feat: add TypeScript type definitions for multi-byte.js (#31)

Co-authored-by: Nikita Skovoroda <chalkerx@gmail.com>

Author: Copilot

README.md

@@ -306,17 +306,18 @@ const windows1252fromString = createSinglebyteEncoder('windows-1252', { mode: 'f
 
 ### `@exodus/bytes/multi-byte.js`
 
-```js
-import { createMultibyteDecoder } from '@exodus/bytes/multi-byte.js'
-```
-
-Decode the legacy multi-byte encodings according to the [Encoding standard](https://encoding.spec.whatwg.org/)
+Decode / encode the legacy multi-byte encodings according to the
+[Encoding standard](https://encoding.spec.whatwg.org/)
 ([§10](https://encoding.spec.whatwg.org/#legacy-multi-byte-chinese-(simplified)-encodings),
 [§11](https://encoding.spec.whatwg.org/#legacy-multi-byte-chinese-(traditional)-encodings),
 [§12](https://encoding.spec.whatwg.org/#legacy-multi-byte-japanese-encodings),
 [§13](https://encoding.spec.whatwg.org/#legacy-multi-byte-korean-encodings)).
 
-Supports all legacy multi-byte encodings listed in the standard:
+```js
+import { createMultibyteDecoder, createMultibyteEncoder } from '@exodus/bytes/multi-byte.js'
+```
+
+Supports all legacy multi-byte encodings listed in the WHATWG Encoding standard:
 `gbk`, `gb18030`, `big5`, `euc-jp`, `iso-2022-jp`, `shift_jis`, `euc-kr`.
 
 #### `createMultibyteDecoder(encoding, loose = false)`
@@ -325,7 +326,18 @@ Create a decoder for a supported legacy multi-byte `encoding`, given its lowerca
 
 Returns a function `decode(arr, stream = false)` that decodes bytes to a string.
 
-That function will have state while `stream = true` is used.
+The returned function will maintain internal state while `stream = true` is used, allowing it to
+handle incomplete multi-byte sequences across multiple calls.
+State is reset when `stream = false` or when the function is called without the `stream` parameter.
+
+#### `createMultibyteEncoder(encoding, { mode = 'fatal' })`
+
+Create an encoder for a supported legacy multi-byte `encoding`, given its lowercased name `encoding`.
+
+Returns a function `encode(string)` that encodes a string to bytes.
+
+In `'fatal'` mode (default), will throw on non well-formed strings or any codepoints which could
+not be encoded in the target encoding.
 
 ### `@exodus/bytes/bigint.js`
 

multi-byte.d.ts

@@ -0,0 +1,57 @@
+/**
+ * Decode / encode the legacy multi-byte encodings according to the
+ * [Encoding standard](https://encoding.spec.whatwg.org/)
+ * ([§10](https://encoding.spec.whatwg.org/#legacy-multi-byte-chinese-(simplified)-encodings),
+ * [§11](https://encoding.spec.whatwg.org/#legacy-multi-byte-chinese-(traditional)-encodings),
+ * [§12](https://encoding.spec.whatwg.org/#legacy-multi-byte-japanese-encodings),
+ * [§13](https://encoding.spec.whatwg.org/#legacy-multi-byte-korean-encodings)).
+ *
+ * ```js
+ * import { createMultibyteDecoder, createMultibyteEncoder } from '@exodus/bytes/multi-byte.js'
+ * ```
+ *
+ * Supports all legacy multi-byte encodings listed in the WHATWG Encoding standard:
+ * `gbk`, `gb18030`, `big5`, `euc-jp`, `iso-2022-jp`, `shift_jis`, `euc-kr`.
+ *
+ * @module @exodus/bytes/multi-byte.js
+ */
+
+/// <reference types="node" />
+
+import type { Uint8ArrayBuffer } from './array.js';
+
+/**
+ * Create a decoder for a supported legacy multi-byte `encoding`, given its lowercased name `encoding`.
+ *
+ * Returns a function `decode(arr, stream = false)` that decodes bytes to a string.
+ *
+ * The returned function will maintain internal state while `stream = true` is used, allowing it to
+ * handle incomplete multi-byte sequences across multiple calls.
+ * State is reset when `stream = false` or when the function is called without the `stream` parameter.
+ *
+ * @param encoding - The encoding name (e.g., 'gbk', 'gb18030', 'big5', 'euc-jp', 'iso-2022-jp', 'shift_jis', 'euc-kr')
+ * @param loose - If true, replaces unmapped bytes with replacement character instead of throwing (default: false)
+ * @returns A function that decodes bytes to string, with optional streaming support
+ */
+export function createMultibyteDecoder(
+  encoding: string,
+  loose?: boolean
+): (arr: Uint8ArrayBuffer, stream?: boolean) => string;
+
+/**
+ * Create an encoder for a supported legacy multi-byte `encoding`, given its lowercased name `encoding`.
+ *
+ * Returns a function `encode(string)` that encodes a string to bytes.
+ *
+ * In `'fatal'` mode (default), will throw on non well-formed strings or any codepoints which could
+ * not be encoded in the target encoding.
+ *
+ * @param encoding - The encoding name (e.g., 'gbk', 'gb18030', 'big5', 'euc-jp', 'iso-2022-jp', 'shift_jis', 'euc-kr')
+ * @param options - Encoding options
+ * @param options.mode - Encoding mode (default: 'fatal'). Currently, only 'fatal' mode is supported.
+ * @returns A function that encodes string to bytes
+ */
+export function createMultibyteEncoder(
+  encoding: string,
+  options?: { mode?: 'fatal' }
+): (string: string) => Uint8ArrayBuffer;

package.json

@@ -105,6 +105,7 @@
     "/index.js",
     "/index.d.ts",
     "/multi-byte.js",
+    "/multi-byte.d.ts",
     "/multi-byte.node.js",
     "/single-byte.js",
     "/single-byte.d.ts",
@@ -153,6 +154,7 @@
       "default": "./hex.js"
     },
     "./multi-byte.js": {
+      "types": "./multi-byte.d.ts",
       "node": "./multi-byte.node.js",
       "default": "./multi-byte.js"
     },