pistachio/arena.c

arena.c

// A non-thread-safe expandable table of memory pools

#include "pistachio.h"

#define POOLS_PER_STAND 16

char **pools = NULL;int n_pools = 0;int table_len = 0;

void find_next_pool(Arena *a) { while (a->pool < table_len && pools[a->pool]) a->pool++;

if (a->pool >= table_len) { pools = realloc(pools, (table_len + POOLS_PER_STAND) * sizeof(char*)); memset(&pools[table_len], 0, POOLS_PER_STAND * sizeof(char*)); table_len += POOLS_PER_STAND; }

if (a->pool >= n_pools) n_pools = a->pool + 1;}

void make_arena(int pool_size, Arena *a) { if (!pools) { pools = calloc(POOLS_PER_STAND, sizeof(char*)); table_len = POOLS_PER_STAND; }

*a = (Arena) { .pool_size = pool_size, .pool = 0, .idx = 0, .allow_overflow = true, .initialized = true };

find_next_pool(a); pools[a->pool] = malloc(a->pool_size);}

void *allocate(Arena *a, int size) { if (a->idx + size > a->pool_size) { if (!a->allow_overflow) return NULL;

a->idx = 0; find_next_pool(a);

// if the allocation request is too large for a pool, make it its own pool if (size > a->pool_size) { pools[a->pool] = malloc(size); void *ptr = (void*)pools[a->pool];

find_next_pool(a); return ptr; }

if (!pools[a->pool]) pools[a->pool] = malloc(a->pool_size); }

void *ptr = (void*)&pools[a->pool][a->idx]; a->idx += size; return ptr;}

void destroy_all_arenas() { if (!pools) return;

for (int i = 0; i < table_len; i++) { if (pools[i]) free(pools[i]); }

free(pools); pools = NULL;}

void defer_arena_destruction() { atexit(destroy_all_arenas);}