1 files changed, 88 insertions, 0 deletions
diff --git a/page.cpp b/page.cpp
new file mode 100644
index 0000000..7f56fc9
--- /dev/null
+++ b/page.cpp
@@ -0,0 +1,88 @@
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#ifndef PAGE_SIZE
+#define PAGE_SIZE 4096
+#endif
+
+struct Page {
+	uint8_t *elements;
+	Page *next;
+	Page *prev;
+	uint16_t gap_start;
+	uint16_t gap_end;
+	uint16_t element_count;
+
+	Page() {
+		elements = new uint8_t[PAGE_SIZE];
+		gap_start = 0;
+		gap_end = PAGE_SIZE;
+		element_count = 0;
+		next = nullptr;
+		prev = nullptr;
+	}
+
+	~Page() {
+		if (prev) prev->next = next;
+		if (next) next->prev = prev;
+		delete[] elements;
+	}
+
+	void split() {
+		Page *front = new Page();
+
+		memcpy(front->elements, elements + PAGE_SIZE / 2, PAGE_SIZE / 2);
+
+		front->gap_start = PAGE_SIZE / 2;
+		front->gap_end = PAGE_SIZE;
+		front->element_count = PAGE_SIZE / 2;
+
+		gap_start = PAGE_SIZE / 2;
+		gap_end = PAGE_SIZE;
+		element_count = PAGE_SIZE / 2;
+
+		if (next) {
+			next->prev = front;
+		}
+		front->next = next;
+		front->prev = this;
+		next = front;
+	}
+
+	void copy_to(Page *dest) {
+		memcpy(dest->elements, elements, PAGE_SIZE);
+		dest->gap_start = gap_start;
+		dest->gap_end = gap_end;
+		dest->element_count = element_count;
+	}
+
+	void operator++(int) {
+		assert(gap_end < PAGE_SIZE);
+		elements[gap_start] = elements[gap_end];
+		gap_start++;
+		gap_end++;
+	}
+
+	void operator--(int) {
+		assert(gap_start > 0);
+		gap_end--;
+		gap_start--;
+		elements[gap_end] = elements[gap_start];
+	}
+
+	void push(uint8_t c) {
+		assert(element_count < PAGE_SIZE);
+		elements[gap_start] = c;
+		gap_start++;
+		element_count++;
+	}
+
+	void pop() {
+		assert(gap_start > 0);
+		gap_start--;
+		element_count--;
+	}
+
+};