diff options
| -rw-r--r-- | liblux.c | 168 | ||||
| -rw-r--r-- | lux.h | 36 |
2 files changed, 204 insertions, 0 deletions
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+"); +} @@ -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 */ |