1 files changed, 58 insertions, 0 deletions
diff --git a/src/luxset.c b/src/luxset.c
new file mode 100644
index 0000000..b707efd
--- /dev/null
+++ b/src/luxset.c
@@ -0,0 +1,58 @@
+/*
+ * BSD Zero Clause License
+ *
+ * Copyright (c) 2022 Thomas Voss
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+
+#include "common.h"
+#include "lux.h"
+
+static int intlen(int);
+
+int
+luxset(lux_t *disp, int n)
+{
+	/* The same deal as in luxget() */
+	if (disp->__bstream == NULL) {
+		if ((disp->__bstream = getbstream(disp->__dirfd)) == NULL)
+			return -1;
+	} else
+		rewind(disp->__bstream);
+
+	/* After writing the new brightness value to the brightness file, we
+	 * need to truncate it so that luxset(disp, 1234); luxset(disp, 9);
+	 * gives us a final brightness of 2 and not 9234.
+	 */
+	fprintf(disp->__bstream, "%d", n);
+	ftruncate(fileno(disp->__bstream), intlen(n));
+	return n;
+}
+
+int
+intlen(int n)
+{
+	return    n < 10         ? 1
+		: n < 100        ? 2
+		: n < 1000       ? 3
+		: n < 10000      ? 4
+		: n < 100000     ? 5
+		: n < 1000000    ? 6
+		: n < 10000000   ? 7
+		: n < 100000000  ? 8
+		: n < 1000000000 ? 9
+		: 10;
+}