render files with tabs etc

Makefile

@@ -1,2 +1,2 @@
 level: level.cpp
-	$(CC) level.cpp -o level -Wall -Wextra -pedantic
+	$(CC) level.cpp -o level -Wall -Wextra -pedantic

level.cpp

@@ -1,17 +1,25 @@
 /*** includes ***/
 
+#define _DEFAULT_SOURCE
+#define _BSD_SOURCE
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif //_GNU_SOURCE
+
 #include<ctype.h>
 #include<errno.h>
 #include<stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
+#include <sys/types.h>
 #include <termios.h>
 #include <unistd.h>
 
 /*** defines ***/
 
 #define LEVEL_VERSION "0.0.1"
+#define LEVEL_TAB_STOP 8
 
 #define CTRL_KEY(k) ((k) & 0x1f)
 
@@ -29,10 +37,22 @@ enum editorKey {
 
 /*** data ***/
 
+// erow stands for "editor row"
+typedef struct erow {
+	int size;
+	int resize;
+	char *chars;
+	char *render;
+} erow;
+
 struct editorConfig {
 	int cx, cy;
+	int rowoff;
+	int coloff;
 	int screenrows;
 	int screencols;
+	int numrows;
+	erow *row;
 	struct termios orig_termios;
 };
 
@@ -128,7 +148,7 @@ int editorReadKey() {
 	}
 }
 
-int getCursorPosition(int* rows, int* cols) {
+int getCursorPosition(int *rows, int *cols) {
 	char buf[32];
 	unsigned int i = 0;
 
@@ -160,10 +180,70 @@ int getWindowSize(int *rows, int *cols) {
 	}
 }
 
+/*** row operations ***/
+
+void editorUpdateRow(erow *row) {
+	int tabs = 0;
+	for (int j = 0; j < row->size; j++) {
+		if (row->chars[j] == '\t') tabs++;
+	}
+
+	free(row->render);
+	row->render = malloc(row->size + tabs*(LEVEL_TAB_STOP - 1) + 1);
+
+	int idx = 0;
+	for (int j = 0; j < row->size; j++) {
+		if (row->chars[j] == '\t') {
+			row->render[idx++] = ' ';
+			while (idx % LEVEL_TAB_STOP != 0) row->render(idx++) = ' ';
+		} else {
+			row->render[idx++] = row->chars[j];
+		}
+	}
+	row->render[idx] = '\0';
+	row->rsize = idx;
+}
+
+void editorAppendRow(char *s, size_t len) {
+	E.row = (erow*)realloc(E.row, sizeof(erow) * (E.numrows + 1));
+
+	int at = E.numrows;
+	E.row[at].size = len;
+	E.row[at].chars = (char*)malloc(len + 1);
+	memcpy(E.row[at].chars, s, len);
+	E.row[at].chars[len] = '\0';
+
+	E.row[at].rsize = 0;
+	E.row[at].render = NULL;
+	editorUpdateRow(&E.row[at]);
+
+	E.numrows++;
+}
+
+/*** file i/o ***/
+
+void editorOpen(char *filename) {
+	FILE *fp = fopen(filename, "r");
+	if (!fp) die("fopen");
+
+	char *line = NULL;
+	size_t linecap = 0;
+	ssize_t linelen;
+	while ((linelen = getline(&line, &linecap, fp)) != -1) {
+		while (linelen > 0 && (line[linelen - 1] == '\n' ||
+								 line[linelen - 1] == '\r'))
+			linelen--;
+		editorAppendRow(line, linelen);
+	}
+	free(line);
+	fclose(fp);
+
+}
+
 /*** append buffer ***/
 
 struct abuf {
-	char* b;
+	char *b;
 	int len;
 };
 
@@ -178,28 +258,43 @@ void abAppend(struct abuf *ab, const char *s, int len) {
 	ab->len += len;
 }
 
-void abFree(struct abuf* ab) {
+void abFree(struct abuf *ab) {
 	free(ab->b);
 }
 
 /*** output ***/
 
+void editorScroll() {
+	if (E.cy < E.rowoff) E.rowoff = E.cy;
+	if (E.cy >= E.rowoff + E.screenrows) E.rowoff = E.cy - E.screenrows + 1;
+	if (E.cx < E.coloff) E.coloff = E.cx;
+	if (E.cx >= E.coloff + E.screencols) E.coloff = E.cx - E.screencols + 1;
+}
+
 void editorDrawRows(struct abuf *ab) {
 	for (int y = 0; y < E.screenrows; y++) {
-		if (y == E.screenrows / 3) {
+		int filerow = y + E.rowoff;
-			char welcome[80];
+		if (filerow >= E.numrows) {
-			int welcomelen = snprintf(welcome, sizeof(welcome),
+			if (E.numrows == 0 && y == E.screenrows / 3) {
-				"Level editor -- version %s", LEVEL_VERSION);
+				char welcome[80];
-			if (welcomelen > E.screencols) welcomelen = E.screencols;
+				int welcomelen = snprintf(welcome, sizeof(welcome),
-			int padding = (E.screencols - welcomelen) / 2;
+					"Level editor -- version %s", LEVEL_VERSION);
-			if (padding) {
+				if (welcomelen > E.screencols) welcomelen = E.screencols;
+				int padding = (E.screencols - welcomelen) / 2;
+				if (padding) {
+					abAppend(ab, "~", 1);
+					padding--;
+				}
+				while (padding--) abAppend(ab, " ", 1);
+				abAppend(ab, welcome, welcomelen);
+			} else {
 				abAppend(ab, "~", 1);
-				padding--;
 			}
-			while (padding--) abAppend(ab, " ", 1);
-			abAppend(ab, welcome, welcomelen);
 		} else {
-			abAppend(ab, "~", 1);
+			int len = E.row[filerow].rsize - E.coloff;
+			if (len < 0) len = 0;
+			if (len > E.screencols) len = E.screencols;
+			abAppend(ab, &E.row[filerow].render[E.coloff], len);
 		}
 
 		abAppend(ab, "\x1b[K", 3);
@@ -208,6 +303,8 @@ void editorDrawRows(struct abuf *ab) {
 }
 
 void editorRefreshScreen() {
+	editorScroll();
+
 	struct abuf ab = ABUF_INIT;
 
 	abAppend(&ab, "\x1b[?25l", 6);
@@ -217,7 +314,8 @@ void editorRefreshScreen() {
 	editorDrawRows(&ab);
 
 	char buf[32];
-	snprintf(buf, sizeof(buf), "\x1b[%d;%dH", E.cy + 1, E.cx + 1);
+	snprintf(buf, sizeof(buf), "\x1b[%d;%dH", (E.cy - E.rowoff) + 1, 
+												(E.cx - E.coloff) + 1);
 	abAppend(&ab, buf, strlen(buf));
 
 	abAppend(&ab, "\x1b[?25h", 6);
@@ -229,20 +327,26 @@ void editorRefreshScreen() {
 /*** input ***/
 
 void editorMoveCursor(int key) {
+	erow* row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
+
 	switch (key) {
 		case ARROW_LEFT:
 			if (E.cx != 0) E.cx--;
 			break;
 		case ARROW_RIGHT:
-			if (E.cx != E.screencols -1) E.cx++;
+			if (row && E.cx < row->size) E.cx++;
 			break;
 		case ARROW_UP:
 			if (E.cy != 0) E.cy--;
 			break;
 		case ARROW_DOWN:
-			if (E.cy != E.screenrows - 1) E.cy++;
+			if (E.cy < E.numrows - 1) E.cy++;
 			break;
 	}
+
+	row = (E.cy >= E.numrows) ? NULL : &E.row[E.cy];
+	int rowlen = row ? row->size : 0;
+	if (E.cx > rowlen) E.cx = rowlen;
 }
 
 void editorProcessKeypress() {
@@ -287,13 +391,18 @@ void editorProcessKeypress() {
 void initEditor() {
 	E.cx = 0;
 	E.cy = 0;
+	E.rowoff = 0;
+	E.coloff = 0;
+	E.numrows = 0;
+	E.row = NULL;
 
 	if (getWindowSize(&E.screenrows, &E.screencols) == -1) die("getWindowSize");
 }
 
-int main() {
+int main(int argc, char *argv[]) {
 	enableRawMode();
 	initEditor();
+	if (argc >= 2) editorOpen(argv[1]);
 
 	while (1) {
 		editorRefreshScreen();