1 files changed, 87 insertions, 0 deletions
diff --git a/point.c b/point.c
new file mode 100644
index 0000000..e9d6472
--- /dev/null
+++ b/point.c
@@ -0,0 +1,87 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+struct point {
+	struct page *page;
+	uint16_t index;
+};
+
+uint16_t index_to_offset(struct point *point) {
+	if (point->index < point->page->gap_start) {
+		return point->index;
+	} else {
+		return point->index + (point->page->gap_end - point->page->gap_start);
+	}
+}
+
+uint8_t element(struct point *point) {
+	return point->page->buffer[index_to_offset(point)];
+}
+
+bool at_eof(struct point *point) {
+	return point->index == point->page->element_count;
+}
+
+void move_point_forward(struct point *point) {
+	if (point->index < point->page->element_count) {
+		point->index++;
+	}
+	if (point->index == point->page->element_count && point->page->next) {
+		point->index = 0;
+		point->page = point->page->next;
+	}
+}
+
+void move_point_backward(struct point *point) {
+	if (point->index == 0 && point->page->prev) {
+		point->index = point->page->prev->element_count;
+		point->page = point->page->prev;
+	}
+	if (point->index > 0) {
+		point->index--;
+	}
+}
+
+void align_gap(struct point *point) {
+	while (point->page->gap_end < index_to_offset(point)) {
+		move_gap_forward(point->page);
+	}
+	while (point->page->gap_end > index_to_offset(point)) {
+		move_gap_backward(point->page);
+	}
+}
+
+void insert_at_point(struct point *point, uint8_t c) {
+	if (point->page->gap_start == point->page->gap_end) {
+		split_page(point->page);
+		if (point->index >= PAGE_SIZE / 2) {
+			point->page = point->page->next;
+			point->index -= PAGE_SIZE / 2;
+		}
+	}
+	align_gap(point);
+	point->page->buffer[point->page->gap_start] = c;
+	point->page->gap_start++;
+	point->page->element_count++;
+	move_point_forward(point);
+}
+
+void delete_at_point(struct point *point) {
+	if (point->page->element_count == 0) {
+		if (point->page->prev) {
+			point->page = point->page->prev;
+			point->index = point->page->element_count;
+			free_page(point->page->next);
+		} else if (point->page->next) {
+			point->page = point->page->next;
+			point->index = 0;
+			free_page(point->page->prev);
+		}
+	}
+	align_gap(point);
+	if (point->page->gap_start != 0) {
+		point->page->gap_start--;
+		point->page->element_count--;
+		move_point_backward(point);
+	}
+}