syntax.h

#include <ctype.h>
#define MAGENTA 2
#define YELLOW 3
#define CYAN 4
#define GREEN 5
#define WHITE 6

int is_separator(char ch) { // function for checking if char is separator
	return isspace(ch) || ch=='\n' || strchr(",.()+-/*=~%<>[];", ch)!=NULL; // strchr checks if ch is any of the chars in string given
}
void update_syntax(buffer *buff) {
	line *curr_line=buff->top;
	dNode *curr_node=curr_line->start;
	char ch;
	int in_string=0;
	char *keywords1[] = {"switch", "if", "while", "for", "break", "continue", "return", "else", "struct", "typedef", "case", "int", "long", "double", "float", "char", "unsigned", "signed", "void"}; // 19 keywords

	while(curr_line!=NULL) { //reset
		while(curr_node!=NULL) {
			curr_node->color=WHITE;
			curr_node=curr_node->next;
		}
		curr_line=curr_line->next_line;
		if(curr_line==NULL) break;
		curr_node=curr_line->start;
	}
	curr_line=buff->top;
	curr_node=curr_line->start;
	while(curr_line!=NULL) {
		while(curr_node!=NULL) { 
			ch=curr_node->ch;
			if(curr_node->prev==NULL) { // for digits and keywords at the beginning of lines
				if(isdigit(ch)) {
					curr_node->color=MAGENTA;
				}
				if(ch=='#') {
					dNode *temp=curr_node;
					while(temp->next!=NULL) {
						temp->color=MAGENTA;
						temp=temp->next;
					}
				}
				else if(ch=='/' && curr_node->next->ch=='/') { //for single line comments
					dNode *curr=curr_node;
					while(curr->next!=NULL) {
						curr->color=CYAN;
						curr=curr->next;
					}
					break;
				}
					int j;
					for(j=0; j<19; j++){
						int slen=strlen(keywords1[j]), count=0;
						dNode *search=curr_node, *started=curr_node;
						while(search->next!=NULL && search->ch==keywords1[j][count]) {
							search=search->next;
							count++;
						}
						if(keywords1[j][count]=='\0') {
							if(search->next==NULL) {
								while(started!=search) {
									started->color=YELLOW;
									started=started->next;
								} started->color=YELLOW;
								break;
							}
							else if(is_separator(search->ch)) {
								search=search->prev;
								while(started!=search) {
									started->color=YELLOW;
									started=started->next;
								} started->color=YELLOW;
								break;
							}
						}
					}	
			}
			else if(isdigit(ch) && (curr_node->prev->color==MAGENTA || is_separator(curr_node->prev->ch))) { //if current char is a digit
				curr_node->color=MAGENTA;
			}
			else if(in_string) { //for strings
				curr_node->color=GREEN;
				if(ch==in_string||ch=='>') in_string=0;
			}
			else if(ch=='"'||ch=='\''||ch=='<') { // for checking if strings are closed
				in_string=ch;
				curr_node->color=GREEN;
			}
			else if(ch=='/' && curr_node->next->ch=='/') { //for single line comments
				dNode *curr=curr_node;
				while(curr->next!=NULL) {
					curr->color=CYAN;
					curr=curr->next;
				}
				break;
			}
			else if(curr_node->prev!=NULL) { //for keywords in body of line
				if(is_separator(curr_node->prev->ch)) {
					int j;
					for(j=0; j<19; j++){
						int slen=strlen(keywords1[j]), count=0;
						dNode *search=curr_node, *started=curr_node;
						while(search->next!=NULL && search->ch==keywords1[j][count]) {
							search=search->next;
							count++;
						}
						if(keywords1[j][count]=='\0') {
							if(search->next==NULL) {
								while(started!=search) {
									started->color=YELLOW;
									started=started->next;
								} started->color=YELLOW;
								break;
							}
							else if(is_separator(search->ch)) {
								search=search->prev;
								while(started!=search) {
									started->color=YELLOW;
									started=started->next;
								} started->color=YELLOW;
								break;
							}
						}
					}	
				}
			}
			curr_node=curr_node->next;
		}
		curr_line=curr_line->next_line;
		if(curr_line==NULL) break;
		curr_node=curr_line->start;
	}
}