sched: Introduce sched_{read,write}_ok().

[paraslash.git] / fd.c

diff --git a/fd.c b/fd.c
index 2f3ec997c11e796fc5ff8ada46c40a662e0aef13..f7e0e42b3680707774cddd5c3bbd0c56cfc54bcb 100644 (file)
--- a/fd.c
+++ b/fd.c
@@ -177,14 +177,11 @@ __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
  * \param fd The file descriptor to read from.
  * \param iov Scatter/gather array used in readv().
  * \param iovcnt Number of elements in \a iov.
- * \param rfds An optional fd set pointer.
  * \param num_bytes Result pointer. Contains the number of bytes read from \a fd.
  *
- * If rfds is not NULL and the (non-blocking) file descriptor fd is not set in
- * rfds, this function returns early without doing anything. Otherwise it tries
- * to read up to sz bytes from fd, where sz is the sum of the lengths of all
- * vectors in iov. Like \ref xwrite(), EAGAIN and EINTR are not considered
- * error conditions. However, EOF is.
+ * This function tries to read up to sz bytes from fd, where sz is the sum of
+ * the lengths of all vectors in iov. Like \ref xwrite(), EAGAIN and EINTR are
+ * not considered error conditions. However, EOF is.
  *
  * \return Zero or a negative error code. If the underlying call to readv(2)
  * returned zero (indicating an end of file condition) or failed for some
@@ -198,24 +195,12 @@ __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
  *
  * \sa \ref xwrite(), read(2), readv(2).
  */
-int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
-               size_t *num_bytes)
+int readv_nonblock(int fd, struct iovec *iov, int iovcnt, size_t *num_bytes)
 {
        int ret, i, j;
 
        *num_bytes = 0;
-       /*
-        * Avoid a shortcoming of select(): Reads from a non-blocking fd might
-        * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET()
-        * returning false definitely means that no data can currently be read.
-        * This is the common case, so it is worth to avoid the overhead of the
-        * read() system call in this case.
-        */
-       if (rfds && !FD_ISSET(fd, rfds))
-               return 0;
-
        for (i = 0, j = 0; i < iovcnt;) {
-
                /* fix up the first iov */
                assert(j < iov[i].iov_len);
                iov[i].iov_base += j;
@@ -252,7 +237,6 @@ int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
  * \param fd The file descriptor to read from.
  * \param buf The buffer to read data to.
  * \param sz The size of \a buf.
- * \param rfds \see \ref readv_nonblock().
  * \param num_bytes \see \ref readv_nonblock().
  *
  * This is a simple wrapper for readv_nonblock() which uses an iovec with a single
@@ -260,10 +244,10 @@ int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
  *
  * \return The return value of the underlying call to readv_nonblock().
  */
-int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
+int read_nonblock(int fd, void *buf, size_t sz, size_t *num_bytes)
 {
        struct iovec iov = {.iov_base = buf, .iov_len = sz};
-       return readv_nonblock(fd, &iov, 1, rfds, num_bytes);
+       return readv_nonblock(fd, &iov, 1, num_bytes);
 }
 
 /**
@@ -272,7 +256,6 @@ int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
  * \param fd The file descriptor to receive from.
  * \param pattern The expected pattern.
  * \param bufsize The size of the internal buffer.
- * \param rfds Passed to read_nonblock().
  *
  * This function tries to read at most \a bufsize bytes from the non-blocking
  * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been
@@ -284,11 +267,11 @@ int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes)
  *
  * \sa \ref read_nonblock(), \sa strncasecmp(3).
  */
-int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds)
+int read_pattern(int fd, const char *pattern, size_t bufsize)
 {
        size_t n, len;
        char *buf = para_malloc(bufsize + 1);
-       int ret = read_nonblock(fd, buf, bufsize, rfds, &n);
+       int ret = read_nonblock(fd, buf, bufsize, &n);
 
        buf[n] = '\0';
        if (ret < 0)
@@ -644,6 +627,33 @@ int para_munmap(void *start, size_t length)
        return -ERRNO_TO_PARA_ERROR(err);
 }
 
+static int xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+       int ret;
+
+       do
+               ret = poll(fds, nfds, timeout);
+       while (ret < 0 && errno == EINTR);
+       return ret < 0? -ERRNO_TO_PARA_ERROR(errno) : ret;
+}
+
+/**
+ * Check a file descriptor for readability.
+ *
+ * \param fd The file descriptor.
+ *
+ * \return positive if fd is ready for reading, zero if it isn't, negative if
+ * an error occurred.
+ *
+ * \sa \ref write_ok().
+ */
+int read_ok(int fd)
+{
+       struct pollfd pfd = {.fd = fd, .events = POLLIN};
+       int ret = xpoll(&pfd, 1, 0);
+       return ret < 0? ret : pfd.revents & POLLIN;
+}
+
 /**
  * Check a file descriptor for writability.
  *
@@ -651,18 +661,14 @@ int para_munmap(void *start, size_t length)
  *
  * \return positive if fd is ready for writing, zero if it isn't, negative if
  * an error occurred.
+ *
+ * \sa \ref read_ok().
  */
 int write_ok(int fd)
 {
-       int ret;
        struct pollfd pfd = {.fd = fd, .events = POLLOUT};
-
-       do
-               ret = poll(&pfd, 1, 0);
-       while (ret < 0 && errno == EINTR);
-       if (ret < 0)
-               return -ERRNO_TO_PARA_ERROR(errno);
-       return pfd.revents & POLLOUT;
+       int ret = xpoll(&pfd, 1, 0);
+       return ret < 0? ret : pfd.revents & POLLOUT;
 }
 
 /**