From 36059938f691c278defc1f8318645b84dff08079 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Mon, 19 Aug 2019 13:23:54 -0400
Subject: [PATCH] Open files, and scroll through them

---
 kilo.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 111 insertions(+), 21 deletions(-)

diff --git a/kilo.c b/kilo.c
index 7b569a9..4012d9f 100644
--- a/kilo.c
+++ b/kilo.c
@@ -1,10 +1,16 @@
 /*** includes ***/
+
+#define _DEFAULT_SOURCE
+#define _BSD_SOURCE
+#define _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>
 
@@ -28,10 +34,18 @@ enum editorKey {
 
 /*** data ***/
 
+typedef struct erow {
+	int size;
+	char *chars;
+} erow;
+
 struct editorConfig {
 	int cx, cy;
+	int rowoff;
 	int screenrows;
 	int screencols;
+	int numrows;
+	erow *row;
 	struct termios orig_termios;
 };
 
@@ -216,6 +230,46 @@ int getWindowSize(int *rows, int *cols)
 	return 0;
 }
 
+/*** row operations ***/
+void editorAppendRow(char *s, size_t len)
+{
+	E.row = realloc(E.row, sizeof(erow) * (E.numrows + 1));
+
+	int at = E.numrows;
+	E.row[at].size = len;
+	E.row[at].chars = malloc(len + 1);
+	memcpy(E.row[at].chars, s, len);
+	E.row[at].chars[len] = '\0';
+	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 {
@@ -246,39 +300,66 @@ void abFree(struct abuf *ab)
 
 /*** 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;
+	}
+}
+
 void editorDrawRows(struct abuf *ab)
 {
 	int y;
 	for (y = 0; y < E.screenrows; y++)
 	{
-		if (y == E.screenrows / 3)
+		int filerow = y + E.rowoff;
+		if (filerow >= E.numrows)
 		{
-			char welcome[80];
-			int welcomelen = snprintf(welcome, sizeof(welcome),
-				"Kilo editor -- version %s", KILO_VERSION);
-
-			if (welcomelen > E.screencols)
+			if (E.numrows == 0 && y == E.screenrows / 3)
 			{
-				welcomelen = E.screencols;
-			}
+				char welcome[80];
+				int welcomelen = snprintf(welcome, sizeof(welcome),
+						"Kilo editor -- version %s", KILO_VERSION);
 
-			int padding = (E.screencols - welcomelen) / 2;
-			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].size;
+			if (len > E.screencols)
+			{
+				len = E.screencols;
+			}
+
+			abAppend(ab, E.row[filerow].chars, len);
 		}
 
 		abAppend(ab, "\x1b[K", 3);
@@ -291,6 +372,8 @@ void editorDrawRows(struct abuf *ab)
 
 void editorRefreshScreen()
 {
+	editorScroll();
+
 	struct abuf ab = ABUF_INIT;
 
 	abAppend(&ab, "\x1b[?25l", 6);
@@ -336,7 +419,7 @@ void editorMoveCursor(int key)
 		break;
 
 		case ARROW_DOWN:
-			if (E.cy != E.screenrows - 1)
+			if (E.cy < E.numrows)
 			{
 				E.cy++;
 			}
@@ -389,6 +472,9 @@ void initEditor()
 {
 	E.cx = 0;
 	E.cy = 0;
+	E.rowoff = 0;
+	E.numrows = 0;
+	E.row = NULL;
 
 	if (getWindowSize(&E.screenrows, &E.screencols) == -1)
 	{
@@ -396,10 +482,14 @@ void initEditor()
 	}
 }
 
-int main()
+int main(int argc, char *argv[])
 {
 	enableRawMode();
 	initEditor();
+	if (argc >= 2)
+	{
+		editorOpen(argv[1]);
+	}
 
 	while (1)
 	{