Method arraySpliceImpl

src/lib/json_buffer.ts:1123–1192

(
    target: Pointer,
    start: number,
    deleteCount: number,
    items: any[] = [],
  )

  }

  private arraySpliceImpl(
    target: Pointer,
    start: number,
    deleteCount: number,
    items: any[] = [],
  ): any[] {
    this.resolvePtr(target.__ptr);
    const len = this.scratchLen;
    const actualStart = start < 0
      ? Math.max(len + start, 0)
      : Math.min(start, len);
    const actualDeleteCount = Math.min(
      Math.max(deleteCount, 0),
      len - actualStart,
    );

    // 1. Read deleted items to return
    const deletedItems: any[] = [];
    for (let i = 0; i < actualDeleteCount; i++) {
      const offset = this.scratchStart + (actualStart + i) * 8;
      deletedItems.push(this.readSlot(offset));
    }

    const insertCount = items.length;
    const delta = insertCount - actualDeleteCount;
    const newLen = len + delta;

    // 2. Ensure Capacity (Allocates new buffer if needed)
    this.arrayEnsureCapacity(target, newLen);
    // After this, this.s_start, s_ptr, s_cap are updated to potentially new location

    // 3. Move Memory (Shift tail)
    if (delta !== 0) {
      const tailCount = len - (actualStart + actualDeleteCount);
      const srcIdx = actualStart + actualDeleteCount;
      const destIdx = actualStart + insertCount;

      const srcOffset = this.scratchStart + srcIdx * 8;
      const destOffset = this.scratchStart + destIdx * 8;
      const byteLen = tailCount * 8;

      this.u8.copyWithin(destOffset, srcOffset, srcOffset + byteLen);
    }

    // 4. Insert Items
    for (let i = 0; i < insertCount; i++) {
      const val = items[i];
      const valResult = this.writeValue(val);
      const valHandle = { __ptr: valResult.payload };
      const isValPtr = valResult.type >= TYPE_NUMBER;

      if (isValPtr) {
        this.tempRoots.push({ handle: valHandle, type: valResult.type });
      }

      this.resolvePtr(target.__ptr);
      const offset = this.scratchStart + (actualStart + i) * 8;
      const oIdx = offset >> 2;