我对信号量以及互斥和论坛的概念不熟悉。我应该使用多线程以递归方式在文件中通过目录进行文本搜索。线程数由用户给出。这段代码的问题是它通过一个目录然后等待。我无法弄清楚出了什么问题。我遇到了分段错误错误。无法弄清楚为什么会这样。我尽快得到帮助。谢谢
#include <iostream>
#include <sys/wait.h>
#include <sys/types.h>
#include <pthread.h>
#include <string.h>
#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>
#include <fstream>
#include <limits.h>
#include <stdlib.h>
#include <semaphore.h>
using namespace std;
#include <stdio.h>
int iDirectories=0;
pthread_mutex_t mutex=PTHREAD_MUTEX_INITIALIZER;
sem_t semaphore1;
char searchStringThread[PATH_MAX];
int directories=0;
class directoryQueue
{
private:
struct Node
{
char directoryPath[PATH_MAX];
Node *next;
};
Node *front;
Node *rear;
Node *nodeCount;
public:
directoryQueue(void)
{
front=NULL;
rear=NULL;
nodeCount=0;
}
void Enqueue(char array[PATH_MAX])
{
Node *newNode;
newNode=new Node;
strcpy(newNode->directoryPath,array);
newNode->next=NULL;
if(isEmpty())
{
front=newNode;
rear=newNode;
}
else
{
rear->next=newNode;
rear=newNode;
}
nodeCount++;
}
char * Dequeue(void)
{
Node *temp;
if (isEmpty())
cout << "Error ! Empty Queue "<<endl;
else
{
char *deque;
deque=new char[PATH_MAX];
strcpy(deque,front->directoryPath);
temp = front->next;
front = temp;
nodeCount--;
return deque;
}
}
bool isEmpty(void)
{
if(nodeCount)
return false;
else
return true;
}
void makeNull(void)
{
while(!isEmpty())
{
Dequeue();
}
}
~directoryQueue(void)
{
makeNull();
}
};
directoryQueue saveDirectory;
void *threadHandler(void *)
{
int thpath_length;
char thPath[PATH_MAX];
char saveITDirectory[PATH_MAX];
char itDirectory[PATH_MAX];
int threadCount;
struct dirent *iWalker;
DIR *iDirectory;
pthread_mutex_lock(&mutex);
threadCount=iDirectories++;
pthread_mutex_unlock(&mutex);
sem_wait(&semaphore1);
pthread_mutex_lock(&mutex);
strcpy(itDirectory,saveDirectory.Dequeue());
pthread_mutex_unlock(&mutex);
iDirectory=opendir(itDirectory);
if(iDirectory==NULL)
{
cout<<"Error"<<endl;
cout<<itDirectory<<" Cannot be Opened"<<endl;
exit(10000);
}
while((iWalker=readdir(iDirectory)) !=NULL)
{
if(iWalker->d_type==DT_REG)
{
strcpy(saveITDirectory,iWalker->d_name);
cout<<itDirectory<<"/"<<endl;
if (strcmp (saveITDirectory, "..") == 0 ||
strcmp (saveITDirectory, ".") == 0)
{
continue;
}
else
{
thpath_length = snprintf(thPath,PATH_MAX,"%s/%s",itDirectory,saveITDirectory);
cout<<thPath<<endl;
if (thpath_length >= PATH_MAX)
{
cout<<"Path is too long"<<endl;
exit (1000);
}
ifstream openFile;
openFile.open(thPath);
char line[1500];
int currentLine = 0;
if (openFile.is_open()) {
while (openFile.good()) {
currentLine++;
openFile.getline(line, 1500);
if (strstr(line, searchStringThread) != NULL){
cout<<thPath<<": "<<currentLine<<": "<<line<<endl;
cout<<"This was performed by Thread no. "<<threadCount<<endl;
cout<<"ID :"<<pthread_self();
}
}
}
openFile.close();
}
}
if (closedir (iDirectory))
{
cout<<"Unable to close "<<itDirectory<<endl;
exit (1000);
}
}
}
void walkThroughDirectory(char directory_name[PATH_MAX],char searchString[PATH_MAX])
{
DIR * directory;
struct dirent * walker;
char d_name[PATH_MAX];
int path_length;
char path[PATH_MAX];
directory=opendir(directory_name);
if(directory==NULL)
{
cout<<"Error"<<endl;
cout<<directory_name<<" Cannot be Opened"<<endl;
exit(10000);
}
while((walker=readdir(directory)) !=NULL)
{
strcpy(d_name,walker->d_name);
cout<<directory_name<<"/"<<endl;
if (strcmp (d_name, "..") == 0 ||
strcmp (d_name, ".") == 0)
{
continue;
}
else
{
path_length = snprintf(path,PATH_MAX,"%s/%s",directory_name,d_name);
cout<<path<<endl;
if (path_length >= PATH_MAX)
{
cout<<"Path is too long"<<endl;
exit (1000);
}
if(walker->d_type==DT_DIR)
{
pthread_mutex_lock(&mutex);
saveDirectory.Enqueue(path);
pthread_mutex_lock(&mutex);
sem_post(&semaphore1);
directories++;
walkThroughDirectory (path,searchString);
}
else if(walker->d_type==DT_REG)
{
ifstream openFile;
openFile.open(path);
char line[1500];
int currentLine = 0;
if (openFile.is_open()) {
while (openFile.good()) {
currentLine++;
openFile.getline(line, 1500);
if (strstr(line, searchString) != NULL)
cout<<path<<": "<<currentLine<<": "<<line<<endl;
}
}
openFile.close();
}
}
}
if (closedir (directory))
{
cout<<"Unable to close "<<directory_name<<endl;
exit (1000);
}
}
int main(int argc,char *argv[])
{
char * name;
cout<<"Total Directories "<< directories<<endl;
name=get_current_dir_name();
cout<<"Current Directory is: "<<name<<endl;
sem_init(&semaphore1,0,0);
strcpy(searchStringThread,argv[1]);
int number_of_threads=atoi(argv[3]);
pthread_t threads[number_of_threads];
walkThroughDirectory(argv[2],argv[1]);
pthread_mutex_lock(&mutex);
saveDirectory.Enqueue(argv[2]);
pthread_mutex_unlock(&mutex);
sem_post(&semaphore1);
for(int i=0;i<number_of_threads;i++)
{
pthread_create(&threads[i],NULL,threadHandler,NULL);
}
for(int j=0;j<number_of_threads;j++)
{
pthread_join(threads[j],NULL);
}
while(saveDirectory.isEmpty())
{
cout<<"Queue is Empty"<<endl;
cout<<"Exiting"<<endl;
exit(10000);
}
free(name);
cout<<"Total Directories "<< directories<<endl;
return 0;
}
答案 0 :(得分：2)
有一个简单的错误，你可以锁定互斥锁两次，而不是在完成时将其解锁：
pthread_mutex_lock(&mutex);
saveDirectory.Enqueue(path);
pthread_mutex_lock(&mutex);
应该是：
pthread_mutex_lock(&mutex);
saveDirectory.Enqueue(path);
pthread_mutex_unlock(&mutex);
注意：这并不是说没有其他问题 - 只是这可能是你的直接问题。
最大的问题是，看起来你把目录放在saveDirectory队列上（所以另一个线程可以将其拉出来处理它），然后在刚刚放入的线程中递归进行该目录的进程它在队列中。我认为你需要更多地考虑如何在线程之间划分工作。
还有一些小问题：
std::string。它应该使你的一些字符串处理更简单（例如，你从directoryQueue::Dequeue()返回的数据泄漏内存）directoryQueue类存在的主要原因是为多个线程保存工作项，那么它可能应该管理它自己的互斥锁，因此调用者不需要处理这种复杂性