rawmode.c

#include "headers.h"

void die(const char *s) {
    perror(s);
    exit(1);
}

struct termios orig_termios;

void disableRawMode() {
    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios) == -1)
        die("tcsetattr");
}

/**
 * Enable row mode for the terminal
 * The ECHO feature causes each key you type to be printed to the terminal, so you can see what you’re typing.
 * Terminal attributes can be read into a termios struct by tcgetattr().
 * After modifying them, you can then apply them to the terminal using tcsetattr().
 * The TCSAFLUSH argument specifies when to apply the change: in this case, it waits for all pending output to be written to the terminal, and also discards any input that hasn’t been read.
 * The c_lflag field is for “local flags”
*/
void enableRawMode() {
    if (tcgetattr(STDIN_FILENO, &orig_termios) == -1) die("tcgetattr");
    atexit(disableRawMode);
    struct termios raw = orig_termios;
    raw.c_lflag &= ~(ICANON | ECHO | ISIG);
    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) die("tcsetattr");
}

/**
 * stdout and stdin are buffered we disable buffering on that
 * After entering in raw mode we read characters one by one
 * Up arrow keys and down arrow keys are represented by 3 byte escape codes
 * starting with ascii number 27 i.e. ESC key
 * This way we interpret arrow keys
 * Tabs are usually handled by the term, but here we are simulating tabs for the sake of simplicity
 * Backspace move the cursor one control character to the left
 * @return
*/
char* set_raw() {
    char *inp = malloc(sizeof(char) * 1024);
    char c;
    setbuf(stdout, NULL);
    enableRawMode();
    // printf("Prompt>");
    memset(inp, '\0', 1024);
    int pt = 0;
    while (read(STDIN_FILENO, &c, 1) == 1) {
        if (iscntrl(c)) {
            if(c == 3)
            {
                printf("\n");
                break;                
            }
            else if (c == 10) 
            {
                printf("\n");
                break;
            }
            else if(c == 26)
            {
                continue;
            }
            else if (c == 27) {
                char buf[3];
                buf[2] = 0;
                if (read(STDIN_FILENO, buf, 2) == 2) { // length of escape code
                    // printf("\rarrow key: %s", buf);
                }
            } else if (c == 127) { // backspace
                if (pt > 0) {
                    if (inp[pt-1] == 9) {
                        for (int i = 0; i < 7; i++) {
                            printf("\b");
                        }
                    }
                    inp[--pt] = '\0';
                    printf("\b \b");
                }
            } else if (c == 9) { // TAB character
                inp[pt++] = c;
                for (int i = 0; i < 8; i++) { // TABS should be 8 spaces
                    printf(" ");
                }
            } else if (c == 4) {
                kill_all();
                fflush(stdout);
                exit(0);
            } else {
                printf("%d\n", c);
            }
        } else {
            inp[pt++] = c;
            printf("%c", c);
        }
    }
    disableRawMode();
    return inp;
}