Vehicles

tools/img.js

@@ -0,0 +1,63 @@
+// IMG archive reader.
+//
+// San Andreas ships VER2 archives: the 'VER2' tag, a u32 entry count, then one
+// 32 byte directory entry per file -
+//   u32 offset, in 2048 byte sectors
+//   u16 streaming size, u16 size in archive (zero on retail, so prefer the former)
+//   char name[24], null padded
+// Bodies follow the directory, each starting on a sector boundary.
+
+const fs = require('fs');
+
+const SECTOR = 2048;
+
+class Img {
+  constructor(file) {
+    this.fd = fs.openSync(file, 'r');
+    this.path = file;
+
+    const header = Buffer.alloc(8);
+    fs.readSync(this.fd, header, 0, 8, 0);
+    if (header.toString('ascii', 0, 4) !== 'VER2') {
+      throw new Error(`${file} is not a VER2 img archive`);
+    }
+    const count = header.readUInt32LE(4);
+
+    const dir = Buffer.alloc(count * 32);
+    fs.readSync(this.fd, dir, 0, dir.length, 8);
+
+    // Lower cased, because the ide names and the archive names disagree on case.
+    this.entries = new Map();
+    for (let i = 0; i < count; i++) {
+      const at = i * 32;
+      const name = dir.toString('ascii', at + 8, at + 32).split('\0')[0];
+      const sectors = dir.readUInt16LE(at + 4) || dir.readUInt16LE(at + 6);
+      this.entries.set(name.toLowerCase(), {
+        name,
+        offset: dir.readUInt32LE(at) * SECTOR,
+        size: sectors * SECTOR,
+      });
+    }
+  }
+
+  has(name) {
+    return this.entries.has(name.toLowerCase());
+  }
+
+  // Entry bodies are padded out to the sector size, and every reader downstream
+  // walks chunk headers rather than trusting the length, so the padding is
+  // harmless and gets written as-is.
+  read(name) {
+    const entry = this.entries.get(name.toLowerCase());
+    if (!entry) return null;
+    const buffer = Buffer.alloc(entry.size);
+    fs.readSync(this.fd, buffer, 0, entry.size, entry.offset);
+    return buffer;
+  }
+
+  close() {
+    fs.closeSync(this.fd);
+  }
+}
+
+module.exports = { Img };