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#include <stdint.h>
#include <assert.h>
#include <stdbool.h>
size_t byte_type(uint8_t byte) {
if (byte & 1 << 7) {
if (byte & 1 << 6) {
if (byte & 1 << 5) {
if (byte & 1 << 4) {
return 4;
} else {
return 3;
}
} else {
return 2;
}
} else {
return 0;
}
} else {
return 1;
}
}
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;
}
}
void pop_byte() {
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;
}
}
}
public:
Point() : page(new Page()), index(0) {}
Point(Page *page, uint16_t index) : page(page), index(index) {}
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) {
do {
if (index == page->element_count) move_forward();
move_forward();
} while (!byte_type(next_byte()));
}
void operator--(int) {
do {
move_backward();
if (index == 0) move_backward();
} while (!byte_type(next_byte()));
}
wchar_t element() {
size_t type = byte_type(next_byte());
wchar_t rune = next_byte() & (0xff >> type);
Point iter(*this);
for (size_t i = 1; i < type; i++) {
rune <<= 6;
iter.move_forward();
rune |= (iter.next_byte() & 0x3f);
}
return rune;
}
uint64_t seek(uint8_t c, uint64_t limit) {
uint64_t travel_distance = 0;
while (!at_end() && next_byte() != c && travel_distance < limit) {
(*this)++;
travel_distance++;
}
return travel_distance;
}
uint64_t rseek(uint8_t c, uint64_t limit) {
uint64_t travel_distance = 0;
while (!at_start() && prev_byte() != c && travel_distance < limit) {
(*this)--;
travel_distance++;
}
return travel_distance;
}
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() {
while (!byte_type(prev_byte())) {
pop_byte();
}
pop_byte();
}
};
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