From ccc88f0d865189821ad7f67ecfac4feec354e607 Mon Sep 17 00:00:00 2001
From: Thomas Voss <thomasvoss@live.com>
Date: Tue, 9 Aug 2022 12:32:49 +0200
Subject: Add source code files in their uncompleted state
The current state of the library contains support for the following
functions:
- int luxinit(struct luxdisp *) | Init a luxdisp struct
- int luxget(struct luxdisp *) | Get the current brightness
- int luxset(struct luxdisp *, int) | Set the current brightness
- int luxmax(struct luxdisp *) | Get the maximum brightness
- void luxfree(struct luxdisp *) | Free a luxdisp struct
---
liblux.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
lux.h | 36 ++++++++++++++
2 files changed, 204 insertions(+)
create mode 100644 liblux.c
create mode 100644 lux.h
diff --git a/liblux.c b/liblux.c
new file mode 100644
index 0000000..3195342
--- /dev/null
+++ b/liblux.c
@@ -0,0 +1,168 @@
+/*
+ * 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.
+ */
+
+#define _POSIX_C_SOURCE 200809L
+
+#include <sys/types.h>
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "lux.h"
+
+#ifdef O_PATH
+ #define GETDIR_FLAGS O_PATH
+#else
+ #define GETDIR_FLAGS (O_RDONLY | O_DIRECTORY)
+#endif
+
+static int intlen(int);
+static int getdir(void);
+static FILE *getbstream(int);
+
+int
+luxinit(struct luxdisp *disp)
+{
+ /* Set the default values for the luxdisp struct. We want to be as lazy
+ * as possible, so we don't bother with __bstream and __max yet. We do
+ * need __dirfd though.
+ */
+ *disp = (struct luxdisp) {
+ .__bstream = NULL,
+ .__max = -1,
+ .__dirfd = getdir()
+ };
+ return disp->__dirfd;
+}
+
+int
+luxget(struct luxdisp *disp)
+{
+ /* If we don't have an open stream with the brightness file yet then
+ * open one. If we do, we instead rewind to the start of the file so
+ * that we don't just read an EOF.
+ */
+ if (disp->__bstream == NULL) {
+ if ((disp->__bstream = getbstream(disp->__dirfd)) == NULL)
+ return -1;
+ } else
+ rewind(disp->__bstream);
+
+ int n;
+ fscanf(disp->__bstream, "%d", &n);
+ return n;
+}
+
+int
+luxset(struct luxdisp *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
+luxmax(struct luxdisp *disp)
+{
+ /* The maximum brightness shouldn't change, so we can cache it in the
+ * struct.
+ */
+ if (disp->__max != -1)
+ return disp->__max;
+
+ int fd = openat(disp->__dirfd, "max_brightness", O_RDONLY);
+ if (fd == -1)
+ return -1;
+ FILE *stream = fdopen(fd, "r");
+ if (stream == NULL) {
+ close(fd);
+ return -1;
+ }
+
+ fscanf(stream, "%d", &disp->__max);
+ fclose(stream);
+ return disp->__max;
+}
+
+void
+luxfree(struct luxdisp *disp)
+{
+ if (disp->__dirfd != -1)
+ close(disp->__dirfd);
+ if (disp->__bstream != NULL)
+ fclose(disp->__bstream);
+}
+
+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;
+}
+
+int
+getdir(void)
+{
+ int fd, dfd;
+ struct dirent *dp;
+ DIR *dir;
+
+ /* To get the file descriptor for the directory where all the brightness
+ * files are located, we first need to open BACKLIGHT_DIR which is the
+ * directory where the backlight directories are located. Then we need
+ * to get a DIR* of that directory and get the 3rd entry. We need the
+ * third because the fist and second are the . and .. folders. Finally
+ * we open the folder so that we have a file descriptor we can return.
+ */
+ if ((dfd = open(BACKLIGHT_DIR, O_RDONLY)) == -1
+ || (dir = fdopendir(dfd)) == NULL
+ || (dp = readdir(dir)) == NULL
+ || (dp = readdir(dir)) == NULL
+ || (dp = readdir(dir)) == NULL
+ || (fd = openat(dfd, dp->d_name, GETDIR_FLAGS)) == -1)
+ return -1;
+
+ closedir(dir);
+ return fd;
+}
+
+FILE *
+getbstream(int dirfd)
+{
+ return fdopen(openat(dirfd, "brightness", O_RDWR), "r+");
+}
diff --git a/lux.h b/lux.h
new file mode 100644
index 0000000..12198f9
--- /dev/null
+++ b/lux.h
@@ -0,0 +1,36 @@
+/*
+ * 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.
+ */
+
+#ifndef LUX_H
+#define LUX_H
+
+#include <stdio.h>
+
+#define BACKLIGHT_DIR "/sys/class/backlight"
+
+struct luxdisp {
+ int __dirfd, __max;
+ FILE *__bstream;
+};
+
+int luxinit(struct luxdisp *);
+int luxget(struct luxdisp *);
+int luxset(struct luxdisp *, int);
+int luxmax(struct luxdisp *);
+void luxfree(struct luxdisp *);
+
+#endif /* !LUX_H */
--
cgit v1.2.3