X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=fd.c;h=d56a31101ade30bd8790d8082f8a3be5f5b84004;hp=46be22891e93f2f094f3118daef5780c067b4cea;hb=98f2c8aea52a49fad3fd6df67b1eb32c1499176c;hpb=3aca09b886727eeae5c7084331b4f78ed21c261b

diff --git a/fd.c b/fd.c
index 46be2289..d56a3110 100644
--- a/fd.c
+++ b/fd.c
@@ -11,12 +11,12 @@
 #include <dirent.h>
 #include <sys/mman.h>
 #include <fcntl.h>
-#include <sys/select.h>
 #include <sys/uio.h>
 
 #include "para.h"
 #include "error.h"
 #include "string.h"
+#include "fd.h"
 
 /**
  * Write a buffer to a file descriptor, re-write on short writes.
@@ -82,6 +82,101 @@ int write_nonblock(int fd, const char *buf, size_t len,
 	return written;
 }
 
+/**
+ * Read from a non-blocking file descriptor into multiple buffers.
+ *
+ * \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 \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is
+ * not set in \a rfds, this function returns early without doing anything.
+ * Otherwise The function tries to read up to \a sz bytes from \a fd. As for
+ * write_nonblock(), EAGAIN is not considered an error condition. 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
+ * reason other than \p EAGAIN, a negative return value is returned.
+ *
+ * In any case, \a num_bytes contains the number of bytes that have been
+ * successfully read from \a fd (zero if the first readv() call failed with
+ * EAGAIN). Note that even if the function returns negative, some data might
+ * have been read before the error occured. In this case \a num_bytes is
+ * positive.
+ *
+ * \sa \ref write_nonblock(), read(2), readv(2).
+ */
+int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds,
+		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;
+		iov[i].iov_len -= j;
+		ret = readv(fd, iov + i, iovcnt - i);
+		iov[i].iov_base -= j;
+		iov[i].iov_len += j;
+
+		if (ret == 0)
+			return -E_EOF;
+		if (ret < 0) {
+			if (errno == EAGAIN)
+				return 0;
+			return -ERRNO_TO_PARA_ERROR(errno);
+		}
+		*num_bytes += ret;
+		while (ret > 0) {
+			if (ret < iov[i].iov_len - j) {
+				j += ret;
+				break;
+			}
+			ret -= iov[i].iov_len - j;
+			j = 0;
+			if (++i >= iovcnt)
+				break;
+		}
+	}
+	return 0;
+}
+
+/**
+ * Read from a non-blocking file descriptor into a single buffer.
+ *
+ * \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
+ * buffer.
+ *
+ * \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)
+{
+	struct iovec iov = {.iov_base = buf, .iov_len = sz};
+	return readv_nonblock(fd, &iov, 1, rfds, num_bytes);
+}
+
 /**
  * Simple wrapper for readv().
  *