReadByte();
+        var minorVersion = buffer.ReadByte();
+        var encoderType = buffer.ReadByte();
+        var encoderMethod = buffer.ReadByte();
+        var flags = buffer.ReadUInt16();
+
+        return new DracoHeader(
+            majorVersion: majorVersion,
+            minorVersion: minorVersion,
+            encoderType: encoderType,
+            encoderMethod: encoderMethod,
+            flags: flags
+        );
+    }
+}