ebook【Delphi跨平台資料庫程式設計火速上手】電子書出版 (CHT)

Delphi 跨平台資料庫程式設計火速上手,是本關於整合 Delphi 的跨平台技術打造 2-Tier 架構的跨平台 APP 的入門技術書。 全書沒有需要理解的技術知識,只講套路。 力求短時間把製作 APP 的工法熟悉,未來要開發其它的應用程式也能舉一反三。 底下...


Using critical sections

話說BCB在執行緒中有同步的指令,但這是應用在VCL元件上面,在不用到VCL的埸合時,我們就可以利用「Critical Sections」來對多執行緒做排序處理,以下是從BCB的help中節錄出來的:

If objects do not provide built-in locking, you can use a critical section. Critical sections work like gates that allow only a single thread to enter at a time. To use a critical section, create a global instance of TCriticalSection. TCriticalSection has two methods, Acquire (which blocks other threads from executing the section) and Release (which removes the block).

Each critical section is associated with the global memory you want to protect. Every thread that accesses that global memory should first use the Acquire method to ensure that no other thread is using it. When finished, threads call the Release method so that other threads can access the global memory by calling Acquire.

Warning: Critical sections only work if every thread uses them to access the associated global memory. Threads that ignore the critical section and access the global memory without calling Acquire can introduce problems of simultaneous access.

For example, consider an application that has a global critical section variable, pLockXY, that blocks access to global variables X and Y. Any thread that uses X or Y must surround that use with calls to the critical section such as the following:
pLockXY->Acquire(); // lock out other threads
  Y = sin(X);