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#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#define NELEM(x) (sizeof(x) / sizeof(x[0]))
typedef int T;
#define START_MAP_CAPACITY 4
#define CHUNK_CAPACITY 17
struct deque {
T **map;
size_t map_begin;
size_t map_end;
size_t map_capacity;
size_t offset;
size_t size;
};
void
deque_init(struct deque *d)
{
d->map_begin = 0;
d->map_end = 0;
d->offset = 0;
d->size = 0;
// TODO: Error handling
d->map = calloc(START_MAP_CAPACITY, sizeof *d->map);
if ( d->map != NULL ) {
d->map_capacity = START_MAP_CAPACITY;
for ( size_t i = 0; i != d->map_capacity; ++i ) {
d->map[i] = NULL;
}
}
}
void
deque_free(struct deque *d)
{
// free all chunks
for ( size_t i = 0; i != d->map_capacity; ++i ) {
free(d->map[i]);
}
// free the map itself
free(d->map);
}
static void
grow_map(struct deque *d)
{
const size_t capacity = d->map_capacity + d->map_capacity / 2;
T ** map = calloc(capacity, sizeof *map);
// copy elements
size_t i;
for ( i = 0; i != d->map_capacity; ++i ) {
map[i] = d->map[(i + d->map_begin) % d->map_capacity];
}
// initialize the rest (new) elements with NULL
for ( ; i != capacity; ++i ) {
map[i] = NULL;
}
// free old & assign new map
free(d->map);
d->map = map;
// adjust pointers
d->map_begin = 0;
d->map_end = d->map_capacity - 1;
// set new map_capacity
d->map_capacity = capacity;
}
static void
map_append_chunk(struct deque *d)
{
size_t next = (d->map_end + 1) % d->map_capacity;
if ( next == d->map_begin ) { // Resize the map
grow_map(d);
next = d->map_end + 1;
}
d->map[d->map_end] = calloc(CHUNK_CAPACITY, sizeof **d->map);
d->map_end = next;
}
static void
map_prepend_chunk(struct deque *d)
{
size_t prev = (d->map_begin + d->map_capacity - 1) % d->map_capacity;
if ( prev == d->map_end ) {
grow_map(d);
prev = d->map_capacity - 1;
}
d->map[prev] = calloc(CHUNK_CAPACITY, sizeof **d->map);
d->map_begin = prev;
}
static void
map_remove_front_chunk(struct deque *d)
{
if ( d->map_begin == d->map_end )
return;
const size_t next = (d->map_begin + 1) % d->map_capacity;
free(d->map[d->map_begin]);
d->map[d->map_begin] = NULL;
d->map_begin = next;
}
static void
map_remove_tail_chunk(struct deque *d)
{
if ( d->map_begin == d->map_end )
return;
const size_t prev = (d->map_end + d->map_capacity - 1) % d->map_capacity;
free(d->map[prev]);
d->map[prev] = NULL;
d->map_end = prev;
}
void
deque_get_at(struct deque *d, size_t idx, T *data)
{
const size_t offset = d->offset + idx;
const size_t chunk_off = offset % CHUNK_CAPACITY;
const size_t chunk_num = (offset / CHUNK_CAPACITY + d->map_begin) % d->map_capacity;
*data = d->map[chunk_num][chunk_off];
}
void
deque_push_back(struct deque *d, T data)
{
const size_t offset = d->offset + d->size;
const size_t chunk_off = offset % CHUNK_CAPACITY;
size_t chunk_num = (offset / CHUNK_CAPACITY + d->map_begin) % d->map_capacity;
if ( chunk_num == d->map_end ) {
map_append_chunk(d);
chunk_num = (offset / CHUNK_CAPACITY + d->map_begin) % d->map_capacity;
}
d->map[chunk_num][chunk_off] = data;
++d->size;
}
void
deque_push_front(struct deque *d, T data)
{
if ( d->offset == 0 ) { // Im ersten Element ist kein Platz mehr frei!
map_prepend_chunk(d);
d->offset = CHUNK_CAPACITY;
}
++d->size;
--d->offset;
size_t chunk_num = (d->offset / CHUNK_CAPACITY + d->map_begin) % d->map_capacity;
d->map[chunk_num][d->offset] = data;
}
bool
deque_pop_back(struct deque *d, T *data)
{
if ( d->size == 0 )
return false;
--d->size;
const size_t offset = d->offset + d->size;
const size_t chunk_off = offset % CHUNK_CAPACITY;
const size_t chunk_num = (offset / CHUNK_CAPACITY + d->map_begin) % d->map_capacity;
*data = d->map[chunk_num][chunk_off];
if ( d->size == 0 || chunk_off == 0 ) {
map_remove_tail_chunk(d);
}
return true;
}
bool
deque_pop_front(struct deque *d, T *data)
{
if ( d->size == 0 )
return false;
const size_t chunk_num = (d->offset / CHUNK_CAPACITY + d->map_begin) % d->map_capacity;
*data = d->map[chunk_num][d->offset];
--d->size;
++d->offset;
if ( d->size == 0 || d->offset == CHUNK_CAPACITY ) {
map_remove_front_chunk(d);
d->offset = 0;
}
return true;
}
static void
deque_show(struct deque *d)
{
printf("first: %zu -- last: %zu -- size: %zu -- map_capacity: %zu -- offset: %zu\n",
d->map_begin, d->map_end, d->size, d->map_capacity, d->offset);
for ( size_t i = 0; i != d->map_capacity; ++i ) {
printf("%zu(%p) ", i, (void *) d->map[i]);
}
puts("");
}
int
main(void)
{
struct deque c;
deque_init(&c);
for ( int i = 0; i != 100; ++i ) {
deque_push_back(&c, i);
//deque_show(&c);
}
for ( int i = 0; i != 100; ++i ) {
deque_push_front(&c, 1000 + i);
}
T data;
while ( deque_pop_front(&c, &data) ) {
printf("%u, ", data);
}
putchar('\n');
deque_show(&c);
deque_free(&c);
return 0;
}
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