Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

/* ---- Simple linear arena allocator ---- */
typedef struct {
    uint8_t *base;
    size_t   used;
    size_t   capacity;
} Arena;

Arena arena_create(size_t capacity)
{
    Arena a;
    a.base     = malloc(capacity);
    a.used     = 0;
    a.capacity = capacity;
    return a;
}

void *arena_alloc(Arena *a, size_t size)
{
    /* Align to 8 bytes */
    size = (size + 7) & ~(size_t)7;
    if (a->used + size > a->capacity) return NULL;
    void *ptr = a->base + a->used;
    a->used  += size;
    return ptr;
}

void arena_free(Arena *a)
{
    free(a->base);
    a->base     = NULL;
    a->used     = 0;
    a->capacity = 0;
}

typedef struct { int x, y; } Point;

int main(void)
{
    Arena arena = arena_create(1024);
    if (!arena.base) { perror("malloc"); return EXIT_FAILURE; }

Point *points[10];
    for (int i = 0; i < 10; i++) {
        points[i] = arena_alloc(&arena, sizeof(Point));
        points[i]->x = i;
        points[i]->y = i * i;
    }

printf("Arena used: %zu / %zu bytes
", arena.used, arena.capacity);
    for (int i = 0; i < 10; i++)
        printf("  (%d, %d)
", points[i]->x, points[i]->y);

arena_free(&arena);  /* free everything in one shot */
    printf("Arena freed.
");
    return EXIT_SUCCESS;
}