buddy.h

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#pragma once
 
#include <datatypes/bitmap.h>
 
#include <assert.h>
#include <stdalign.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
 
#define B_TOTAL_EXP 16U
#define B_BLOCK_EXP 6U
 
#define next_exp_of_2(i) (sizeof(i) * CHAR_BIT - intrinsics_clz(i))
#define buddy_allocation_block_compute(req_size) next_exp_of_2(max(req_size, 1U << B_BLOCK_EXP) - 1);
 
#define buddy_left_child(i) (((i) << 1U) + 1U)
#define buddy_right_child(i) (((i) << 1U) + 2U)
#define buddy_parent(i) ((((i) + 1) >> 1U) - 1U)
 
struct buddy_state {
 
    alignas(16) uint8_t longest[(1U << (B_TOTAL_EXP - B_BLOCK_EXP + 1))];
    alignas(16) unsigned char base_mem[1U << B_TOTAL_EXP];
    block_bitmap dirty[
        bitmap_required_size(
        // this tracks writes to the allocation tree
            (1 << (B_TOTAL_EXP - 2 * B_BLOCK_EXP + 1)) +
        // while this tracks writes to the actual memory buffer
            (1 << (B_TOTAL_EXP - B_BLOCK_EXP))
        )
    ];
};
 
static_assert(
    offsetof(struct buddy_state, longest) ==
    offsetof(struct buddy_state, base_mem) -
    sizeof(((struct buddy_state *)0)->longest),
    "longest and base_mem are not contiguous, this will break incremental checkpointing");
 
extern void buddy_init(struct buddy_state *self);
extern void *buddy_malloc(struct buddy_state *self, uint_fast8_t req_blks_exp);
extern uint_fast32_t buddy_free(struct buddy_state *self, void *ptr);
 
struct buddy_realloc_res {
    bool handled;
    union {
        int_fast32_t variation;
        uint_fast32_t original;
    };
};
extern struct buddy_realloc_res buddy_best_effort_realloc(struct buddy_state *self, void *ptr, size_t req_size);
extern void buddy_dirty_mark(struct buddy_state *self, const void *ptr, size_t s);