pound: implement backspace

apps/pound.c

@@ -46,6 +46,10 @@ void die(char *reason, bool clear) {
     cpm_warmboot();
 }
 
+void __zfree_null(void) {
+    die("zfree NULL", true);
+}
+
 // -------------------- ROW OPERATIONS --------------------
 
 // return false when out of memory
@@ -74,6 +78,18 @@ bool editorAppendRow(char *s, size_t len) {
     return E.dirty = true;
 }
 
+void editorFreeRow(struct erow *row) {
+    zfree(row->chars);
+}
+
+void editorDelRow(int at) {
+    if (at < 0 || at >= E.numrows) return;
+    editorFreeRow(&E.row[at]);
+    memmove(&E.row[at], &E.row[at + 1], sizeof(struct erow) * (E.numrows - at - 1));
+    E.numrows--;
+    E.dirty = true;
+}
+
 bool editorRowInsertChar(struct erow *row, int at, uint8_t c) {
     if (at < 0 || at > row->size) at = row->size;
 
@@ -88,6 +104,25 @@ bool editorRowInsertChar(struct erow *row, int at, uint8_t c) {
     return E.dirty = true;
 }
 
+// return false when out of memory
+//
+bool editorRowAppendString(struct erow *row, char *s, size_t len) {
+    void *tmp = zrealloc(row->chars, row->size + len + 1);
+    if (!tmp) return false;
+    row->chars = tmp;
+    memcpy(&row->chars[row->size], s, len);
+    row->size += len;
+    row->chars[row->size] = '\0';
+    return E.dirty = true;
+}
+
+void editorRowDelChar(struct erow *row, int at) {
+    if (at < 0 || at >= row->size) return;
+    memmove(&row->chars[at], &row->chars[at + 1], row->size - at);
+    row->size--;
+    E.dirty = true;;
+}
+
 // -------------------- EDITOR OPERATIONS --------------------
 
 void editorDrawStatusMsg(char *msg);
@@ -104,6 +139,27 @@ void editorInsertChar(uint8_t c) {
     editorDrawStatusMsg(OUT_OF_MEMORY_STRING);
 }
 
+void editorDelChar(void) {
+    if (E.cy == E.numrows) return;
+    if (E.cx == 0 && E.cy == 0) return;
+
+    struct erow *row = &E.row[E.cy];
+    if (E.cx > 0) {
+        editorRowDelChar(row, E.cx - 1);
+        E.cx--;
+    } else {
+        E.cx = E.row[E.cy - 1].size;
+        if (!editorRowAppendString(&E.row[E.cy - 1], row->chars, row->size))
+            goto failed;
+        editorDelRow(E.cy);
+        E.cy--;
+    }
+    return;
+
+failed:
+    editorDrawStatusMsg(OUT_OF_MEMORY_STRING);
+}
+
 // -------------------- FILE INPUT/OUTPUT --------------------
 
 static inline uint8_t write_byte(FCB *fcb, uint8_t c, uint8_t *opos) {
@@ -414,6 +470,12 @@ void editorProcessKeypress(void) {
                 editorMoveCursor(c == CTRL('R') ? CTRL('E') : CTRL('X'));
         }
         break;
+
+    case 127:
+    case CTRL('H'):
+        editorDelChar();
+        break;
+
     case CTRL('K'):
         ctrlk = true;
         break;