iv_fd_pump (3) - Linux Manuals

iv_fd_pump: pump data between file descriptors


IV_FD_PUMP_INIT, iv_fd_pump_init, iv_fd_pump_destroy, iv_fd_pump_pump, iv_fd_pump_is_done - pump data between file descriptors


#include <iv_fd_pump.h>

struct iv_fd_pump {
        int             from_fd;
        int             to_fd;
        void            *cookie;
        void            (*set_bands)(void *cookie, int pollin, int pollout);
        unsigned int    flags;

void IV_FD_PUMP_INIT(struct iv_fd_pump *this);
void iv_fd_pump_init(struct iv_fd_pump *this);
void iv_fd_pump_destroy(struct iv_fd_pump *this);
int iv_fd_pump_pump(struct iv_fd_pump *this);
int iv_fd_pump_is_done(struct iv_fd_pump *this);


iv_fd_pump provides a way for moving data between two file descriptors.

To set up iv_fd_pump for moving data, call IV_FD_PUMP_INIT on a struct iv_fd_pump object, fill in the ->from_fd, ->to_fd, ->cookie, ->set_bands and ->flags members, and then call iv_fd_pump_init on the object.

Conversely, to destroy a struct iv_fd_pump object, call iv_fd_pump_destroy. There are no restrictions on when this function can be called.

A call to iv_fd_pump_pump will attempt to move data from ->from_fd to ->to_fd via an internal buffer associated with the struct iv_fd_pump object.

During calls to iv_fd_pump_init, iv_fd_pump_destroy and iv_fd_pump_pump, the callback function specified by ->set_bands may be invoked (with ->cookie as its first argument), by which iv_fd_pump indicates under which circumstances it wishes for future invocations of iv_fd_pump_pump to be done.

If the pollin argument to ->set_bands is true, there is space left in the internal buffer (and we have not yet seen an end-of-file condition on input), and so you should call iv_fd_pump_pump again when there is a POLLIN condition on ->from_fd.

If the pollout argument to ->set_bands is true, there is data in the internal buffer that could not all be transferred to ->to_fd, and so you should call iv_fd_pump_pump again when there is a POLLOUT condition on ->to_fd.

If IV_FD_PUMP_FLAG_RELAY_EOF is set in ->flags, iv_fd_pump_pump will call shutdown(2) on ->to_fd with SHUT_WR as its second argument upon seeing an end-of-file condition on ->from_fd (but only after all data from the internal buffer has been drained into ->to_fd first).

iv_fd_pump_pump will return -1 if there was an error, 0 if we're done pumping data (meaning that an end-of-file condition was seen on the input file descriptor and that all data in the internal buffer has been drained into the output file descriptor), or 1 if there is more data left to be pumped.

iv_fd_pump_is_done will return a true value if iv_fd_pump_pump has previously returned 0, otherwise it will return false.

Internally, iv_fd_pump_pump will use splice(2) if it is available, otherwise it will fall back to read(2) and write(2).


ivykis(3), splice(2)