libstddjb
libskarnet
skalibs
Software
skarnet.org
The following functions are declared in the skalibs/allreadwrite.h header, and implemented in the libskarnet.a or libskarnet.so library.
allreadwrite is a set of IO function helpers. It's the basis for safe reading and writing, either in blocking or in non-blocking mode. The buffer interface relies heavily on allreadwrite.
Unless the IO you need is very simple, you generally should not be using the allreadwrite functions directly; you should use higher-level APIs such as bufalloc.
typedef ssize_t iofunc_t (int fd, char *buf, size_t len)
This is the simplified type of IO functions such as
read()
and
write().
typedef size_t alliofunc_t (int fd, char *buf, size_t len)
This is the type of an IO operation that expects all of its
len bytes to be sent or received, and that will loop around a
lower-level IO function until either len bytes have been
transmitted or an error has occurred. The return value is the actual
number of transmitted bytes; if this value is lesser than len,
it means that an error has occurred and errno is set.
ssize_t sanitize_read (ssize_t r)
Reading functions such as read() and fd_read return
a positive number when they succeed, -1 when they fail, and 0 when they
read an EOF. No data available on the descriptor when reading in
non-blocking mode is treated as a failure: -1 EWOULDBLOCK. But sometimes
(namely, in asynchronous IO loops) it's preferrable to handle EOF as an
exception condition and EWOULDBLOCK as a normal condition.
sanitize_read(), when applied to the result of a basic reading
function, returns 0 if r is -1 and errno is EWOULDBLOCK (or
EAGAIN). If r is zero, it returns -1 EPIPE. Else it returns r.
(No system reading function can ever set errno to EPIPE, and the semantics are appropriate, so EPIPE is a good candidate to signal EOF on reading.)
size_t allreadwrite (iofunc_t *f, int fd, char *s, size_t len)
*f must be a basic reading or writing function such as
fd_read or fd_write. allreadwrite() performs
*f on fd, s and len until len
bytes have been read or written, or until an error occurs. It returns the
total number of handled bytes, and sets errno if this number is not
len. allreadwrite may block if fd is in
blocking mode; if fd is in non-blocking mode, it might
set errno to EWOULDBLOCK or EAGAIN.
ssize_t fd_read (int fd, char *s, size_t len)
Safe wrapper around the
read()
function.
ssize_t fd_write (int fd, char const *s, size_t len)
Safe wrapper around the
write()
function.
ssize_t fd_recv (int fd, char *s, size_t len, unsigned int flags)
Safe wrapper around the
recv()
function.
ssize_t fd_send (int fd, char const *s, size_t len, unsigned int flags)
Safe wrapper around the
send()
function.
size_t allread (int fd, char *s, size_t len)
Equivalent to allreadwrite(&fd_read, fd, s, len) : attempts
to read len bytes from fd into s, looping around
fd_read() if necessary, until either len bytes are read or
an error occurs. EOF is reported as EPIPE.
size_t allwrite (int fd, char const *s, size_t len)
Equivalent to allreadwrite((iofunc_t *)&fd_write, fd, s, len) :
attempts to write len bytes from s to fd, looping
around fd_write() if necessary, until either len bytes are
written or an error occurs.