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How to carry out FileZilla source code analysis, in view of this problem, this article introduces the corresponding analysis and answers in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

FileZilla is a fast and reliable FTP client and server-side open source program with a variety of features and intuitive interfaces. The editor will analyze the source code of FileZilla for you.

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Review of win32 synchronization Control Mechanism (Synchronization)

1. Critical Sections (critical domain)

The simplest synchronization mechanism, the functions to create and destroy are:

InitializeCriticalSection ()

DeleteCriticalSection ()

After being created, use the following function to achieve thread synchronization

EnterCritSection ()

... Code that requires synchronization

LeaveCritSection ()

That is, the code between EnterCritSection and LeaveCritSection can only be processed by one thread at a time. The questions to be noted are:

A variable of type Critical Sections is not a core object, that is, there is no handle

It exists in the memory space of the process, that is, it cannot be used across processes.

Could lead to deadlock.

2. Mutexes (mutex)

The functions to create and destroy are:

CreateMutex ()

CloseHandle ()

If the Mutex has been created, turn it on and off like this:

OpenMutex ()

ReleaseMutex ()

When using, use the wait function to wait for the Mutex. Once no thread owns the Mutex, the thread will get the Mutex. After the thread has finished processing, calling ReleaseMutex () will release the Mutex, and other waiting threads will re-compete for the Mutex. At the same time, only one thread can get the Mutex, and the uncontested thread will be in the blocking blocking state. Common wait functions are:

WaitForSingleObject () / / wait for a mutex

WaitForMultipleObjects () / / wait for multiple mutex at the same time, or have multiple at the same time, or none at all

Compared to Critical Sections, mutex is a core object, so it is cross-process, that is, multiple processes can use the same mutex, and CreateMutex () is much more expensive than InitializeCriticalSection ().

Mutex, by contrast, is more heavyweight, slower, but also more flexible.

3. Semaphore (Semaphores)

The functions to create and destroy are:

CreateSemaphore ()

CloseHandle ()

The functions that get this Semaphore are also those wait functions WaitForSingleObject (), WaitForMultipleObjects (), and so on.

Using Semaphores means that Semaphores can be owned by multiple threads at the same time, but when CreateSemaphore (), it will specify the number of threads that own the Semaphore at the same time, that is, when each thread calls the wait function to obtain the Semaphore, the available value within the Semaphore will be reduced by 1. Once the available value is 0, the thread must wait. When the thread that hosts the Semaphore is finished, you should also call ReleaseSemaphore () to release it.

Unlike Mutexes, the thread that calls ReleaseSemaphore () is not necessarily the one that calls wait and gains ownership, that is, any thread can call ReleaseSemaphore () at any time to unlock Semaphore that is locked by any thread.

In a sense, Mutexes can be seen as a special case of Semaphore, that is, Semaphore that can only be locked by one thread at the same time.

Semaphore is also the core object.

4. Event (Event Objects)

The most flexible of win32 should be events, which is also a core object.

The meaning of events is that events has two states, active and inactive, and when the events is activated, those waiting threads are awakened.

The functions to create and destroy are:

CreateEvent (), which can be created to specify that events is manual or automatic,manual, meaning that the state of events is set by the programmer. Automatic means that events automatically becomes inactive immediately after it becomes a harrowing word.

CloseHandle ()

The functions that get this events are also those wait functions WaitForSingleObject (), WaitForMultipleObjects (), and so on.

There are three ways to change the state of events:

SetEvent (): set events to active

ResetEvent (): set events to inactive

PulseEvent (): activate events, then immediately high to inactive. If the events is manual, wake up all waiting threads, and if the events is automatic, wake up "one" waiting thread.

Note that if event is manual, after SetEvent is called, if ResetEvent is not called, the waiting thread will be constantly awakened, that is, the lpStartAddress method specified by CreateThread will be executed continuously.

In addition, the windows system can guarantee that one thread after another will be awakened, that is, no thread will always be awakened, and some threads will starve to death.

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The answer to the question about how to analyze the FileZilla source code is shared here. I hope the above content can be of some help to you. If you still have a lot of doubts to solve, you can follow the industry information channel to learn more about it.

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