1 files changed, 89 insertions, 0 deletions
diff --git a/libc/stdio/_trans2w.c b/libc/stdio/_trans2w.c
new file mode 100644
index 000000000..fdde2bebf
--- /dev/null
+++ b/libc/stdio/_trans2w.c
@@ -0,0 +1,89 @@
+/* Copyright (C) 2004       Manuel Novoa III    <mjn3@codepoet.org>
+ *
+ * GNU Library General Public License (LGPL) version 2 or later.
+ *
+ * Dedicated to Toni.  See uClibc/DEDICATION.mjn3 for details.
+ */
+
+#include "_stdio.h"
+
+/* Function to handle transition to writing.
+ *   Initialize or verify the stream's orientation (even if readonly).
+ *   Check that the stream is writable.
+ *   If currently reading, check that we can transition to writing.
+ *      C99 requires that the stream is at EOF, but attempting to
+ *      auto-transition via fseek() is a configurable option.
+ *   Returns 0 on success and EOF otherwise.
+ *
+ * Notes:
+ *   There are two function signatures, depending on wchar support,
+ *   since with no wchar support the orientation is narrow by default.
+ */
+
+#ifdef __UCLIBC_HAS_WCHAR__
+int __stdio_trans2w_o(FILE * __restrict stream, int oflag)
+#else
+int __stdio_trans2w(FILE * __restrict stream)
+#endif
+{
+	__STDIO_STREAM_VALIDATE(stream);
+	assert(!__STDIO_STREAM_IS_WRITING(stream));
+
+#ifdef __UCLIBC_HAS_WCHAR__
+	if (!(stream->__modeflags & oflag)) {
+		if (stream->__modeflags & (__FLAG_NARROW|__FLAG_WIDE)) {
+			__UNDEFINED_OR_NONPORTABLE;
+			goto DO_EBADF;
+		}
+		stream->__modeflags |= oflag;
+	}
+#endif
+
+	if (stream->__modeflags & __FLAG_READONLY) {
+	DO_EBADF:
+		__set_errno(EBADF);
+	ERROR:
+		__STDIO_STREAM_SET_ERROR(stream);
+		__STDIO_STREAM_VALIDATE(stream);
+		return EOF;
+	}
+
+	if (__STDIO_STREAM_IS_READING(stream)) {
+		if (!__FEOF_UNLOCKED(stream)) {
+#ifdef __UCLIBC_HAS_STDIO_AUTO_RW_TRANSITION__
+			/* Need to seek to correct position if we have buffered
+			 * read data or ungots.  If appending, we might as well
+			 * seek to the end.
+			 *
+			 * NOTE: If the OS does not handle append files correctly,
+			 *   this is insufficient since we would need to seek to
+			 *   the end even if not reading.*/
+			if (((__STDIO_STREAM_BUFFER_RAVAIL(stream))
+				 || (stream->__modeflags & __FLAG_UNGOT))
+				&& fseek(stream, 0L,
+						 ((stream->__modeflags & __FLAG_APPEND)
+						  ? SEEK_END : SEEK_CUR))
+				) {
+				/* fseek() only sets error indicator on read/write error. */
+				goto ERROR;
+			}
+#else
+			/* C99 requires either at EOF or currently not reading. */
+			__UNDEFINED_OR_NONPORTABLE;
+			goto DO_EBADF;
+#endif
+		}
+		__STDIO_STREAM_CLEAR_READING_AND_UNGOTS(stream);
+		__STDIO_STREAM_DISABLE_GETC(stream);
+		/* Reaching EOF does not reset buffer pointers... */
+		__STDIO_STREAM_INIT_BUFREAD_BUFPOS(stream);
+	}
+
+	__STDIO_STREAM_SET_WRITING(stream);
+	if (__STDIO_STREAM_IS_NARROW_FBF(stream)) {
+		__STDIO_STREAM_ENABLE_PUTC(stream);
+	}
+
+	__STDIO_STREAM_VALIDATE(stream);
+	return 0;
+}