1 files changed, 64 insertions, 0 deletions
diff --git a/lib/libc/stdio/fflush_unlocked.c b/lib/libc/stdio/fflush_unlocked.c
new file mode 100644
index 00000000..b4ee3e43
--- /dev/null
+++ b/lib/libc/stdio/fflush_unlocked.c
@@ -0,0 +1,64 @@
+#include <__stdio.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/cdefs.h>
+#include <unistd.h>
+
+int fflush_unlocked(struct __FILE *stream)
+{
+	if (stream == NULL) {
+		// TODO: flush all streams
+		return 0;
+	}
+
+	if (__predict_false(stream->fd) == -1) {
+		stream->buf_len = 0;
+		return 0;
+	}
+
+	if (__predict_false(stream->buf == 0)) {
+		return 0;
+	}
+
+	if (stream->flags & _IO_ERR) {
+		errno = EIO;
+		return EOF;
+	}
+
+	if ((stream->flags & O_ACCMODE) == O_RDONLY) {
+		errno = EBADF;
+		return EOF;
+	}
+
+	size_t bytes_to_write = stream->buf_len;
+	size_t total_written = 0;
+	char *buf_ptr = stream->buf;
+
+	while (total_written < bytes_to_write) {
+		ssize_t result = write(stream->fd, buf_ptr + total_written, bytes_to_write - total_written);
+
+		if (result < 0) {
+			stream->flags |= _IO_ERR;
+			return EOF;
+		}
+
+		if (result == 0) {
+			break;
+		}
+
+		total_written += result;
+	}
+
+	if (total_written == bytes_to_write) {
+		stream->buf_len = 0;
+		stream->buf_pos = 0;
+	} else {
+		size_t remaining = bytes_to_write - total_written;
+		memmove(stream->buf, stream->buf + total_written, remaining);
+		stream->buf_len = remaining;
+		stream->buf_pos = 0;
+	}
+
+	return (total_written == bytes_to_write) ? 0 : EOF;
+}