- c - 在位数组中找到第一个零
- linux - Unix 显示有关匹配两种模式之一的文件的信息
- 正则表达式替换多个文件
- linux - 隐藏来自 xtrace 的命令
我正在寻找使用 pthread 同步语义的 C 语言中线程安全阻塞队列(多生产者/消费者)的推荐实现。
最佳答案
这是我用的
线程队列.h
#ifndef _THREADQUEUE_H_
#define _THREADQUEUE_H_ 1
#include <pthread.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @defgroup ThreadQueue ThreadQueue
*
* Little API for waitable queues, typically used for passing messages
* between threads.
*
*/
/**
* @mainpage
*/
/**
* A thread message.
*
* @ingroup ThreadQueue
*
* This is used for passing to #thread_queue_get for retreive messages.
* the date is stored in the data member, the message type in the #msgtype.
*
* Typical:
* @code
* struct threadmsg;
* struct myfoo *foo;
* while(1)
* ret = thread_queue_get(&queue,NULL,&message);
* ..
* foo = msg.data;
* switch(msg.msgtype){
* ...
* }
* }
* @endcode
*
*/
struct threadmsg{
/**
* Holds the data.
*/
void *data;
/**
* Holds the messagetype
*/
long msgtype;
/**
* Holds the current queue lenght. Might not be meaningful if there's several readers
*/
long qlength;
};
/**
* A TthreadQueue
*
* @ingroup ThreadQueue
*
* You should threat this struct as opaque, never ever set/get any
* of the variables. You have been warned.
*/
struct threadqueue {
/**
* Length of the queue, never set this, never read this.
* Use #threadqueue_length to read it.
*/
long length;
/**
* Mutex for the queue, never touch.
*/
pthread_mutex_t mutex;
/**
* Condition variable for the queue, never touch.
*/
pthread_cond_t cond;
/**
* Internal pointers for the queue, never touch.
*/
struct msglist *first,*last;
/**
* Internal cache of msglists
*/
struct msglist *msgpool;
/**
* No. of elements in the msgpool
*/
long msgpool_length;
};
/**
* Initializes a queue.
*
* @ingroup ThreadQueue
*
* thread_queue_init initializes a new threadqueue. A new queue must always
* be initialized before it is used.
*
* @param queue Pointer to the queue that should be initialized
* @return 0 on success see pthread_mutex_init
*/
int thread_queue_init(struct threadqueue *queue);
/**
* Adds a message to a queue
*
* @ingroup ThreadQueue
*
* thread_queue_add adds a "message" to the specified queue, a message
* is just a pointer to a anything of the users choice. Nothing is copied
* so the user must keep track on (de)allocation of the data.
* A message type is also specified, it is not used for anything else than
* given back when a message is retreived from the queue.
*
* @param queue Pointer to the queue on where the message should be added.
* @param data the "message".
* @param msgtype a long specifying the message type, choice of the user.
* @return 0 on succes ENOMEM if out of memory EINVAL if queue is NULL
*/
int thread_queue_add(struct threadqueue *queue, void *data, long msgtype);
/**
* Gets a message from a queue
*
* @ingroup ThreadQueue
*
* thread_queue_get gets a message from the specified queue, it will block
* the caling thread untill a message arrives, or the (optional) timeout occurs.
* If timeout is NULL, there will be no timeout, and thread_queue_get will wait
* untill a message arrives.
*
* struct timespec is defined as:
* @code
* struct timespec {
* long tv_sec; // seconds
* long tv_nsec; // nanoseconds
* };
* @endcode
*
* @param queue Pointer to the queue to wait on for a message.
* @param timeout timeout on how long to wait on a message
* @param msg pointer that is filled in with mesagetype and data
*
* @return 0 on success EINVAL if queue is NULL ETIMEDOUT if timeout occurs
*/
int thread_queue_get(struct threadqueue *queue, const struct timespec *timeout, struct threadmsg *msg);
/**
* Gets the length of a queue
*
* @ingroup ThreadQueue
*
* threadqueue_length returns the number of messages waiting in the queue
*
* @param queue Pointer to the queue for which to get the length
* @return the length(number of pending messages) in the queue
*/
long thread_queue_length( struct threadqueue *queue );
/**
* @ingroup ThreadQueue
* Cleans up the queue.
*
* threadqueue_cleanup cleans up and destroys the queue.
* This will remove all messages from a queue, and reset it. If
* freedata is != 0 free(3) will be called on all pending messages in the queue
* You cannot call this if there are someone currently adding or getting messages
* from the queue.
* After a queue have been cleaned, it cannot be used again untill #thread_queue_init
* has been called on the queue.
*
* @param queue Pointer to the queue that should be cleaned
* @param freedata set to nonzero if free(3) should be called on remaining
* messages
* @return 0 on success EINVAL if queue is NULL EBUSY if someone is holding any locks on the queue
*/
int thread_queue_cleanup(struct threadqueue *queue, int freedata);
#ifdef __cplusplus
}
#endif
#endif
线程队列.c
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
#include <sys/time.h>
#include "../h/threadqueue.h"
#define MSGPOOL_SIZE 256
struct msglist {
struct threadmsg msg;
struct msglist *next;
};
static inline struct msglist *get_msglist(struct threadqueue *queue)
{
struct msglist *tmp;
if(queue->msgpool != NULL) {
tmp = queue->msgpool;
queue->msgpool = tmp->next;
queue->msgpool_length--;
} else {
tmp = malloc(sizeof *tmp);
}
return tmp;
}
static inline void release_msglist(struct threadqueue *queue,struct msglist *node)
{
if(queue->msgpool_length > ( queue->length/8 + MSGPOOL_SIZE)) {
free(node);
} else {
node->msg.data = NULL;
node->msg.msgtype = 0;
node->next = queue->msgpool;
queue->msgpool = node;
queue->msgpool_length++;
}
if(queue->msgpool_length > (queue->length/4 + MSGPOOL_SIZE*10)) {
struct msglist *tmp = queue->msgpool;
queue->msgpool = tmp->next;
free(tmp);
queue->msgpool_length--;
}
}
int thread_queue_init(struct threadqueue *queue)
{
int ret = 0;
if (queue == NULL) {
return EINVAL;
}
memset(queue, 0, sizeof(struct threadqueue));
ret = pthread_cond_init(&queue->cond, NULL);
if (ret != 0) {
return ret;
}
ret = pthread_mutex_init(&queue->mutex, NULL);
if (ret != 0) {
pthread_cond_destroy(&queue->cond);
return ret;
}
return 0;
}
int thread_queue_add(struct threadqueue *queue, void *data, long msgtype)
{
struct msglist *newmsg;
pthread_mutex_lock(&queue->mutex);
newmsg = get_msglist(queue);
if (newmsg == NULL) {
pthread_mutex_unlock(&queue->mutex);
return ENOMEM;
}
newmsg->msg.data = data;
newmsg->msg.msgtype = msgtype;
newmsg->next = NULL;
if (queue->last == NULL) {
queue->last = newmsg;
queue->first = newmsg;
} else {
queue->last->next = newmsg;
queue->last = newmsg;
}
if(queue->length == 0)
pthread_cond_broadcast(&queue->cond);
queue->length++;
pthread_mutex_unlock(&queue->mutex);
return 0;
}
int thread_queue_get(struct threadqueue *queue, const struct timespec *timeout, struct threadmsg *msg)
{
struct msglist *firstrec;
int ret = 0;
struct timespec abstimeout;
if (queue == NULL || msg == NULL) {
return EINVAL;
}
if (timeout) {
struct timeval now;
gettimeofday(&now, NULL);
abstimeout.tv_sec = now.tv_sec + timeout->tv_sec;
abstimeout.tv_nsec = (now.tv_usec * 1000) + timeout->tv_nsec;
if (abstimeout.tv_nsec >= 1000000000) {
abstimeout.tv_sec++;
abstimeout.tv_nsec -= 1000000000;
}
}
pthread_mutex_lock(&queue->mutex);
/* Will wait until awakened by a signal or broadcast */
while (queue->first == NULL && ret != ETIMEDOUT) { //Need to loop to handle spurious wakeups
if (timeout) {
ret = pthread_cond_timedwait(&queue->cond, &queue->mutex, &abstimeout);
} else {
pthread_cond_wait(&queue->cond, &queue->mutex);
}
}
if (ret == ETIMEDOUT) {
pthread_mutex_unlock(&queue->mutex);
return ret;
}
firstrec = queue->first;
queue->first = queue->first->next;
queue->length--;
if (queue->first == NULL) {
queue->last = NULL; // we know this since we hold the lock
queue->length = 0;
}
msg->data = firstrec->msg.data;
msg->msgtype = firstrec->msg.msgtype;
msg->qlength = queue->length;
release_msglist(queue,firstrec);
pthread_mutex_unlock(&queue->mutex);
return 0;
}
//maybe caller should supply a callback for cleaning the elements ?
int thread_queue_cleanup(struct threadqueue *queue, int freedata)
{
struct msglist *rec;
struct msglist *next;
struct msglist *recs[2];
int ret,i;
if (queue == NULL) {
return EINVAL;
}
pthread_mutex_lock(&queue->mutex);
recs[0] = queue->first;
recs[1] = queue->msgpool;
for(i = 0; i < 2 ; i++) {
rec = recs[i];
while (rec) {
next = rec->next;
if (freedata) {
free(rec->msg.data);
}
free(rec);
rec = next;
}
}
pthread_mutex_unlock(&queue->mutex);
ret = pthread_mutex_destroy(&queue->mutex);
pthread_cond_destroy(&queue->cond);
return ret;
}
long thread_queue_length(struct threadqueue *queue)
{
long counter;
// get the length properly
pthread_mutex_lock(&queue->mutex);
counter = queue->length;
pthread_mutex_unlock(&queue->mutex);
return counter;
}
关于c - pthread 同步阻塞队列,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4577961/
#include using namespace std; class C{ private: int value; public: C(){ value = 0;
这个问题已经有答案了: What is the difference between char a[] = ?string?; and char *p = ?string?;? (8 个回答) 已关闭
关闭。此题需要details or clarity 。目前不接受答案。 想要改进这个问题吗?通过 editing this post 添加详细信息并澄清问题. 已关闭 7 年前。 此帖子已于 8 个月
除了调试之外,是否有任何针对 c、c++ 或 c# 的测试工具,其工作原理类似于将独立函数复制粘贴到某个文本框,然后在其他文本框中输入参数? 最佳答案 也许您会考虑单元测试。我推荐你谷歌测试和谷歌模拟
我想在第二台显示器中移动一个窗口 (HWND)。问题是我尝试了很多方法,例如将分辨率加倍或输入负值,但它永远无法将窗口放在我的第二台显示器上。 关于如何在 C/C++/c# 中执行此操作的任何线索 最
我正在寻找 C/C++/C## 中不同类型 DES 的现有实现。我的运行平台是Windows XP/Vista/7。 我正在尝试编写一个 C# 程序,它将使用 DES 算法进行加密和解密。我需要一些实
很难说出这里要问什么。这个问题模棱两可、含糊不清、不完整、过于宽泛或夸夸其谈,无法以目前的形式得到合理的回答。如需帮助澄清此问题以便重新打开,visit the help center . 关闭 1
有没有办法强制将另一个 窗口置于顶部? 不是应用程序的窗口,而是另一个已经在系统上运行的窗口。 (Windows, C/C++/C#) 最佳答案 SetWindowPos(that_window_ha
假设您可以在 C/C++ 或 Csharp 之间做出选择,并且您打算在 Windows 和 Linux 服务器上运行同一服务器的多个实例,那么构建套接字服务器应用程序的最明智选择是什么? 最佳答案 如
你们能告诉我它们之间的区别吗? 顺便问一下,有什么叫C++库或C库的吗? 最佳答案 C++ 标准库 和 C 标准库 是 C++ 和 C 标准定义的库,提供给 C++ 和 C 程序使用。那是那些词的共同
下面的测试代码,我将输出信息放在注释中。我使用的是 gcc 4.8.5 和 Centos 7.2。 #include #include class C { public:
很难说出这里问的是什么。这个问题是含糊的、模糊的、不完整的、过于宽泛的或修辞性的,无法以目前的形式得到合理的回答。如需帮助澄清此问题以便重新打开它,visit the help center 。 已关
我的客户将使用名为 annoucement 的结构/类与客户通信。我想我会用 C++ 编写服务器。会有很多不同的类继承annoucement。我的问题是通过网络将这些类发送给客户端 我想也许我应该使用
我在 C# 中有以下函数: public Matrix ConcatDescriptors(IList> descriptors) { int cols = descriptors[0].Co
我有一个项目要编写一个函数来对某些数据执行某些操作。我可以用 C/C++ 编写代码,但我不想与雇主共享该函数的代码。相反,我只想让他有权在他自己的代码中调用该函数。是否可以?我想到了这两种方法 - 在
我使用的是编写糟糕的第 3 方 (C/C++) Api。我从托管代码(C++/CLI)中使用它。有时会出现“访问冲突错误”。这使整个应用程序崩溃。我知道我无法处理这些错误[如果指针访问非法内存位置等,
关闭。这个问题不符合Stack Overflow guidelines .它目前不接受答案。 我们不允许提问寻求书籍、工具、软件库等的推荐。您可以编辑问题,以便用事实和引用来回答。 关闭 7 年前。
已关闭。此问题不符合Stack Overflow guidelines 。目前不接受答案。 要求我们推荐或查找工具、库或最喜欢的场外资源的问题对于 Stack Overflow 来说是偏离主题的,因为
我有一些 C 代码,将使用 P/Invoke 从 C# 调用。我正在尝试为这个 C 函数定义一个 C# 等效项。 SomeData* DoSomething(); struct SomeData {
这个问题已经有答案了: Why are these constructs using pre and post-increment undefined behavior? (14 个回答) 已关闭 6
我是一名优秀的程序员,十分优秀!