idz: Add utilities for binary I/O

src/idz/util/bin.ts

@@ -0,0 +1,62 @@
+import iconv from "iconv-lite";
+
+const ASCII = "ascii";
+const SHIFT_JIS = "shift_jis";
+
+function readStr(buf: Buffer, begin: number, end: number, encoding: string) {
+  end = Math.min(buf.indexOf(0, begin), end);
+
+  return iconv.decode(buf.slice(begin, end), encoding);
+}
+
+export function readAsciiStr(buf: Buffer, begin: number, end: number) {
+  return readStr(buf, begin, end, ASCII);
+}
+
+export function readSjisStr(buf: Buffer, begin: number, end: number) {
+  return readStr(buf, begin, end, SHIFT_JIS);
+}
+
+// WARNING: This is sent little-endian.
+export function writeIpAddr(buf: Buffer, str: string, pos: number) {
+  const bits = str.split(".");
+
+  for (let i = 0; i < 4; i++) {
+    buf.writeUInt8(parseInt(bits[3 - i]), pos + i);
+  }
+}
+
+function writeStr(
+  buf: Buffer,
+  begin: number,
+  end: number,
+  str: string,
+  encoding: string
+) {
+  const tmp = iconv.encode(str + "\0", encoding);
+
+  if (tmp.length >= end - begin) {
+    throw new Error("String field overflow");
+  }
+
+  tmp.copy(buf, begin);
+  buf.writeUInt8(0, begin + tmp.length);
+}
+
+export function writeAsciiStr(
+  buf: Buffer,
+  begin: number,
+  end: number,
+  str: string
+) {
+  writeStr(buf, begin, end, str, ASCII);
+}
+
+export function writeSjisStr(
+  buf: Buffer,
+  begin: number,
+  end: number,
+  str: string
+) {
+  writeStr(buf, begin, end, str, SHIFT_JIS);
+}