wah getting fucked up on endian business

2024-09-29 15:17:58 -06:00
parent 94ab274246
commit 6dbc577566
11 changed files with 2430 additions and 57 deletions
@@ -0,0 +1,57 @@
+using System.Text;
+
+namespace fxl.codes.kisekae.data.Archives.Algorithms;
+
+internal class LZW : IAlgorithm
+{
+    private readonly int Max;
+
+    internal LZW(int max = short.MaxValue)
+    {
+        Max = max;
+    }
+
+    public byte[] Decode(ReadOnlySpan<byte> stream)
+    {
+        uint next = byte.MaxValue + 1;
+        var dictionary = new Dictionary<uint, string>();
+        for (uint i = 0; i <= byte.MaxValue; i++) dictionary.Add(i, $"{(char)i}");
+
+        var buffer = "";
+        var decoded = new List<string>();
+        for (var i = 0; i < stream.Length; i += 4)
+        {
+            var code = BitConverter.ToUInt32(stream[i..(i + 4)]);
+            if (!dictionary.ContainsKey(code)) dictionary[code] = buffer + buffer[0];
+
+            decoded.Add(dictionary[code]);
+            if (buffer.Length > 0 && next <= Max) dictionary[next++] = buffer + dictionary[code][0];
+
+            buffer = dictionary[code];
+        }
+
+        return decoded.SelectMany(Encoding.UTF8.GetBytes).ToArray();
+    }
+
+    public byte[] Encode(ReadOnlySpan<byte> stream)
+    {
+        var next = byte.MaxValue + 1;
+        var dictionary = new Dictionary<string, int>();
+        for (var i = 0; i <= byte.MaxValue; i++) dictionary.Add($"{(char)i}", i);
+
+        var buffer = "";
+        var encoded = new List<int>();
+        foreach (var part in stream)
+        {
+            var charValue = (char)part;
+            buffer += charValue;
+            if (dictionary.ContainsKey(buffer)) continue;
+            if (next <= Max) dictionary.Add(buffer, next++);
+            encoded.Add(dictionary[$"{buffer[..^1]}"]);
+            buffer = $"{charValue}";
+        }
+
+        encoded.Add(dictionary[buffer]);
+        return encoded.SelectMany(BitConverter.GetBytes).ToArray();
+    }
+}