setcolors.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <getopt.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/kd.h>

#define PALETTE_SIZE 16

#define HELP \
"Usage: setcolors [-c device] [config-file]\n"\
"Updates the linux VT101 console default color palette\n"\
"\n"\
"The color configuration file passed should contain at most 16 hexadecimal\n"\
"values separated by new lines. You can specify the color ID by prefixing\n"\
"the hexadecimal value with the color Id (between 0 and 15) and a `#'\n"\
"\n"\
"If no color config file is passed the colors will be reset to the defaults\n"\
"\n"\
" -c, --console   Indicate console device to be used.\n"\
" -h, --help      Show this help text"

static const char *console_paths[] = {
	"/proc/self/fd/0",
	"/dev/tty",
	"/dev/tty0",
	"/dev/vc/0",
	"/dev/systty",
	"/dev/console",
	NULL
};

static const char default_color_set[PALETTE_SIZE][7] = {
	"000000","aa0000","00aa00","aa5500",
	"0000aa","aa00aa","00aaaa","aaaaaa",
	"555555","ff5555","55ff55","ffff55",
	"5555ff","ff55ff","55ffff","ffffff" };

/**
 * The palette struct is the type expected by ioctl PIO_CMAP
 */
struct palette { unsigned char colors[PALETTE_SIZE * 7]; };

/**
 * Convert a list of colors in hex format to their actual hex formats suitable
 * for passing to the ioctl function
 */
static struct palette
get_palette_from_color_set(const char colors[][7])
{
	struct palette palette;
	unsigned int red, green, blue;
	int i, k;

	for (i = k = 0; i < PALETTE_SIZE; ++i)
	{
		if (sscanf(colors[i], "%2x%2x%2x", &red, &green, &blue) != 3)
		{
			fprintf(stderr, "Color %d: Invalid hex code\n", i);
			exit(1);
		}

		palette.colors[k++] = red;
		palette.colors[k++] = green;
		palette.colors[k++] = blue;
	}

	return palette;
}

/**
 * Get a file descriptor for a console to write to
 */
static int
get_console_fd(const char *console_path)
{
	int i, fd;
	char type = '\0';

	// Use one of the default console paths
	if ( ! console_path)
	{
		for (i = 0; console_paths[i]; ++i)
		{
			if ((fd = get_console_fd(console_paths[i])) > 0)
				return fd;
		}

		return -1;
	}

	// Attempt to open the FD, and make sure it's a tty
	if ((fd = open(console_path, O_RDWR | O_NOCTTY)) < 0)
		return -1;

	// Make sure the tty is a linux VT101 terminal
	if ( ! isatty(fd) || ioctl(fd, KDGKBTYPE, &type) < 0 || type != KB_101)
		return -1;

	return fd;
}

/**
 * Read color strings in from a file terminated by new lines
 */
static int
get_color_set_from_file(const char *file_path, char color_set[][7])
{
	int i;
	FILE *fd;
	char *line = NULL, *color = NULL;
	size_t read = 0;

	if ((fd = fopen(file_path, "r")) == NULL)
		return -1;

	for (i = 0; getline(&line, &read, fd) > 0; ++i)
	{
		// Don't read more colors than we can fit in our color set
		if ( ! color_set[i])
			break;

		color = line;

		// Skip blank lines
		if (color[0] == '\n')
		{
			--i;
			continue;
		}

		if (color[0] == '#')
			++color;

		// Use the color ID specified if possible
		sscanf(color, "%d#%s", &i, color);

		if (i >= PALETTE_SIZE)
			continue;

		if (strlen(color) < 6)
		{
			fprintf(stderr, "Color %d: value too short, skipping\n", i);
			continue;
		}

		// color_set will already have null terminating characters at index 7
		strncpy(color_set[i], color, 6);
	}

	if (i < 16)
		fprintf(stderr, "Warning: Less than 16 colors in configuration\n");

	if (line)
		free(line);

	fclose(fd);
	return 0;
}

int
main(int argc, char *argv[])
{
	// Default the color set to the default colors if none specified
	char color_set[PALETTE_SIZE][7];
	memcpy(color_set, default_color_set, PALETTE_SIZE * 7);

	// By default let the console path be detected
	char *console_path = NULL;

	struct option options[] =
	{
		{"console",  required_argument, 0, 'c'},
		{"help",     no_argument,       0, 'h'},
		{0, 0, 0, 0}
	};

	int c;
	while((c = getopt_long(argc, argv, "-c:h", options, NULL)) != -1)
	{
		switch(c)
		{
			case 'c':
				console_path = optarg;
				break;
			case 'h':
				printf("%s\n", HELP);
				return 0;
			case '\1':
				if (get_color_set_from_file(optarg, color_set) < 0)
				{
					perror("Unable to load color set from file");
					exit(1);
				}
				break;
			default:
				exit(1);
		}
	}

	struct palette new_palette = get_palette_from_color_set((const char (*)[]) color_set);
	int fd;

	if ((fd = get_console_fd(console_path)) < 0)
	{
		perror("Unable to open console");
		exit(1);
	}

	if (ioctl(fd, PIO_CMAP, &new_palette) < 0)
	{
		perror("Failed to set new color map on console");
		exit(1);
	}

	// Clear console to fix color artifacts
	write(fd, "\033[2J\033[1;1H", 10);

	close(fd);
	return 0;
}