feat: implement binary meta

utils/lt-code/binary-meta.ts

@@ -0,0 +1,77 @@
+/**
+ * Merge multiple Uint8Array into a single Uint8Array
+ * Each chunk is prefixed with a 4-byte Uint32 to store the length of the chunk
+ */
+export function mergeUint8Arrays(arrays: Uint8Array[]) {
+  const totalLength = arrays.reduce((sum, arr) => sum + arr.length + 4, 0) // 4 是為了存每個數組的長度 (Uint32)
+
+  const mergedArray = new Uint8Array(totalLength)
+  let offset = 0
+
+  arrays.forEach((arr) => {
+    const length = arr.length
+    // 將長度存成 4 bytes 的 Uint32
+    mergedArray[offset++] = (length >> 24) & 0xFF
+    mergedArray[offset++] = (length >> 16) & 0xFF
+    mergedArray[offset++] = (length >> 8) & 0xFF
+    mergedArray[offset++] = length & 0xFF
+
+    // 複製 Uint8Array 到合併數組中
+    mergedArray.set(arr, offset)
+    offset += length
+  })
+
+  return mergedArray
+}
+
+/**
+ * Split a merged Uint8Array into multiple Uint8Array
+ */
+export function splitUint8Arrays(mergedArray: Uint8Array): Uint8Array[] {
+  const arrays = []
+  let offset = 0
+
+  while (offset < mergedArray.length) {
+    // 讀取 Uint8Array 的長度 (從 4 bytes)
+    const length = (mergedArray[offset++]! << 24)
+      | (mergedArray[offset++]! << 16)
+      | (mergedArray[offset++]! << 8)
+      | mergedArray[offset++]!
+
+    // 根據長度切割出原始 Uint8Array
+    const arr = mergedArray.slice(offset, offset + length)
+    arrays.push(arr)
+    offset += length
+  }
+
+  return arrays
+}
+
+export function appendMetaToBuffer<T>(data: Uint8Array, meta: T): Uint8Array {
+  const json = JSON.stringify(meta)
+  const metaBuffer = stringToUint8Array(json)
+  return mergeUint8Arrays([metaBuffer, data])
+}
+
+export function readMetaFromBuffer<T>(buffer: Uint8Array): [data: Uint8Array, meta: T] {
+  const splitted = splitUint8Arrays(buffer) as [Uint8Array, Uint8Array]
+  if (splitted.length !== 2) {
+    throw new Error('Invalid buffer')
+  }
+  const [metaBuffer, data] = splitted
+  const meta = JSON.parse(uint8ArrayToString(metaBuffer!))
+  return [data, meta]
+}
+
+export function stringToUint8Array(str: string): Uint8Array {
+  const data = new Uint8Array(str.length)
+  for (let i = 0; i < str.length; i++) {
+    data[i] = str.charCodeAt(i)
+  }
+
+  return data
+}
+
+export function uint8ArrayToString(data: Uint8Array): string {
+  return String.fromCharCode(...data)
+}

utils/lt-code/shared.ts

@@ -92,15 +92,6 @@ export function xorUint8Array(a: Uint8Array, b: Uint8Array): Uint8Array {
   return result
 }
 
-export function stringToUint8Array(str: string): Uint8Array {
-  const data = new Uint8Array(str.length)
-  for (let i = 0; i < str.length; i++) {
-    data[i] = str.charCodeAt(i)
-  }
-
-  return data
-}
-
 /**
  * Convert Content-Type string to @see ContentType enum.
  *