我遇到的问题是，当文件尝试复制时，它只复制文件的一部分，而另一部分是一堆不可读的字符。这是针对希望我们使用屏障同步的学术作业，因此我们需要使用打开、写入和读取。
我已经多次修改了线程函数，但如果是问题，我可以再次更改它，我根本没有更改 main 中的 for 循环，所以即使这可能是问题，但我不知道它可能是什么。最后，我真的不知道如何处理障碍；我的教授很含糊，我真的不能问他问题，也许障碍是我真正缺少的部分。
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <semaphore.h>
#include <pthread.h>
#include <unistd.h>
typedef struct args {
int fd;
int copy;
long int start;
long int size;
}threadarg;
int barrier = 0;
int main(int argc, char *argv[])
{
void usage(char *progname);
int chkdst(char **argv);
void die(char *why);
long int filesize(char *srcpath);
void buildpath(char *src, char *dst, char **dstpath);
int isvalid(char *path, char *dst);
void *dowork(void *arg);
if (argc < 4) usage("a8");
int workers, i;
char *check;
workers = strtol(argv[3], &check, 10);
if (!check) usage("a8");
else if (!chkdst(&argv[2])) die ("DST not valid!");
long int size = filesize(argv[1]);
if (size == -1) die ("Could not find file size");
char *dstpath; buildpath(argv[1], argv[2], &dstpath);
if (!isvalid(argv[1], dstpath)) die ("scr not valid!");
long int chunksize = size / workers;
long int remainder = size % workers;
int fd = open(argv[1], O_RDONLY);
int copy = open(dstpath, O_CREAT | O_RDWR, 0644);
if (fd < 0 || copy < 0) die("Fail to access or create files");
barrier = workers;
threadarg threadargs[workers];
pthread_t threads[workers];
for (i = 0; i < workers; i++)
{
threadargs[i].fd = fd;
threadargs[i].copy = copy;
threadargs[i].start = i * chunksize;
if (i == workers - 1)
threadargs[i].size = chunksize + remainder;
else
threadargs[i].size = chunksize;
if (pthread_create(&threads[i], NULL, dowork, (void *) &threadargs[i]))
die("Thread Creation Failure");
}
for (i = 0; i < workers; i++)
pthread_join(threads[i], NULL);
}
void usage(char *progname)
{
fprintf(stderr, "./%s srcpath dstpath workercount\n", progname);
exit(0);
}
void die(char *why)
{
fprintf(stderr, "Program Killed...\nReason: %s\n", why);
exit(1);
}
long int filesize(char *srcpath)
{
struct stat st;
if(stat(srcpath, &st) != 0) return 0;
return st.st_size;
}
/*
void domd5(char *path)
{
}
*/
void *dowork(void *arg)
{
threadarg *args = (threadarg *)arg;
int fd = args->fd,
copy = args->copy, rd;
long int start = args->start,
size = args->size;
char bufs[2048], *remains;
lseek(fd, start, SEEK_SET);
lseek(copy, start, SEEK_SET);
printf("%d thread with offset %ldKB, reached barrier\n", (int) pthread_self(), start);
barrier--;
while (barrier > 0);
long int count = 0, remainder = 0, i;
for (i = 0; i < size; i += 2048)
{
if (i + 2048 > size)
{
remainder = size - count;
remains = malloc(remainder * sizeof(char));
rd = read (fd, remains, sizeof(remains));
if (write(copy, remains, rd) != rd)
die("Error accessing files during copy");
count += remainder;
}
else
{
rd = read(fd, bufs, sizeof(bufs));
if (write(copy, bufs, rd) != rd)
die("Error accessing files during copy");
count += 2048;
}
}
pthread_exit(NULL);
}
/* Takes a single pointer, *argv, and passes it to isdir()
to check if the directory exists. If isdir returns a 1 a
1 is returned from this module. Otherwise, an error message
is printed and a 0 is returned.
Calls isdir().
Called by main().
*/
int chkdst(char **argv)
{
int isdir(char *path);
if (isdir(*argv)) return 1;
return 0;
}
/* Uses the Stat struct to construct a struct, sbuf,
and uses stat() to obtain information from the file and
write it to sbuf. Uses S_ISDIR() on sbuf.st_mode to see
the mode of the file. A 1 is returned if the file is a
directory otherwise a 0 is returned.
Called by isvalid().
*/
int isdir(char *path)
{
struct stat sbuf;
if (stat(path, &sbuf)) return 0;
return S_ISDIR(sbuf.st_mode);
}
/* Uses the Stat struct to construct a struct, sbuf,
and uses stat() to obtain information from the file and
write it to sbuf. Uses S_ISREG on sbuf.st_mode to see if
the file is regular. A 1 is returned if the S_ISREG is true
otherwise a 0 is returned.
Called by isvalid().
*/
int isregular(char *path)
{
struct stat sbuf;
if (stat(path, &sbuf)) return 0;
return S_ISREG(sbuf.st_mode);
}
/* Checks if the source path is a directory first, then if its
a regular file return 0 if it is dir and if it isn't a regular
file, then checks if the destionation path was created or if
the file exist at the destination if either return 0, if none
of these return 1.
Calls isdir() and isregular().
Called by copyfiles().
*/
int isvalid(char *path, char *dst)
{
if (isdir(path))
{
return 0;
}
else if (!isregular(path))
{
return 0;
}
else if (dst == NULL)
{
return 0;
}
else if (isregular(dst))
{
return 0;
}
return 1;
}
/* Builds destination-path using strrchr() function from library,
dstpath is null on error and defined otherwise. The src file has
its original destination removed and replaced with the new one if
it has a original destination on it otherwise it is just added to
the end of the existing name of the file.
Called by copyfiles().
*/
void buildpath(char *src, char *dst, char **dstpath)
{
char *ptr;
int n;
ptr = strrchr(src, '/');
if (ptr) n = strlen(dst) + strlen(ptr) + 2;
else n = strlen(dst) + strlen(src) + 2;
*dstpath = malloc(n);
if (!dstpath) return;
if (ptr)
{
strcpy(*dstpath, dst);
strcat(*dstpath, ptr);
}
else
{
strcpy(*dstpath, dst);
strcat(*dstpath, "/");
strcat(*dstpath, src);
}
}