4 files changed, 364 insertions, 0 deletions
diff --git a/src/server/buffer.cpp b/src/server/buffer.cpp
new file mode 100644
index 0000000..7b4c92d
--- /dev/null
+++ b/src/server/buffer.cpp
@@ -0,0 +1,45 @@
+struct Buffer {
+	const char *name;
+	Page *storage;
+
+	Buffer(const char *name) : name(name), storage(new Page()) {}
+
+	void free_storage() {
+		while (storage) {
+			Page *iter = storage;
+			storage = storage->next;
+			delete iter;
+		}
+	}
+
+	void read_file(const char *pathname) {
+		free_storage();
+		int file = open(pathname, O_RDONLY);
+		storage = new Page();
+		int bytes_read = read(file, storage->elements, PAGE_SIZE);
+		Page *iter = storage;
+		while (bytes_read > 0) {
+			iter->gap_start = bytes_read;
+			iter->element_count = bytes_read;
+			iter->next = new Page();
+			iter->next->prev = iter;
+			iter = iter->next;
+			bytes_read = read(file, iter->elements, PAGE_SIZE);
+		}
+		if (iter->element_count == 0) {
+			delete iter;
+		}
+		close(file);
+	}
+
+	void write_file(const char *pathname) {
+		int file = open(pathname, O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+		Page *iter = storage;
+		while (iter) {
+			write(file, iter->elements, iter->gap_start);
+			write(file, iter->elements + iter->gap_end, PAGE_SIZE - iter->gap_end);
+			iter = iter->next;
+		}
+		close(file);
+	}
+};
diff --git a/src/server/client.cpp b/src/server/client.cpp
new file mode 100644
index 0000000..bed62c5
--- /dev/null
+++ b/src/server/client.cpp
@@ -0,0 +1,93 @@
+#define MAX_MSG_SIZE 128
+#define pos(x, y) (x) + (y) * window_w
+
+struct Client {
+	int sockfd;
+	Point cursor;
+	Point window_start;
+
+	Client(const Buffer &b) : cursor(b), window_start(cursor) {}
+
+	void parse_message() {
+		int8_t message[MAX_MSG_SIZE] = {};
+		read(sockfd, message, MAX_MSG_SIZE - 1);
+		int8_t *iter = message;
+		while (*iter) {
+			switch (*iter) {
+				case OP_MOVE1:
+					move(iter[1]);
+					iter += 2;
+					break;
+				case OP_MOVE2:
+					move(decode2(iter, 1));
+					iter += 3;
+					break;
+				case OP_MOVE4:
+					move(decode4(iter, 1));
+					iter += 5;
+					break;
+				case OP_MOVE8:
+					move(decode8(iter, 1));
+					iter += 9;
+					break;
+				case OP_INSERT:
+					push(iter[1]);
+					iter += 2;
+					break;
+				case OP_DELETE:
+					pop();
+					iter += 1;
+					break;
+				case OP_SHOW:
+					show(decode2(iter, 1), decode2(iter, 3));
+					iter += 6;
+					break;
+			}
+		}
+	}
+
+	void show(size_t window_w, size_t window_h) {
+		char *view = new char[window_w * window_h];
+
+		Point window_end(window_start);
+		for (int i = 0; i < window_h; i++) {
+			for (int j = 0; j < window_w; j++) {
+				view[pos(j, i)] = window_end.element();
+				if (window_end.element() == '\n') {
+					for (int k = j + 1; k < window_w; k++) {
+						view[pos(k, i)] = 0;
+					}
+					j = window_w;
+				} else if (window_end.element() == '\t') {
+					for (int k = j + 1; k < j + 8; k++) {
+						view[pos(k, i)] = 0;
+					}
+					j = j + 7;
+				}
+				window_end++;
+			}
+		}
+
+		write(sockfd, view, window_w * window_h);
+		delete[] view;
+	}
+
+	void move(int64_t target) {
+		while (target > 0) {
+			cursor++;
+			target--;
+		}
+		while (target < 0) {
+			cursor--;
+			target++;
+		}
+	}
+
+	void push(int8_t input) {
+		cursor.push(input);
+	}
+
+	void pop() {
+		cursor.pop();
+	}
+};
diff --git a/src/server/page.cpp b/src/server/page.cpp
new file mode 100644
index 0000000..77cf686
--- /dev/null
+++ b/src/server/page.cpp
@@ -0,0 +1,87 @@
+#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 move_gap_forward() {
+		elements[gap_start] = elements[gap_end];
+		gap_start++;
+		gap_end++;
+	}
+
+	void move_gap_backward() {
+		gap_end--;
+		gap_start--;
+		elements[gap_end] = elements[gap_start];
+	}
+
+	void push(uint8_t c) {
+		elements[gap_start] = c;
+		gap_start++;
+		element_count++;
+	}
+
+	void pop() {
+		gap_start--;
+		element_count--;
+	}
+
+	bool is_empty() {
+		return element_count == 0;
+	}
+
+	bool is_full() {
+		return gap_start == gap_end;
+	}
+
+};
diff --git a/src/server/point.cpp b/src/server/point.cpp
new file mode 100644
index 0000000..ab9f70f
--- /dev/null
+++ b/src/server/point.cpp
@@ -0,0 +1,139 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+struct Point {
+	Page *page;
+	uint16_t index;
+
+	uint16_t index_to_offset() {
+		if (index < page->gap_start) {
+			return index;
+		} else {
+			return index + (page->gap_end - page->gap_start);
+		}
+	}
+
+	uint8_t prev_byte() {
+		if (index == 0) {
+			if (page->prev) {
+				return page->prev->elements[Point(page->prev, page->prev->element_count - 1).index_to_offset()];
+			} else {
+				return 0;
+			}
+		} else {
+			return page->elements[Point(page, index - 1).index_to_offset()];
+		}
+	}
+
+	uint8_t next_byte() {
+		if (index == page->element_count) {
+			if (page->next) {
+				return page->next->elements[Point(page->next, 0).index_to_offset()];
+			} else {
+				return 0;
+			}
+		} else {
+			return page->elements[index_to_offset()];
+		}
+	}
+
+	void move_forward() {
+		if (index < page->element_count) {
+			index++;
+		} else if (page->next) {
+			page = page->next;
+			index = 0;
+		}
+	}
+
+	void move_backward() {
+		if (index > 0) {
+			index--;
+		} else if (page->prev) {
+			page = page->prev;
+			index = page->element_count;
+		}
+	}
+
+
+	public:
+
+	Point() : page(0), index(0) {}
+	Point(Page* page, uint16_t index) : page(page), index(index) {}
+	Point(const Buffer &b) : page(b.storage), index(0) {}
+	Point(const Point &p) : page(p.page), index(p.index) {}
+
+	bool operator==(Point p) {
+		return page == p.page && index == p.index;
+	}
+
+	bool operator!=(Point p) {
+		return page != p.page || index != p.index;
+	}
+
+	bool at_start() {
+		return index == 0 && !page->prev;
+	}
+
+	bool at_end() {
+		return index == page->element_count && !page->next;
+	}
+
+	void operator++(int) {
+		if (index == page->element_count) move_forward();
+		move_forward();
+	}
+
+	void operator--(int) {
+		move_backward();
+		if (index == 0) move_backward();
+	}
+
+	char element() {
+		return next_byte();
+	}
+
+	void align_gap() {
+		while (page->gap_end < index_to_offset()) {
+			page->move_gap_forward();
+		}
+		while (page->gap_end > index_to_offset()) {
+			page->move_gap_backward();
+		}
+	}
+
+	void push(uint8_t c) {
+		if (page->is_full()) {
+			page->split();
+			if (index >= PAGE_SIZE / 2) {
+				page = page->next;
+				index -= PAGE_SIZE / 2;
+			}
+		}
+		align_gap();
+		page->push(c);
+		move_forward();
+	}
+
+	void pop() {
+		if (!at_start()) {
+			align_gap();
+			page->pop();
+			move_backward();
+			if (index == 0) {
+				move_backward();
+			}
+		}
+		if (page->is_empty()) {
+			if (page->prev) {
+				move_backward();
+				delete page->next;
+			} else if (page->next) {
+				page->next->copy_to(page);
+				delete page->next;
+				index = 0;
+			}
+		}
+	}
+
+};