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gutenberg.c
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gutenberg.c
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#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <termios.h>
/*** defines ***/
// 0x1F decimal 31
// As I want to bind exit to CTRL + Q
// 01010001&00011111=00010001 so 17 in ASCII
#define CTRL_KEY(k) ((k) & 0x1F)
/*** data ***/
struct editorConfig {
struct termios orig_termios;
};
struct editorConfig E;
/*** terminal ***/
void die(const char *s) {
write(STDOUT_FILENO, "\x1b[2J", 4);
write(STDOUT_FILENO, "\x1b[H", 3);
perror(s);
exit(1);
}
void disableRawMode(void) {
if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &E.orig_termios) == -1) {
die("tcsetattr");
}
}
void enableRawMode(void) {
if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1) die("tcgetattr");
atexit(disableRawMode);
struct termios raw = E.orig_termios;
/*
https://www.man7.org/linux/man-pages/man3/termios.3.html
c_lflag is local flags
strange &= and ~ are bitwise operations
ECHO is 00000000000000000000000000001000 in binary
~(ECHO) is 11111111111111111111111111110111
and &= is to set the fourth bit to be 1 but retain other bits to stay 1 as well.
c_lflag flag constants:
ISIG When any of the characters INTR, QUIT, SUSP, or DSUSP are
received, generate the corresponding signal.
ICANON Enable canonical mode (described below).
*/
raw.c_lflag &= ~(ECHO | ICANON | ISIG | IEXTEN);
raw.c_oflag &= ~(OPOST);
raw.c_iflag &= ~(BRKINT | IXON | ICRNL);
raw.c_cc[VMIN] = 0;
raw.c_cc[VTIME] = 1;
if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) die("tcsetattr");
}
char editorReadKey(void) {
int nread;
char c;
while ((nread = read(STDIN_FILENO, &c, 1)) != 1) {
// To make it work in Cygwin, I won’t treat EAGAIN as an error.
if (nread == -1 && errno != EAGAIN) die("read");
}
return c;
}
/*** output ***/
void editorDrawRows(void) {
int y;
for (y = 0; y < 24; y++) {
write(STDOUT_FILENO, "~\r\n", 3);
}
}
// \x1b is ESC
// [2J is an escape sequence that tells the terminal to clear the entire screen
void editorRefreshScreen(void) {
write(STDOUT_FILENO, "\x1b[2J", 4);
write(STDOUT_FILENO, "\x1b[H", 3);
editorDrawRows();
write(STDOUT_FILENO, "\x1b[H", 3);
}
/*** input ***/
void editorProcessKeypress(void) {
char c = editorReadKey();
switch (c) {
case CTRL_KEY('q'):
exit(0);
break;
}
}
/*** init ***/
int main(void) {
enableRawMode();
while (1) {
editorRefreshScreen();
editorProcessKeypress();
}
return 0;
}