Chapter4Halfway

kilo.c

@@ -1,11 +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 <unistd.h>
 #include <termios.h>
 
@@ -30,11 +35,20 @@ enum editorKey
 
 /*** data ***/
 
+typedef struct erow {
+  int size;
+  char *chars;
+} erow;
+
 struct editorConfig
 {
   int cx, cy;
+  int rowoff; // Row offset
+  int coloff; // Col offset
   int screenrows;
   int screencols;
+  int numrows;
+  erow *row;
   struct termios orig_termios;
 };
 
@@ -191,6 +205,37 @@ int getWindowSize(int *rows, int *cols)
   }
 }
 
+/*** 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
@@ -222,33 +267,56 @@ 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;
+  }
+  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)
 {
   int y;
   for (y = 0; y < E.screenrows; y++)
   {
-    if (y == E.screenrows / 3)
-    {
-      char welcome[80];
-      int welcomelen = snprintf(welcome, sizeof(welcome),
-                                "Kilo editor -- version %s", KILO_VERSION);
-      if (welcomelen > E.screencols)
-        welcomelen = E.screencols;
-      int padding = (E.screencols - welcomelen) / 2;
-      if (padding)
+    int filerow = y + E.rowoff;
+    if (filerow >= E.numrows) {
+      if (E.numrows == 0 && y == E.screenrows / 3)
+      {
+        char welcome[80];
+        int welcomelen = snprintf(welcome, sizeof(welcome),
+                                  "Kilo editor -- version %s", KILO_VERSION);
+        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);
-    }
 
+    } else {
+      int len = E.row[filerow].size - E.coloff;
+      if (len < 0) len = 0;
+      if (len > E.screencols) len = E.screencols;
+      abAppend(ab, &E.row[filerow].chars[E.coloff], len);
+    }
     abAppend(ab, "\x1b[K", 3);
     if (y < E.screenrows - 1)
     {
@@ -259,6 +327,7 @@ void editorDrawRows(struct abuf *ab)
 
 void editorRefreshScreen()
 {
+  editorScroll();
   struct abuf ab = ABUF_INIT;
 
   abAppend(&ab, "\x1b[?25l", 6);
@@ -267,7 +336,7 @@ 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);
@@ -279,6 +348,7 @@ void editorRefreshScreen()
 
 void editorMoveCursor(int key)
 {
+  erow *row = (E.cy >=E.numrows) ? NULL : &E.row[E.cy];
   switch (key)
   {
   case ARROW_LEFT:
@@ -288,10 +358,9 @@ void editorMoveCursor(int key)
     }
     break;
   case ARROW_RIGHT:
-    if (E.cx != E.screencols - 1)
-    {
-      E.cx++;
-    }
+      if (row && E.cx < row->size) {
+        E.cx++;
+      }
     break;
 
   case ARROW_UP:
@@ -301,7 +370,7 @@ void editorMoveCursor(int key)
     }
     break;
   case ARROW_DOWN:
-    if (E.cy != E.screenrows - 1)
+    if (E.cy < E.numrows)
     {
       E.cy++;
     }
@@ -353,14 +422,22 @@ 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)
   {