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#include <stdlib.h> |
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#include <stdio.h> |
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#include <stdatomic.h> |
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/* API */ |
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typedef struct shared_ptr shared_ptr; |
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shared_ptr* sp_new(void **obj, void (*free_fn)(void *)); |
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shared_ptr* sp_copy(const shared_ptr *sp); |
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void sp_free(shared_ptr *sp); |
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void *sp_get(const shared_ptr *sp); |
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/* Implementation */ |
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// #define ALLOC_TEST |
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#ifdef ALLOC_TEST |
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int malloc_count = 0; |
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int free_count = 0; |
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void *_malloc(size_t size) { |
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malloc_count++; |
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return malloc(size); |
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} |
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void _free(void *ptr) { |
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free_count++; |
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free(ptr); |
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} |
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#define malloc _malloc |
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#define free _free |
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#endif |
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typedef struct obj { |
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char *content; |
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} obj; |
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typedef struct inner_ptr { |
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_Atomic int count; |
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void *obj; |
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void (*free_fn)(void *); |
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} inner_ptr; |
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struct shared_ptr { |
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inner_ptr *ptr; |
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}; |
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shared_ptr* sp_new(void **obj, void (*free_fn)(void *)) { |
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shared_ptr *sp = malloc(sizeof(shared_ptr)); |
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sp->ptr = malloc(sizeof(inner_ptr)); |
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sp->ptr->count = 1; |
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sp->ptr->obj = *obj; |
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sp->ptr->free_fn = free_fn; |
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*obj = NULL; |
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return sp; |
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} |
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shared_ptr* sp_copy(const shared_ptr *sp) { |
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atomic_fetch_add(&sp->ptr->count, 1); |
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shared_ptr *new_sp = malloc(sizeof(shared_ptr)); |
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new_sp->ptr = sp->ptr; |
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return new_sp; |
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} |
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void sp_free(shared_ptr *sp) { |
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if (atomic_fetch_sub(&sp->ptr->count, 1) == 1) { |
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sp->ptr->free_fn(sp->ptr->obj); |
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free(sp->ptr); |
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} |
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free(sp); |
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} |
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void *sp_get(const shared_ptr *sp) { |
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return sp->ptr->obj; |
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} |
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/* Example */ |
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int main(int argc, char const *argv[]) |
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{ |
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obj *o = malloc(sizeof(struct obj)); |
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o->content = "Hello World"; |
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shared_ptr *sp = sp_new((void **)&o, free); |
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if (o == NULL) { |
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printf("cool\n"); |
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} |
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printf("%s\n", ((obj*)(sp_get(sp)))->content); |
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shared_ptr *sp2 = sp_copy(sp); |
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printf("%s\n", ((obj*)(sp_get(sp2)))->content); |
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printf("%s\n", ((obj*)(sp_get(sp)))->content); |
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sp_free(sp2); |
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printf("%s\n", ((obj*)(sp_get(sp)))->content); |
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sp_free(sp); |
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#ifdef ALLOC_TEST |
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printf("mallocs: %d\n", malloc_count); |
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printf("frees: %d\n", free_count); |
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#endif |
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return 0; |
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} |
