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I am currently doing r&D as how to use splice to write and receive files from the socket .
Here is my code to send data from a file to socket
#include <iostream>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
struct MyFds
{
int fdin;
int fdout;
int readpipe;
int writepipe;
loff_t size;
MyFds(int p_fdin, int p_fdout, int p_readpipe, int p_writepipe,
loff_t p_size) :
fdin(p_fdin), fdout(p_fdout), readpipe(p_readpipe),
writepipe(p_writepipe), size(p_size)
{
};
};
static void * splicecopywriter(void * threadparam)
{
const MyFds * fds = (const MyFds *) threadparam;
std::cout << "In writer thread " << std::endl;
loff_t offset = 0;
size_t bytesleft = fds->size;
int splices=0;
while (bytesleft > 0) {
splices ++;
ssize_t bytes = splice(fds->readpipe, (loff_t *) 0,
fds->fdout, & offset,
bytesleft, 0 /* flags */ );
if (bytes == -1) {
break;
}
bytesleft -= bytes;
}
int spliceerr = errno;
std::cout << "writer:splices= " << splices << " errno=" <<
spliceerr << std::endl;
std::cout << "still in writer thread " << std::endl;
return (void *) 0;
}
static int splicecopyreader(const MyFds *fds)
{
loff_t offset = 0;
size_t bytesleft = fds->size;
int splices = 0;
while (bytesleft > 0) {
splices ++;
ssize_t bytes = splice(fds->fdin, &offset, fds->writepipe,
(loff_t *) 0,
(size_t) fds->size, 0 /* flags */ );
if (bytes == -1) {
break;
}
bytesleft -= bytes;
}
int spliceerr = errno;
std::cout << "reader: splices=" << splices << " errno=" <<
spliceerr << std::endl;
close(fds->writepipe);
}
static int splicecopypipes(const MyFds *fds)
{
// Main thread reads from disc and into pipe;
// writerthread reads from pipe and on to disc.
pthread_t writerthread;
int res = pthread_create(&writerthread,
(const pthread_attr_t *) 0,
splicecopywriter,
(void *) fds);
std::cout << "In main thread" << std::endl;
splicecopyreader(fds);
int threadres;
pthread_join(writerthread, (void **) (& threadres) );
std::cout << "Joined" << std::endl;
return threadres;
}
static int splicecopyfd(int fdin, int fdout)
{
// Work out how big it is
struct stat st;
if (fstat(fdin, &st) != 0) {
std::cerr << "Stat failed" << std::endl;
return 3;
}
int pipes[2];
if (pipe(pipes) != 0) {
std::cerr << "Pipe failed" << std::endl;
return 4;
}
int readpipe = pipes[0];
int writepipe = pipes[1];
MyFds fds(fdin, fdout, readpipe, writepipe, st.st_size);
int res = splicecopypipes(&fds);
close(pipes[0]);
close(pipes[1]);
return res;
}
static int splicecopy(const char *srcfile)
{
int fdin = open(srcfile, O_RDONLY);
if (-1 == fdin) {
std::cerr << "Failed to open src file" << std::endl;
return 1;
}
struct sockaddr_in lstServerAddr.
inet_aton("172.20.101.38", &(lstServerAddr.sin_addr));
lstServerAddr.sin_port = htons(8000);
lstServerAddr.sin_family = AF_INET;
int fdout = socket(AF_INET, SOCK_STREAM, 0);
if (fdout == -1)
{
printf("failed due to %s", strerror(errno));
return 1;
}
if (connect(fdout, (struct sockaddr*)&lstServerAddr, sizeof(sockaddr_in)) == -1)
{
printf("connect failed due to %s", strerror(errno));
return 1;
}
int res = splicecopyfd(fdin, fdout);
close(fdin);
close(fdout);
return res;
}
int main(int argc, const char * argv[])
{
if (argc < 2) {
std::cerr << "Source required" << std::endl;
return 1;
}
const char *srcfile = argv[1];
return splicecopy(srcfile);
}while writing to the socket it gives error as Invalid argument ie in the writer thread it give error Invalid Argument (EINVAL).
I have also tried setting both the offset to null while sending that doesn't work.
Please suggest as what os wrong exactly.
Thanks
Pankaj
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You've really tried using NULL for all offsets? Because, that would be my guess as to your problem... Specifically, trying to specify an offset for the socket, which is non-seekable...
Also, I found when using splice(), it was wise to limit single calls to no more than about 60K at a time, due to the pipe buffer size... And, when copying to a socket, performance is greatly improved by using the SPLICE_F_MORE flag when you know you have more to write still to come... And, when doing a double-splice() with your own pipe (to copy between non-pipe FDs) as you're doing, you'd also be well-advised to add SPLICE_F_MOVE in the second splice() (the one copying from the pipe to the socket)...
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Hi Robseace,
you were right i rechecked the code and it worked fine.
and as per your advise i have set the flag to SPLICE_F_MORE | SPLICE_F_MOVE in the second splice (coping from pipe to socket).
Thank you for the reply.
Regards,
Nithesh
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I have sucessfully send data from a file to a socket using splice. Now while receiving / writing data from a socket to file using socket it
gives me EWOULDBLOCK error.
here is the Sample code.
int ReadData(int nSocketFD, int FileFd, int readpipe, int writepipe)
{
int lnRetValue = 0;
loff_t lSocketOffSet = 0;
loff_t lFileOffSet = 0;
while(true)
{
lnRetValue = splice(lnFd, &lSocketOffSet/*NULL*/, writepipe, (loff_t*)0, 1024, 0) ;
if (lnRetValue > 0)
{
if (lnRetValue == 1024)
{
break;
}
else
{
lnRetValue += lnRetValue;
}
}
else if (lnRetValue == -1)
{
printf("Splice failed due to %s", strerror(errno));
return 1;
}
}
lnRetValue = splice(readpipe, (loff_t*)0, lnFileFd, &lFileOffSet, 1024, 0);
if (lnRetValue < 0)
{
printf("splice 1 failed due to %s", strerror(errno));
return 1;
}
return 0;
}pipe used are non blocking. tried setting the socketoffset to NULL.
Please advise as what am i doing wrong.
Regards,
Pankaj
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Unless I can see the real code (and all of it), there's not really any way I can know what you're doing wrong... If you're getting EINVAL and truly are passing NULL for both offsets, then I'd have to guess your write pipe isn't really a pipe, or has been closed, or something like that... *shrug* All I can do is guess randomly without seeing all the real code which is actually producing the problem...
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