【发布时间】：2009-05-24 23:34:37
【问题描述】：
我有以下两个程序，一个作为阅读器，另一个作为编写器。作者似乎只正确发送了大约 3/4 的数据以供读者阅读。有没有办法保证所有数据都被发送？我想我已经对其进行了设置，使其能够可靠地读取和写入，但它似乎仍然丢失了 1/4 的数据。
这里是作者的来源
#define pipe "/tmp/testPipe"
using namespace std;
queue<string> sproutFeed;
ssize_t r_write(int fd, char *buf, size_t size) {
char *bufp;
size_t bytestowrite;
ssize_t byteswritten;
size_t totalbytes;
for (bufp = buf, bytestowrite = size, totalbytes = 0;
bytestowrite > 0;
bufp += byteswritten, bytestowrite -= byteswritten) {
byteswritten = write(fd, bufp, bytestowrite);
if(errno == EPIPE)
{
signal(SIGPIPE,SIG_IGN);
}
if ((byteswritten) == -1 && (errno != EINTR))
return -1;
if (byteswritten == -1)
byteswritten = 0;
totalbytes += byteswritten;
}
return totalbytes;
}
void* sendData(void *thread_arg)
{
int fd, ret_val, count, numread;
string word;
char bufpipe[5];
ret_val = mkfifo(pipe, 0777); //make the sprout pipe
if (( ret_val == -1) && (errno != EEXIST))
{
perror("Error creating named pipe");
exit(1);
}
while(1)
{
if(!sproutFeed.empty())
{
string s;
s.clear();
s = sproutFeed.front();
int sizeOfData = s.length();
snprintf(bufpipe, 5, "%04d\0", sizeOfData);
char stringToSend[strlen(bufpipe) + sizeOfData +1];
bzero(stringToSend, sizeof(stringToSend));
strncpy(stringToSend,bufpipe, strlen(bufpipe));
strncat(stringToSend,s.c_str(),strlen(s.c_str()));
strncat(stringToSend, "\0", strlen("\0"));
int fullSize = strlen(stringToSend);
signal(SIGPIPE,SIG_IGN);
fd = open(pipe,O_WRONLY);
int numWrite = r_write(fd, stringToSend, strlen(stringToSend) );
cout << errno << endl;
if(errno == EPIPE)
{
signal(SIGPIPE,SIG_IGN);
}
if(numWrite != fullSize )
{
signal(SIGPIPE,SIG_IGN);
bzero(bufpipe, strlen(bufpipe));
bzero(stringToSend, strlen(stringToSend));
close(fd);
}
else
{
signal(SIGPIPE,SIG_IGN);
sproutFeed.pop();
close(fd);
bzero(bufpipe, strlen(bufpipe));
bzero(stringToSend, strlen(stringToSend));
}
}
else
{
if(usleep(.0002) == -1)
{
perror("sleeping error\n");
}
}
}
}
int main(int argc, char *argv[])
{
signal(SIGPIPE,SIG_IGN);
int x;
for(x = 0; x < 100; x++)
{
sproutFeed.push("All ships in the sea sink except for that blue one over there, that one never sinks. Most likley because it\'s blue and thats the mightiest colour of ship. Interesting huh?");
}
int rc, i , status;
pthread_t threads[1];
printf("Starting Threads...\n");
pthread_create(&threads[0], NULL, sendData, NULL);
rc = pthread_join(threads[0], (void **) &status);
}
这是读者的来源
#define pipe "/tmp/testPipe"
char dataString[50000];
using namespace std;
char *getSproutItem();
void* readItem(void *thread_arg)
{
while(1)
{
x++;
char *s = getSproutItem();
if(s != NULL)
{
cout << "READ IN: " << s << endl;
}
}
}
ssize_t r_read(int fd, char *buf, size_t size) {
ssize_t retval;
while (retval = read(fd, buf, size), retval == -1 && errno == EINTR) ;
return retval;
}
char * getSproutItem()
{
cout << "Getting item" << endl;
char stringSize[4];
bzero(stringSize, sizeof(stringSize));
int fd = open(pipe,O_RDONLY);
cout << "Reading" << endl;
int numread = r_read(fd,stringSize, sizeof(stringSize));
if(errno == EPIPE)
{
signal(SIGPIPE,SIG_IGN);
}
cout << "Read Complete" << endl;
if(numread > 1)
{
stringSize[numread] = '\0';
int length = atoi(stringSize);
char recievedString[length];
bzero(recievedString, sizeof(recievedString));
int numread1 = r_read(fd, recievedString, sizeof(recievedString));
if(errno == EPIPE)
{
signal(SIGPIPE,SIG_IGN);
}
if(numread1 > 1)
{
recievedString[numread1] = '\0';
cout << "DATA RECIEVED: " << recievedString << endl;
bzero(dataString, sizeof(dataString));
strncpy(dataString, recievedString, strlen(recievedString));
strncat(dataString, "\0", strlen("\0"));
close(fd);
return dataString;
}
else
{
return NULL;
}
}
else
{
return NULL;
}
close(fd);
}
int main(int argc, char *argv[])
{
int rc, i , status;
pthread_t threads[1];
printf("Starting Threads...\n");
pthread_create(&threads[0], NULL, readItem, NULL);
rc = pthread_join(threads[0], (void **) &status);
}
【问题讨论】：
-
你没有说是什么症状导致你相信你缺少字符。你的代码太复杂了，没有明显的错误（查一下）。要获得真正的帮助，您需要创建一些足够简单的东西，让错误显而易见——无论是对您还是对这里的其他人。
-
似乎作者来自java背景，并试图将他的知识盲目地应用于C
-
哎哟。这对我来说是一次学习的经历，没必要这么苛刻
标签： c++ unix named-pipes