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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 10
struct deque {
T **map;
size_t first_chunk;
size_t last_chunk;
size_t capacity;
};
void
deque_init(struct deque *d)
{
d->first_chunk = 0;
d->last_chunk = 0;
// TODO: Error handling
d->map = calloc(START_MAP_CAPACITY, sizeof *d->map);
if ( d->map != NULL ) {
d->capacity = START_MAP_CAPACITY;
for ( size_t i = 0; i != d->capacity; ++i ) {
d->map[i] = NULL;
}
}
}
void
deque_free(struct deque *d)
{
// free all chunks
for ( size_t i = 0; i != d->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->capacity + (d->capacity / 2);
T ** map = calloc(capacity, sizeof *map);
// copy elements
size_t i;
for ( i = 0; i != d->capacity; ++i ) {
map[i] = d->map[(i + d->first_chunk) % d->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->first_chunk = 0;
d->last_chunk = d->capacity - 1;
// set new capacity
d->capacity = capacity;
}
static void
append_chunk(struct deque *d)
{
size_t next = (d->last_chunk + 1) % d->capacity;
if ( next == d->first_chunk ) { // Resize the map
grow_map(d);
next = d->last_chunk + 1;
}
d->map[d->last_chunk] = calloc(CHUNK_CAPACITY, sizeof **d->map);
d->last_chunk = next;
}
static void
prepend_chunk(struct deque *d)
{
size_t prev = (d->first_chunk + d->capacity - 1) % d->capacity;
if ( prev == d->last_chunk ) {
grow_map(d);
prev = d->capacity - 1;
}
d->map[prev] = calloc(CHUNK_CAPACITY, sizeof **d->map);
d->first_chunk = prev;
}
static void
deque_show(struct deque *d)
{
printf("first: %zu -- last: %zu -- capacity: %zu\n", d->first_chunk, d->last_chunk, d->capacity);
for ( size_t i = 0; i != d->capacity; ++i ) {
printf("%zu(%p) ", i, (void *) d->map[i]);
}
puts("");
}
int
main(void)
{
struct deque c;
deque_init(&c);
deque_show(&c);
append_chunk(&c);
deque_show(&c);
append_chunk(&c);
deque_show(&c);
append_chunk(&c);
deque_show(&c);
prepend_chunk(&c);
deque_show(&c);
append_chunk(&c);
deque_show(&c);
prepend_chunk(&c);
deque_show(&c);
prepend_chunk(&c);
deque_show(&c);
deque_free(&c);
return 0;
}
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