Add CpySchedule.

src/encGroup.js

@@ -22,19 +22,32 @@ function makeMessage(msgType, datas) {
   return {type:msgType, data: datas};
 }
 
+class CpySchedule {
+  first = { pos: 0, size: 0 }
+  second = { pos: 0, size: 0 }
+}
+
 /* An abstraction that help to
  * easily to transfer datas to target worker
  * in real time manner */
 export class Channel {
 
-  /* | ReadPointer (4 bytes) | WritePointer (4 Bytes) | Data Area (1-n bytes) */
+  /*  */
 
   /* Size of memory area that help to
    * maintain Channel. Types of meta info
    * are shown below:
    *
    * 1.Write Position
-   * 2.Read Position */
+   * 2.Read Position
+   *
+   * Figure:
+   *  ------------------------------------------------------------------------
+   * | ReadPointer (4 bytes) | WritePointer (4 Bytes) | Data Area (N bytes)  |
+   * -------------------------------------------------------------------------
+   * where N >= 2
+   *
+   * */
   #numOfMetaField = 2
   #fieldSize = 0;
 
@@ -54,6 +67,9 @@ export class Channel {
   // size's unit is byte
   // bufferType parameter is mainly for testability.
   constructor(WW, size, bufferType = SharedArrayBuffer) {
+
+    assert(size >= 2, `Channel require its data area has at least 2 Bytes.`)
+
     this.#WW = WW;
     this.#size = size;
 
@@ -70,6 +86,8 @@ export class Channel {
 
     this.#view.setUint32(0, this.#metaSize);
     this.#view.setUint32(4, this.#metaSize);
+
+    // FIXME: Need to transfer channel itself to worker.
   }
 
   #readPos() {
@@ -104,20 +122,21 @@ export class Channel {
    *          make sure there has enough spaces.*/
   #cpySchedule(size) {
     let firstCpySize = 0, secondCpySize = 0, spaceToTail = 0;
-    let schedule;
+    let schedule = new CpySchedule();
 
     if (this.#writePos >= this.#readPos()) {
       spaceToTail = this.#endPos - this.#writePos;
       firstCpySize = Math.min(size, spaceToTail);
       secondCpySize = firstCpySize < size ? size - firstCpySize : 0;
 
-      schedule = {
-        first : { pos: this.#writePos, size: firstCpySize },
-        second: { pos: secondCpySize > 0 ? this.#metaSize : 0, size: secondCpySize }
-      };
+      schedule.first.pos = this.#writePos;
+      schedule.first.size = firstCpySize;
+      schedule.second.pos = secondCpySize > 0 ? this.#metaSize : 0;
+      schedule.second.size = secondCpySize;
+
     } else {
-      schedule = { first : { pos: this.#writePos, size: firstCpySize },
-                   second: { pos: 0, size: 0 } };
+      schedule.first.pos = this.#writePos;
+      schedule.first.size = firstCpySize;
     }
 
     return schedule;
@@ -182,15 +201,17 @@ export class Channel {
     let schedule = this.#cpySchedule(data.byteLength);
 
     // Perfrom write schedule
-    let srcPos = 0;
+    let srcPos = 0, plan;
+
     for (let key in schedule) {
-      let plan = schedule[key];
+      plan = schedule[key];
+
       if (plan.size == 0)
         continue;
 
-      let d_ = data.slice(srcPos, srcPos+plan.size);
-      this.#buffer.set(d_, plan.pos)
-      srcPos = srcPos + plan.size;
+      this.#buffer.set(
+        data.slice(srcPos, srcPos+plan.size), plan.pos)
+      srcPos += plan.size;
       writePos = plan.pos+plan.size;
     }