WIP

gajumaru-core/src/Testinator.java

@@ -20,6 +20,9 @@ public class Testinator {
                 case "base58" -> {
                     System.out.print(base58(args[1]));
                 }
+                case "rlp" -> {
+                    System.out.print(rlp(args[1]));
+                }
             }
         } catch (IOException e) {
             System.err.println("Error: " + e.getMessage());
@@ -53,4 +56,14 @@ public class Testinator {
         Files.write(decPath, decBytes);
         return encPath.toString() + " " + decPath.toString();
     }
+
+    private static String rlp(String workingPath) throws IOException {
+        Path testPath = Path.of(workingPath, "rlp.test");
+        Path encPath = Path.of(workingPath, "rlp.java.back");
+        byte[] encBytes = Files.readAllBytes(testPath);
+        RLP_Data decRLP = RLP.decode(encBytes),
+        
+        Files.write(decPath, decBytes);
+        return encPath.toString() + " " + decPath.toString();
+    }
 }

gajumaru-core/src/main/java/swiss/qpq/gajumaru/core/encoding/RLP.java

@@ -0,0 +1,191 @@
+/*
+ * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Project: Gajumaru Core Java Libraries <gajumaru.io>
+ *
+ * This program is dual-licensed:
+ * 1) Under the GNU Affero General Public License as published by the Free 
+ *    Software Foundation, either version 3 of the License, or (at your option) 
+ *    any later version (AGPL-3.0-or-later).
+ *
+ * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ *    If you wish to use this software outside the strict constraints of the 
+ *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
+ *    purchase a commercial license from QPQ AG.
+ *
+ * Authors:
+ *   - Craig Everett <craigeverett@qpq.swiss>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
+ */
+
+package swiss.qpq.gajumaru.core.encoding;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public final class RLP {
+
+    // Integrated data models
+    // RLP only has two types: byte arrays and lists of lists of byte arrays
+    // TODO: Comment this better with references.
+
+    public abstract static class RLP_Data {}
+
+    public static final class RLP_Item extends RLP_Data {
+        public final byte[] bytes;
+        public RLP_Item(byte[] bytes) {
+            this.bytes = bytes != null ? bytes : new byte[0];
+        }
+    }
+
+    public static final class RLP_List extends RLP_Data {
+        public final List<RLP_Data> items;
+        public RLP_List(List<RLP_Data> items) {
+            this.items = items != null ? items : new ArrayList<>();
+        }
+    }
+
+    private RLP() {}
+
+    public static byte[] encode(RLP_Data data) {
+        if (data instanceof RLP_Item item) {
+            return encodeItem(item.bytes);
+        } else if (data instanceof RLP_List list) {
+            return encodeList(list.items);
+        }
+        throw new IllegalArgumentException("Unsupported RLP type");
+    }
+
+    private static byte[] encodeItem(byte[] bytes) {
+        if (bytes.length == 1 && (bytes[0] & 0xFF) <= 0x7F) {
+            return bytes;
+        }
+        return prefixData(bytes, 0x80, 0xB7);
+    }
+
+    private static byte[] encodeList(List<RLP_Data> items) {
+        if (items.isEmpty()) {
+            return new byte[] { (byte) 0xC0 };
+        }
+
+        // Pass 1: Encode all sub-elements and compute exact combined byte length
+        byte[][] encodedChildren = new byte[items.size()][];
+        int totalPayloadLength = 0;
+        for (int i = 0; i < items.size(); i++) {
+            encodedChildren[i] = encode(items.get(i));
+            totalPayloadLength += encodedChildren[i].length;
+        }
+
+        // Pass 2: Generate the structural frame list marker
+        byte[] prefix = prefixLength(totalPayloadLength, 0xC0, 0xF7);
+
+        // Pass 3: Flatten all segments directly into a single linear allocation
+        byte[] result = new byte[prefix.length + totalPayloadLength];
+        System.arraycopy(prefix, 0, result, 0, prefix.length);
+        
+        int writePtr = prefix.length;
+        for (byte[] child : encodedChildren) {
+            System.arraycopy(child, 0, result, writePtr, child.length);
+            writePtr += child.length;
+        }
+        return result;
+    }
+
+    private static byte[] prefixData(byte[] payload, int shortOffset, int longOffset) {
+        byte[] prefix = prefixLength(payload.length, shortOffset, longOffset);
+        byte[] result = new byte[prefix.length + payload.length];
+        System.arraycopy(prefix, 0, result, 0, prefix.length);
+        System.arraycopy(payload, 0, result, prefix.length, payload.length);
+        return result;
+    }
+
+    private static byte[] prefixLength(int length, int shortOffset, int longOffset) {
+        if (length <= 55) {
+            return new byte[] { (byte) (shortOffset + length) };
+        }
+        byte[] lengthBytes = intToBigEndian(length);
+        byte[] prefix = new byte[1 + lengthBytes.length];
+        prefix[0] = (byte) (longOffset + lengthBytes.length);
+        System.arraycopy(lengthBytes, 0, prefix, 1, lengthBytes.length);
+        return prefix;
+    }
+
+    private static byte[] intToBigEndian(int val) {
+        if (val == 0) return new byte[0];
+        int size = (Integer.numberOfLeadingZeros(val) == 32) ? 1 : (32 - Integer.numberOfLeadingZeros(val) + 7) / 8;
+        byte[] sigBytes = new byte[size];
+        for (int i = size - 1; i >= 0; i--) {
+            sigBytes[i] = (byte) (val & 0xFF);
+            val >>>= 8;
+        }
+        return sigBytes;
+    }
+
+
+    public static RLP_Data decode(byte[] bytes) {
+        if (bytes == null || bytes.length == 0) {
+            return new RLP_Item(new byte[0]);
+        }
+        return decodeRange(bytes, 0, bytes.length);
+    }
+
+    private static RLP_Data decodeRange(byte[] bytes, int start, int end) {
+        int prefix = bytes[start] & 0xFF;
+
+        if (prefix <= 0x7F) {
+            return new RLP_Item(new byte[] { (byte) prefix });
+        }
+        if (prefix <= 0xB7) {
+            return new RLP_Item(Arrays.copyOfRange(bytes, start + 1, start + 1 + (prefix - 0x80)));
+        }
+        if (prefix <= 0xBF) {
+            int lenLen = prefix - 0xB7;
+            int len = bigEndianToInt(bytes, start + 1, start + 1 + lenLen);
+            return new RLP_Item(Arrays.copyOfRange(bytes, start + 1 + lenLen, start + 1 + lenLen + len));
+        }
+        if (prefix <= 0xF7) {
+            int listLen = prefix - 0xC0;
+            return parseListSequence(bytes, start + 1, start + 1 + listLen);
+        }
+        
+        int lenLen = prefix - 0xF7;
+        int listLen = bigEndianToInt(bytes, start + 1, start + 1 + lenLen);
+        return parseListSequence(bytes, start + 1 + lenLen, start + 1 + lenLen + listLen);
+    }
+
+    private static RLP_List parseListSequence(byte[] bytes, int cursor, int limit) {
+        List<RLP_Data> elements = new ArrayList<>();
+        while (cursor < limit) {
+            int itemStart = cursor;
+            int prefix = bytes[cursor] & 0xFF;
+            int elementTotalSize;
+
+            if (prefix <= 0x7F) {
+                elementTotalSize = 1;
+            } else if (prefix <= 0xB7) {
+                elementTotalSize = 1 + (prefix - 0x80);
+            } else if (prefix <= 0xBF) {
+                int lenLen = prefix - 0xB7;
+                elementTotalSize = 1 + lenLen + bigEndianToInt(bytes, itemStart + 1, itemStart + 1 + lenLen);
+            } else if (prefix <= 0xF7) {
+                elementTotalSize = 1 + (prefix - 0xC0);
+            } else {
+                int lenLen = prefix - 0xF7;
+                elementTotalSize = 1 + lenLen + bigEndianToInt(bytes, itemStart + 1, itemStart + 1 + lenLen);
+            }
+
+            elements.add(decodeRange(bytes, itemStart, itemStart + elementTotalSize));
+            cursor += elementTotalSize;
+        }
+        return new RLP_List(elements);
+    }
+
+    private static int bigEndianToInt(byte[] bytes, int start, int end) {
+        int result = 0;
+        for (int i = start; i < end; i++) {
+            result = (result << 8) | (bytes[i] & 0xFF);
+        }
+        return result;
+    }
+}

gajumaru-core/test/src/gmt.erl

@@ -13,7 +13,8 @@
 
 mods() ->
     #{"base64" => fun base64/0,
-      "base58" => fun base58/0}.
+      "base58" => fun base58/0,
+      "rlp"    => fun rlp/0}.
 
 
 -spec start(ArgV) -> ok
@@ -99,8 +100,8 @@ base58() ->
     ok = filelib:ensure_dir(TestFile),
     ok = file:write_file(TestFile, rand:bytes(rand:uniform(5000))),
     {ok, Bytes} = file:read_file(TestFile),
-    Base64 = base58:binary_to_base58(Bytes),
-    ok = file:write_file(ConvFile, Base64),
+    Base58 = base58:binary_to_base58(Bytes),
+    ok = file:write_file(ConvFile, Base58),
     Run = unicode:characters_to_list(["bin/run base58 ", temp_dir()]),
     [JavaEncPath, JavaDecPath] = string:split(os:cmd(Run), " "),
     {ok, E_Enc_Bytes} = file:read_file(ConvFile),
@@ -112,3 +113,23 @@ base58() ->
     E_BinHash = crypto:hash(sha512, E_Dec_Bytes),
     J_BinHash = crypto:hash(sha512, J_Dec_Bytes),
     E_Hash =:= J_Hash andalso E_BinHash =:= J_BinHash.
+
+rlp() ->
+    Anchor = <<"I thought what I'd do was, I'd pretend I was one of those deaf-mutes.">>,
+    Data =
+        [rand:bytes(rand:uniform(20)),
+         [rand:bytes(rand:uniform(20)),
+          Anchor,
+          rand:bytes(rand:uniform(20)),
+          rand:bytes(rand:uniform(5000))],
+         rand:bytes(rand:uniform(2000))],
+    RLP = gmser_rlp:encode(Data),
+    RLP_File = filename:join(temp_dir(), "rlp.test"),
+    ok = file:write_file(RLP_File, RLP),
+    Run = unicode:characters_to_list(["bin/run rlp ", temp_dir()]),
+    [Found, JavaEncPath] = string:split(os:cmd(Run), " "),
+    {ok, E_Enc_Bytes} = file:read_file(RLP_File),
+    {ok, J_Enc_Bytes} = file:read_file(JavaEncPath),
+    E_Hash = crypto:hash(sha512, E_Enc_Bytes),
+    J_Hash = crypto:hash(sha512, J_Enc_Bytes),
+    E_Hash =:= J_Hash andalso Found =:= Anchor.