Finish chapter 3

Left reading of some terminal codes that I don't think I'll need

kilo.c

@@ -1,12 +1,38 @@
-#include <errno.h>
 #include <ctype.h>
+#include <errno.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/ioctl.h>
 #include <termios.h>
 #include <unistd.h>
 
+struct abuf {
+    char *p;
+    int len;
+};
+
+struct {
+    struct termios orig_termios;
+    int rows;
+    int cols;
+    int cx, cy;
+} E = { .cx = 0, .cy = 0 };
+
+enum keys {
+    ARROW_UP = 0x100 + 1,
+    ARROW_DOWN,
+    ARROW_LEFT,
+    ARROW_RIGHT
+};
+
+#define ABUF_INIT {NULL, 0}
+
+void ab_append(struct abuf *, const char *);
+void ab_free(struct abuf *);
+void ab_write(struct abuf *);
+
 void enable_raw_mode();
 void disable_raw_mode();
 
@@ -16,21 +42,14 @@ int read_cursor_position(int *, int *);
 void editor_init();
 void editor_redraw_screen();
 void editor_clear_screen();
-void editor_draw_rows();
+void editor_draw_rows(struct abuf *);
 void editor_process_key();
-char editor_read_key();
+int editor_read_key();
 
 void die(const char *);
 
 #define CTRL_KEY(key) ((key) & 0x1f)
 
-struct {
-    struct termios orig_termios;
-    int rows;
-    int cols;
-    bool raw;
-} E = { .raw = false };
-
 int main() {
     editor_init();
 
@@ -54,8 +73,6 @@ void editor_init() {
 }
 
 void enable_raw_mode() {
-    if (E.raw) return;
-
     if (tcgetattr(STDIN_FILENO, &E.orig_termios) == -1) die("tcgetattr");
     atexit(disable_raw_mode);
 
@@ -66,8 +83,6 @@ void enable_raw_mode() {
     raw.c_cc[VTIME] = 1;
 
     if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw) == -1) die("tcsetattr");
-
-    E.raw = true;
 }
 
 void disable_raw_mode() {
@@ -85,6 +100,7 @@ int get_window_size(int *rows, int *cols) {
         return 0;
     } else {
         if (write(STDOUT_FILENO, "\x1b[999C\x1b[999B", 12) != 12) return -1;
+
         return read_cursor_position(rows, cols);
     }
 
@@ -93,7 +109,7 @@ int get_window_size(int *rows, int *cols) {
 
 int read_cursor_position(int *rows, int *cols) {
     char buf[32];
-    unsigned int i = 0;
+    int i = 0;
 
     if (write(STDOUT_FILENO, "\x1b[6n", 4) != 4) return -1;
 
@@ -101,7 +117,7 @@ int read_cursor_position(int *rows, int *cols) {
     if (read(STDIN_FILENO, buf, 1) != 1 && *buf != '[') return -1;
 
     do {
-        if (i == sizeof(buf)) return -1;
+        if (i == (int) sizeof(buf)) return -1;
         if (read(STDIN_FILENO, buf+i, 1) == 0) break;
     } while(buf[i++] != 'R');
     buf[i-1] = '\0';
@@ -112,11 +128,21 @@ int read_cursor_position(int *rows, int *cols) {
 }
 
 void editor_redraw_screen() {
-    editor_clear_screen();
+    struct abuf ab = ABUF_INIT;
 
-    editor_draw_rows();
+    ab_append(&ab, "\x1b[?25l");
+    ab_append(&ab, "\x1b[H");
 
-    write(STDOUT_FILENO, "\x1b[H", 3);
+    editor_draw_rows(&ab);
+
+    char buf[32];
+    snprintf(buf, sizeof(buf), "\x1b[%d;%dH", E.cy + 1, E.cx + 1);
+    ab_append(&ab, buf);
+
+    ab_append(&ab, "\x1b[?25h");
+
+    ab_write(&ab);
+    ab_free(&ab);
 }
 
 void editor_clear_screen() {
@@ -124,29 +150,71 @@ void editor_clear_screen() {
     write(STDOUT_FILENO, "\x1b[H", 3);
 }
 
-void editor_draw_rows() {
-    for (int y = 0; y < E.rows - 1; y++)
-        write(STDOUT_FILENO, "~\r\n", 3);
-    write(STDOUT_FILENO, "~", 1);
+void editor_draw_rows(struct abuf *ab) {
+    for (int y = 0; y < E.rows; y++) {
+        ab_append(ab, "~");
+
+        ab_append(ab, "\x1b[K");
+        if (y < E.rows - 1) ab_append(ab, "\r\n");
+    }
 }
 
 void editor_process_key() {
-    char c = editor_read_key();
+    int c = editor_read_key();
+
     switch (c) {
         case CTRL_KEY('Q'):
             editor_clear_screen();
             exit(0);
             break;
+
+        case ARROW_LEFT:
+            if (E.cx > 0) E.cx--;
+            break;
+        case ARROW_DOWN:
+            if (E.cy < E.rows - 1) E.cy++;
+            break;
+        case ARROW_UP:
+            if (E.cy > 0) E.cy--;
+            break;
+        case ARROW_RIGHT:
+            if (E.cx < E.cols - 1) E.cx++;
+            break;
         default:
             printf("%d\r\n", c);
             break;
     }
 }
 
-char editor_read_key() {
+int editor_read_key() {
     char c;
     while (read(STDIN_FILENO, &c, 1) == 0);
-    return c;
+
+    if (c == '\x1b') {
+        char buf[2];
+
+        if (read(STDIN_FILENO, buf+0, 1) != 1) return c;
+        if (read(STDIN_FILENO, buf+1, 1) != 1) return c;
+
+        if (buf[0] == '[') {
+            switch (buf[1]) {
+                case 'A':
+                    return ARROW_UP;
+                    break;
+                case 'B':
+                    return ARROW_DOWN;
+                    break;
+                case 'C':
+                    return ARROW_RIGHT;
+                    break;
+                case 'D':
+                    return ARROW_LEFT;
+                    break;
+            }
+        }
+    }
+
+    return (int) c;
 }
 
 void die(const char *s) {
@@ -155,3 +223,20 @@ void die(const char *s) {
     perror(s);
     exit(1);
 }
+
+void ab_append(struct abuf *ab, const char *s) {
+    int len = strlen(s);
+
+    ab->p = realloc(ab->p, ab->len + len);
+    memcpy(ab->p + ab->len, s, len);
+
+    ab->len += len;
+}
+
+void ab_write(struct abuf *ab) {
+    write(STDOUT_FILENO, ab->p, ab->len);
+}
+
+void ab_free(struct abuf *ab) {
+    free(ab->p);
+}