path: root/guardian.c

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<ctype.h>
#include <sys/types.h>
#include <dirent.h>
/* struct describing the various templates that alerts can use
 * these are loaded from /etc/squishy
 */
struct template {
	//Name of template
	char * name;
	/* The actual template, '#' represents characters that could be
	 * overridden w/ the message this is normalized at read time so that
	 * lines will always end with \n\r, otherwise the alert becomes
	 * misaligned even on systems where lines don't typically end with \r
	 */
	char * template;
	/*
	 *Whether or not the template contains color escape sequences.
         * 0 is none; 1 is 16 color; 2 is 256bit color
	 */
	unsigned int color;
	/* len of name and template, including trailing '\0'
	 *
	 */
	unsigned int name_len;
	unsigned int template_len;
};
/*
 * GLOBAL VARIABLES, collection of templates and the length of that array
 */
struct template * * templates;
unsigned int templates_len = 0;
/*
 * Reads alert template from file, returns null on failure, otherwise returns
 * pointer to the template w/ all data already allocated by the function
 */
struct template *  read_template(char * path) {
	/* file the template is stored in
	 * The encoding scheme does not matter
	 * \n, \n\r, or \r endings will be normalized to \n\r
	 */
	FILE * template_file;
	/*
	 * Pointer to the template that should be returned
	 */
	struct template * tmp;
	template_file = fopen(path, "r");
	if (template_file == NULL) {
		fprintf(stderr,"Error reading from template file \"%s\"\n",path);
		return NULL;
	}
	/*
	 * Allocation of the template struct
	 */
	tmp = (struct template *)malloc(sizeof(struct template));
	if (tmp == NULL) {
		fprintf(stderr,"Error allocating memory for template \"%s\" of \
		size %d bytes\n", path, sizeof(struct template));
		return NULL;
	}
	/*
	 * Length of template name string and first character of that string in
	 * the string 'path'
	 */
	int namelen = 0;
	int parsepos = 0;
	/*
	 * Byte for storing each character of path as it is being scanned
	 */
	char pathchar;
	/* finds the length of the slice of 'path' containing the filename,
	 * inclusive of the trailing '\0'. Since it always tries get atleast the
	 * first character of 'path', we have to make sure 'path' is not null,
	 * although if this were the case fopen() above should have returned
	 * null before it reaches this point.
	 */
	if (path == NULL) {
		fprintf(stderr, "NULL path in reading of template\n");
		return NULL;
	}
	do {
		pathchar = *(path +parsepos);
		if (pathchar == '/' ) {
			namelen = 0;
		} else {
			namelen++;
		}
		parsepos++;
	} while (pathchar != '\0');
	/* as parselen is the position of '\0' + 1, we want it is the total
	 * length of path including the trailing '\0'
	 * Therefore to get the position of the first byte of a slice of length
	 * 'namelen' including the \0 would be parsepos - namelen
	 */
	tmp->name = malloc(namelen * sizeof(char));
	if (tmp->name == NULL ) {
		fprintf(stderr, "Error allocating memory for template name\n");
		return NULL;
	}
	strncpy(tmp->name, path+ (parsepos - namelen), namelen * sizeof(char));
	//Name length
	tmp->name_len = namelen;
	/*
	 * The variable that each byte stored from the stream is stored in
	 */
	char readbyte;
	/*
	 * allocates initial char, which will be the trailing '\0'
	 */
	tmp->template = malloc(1 * sizeof(char));
	tmp->template[0] = '\0';
	//size of template including trailign '\0'
	int t_size = 1;
	/*
	 * Loop goes through every character, reallocates tmp->template to
	 * t_size + 1, then set new t_size -2 to that character, while
	 * also setting t_size - 1 to '\0', thereby preserving the
	 * trailing '\0'.
	 * as the EOF is checked after each iteration, EOF is guaranteed  to be
	 * a part of the string.
	 */
	do {
		readbyte = (char)fgetc(template_file);
		tmp->template = realloc(tmp->template, sizeof(char) *(t_size +1));
		if (tmp->template == NULL) {
			return NULL;
		}
		t_size++;
		tmp->template[t_size - 2] = readbyte;
		tmp->template[t_size - 1] = '\0';
		/*
		 * If the byte is '\n' it will iterate more, since EOF is
		 * checked afterwards anyways, This doesn't matter.
		 */
		if (readbyte == '\n') {
			readbyte = (char)fgetc(template_file);
			if (readbyte != '\r') {
				tmp->template = realloc(tmp->template,
				sizeof(char) * (t_size + 1));
				if (tmp->template == NULL) {
					return NULL;
				}
				t_size++;
				tmp->template[t_size - 2] = readbyte;
				tmp->template[t_size - 1] = '\0';
			} else {
				tmp->template = realloc(tmp->template,
				sizeof(char) * (t_size + 2));
				if (tmp->template == NULL) {
					return NULL;
				}
				t_size = t_size + 2;
				tmp->template[t_size - 3] = '\r';
				tmp->template[t_size - 2] = readbyte;
				tmp->template[t_size - 1] = '\0';
			}
		}
	} while (readbyte != (char)EOF);
	/*
	 * Removes EOF before '\0'
	 */
	tmp->template = realloc(tmp->template, t_size - 1);
	if (tmp->template == NULL) {
		return NULL;
	}
	t_size--;
	tmp->template[t_size -1 ] = '\0';
	//Template Length
	tmp->template_len = t_size;
	/*
	 * Closes template_file
	 */
	fclose(template_file);
	return tmp;
}
/*
 * Prints out an alert message to pts device file output, using message-template
 * as the template and message as the message
 * beep causes it to play the bell-char at the end if it is != 0
 * beep is not a bool because C80/C90 compatibility is important
 */
int alert (FILE * output, struct template * message_template, char * message, int beep) {
	/* alert is the string that will eventually be printed
	 * assuming template_len will never be 0
	 */
	char * alert = malloc(message_template->template_len * sizeof(char));
	if (alert == NULL) {
		fprintf(stderr, "Error Memory Allocation in alert()\n");
		return -1;
	}
	/*
	 * Copies ->template into alert
	 */
	strncpy(alert, message_template->template,
		message_template->template_len * sizeof(char));
	//index of bytes in template
	unsigned int i = 0;
	//index of bytes in message
	unsigned int m_i = 0;
	//boolean for determining whether 'message' has reached it's end
	short m_end = 0;
	/* loop through alert and try to fill '#' with either message or space
	 * This excludes the trailing '\0'
	 */
	while (i < (message_template->template_len-1)) {
		if (alert[i] == '#') {
			if (!m_end) {
				/*
				 * Handles breaking text by inserting a "-"/' '
				 * If this next character is not a #, then there is a
				 * break. If the next cahracter in 'message' is
				 * [A-Z][a-z] then we insert the break
				 * This will apply even if message[m_i] is at
				 * the end of the string as message[m_i+1] would
				 * be the trailing '\0'
				 * The same applies to alert[i+1];
				 */
				if ((alert[i+1] != '#') && 
					(isalpha(message[m_i+1])) &&
					isalpha(message[m_i]) ) {
					/*
					 * If the current message[m_i] and the
					 * previous messae[m_i-1] are alpha
					 * then we use dashes, otherwise it is
					 * replaced with a ' '
					 */
					if (message[m_i] == 0) {
						alert[i] = ' ';
					} else if(isalpha(message[m_i-1])) {
						alert[i] = '-';
					} else {
						alert[i] = ' ';
					}
				} else {
					alert[i] = message[m_i];
					m_i++;
					if (message[m_i] == '\0') {
						m_end = 1;
					}
				}
			} else {
				alert[i] = ' ';
			}
		}
		i++;
	}
	/* actually prints the alert string
	 * \033 = <ESC>
	 * <ESC>7 saves cursor and attributes
	 * <ESC>8 restores
	 * <ESC>[0;0H homes the cursor
	 * <ESC>[?47h
	 * <ESC>[?47l
	 */
	fprintf(output,"\0337\033[0;0H%s\0338",alert);
	/* the below loads an alternative buffer, this is deprecated*/
	//fprintf(output,"\033[?47h%s\033[?47l",alert);
	if (beep) {
		fprintf(output, "\a");
	}
	return 0;
}
/*
 * Concatenates two strings and returns the result as a heap allocated string
 * Returns null on failure
 */
char * str_concat(char * s1, char * s2) {
	char * return_str;
	/*
	 * since strlen does not count the trailing '\0', we need to add one
	 */
	return_str = malloc((strlen(s1) + 1 + strlen(s2)) * sizeof(char) );
	if (return_str == NULL) {
		fprintf(stderr,"Failure to allocate memory in str_concat()\n");
		return NULL;
	}
	/*
	 * copies the nonnull bytes of s1
	 */
	strncpy(return_str,s1,sizeof(char) * strlen(s1));
	/*
	 * Copies the nonnull bytes of s2, which begin at strlen(s1) since that
	 * is the offset from the beginning of s1 where the null byte of s1
	 * would be
	 */
	strncpy((return_str + strlen(s1)),s2,sizeof(char) * strlen(s2));
	/*
	 * Add trailing '\0'
	 */
	strncpy(return_str + strlen(s1) + strlen(s2) ,"\0", sizeof(char) * 1);
	return return_str;
}
struct template * * load_templates() {
	/*ensures that templates is alteast 1 element big*/
	struct template * * templates = (struct template * *)malloc(sizeof(struct template * ));
	/*opens templates dir*/
	DIR * templates_dir = opendir("templates");
	if (templates_dir == NULL) {
		return NULL;
	}
	/*
	 * Structs storing the current loaded template and current directory
	 * entry
	 */
	struct template * tem;
	struct dirent * entry;
	/* the loop keeps reading until entry is nyll, since the evaluation is
	 * at the end, a switch has to ensure that no attempts to handle entry
	 * == NULL are made
	 */
	do {
		entry = readdir(templates_dir);
		if (entry != NULL && entry->d_name[0] != '.') {
			/* since d_name is just the name of the file and we want
			 * the full path
			 */
			char * fullpath = str_concat("templates/",
				entry->d_name);
			if (fullpath == NULL) {
				return NULL;
			}
			/*
			 * Load the template
			 */
			tem = read_template(fullpath);
			//free heap allocated string ASAP
			free(fullpath);
			if ( tem == NULL ) {
				return NULL;
			}
			/*resizing templates*/
			templates_len++;
			templates = (struct template * *)realloc(templates, 
			templates_len * sizeof(struct template * ));
			if (templates == NULL) {
				return NULL;
			}
			templates[templates_len - 1] = tem;
		}

	} while (entry != NULL);
	/*
	 * Close the templates directory
	 */
	closedir(templates_dir);
	return templates;
}
int broadcast(char * template_name, char * message) {
	struct template * tm = NULL;
	/*
	 * loops through for the appropriate template
	 */
	for (int i = 0; i < templates_len; i++) {
		if (strcmp(templates[i]->name,template_name) == 0 ) {
			tm = templates[i];
		}
	}
	/*
	 * if none are found then tm is still null and can not proceed
	 */
	if (tm == NULL) {
		fprintf(stderr, "unable to find template %s",template_name);
		return  -1;
	}
	/*
	 * Directory pts contains all pseudo-terminal devices.
	 * All terminals will have an alert sent to them.
	 */
	DIR * pts_dir = opendir("/dev/pts");
	if (pts_dir == NULL ) {
		return -1;
	}
	/*
	 * for storing the current dirent and pseudotty file
	 */
	struct dirent * pts_entry;
	FILE * pts;
	do {
		pts_entry = readdir(pts_dir);
		/*
		 * Makes sure it's not readin from the ptmx device, a hidden
		 * file, or NULL
		 */
		if ( pts_entry != NULL && 
			pts_entry->d_name[0] != '.' &&
			strcmp(pts_entry->d_name, "ptmx") != 0) {
			/*
			 * Gets full path
			 */
			char * fullpath = str_concat("/dev/pts/",
				pts_entry->d_name);
			/*
			 * opens file in append mode, these are the only
			 * permissions we need
			 */
			pts = fopen(fullpath, "a");
			if (pts == NULL) {
				fprintf(stderr, "unable to open file %s\n",
					fullpath);
				return -1;
			}
			/*frees heap allocated string*/
			free(fullpath);
			alert(pts,tm,message,1);
			/*closes file*/
			fclose(pts);
		}
	} while (pts_entry != NULL);
}
int main (int argc, char * argv[]) {
	templates = load_templates();
	if (templates == NULL) {
		return -1;
	}
	if (broadcast(argv[1],argv[2])) {
		return -1;
	}
}