feat: patches

src/core/blitz/writeDVPL.ts

@@ -0,0 +1,50 @@
+import { crc32 } from 'crc';
+import { encodeBlockHC } from 'lz4';
+
+/**
+ * Thanks Maddoxkkm! Modernized heavily.
+ *
+ * https://github.com/Maddoxkkm/dvpl_converter/
+ */
+export function writeDVPL(buffer: Buffer) {
+  let output = Buffer.alloc(buffer.length);
+  const compressedBlockSize = encodeBlockHC(buffer, output);
+
+  if (compressedBlockSize === 0 || compressedBlockSize >= buffer.length) {
+    const footerBuffer = toDVPLFooter(
+      buffer.length,
+      buffer.length,
+      crc32(buffer),
+      0,
+    );
+
+    return Buffer.concat([buffer, footerBuffer], buffer.length + 20);
+  } else {
+    output = output.subarray(0, compressedBlockSize);
+    const footerBuffer = toDVPLFooter(
+      buffer.length,
+      compressedBlockSize,
+      crc32(output),
+      2,
+    );
+
+    return Buffer.concat([output, footerBuffer], compressedBlockSize + 20);
+  }
+}
+
+function toDVPLFooter(
+  inputSize: number,
+  compressedSize: number,
+  crc32: number,
+  type: number,
+) {
+  const result = Buffer.alloc(20);
+
+  result.writeUInt32LE(inputSize, 0);
+  result.writeUInt32LE(compressedSize, 4);
+  result.writeUInt32LE(crc32, 8);
+  result.writeUInt32LE(type, 12);
+  result.write('DVPL', 16, 4, 'utf8');
+
+  return result;
+}