Base/platform/src-c/alloc/arena.c

#include <librr/alloc/arena.h>
#include <librr/strutil.h>
#include <librr/memory.h>

#include <stdlib.h>

typedef struct rr_arena rr_arena_s;

struct rr_arena
{
    usz_t capacity;
    usz_t offset;
    char *allocation;
};

rr_generic_arena_s rr_new_arena(usz_t capacity)
{
    rr_arena_s *specifics = malloc(sizeof(rr_arena_s) + capacity);
    specifics->capacity = capacity;
    specifics->offset = 0;
    // The arena allocation is right after the head structure.
    specifics->allocation = (void *) (specifics + sizeof(rr_arena_s));

    rr_generic_arena_s arena;
    arena.fn_alloc      = &rr_arena_alloc;
    arena.fn_destruct   = &rr_destruct_arena;
    arena.specifics     = specifics;

    return arena;
}

void rr_destruct_arena(rr_generic_arena_s *generic_arena)
{
    free(generic_arena->specifics);
}



void * rr_arena_alloc(rr_generic_arena_s *generic_arena, usz_t length)
{
    rr_arena_s *arena = generic_arena->specifics;

    if((arena->offset + length) > arena->capacity)
        return NULL;

    void *block = &arena->allocation[arena->offset];
    arena->offset += length;
    return block;
}

char * rr_arena_clone_string(rr_generic_arena_s *generic_arena, const char *string)
{
    usz_t len_string = rr_measure_string(string);
    char *cloned_string = rr_arena_alloc(generic_arena, len_string+1);
    if(cloned_string == NULL)
        return NULL;
    rr_memcopy(cloned_string, string, len_string);
    cloned_string[len_string] = 0x00;

    return cloned_string;
}