Tribblix: manual page: sendfilev.3ext

SENDFILEV(3EXT) Extended Library Functions SENDFILEV(3EXT)

NAME

sendfilev - send a file

SYNOPSIS

cc [ flag... ] file... -lsendfile [ library... ]
#include <sys/sendfile.h>

ssize_t sendfilev(int fildes, const struct sendfilevec *vec,
int sfvcnt, size_t *xferred);

PARAMETERS

The sendfilev() function supports the following parameters:

fildes
A file descriptor to a regular file or to a AF_INET or
AF_INET6 family type SOCK_STREAM socket that is open for
writing.

vec
An array of SENDFILEVEC_T, as defined in the sendfilevec
structure below.

sfvcnt
The number of members in vec.

xferred
The total number of bytes written to out_fd.

DESCRIPTION

The sendfilev() function attempts to write data from the sfvcnt
buffers specified by the members of vec array: vec[0], vec[1], ... ,
vec[sfvcnt-1]. The fildes argument is a file descriptor to a regular
file or to an AF_INET or AF_INET6 family type SOCK_STREAM socket that
is open for writing.

This function is analogous to writev(2), but can read from both
buffers and file descriptors. Unlike writev(), in the case of
multiple writers to a file the effect of sendfilev() is not
necessarily atomic; the writes may be interleaved. Application-
specific synchronization methods must be employed if this causes
problems.

The following is the sendfilevec structure:

typedef struct sendfilevec {
int sfv_fd; /* input fd */
uint_t sfv_flag; /* Flags. see below */
off_t sfv_off; /* offset to start reading from */
size_t sfv_len; /* amount of data */
} sendfilevec_t;

#define SFV_FD_SELF (-2)

To send a file, open the file for reading and point sfv_fd to the
file descriptor returned as a result. See open(2). sfv_off should
contain the offset within the file. sfv_len should have the length of
the file to be transferred.

The xferred argument is updated to record the total number of bytes
written to out_fd.

The sfv_flag field is reserved and should be set to zero.

To send data directly from the address space of the process, set
sfv_fd to SFV_FD_SELF. sfv_off should point to the data, with sfv_len
containing the length of the buffer.

RETURN VALUES

Upon successful completion, the sendfilev() function returns total
number of bytes written to out_fd. Otherwise, it returns -1, and
errno is set to indicate the error. The xferred argument contains the
amount of data successfully transferred, which can be used to
discover the error vector.

ERRORS

EACCES
The process does not have appropriate privileges or
one of the files pointed by sfv_fd does not have
appropriate permissions.

EAFNOSUPPORT
The implementation does not support the specified
address family for socket.

EAGAIN
Mandatory file or record locking is set on either the
file descriptor or output file descriptor if it
points at regular files. O_NDELAY or O_NONBLOCK is
set, and there is a blocking record lock. An attempt
has been made to write to a stream that cannot accept
data with the O_NDELAY or the O_NONBLOCK flag set.

EBADF
The fildes argument is not a valid descriptor open
for writing or an sfv_fd is invalid or not open for
reading.

EFAULT
The vec argument points to an illegal address.

The xferred argument points to an illegal address.

EINTR
A signal was caught during the write operation and no
data was transferred.

EINVAL
The sfvcnt argument was less than or equal to 0. One
of the sfv_len values in vec array was less than or
equal to 0, or greater than the file size. An sfv_fd
is not seekable.

Fewer bytes were transferred than were requested.

EIO
An I/O error occurred while accessing the file
system.

EPIPE
The fildes argument is a socket that has been shut
down for writing. The SIGPIPE signal is generated to
the calling thread. The process dies unless special
provisions were taken to catch or ignore the signal.

EPROTOTYPE
The socket type is not supported.

USAGE

The sendfilev() function has a transitional interface for 64-bit file
offsets. See lf64(7).

EXAMPLES

The following example sends 2 vectors, one of HEADER data and a file
of length 100 over sockfd. sockfd is in a connected state, that is,
socket(), accept(), and bind() operation are complete.

#include <sys/sendfile.h>
.
.
.
int
main (int argc, char *argv[]){
int sockfd;
ssize_t ret;
size_t xfer;
struct sendfilevec vec[2];
.
.
.
vec[0].sfv_fd = SFV_FD_SELF;
vec[0].sfv_flag = 0;
vec[0].sfv_off = "HEADER_DATA";
vec[0].sfv_len = strlen("HEADER_DATA");
vec[1].sfv_fd = open("input_file",.... );
vec[1].sfv_flag = 0;
vec[1].sfv_off = 0;
vec[1].sfv_len = 100;

ret = sendfilev(sockfd, vec, 2, &xfer);
.
.
.
}

ATTRIBUTES