X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=fd.c;h=9942eb925f33f86068d04729faf74bcd41a4566b;hp=d0b5c895a5f25d02b9f566fbe693a38898057203;hb=e59019f183e080486fda280868cf4669955148c2;hpb=cb4dd13c2327c13d486b6abe572f4af2398b65de

diff --git a/fd.c b/fd.c
index d0b5c895..9942eb92 100644
--- a/fd.c
+++ b/fd.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2006-2008 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2006-2009 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -40,6 +40,45 @@ int write_all(int fd, const char *buf, size_t *len)
 	return 1;
 }
 
+/**
+ * Write a buffer to a non-blocking file descriptor.
+ *
+ * \param fd The file descriptor.
+ * \param buf the buffer to write.
+ * \param len the number of bytes of \a buf.
+ * \param max_bytes_per_write Do not write more than that many bytes at once.
+ *
+ * If \a max_bytes_per_write is non-zero, do not send more than that many bytes
+ * per write().
+ *
+ * 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.
+ */
+int write_nonblock(int fd, const char *buf, size_t len,
+		size_t max_bytes_per_write)
+{
+	size_t written = 0;
+	int ret = 0;
+
+	while (written < len) {
+		size_t num = len - written;
+
+		if (max_bytes_per_write && max_bytes_per_write < num)
+			num = max_bytes_per_write;
+		ret = write(fd, buf + written, num);
+		if (ret < 0 && errno == EAGAIN)
+			return written;
+		if (ret < 0)
+			return -ERRNO_TO_PARA_ERROR(errno);
+		written += ret;
+	}
+	return written;
+}
+
 /**
  * Check whether a file exists.
  *
@@ -427,3 +466,24 @@ again:
 		goto again;
 	return ret;
 }
+
+/**
+ * Ensure that file descriptors 0, 1, and 2 are valid.
+ *
+ * Common approach that opens /dev/null until it gets a file descriptor greater
+ * than two.
+ *
+ * \sa okir's Black Hats Manual.
+ */
+void valid_fd_012(void)
+{
+	while (1) {
+		int fd = open("/dev/null", O_RDWR);
+		if (fd < 0)
+			exit(EXIT_FAILURE);
+		if (fd > 2) {
+			close(fd);
+			break;
+		}
+	}
+}