feat: read dvpl

src/core/blitz/readDVPL.ts

@@ -0,0 +1,49 @@
+import { crc32 } from 'crc';
+import { readFile } from 'fs/promises';
+import { decodeBlock } from 'lz4';
+
+/**
+ * Thanks Maddoxkkm! Modernized heavily.
+ *
+ * https://github.com/Maddoxkkm/dvpl_converter/
+ */
+export async function readDVPL(file: string) {
+  const buffer = await readFile(file);
+  const footerBuffer = buffer.slice(buffer.length - 20, buffer.length);
+
+  if (
+    footerBuffer.toString('utf8', 16, 20) !== 'DVPL' ||
+    footerBuffer.length !== 20
+  ) {
+    throw 'InvalidDVPLFooter';
+  }
+
+  const footerData = {
+    oSize: footerBuffer.readUInt32LE(0),
+    cSize: footerBuffer.readUInt32LE(4),
+    crc32: footerBuffer.readUInt32LE(8),
+    type: footerBuffer.readUInt32LE(12),
+  };
+  const targetBlock = buffer.slice(0, buffer.length - 20);
+
+  if (targetBlock.length !== footerData.cSize) throw 'DVPLSizeMismatch';
+  if (crc32(targetBlock) !== footerData.crc32) throw 'DVPLCRC32Mismatch';
+  if (footerData.type === 0) {
+    if (!(footerData.oSize === footerData.cSize && footerData.type === 0)) {
+      throw 'DVPLTypeSizeMismatch';
+    }
+
+    return targetBlock;
+  } else if (footerData.type === 1 || footerData.type === 2) {
+    const deDVPLBlock = Buffer.alloc(footerData.oSize);
+    const DecompressedBlockSize = decodeBlock(targetBlock, deDVPLBlock);
+
+    if (DecompressedBlockSize !== footerData.oSize) {
+      throw 'DVPLDecodeSizeMismatch';
+    }
+
+    return deDVPLBlock;
+  } else {
+    throw new TypeError('Unknown DVPL format');
+  }
+}