feat: implement VLQ parsing

src/me/topchetoeu/jscript/mapping/VLQ.java

@@ -0,0 +1,95 @@
+package me.topchetoeu.jscript.mapping;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class VLQ {
+    private static final String ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+    private static long[] toArray(List<Long> list) {
+        var arr = new long[list.size()];
+        for (var i = 0; i < list.size(); i++) arr[i] = list.get(i);
+        return arr;
+    }
+
+    public static String encode(long... arr) {
+        var raw = new StringBuilder();
+
+        for (var data : arr) {
+            var b = data < 0 ? 1 : 0;
+            data = Math.abs(data);
+            b |= (int)(data & 0b1111) << 1;
+            data >>= 4;
+            b |=  data > 0 ? 0x20 : 0;;
+            raw.append(ALPHABET.charAt(b));
+
+            while (data > 0) {
+                b = (int)(data & 0b11111);
+                data >>= 5;
+                b |= data > 0 ? 0x20 : 0;
+                raw.append(ALPHABET.charAt(b));
+            }
+        }
+
+        return raw.toString();
+    }
+    public static long[] decode(String val) {
+        if (val.length() == 0) return new long[0];
+
+        var list = new ArrayList<Long>();
+
+        for (var i = 0; i < val.length();) {
+            var sign = 1;
+            var curr = ALPHABET.indexOf(val.charAt(i++));
+            var cont = (curr & 0x20) == 0x20;
+            if ((curr & 1) == 1) sign = -1;
+            long res = (curr & 0b11110) >> 1;
+            var n = 4;
+
+            for (; i < val.length() && cont;) {
+                curr = ALPHABET.indexOf(val.charAt(i++));
+                cont = (curr & 0x20) == 0x20;
+                res |= (curr & 0b11111) << n;
+                n += 5;
+                if (!cont) break;
+            }
+
+            list.add(res * sign);
+        }
+
+        return toArray(list);
+    }
+
+    public static String encodeMapping(long[][][] arr) {
+        var res = new StringBuilder();
+        var semicolon = false;
+        
+        for (var line : arr) {
+            var comma = false;
+
+            if (semicolon) res.append(";");
+            semicolon = true;
+
+            for (var el : line) {
+                if (comma) res.append(",");
+                comma = true;
+                res.append(encode(el));
+            }
+        }
+
+        return res.toString();
+    }
+    public static long[][][] decodeMapping(String val) {
+        var lines = new ArrayList<long[][]>();
+
+        for (var line : val.split(";", -1)) {
+            var elements = new ArrayList<long[]>();
+            for (var el : line.split(",", -1)) {
+                elements.add(decode(el));
+            }
+            lines.add(elements.toArray(long[][]::new));
+        }
+
+        return lines.toArray(long[][][]::new);
+    }
+}