fd: Improve error handling of write_nonblock().

[paraslash.git] / fd.c

diff --git a/fd.c b/fd.c
index 429960cc0ab3d822811a1702c56c99a9e4c1ff10..830b15dad62f755ee75e1999b656d78a15890d10 100644 (file)
--- a/fd.c
+++ b/fd.c
@@ -43,33 +43,68 @@ int write_all(int fd, const char *buf, size_t len)
 }
 
 /**
- * Write a buffer to a non-blocking file descriptor.
+ * Send a buffer given by a format string.
  *
  * \param fd The file descriptor.
- * \param buf the buffer to write.
- * \param len the number of bytes of \a buf.
+ * \param fmt A format string.
  *
- * 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 Standard.
+ */
+__printf_2_3 int write_va_buffer(int fd, const char *fmt, ...)
+{
+       char *msg;
+       int ret;
+
+       PARA_VSPRINTF(fmt, msg);
+       ret = write_buffer(fd, msg);
+       free(msg);
+       return ret;
+}
+
+/**
+ * Write a buffer to a file descriptor, re-writing on short writes.
  *
- * \return Negative on errors, number of bytes written else.
+ * \param fd The file descriptor.
+ * \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;
 }