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#include "arena.h"
#include "shared.h"
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <errno.h>
#include <error.h>
typedef struct an {
void *membase;
void *memcur;
size_t allocated;
size_t used;
struct an *next;
} arenanode;
typedef struct arena {
arenanode *start;
arenanode *current;
// For keeping track of the largest possible thing that can be allocated to one node
size_t node_memspace;
} arena;
int arenanode_init(arenanode **an, size_t bytes) {
(*an) = xcalloc(1, sizeof(**an));
if(!(*an))
return -1;
(*an)->allocated = bytes;
(*an)->used = 0;
(*an)->next = NULL;
void *mem = xcalloc(bytes, 1);
if(!mem) {
free((*an));
(*an) = NULL;
return -1;
}
(*an)->membase = mem;
(*an)->memcur = mem;
return 0;
}
int arena_init(arena **a, size_t bytes) {
if(!ISPOWOF2(MEM_ALIGN_BYTES))
XALLOC_EXIT("<arena_init> \"MEM_ALIGN_BYTES\" is not a power of 2. Refusing to create a new arena");
(*a) = xcalloc(1, sizeof(**a));
if(!(*a))
return -1;
(*a)->start = NULL;
(*a)->current = NULL;
(*a)->node_memspace = bytes;
arenanode *base;
if(arenanode_init(&base, bytes) < 0) {
free(*a);
(*a) = NULL;
return -1;
}
(*a)->start = base;
(*a)->current = base;
return 0;
}
void* arena_alloc(arena * const arena, size_t bytes) {
if(!arena) {
errno = EINVAL;
return NULL;
}
if(bytes > arena->node_memspace) {
errno = ENOMEM;
return NULL;
}
if(!ISPOWOF2(MEM_ALIGN_BYTES))
XALLOC_EXIT("<arena_alloc> \"MEM_ALIGN_BYTES\" is not a power of 2. Refusing to allocate any memory");
if(bytes > ((arena->current)->allocated - (arena->current)->used)) {
arenanode *new;
if(arenanode_init(&new, arena->node_memspace) < 0)
return NULL;
arena->current->next = new;
arena->current = new;
}
size_t alignment = MEM_ALIGN(bytes);
size_t offset = bytes + alignment;
void *mem = arena->current->memcur;
arena->current->memcur = (void*)(((uint8_t*)arena->current->memcur) + offset);
arena->current->used += offset;
return mem;
// Note: This implementation assumes that malloc provides already-aligned memory. If it
// doesn't, that sucks and blows everything up
}
int arena_free(arena **arena) {
if(!arena) {
errno = EINVAL;
return -1;
}
if(!(*arena)) {
errno = EINVAL;
return -1;
}
(*arena)->current = (*arena)->start;
for(arenanode *n; (*arena)->current != NULL;) {
n = (*arena)->current->next;
free((*arena)->current->membase);
free((*arena)->current);
(*arena)->current = n;
}
free((*arena));
(*arena) = NULL;
return 0;
}
int arena_clear(arena **arena) {
if(!arena) {
errno = EINVAL;
return -1;
}
if(!(*arena)) {
errno = EINVAL;
return -1;
}
size_t bytes = (*arena)->node_memspace;
int ret = 0;
if((ret = arena_free(arena)) < 0)
return ret;
return arena_init(arena, bytes);
}
// Simple Arena is an arena that can't expand whenever allocating memory, meaning what you originally allocated is what you get
typedef arena simplearena;
int simplearena_init(simplearena **a, size_t bytes) {
return arena_init(a, bytes);
}
void* simplearena_alloc(simplearena * const a, size_t bytes) {
// The criteria to allocate new memory in arena_alloc is 'bytes > ((a->current)->allocated - (a->current)->used)', so if this
// is true, just return NULL & set errno
if(!a) {
errno = EINVAL;
return NULL;
}
if(bytes > ((a->current)->allocated - (a->current)->used)) {
errno = ENOMEM;
return NULL;
}
return arena_alloc(a, bytes);
}
int simplearena_free(simplearena **a) {
return arena_free(a);
}
int simplearena_clear(simplearena **a) {
return arena_clear(a);
}
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