X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=fd.c;h=830b15dad62f755ee75e1999b656d78a15890d10;hp=6f487c410020795a73476fa79ba552c2ad29e4fd;hb=65b6448b8eb6f7442ba64affff58c388306a9159;hpb=748d1368bc96dd7e1af879df1ea41b4d52842f7e

diff --git a/fd.c b/fd.c
index 6f487c41..830b15da 100644
--- a/fd.c
+++ b/fd.c
@@ -62,33 +62,49 @@ __printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
 }
 
 /**
- * Write a buffer to a non-blocking file descriptor.
+ * Write a buffer to a file descriptor, re-writing on short writes.
  *
  * \param fd The file descriptor.
- * \param buf the buffer to write.
- * \param len the number of bytes of \a buf.
- *
- * EAGAIN is not considered an error condition.  For example CCID3 has a
- * sending wait queue which fills up and is emptied asynchronously. The EAGAIN
- * case means that there is currently no space in the wait queue, but this can
- * change at any moment.
- *
- * \return Negative on errors, number of bytes written else.
+ * \param buf The buffer to write.
+ * \param len The number of bytes to write.
+ *
+ * EAGAIN/EWOULDBLOCK is not considered a fatal error condition. For example
+ * DCCP CCID3 has a sending wait queue which fills up and is emptied
+ * asynchronously. The EAGAIN case means that there is currently no space in
+ * the wait queue, but this can change at any moment.
+ *
+ * \return Negative on fatal errors, number of bytes written else. For blocking
+ * file descriptors this function returns either \a len or the error code of
+ * the fatal error that caused the last write call to fail. For nonblocking
+ * file descriptors there is a third possibility: A positive return value < \a
+ * len indicates that some bytes have been written but the next write would
+ * block.
  */
 int write_nonblock(int fd, const char *buf, size_t len)
 {
 	size_t written = 0;
-	int ret = 0;
 
 	while (written < len) {
-		size_t num = len - written;
-
-		ret = write(fd, buf + written, num);
-		if (ret < 0 && errno == EAGAIN)
+		ssize_t ret = write(fd, buf + written, len - written);
+		if (ret >= 0) {
+			written += ret;
+			continue;
+		}
+		if (errno == EINTR)
+			/*
+			 * The write() call was interrupted by a signal before
+			 * any data was written. Try again.
+			 */
+			continue;
+		if (errno == EAGAIN || errno == EWOULDBLOCK)
+			/*
+			 * We don't consider this an error. Note that POSIX
+			 * allows either error to be returned, and does not
+			 * require these constants to have the same value.
+			 */
 			return written;
-		if (ret < 0)
-			return -ERRNO_TO_PARA_ERROR(errno);
-		written += ret;
+		/* fatal error */
+		return -ERRNO_TO_PARA_ERROR(errno);
 	}
 	return written;
 }