Init

2026-05-28 21:17:06 +09:00
commit c20a024eeb
4 changed files with 188 additions and 0 deletions
@@ -0,0 +1,152 @@
+/*
+ * 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.Arrays;
+
+// Stateless Base58 implementation.
+public final class Base58 {
+    
+    private static final char[] ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray();
+    private static final int[]  INDEXES  = new int[128];
+    
+    static {
+        Arrays.fill(INDEXES, -1);
+        for (int i = 0; i < ALPHABET.length; i++) {
+            INDEXES[ALPHABET[i]] = i;
+        }
+    }
+
+    private Base58() {}
+
+    // Encode raw bytes directly to a Base58 string.
+    public static String encode(byte[] input) {
+        if (input == null || input.length == 0) {
+            return "";
+        }
+
+        int zeros = 0;
+        while (zeros < input.length && input[zeros] == 0) {
+            zeros++;
+        }
+
+        byte[] temp = Arrays.copyOf(input, input.length);
+        char[] encoded = new char[temp.length * 2];
+        int outputStart = encoded.length;
+
+        // Treat 'temp' as one giant number. Process until the entire array is reduced to zeros.
+        // i indicates the position of the most significant leading zero.
+        int i = zeros; 
+        while (i < temp.length) {
+            int remainder = 0;
+
+            // Perform long division from left to right across the active bytes
+            for (int j = i; j < temp.length; j++) {
+                int currentByte = temp[j] & 0xFF; // Safe unsigned byte conversion
+                int totalValue = (remainder * 256) + currentByte;
+
+                temp[j]   = (byte) (totalValue / 58); // Mutate array with the quotient
+                remainder = totalValue % 58;          // Carry the remainder to the next byte
+            }
+    
+            // The final remainder of this pass is our next Base58 digit character
+            encoded[--outputStart] = ALPHABET[remainder];
+    
+            // Advance the pointer forward if the current head byte has been ground down to 0
+            if (temp[i] == 0) {
+                i++;
+            }
+        }
+
+        while (outputStart < encoded.length && encoded[outputStart] == ALPHABET[0]) {
+            outputStart++;
+        }
+        while (--zeros >= 0) {
+            encoded[--outputStart] = ALPHABET[0];
+        }
+
+        return new String(encoded, outputStart, encoded.length - outputStart);
+    }
+
+    // Decodes a Base58 string back into its original byte payload.
+    // Throws an IllegalArgumentException if any illegal characters are encountered.
+    // `throw` remains slightly disgusting.
+    public static byte[] decode(String input) throws IllegalArgumentException {
+        if (input == null || input.isEmpty()) {
+            return new byte[0];
+        }
+
+        // Convert the string into numeric index offsets
+        byte[] input58 = new byte[input.length()];
+        for (int i = 0; i < input.length(); i++) {
+            char c = input.charAt(i);
+            int digit = (c < 128) ? INDEXES[c] : -1;
+            if (digit < 0) {
+                // I picked the wrong week to stop drinking...
+                throw new IllegalArgumentException("Illegal Base58 character encountered: " + c);
+            }
+            input58[i] = (byte) digit;
+        }
+
+        // Count leading zeros to reconstruct leading 0 bytes
+        int zeros = 0;
+        while (zeros < input58.length && input58[zeros] == 0) {
+            zeros++;
+        }
+
+        byte[] decoded = new byte[input.length()];
+        int outputStart = decoded.length;
+
+        // Treat input58 as one yuuge base-58 number. Reduce it down to base-256 bytes.
+        int i = zeros;
+        while (i < input58.length) {
+            int remainder = 0;
+    
+            // Long division from left to right across the remaining numeric character indices
+            for (int j = i; j < input58.length; j++) {
+                int currentBase58Digit = input58[j] & 0xFF;
+                int totalValue = (remainder * 58) + currentBase58Digit; // Shift base by 58
+        
+                input58[j] = (byte) (totalValue / 256); // Mutate array with the base-256 quotient
+                remainder  = totalValue % 256;          // Carry the byte remainder forward
+            }
+    
+            // The remainder of this pass is the next raw base-256 byte payload
+            decoded[--outputStart] = (byte) remainder;
+    
+            // Permanently advance past this leading index if its value has been exhausted
+            if (input58[i] == 0) {
+                i++;
+            }
+        }
+
+
+        // Strip extra leading zero allocations from the worst-case boundary buffer
+        while (outputStart < decoded.length && decoded[outputStart] == 0) {
+            outputStart++;
+        }
+
+        // Re-inject the necessary leading padding zeros
+        byte[] result = new byte[decoded.length - outputStart + zeros];
+        System.arraycopy(decoded, outputStart, result, zeros, decoded.length - outputStart);
+        return result;
+    }
+}