feat(Struct)

src/Struct.js

@@ -0,0 +1,93 @@
+import { isHeadless, parse, serialize, sizeof, sizeofHead, Type } from "."
+
+export function Struct(type_obj) {
+  const obj = {}
+  Object.setPrototypeOf(obj, Struct.prototype)
+  
+  obj._info_by_key = new Map
+  obj._headless = false
+  
+  const arg = {}
+  let offset = 0
+
+  for (const [key, value] of Object.entries(type_obj)) {
+    let types
+    if (Array.isArray(value)) {
+      types = value
+    } else {
+      types = [value]
+    }
+
+    arg[key] = types.map(type => type.name)
+
+    const headless = isHeadless(...types)
+    obj._info_by_key.set(key, {
+      offset,
+      types,
+      headless,
+    })
+    obj._headless |= headless
+    offset += sizeofHead(...types)
+  }
+
+  obj._size = offset
+  obj.new(Struct, [arg])
+
+  return obj
+}
+Struct.prototype.serialize = function(dv, src) {
+  let data_offset = this._size
+
+  for (const [key, value] of Object.entries(src)) {
+    const info = this._info_by_key.get(key)
+    
+    if (info.headless) {
+      dv.setUint32(info.offset, data_offset)
+      const frame = new DataView(dv.buffer, dv.byteOffset + data_offset)
+      serialize(frame, value, ...info.types)
+      data_offset += sizeof(value, ...info.types)
+    } else {
+      const frame = new DataView(dv.buffer, dv.byteOffset + info.offset)
+      serialize(frame, value, ...info.types)
+    }
+  }
+}
+Struct.prototype.parse = function(dv) {
+  const res = {}
+
+  for (const [key, info] of this._info_by_key.entries()) {  
+    if (info.headless) {
+      const data_offset = dv.getUint32(info.offset)
+      const frame = new DataView(dv.buffer, dv.byteOffset + data_offset)
+      res[key] = parse(frame, ...info.types)
+    } else {
+      const frame = new DataView(dv.buffer, dv.byteOffset + info.offset)
+      res[key] = parse(frame, ...info.types)
+    }
+  }
+
+  return res
+}
+Struct.prototype.isHeadless = function() {
+  return this._headless
+}
+Struct.prototype.sizeof = function(arg) {
+  if (this._headless) {
+    if (arg === undefined) {
+      throw new Error('unknown size of ' + this)
+    }
+    let size = this._size
+
+    for (const [key, info] of this._info_by_key.entries()) {
+      if (info.headless) {
+        size += sizeof(arg[key], ...info.types)
+      }
+    }
+
+    return size
+  } else {
+    return this._size
+  }
+}
+Object.setPrototypeOf(Struct.prototype, Type.prototype)
+Object.freeze(Struct.prototype)