Block Metadata Quiz

Test understanding of block header design

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. H=24, header byte address=4096, payload capacity=40. What is the first payload byte address?

2. With H=24, what byte distance does block + sizeof(block_header_t) advance for a block_header_t pointer? Select one.

Select one answer.

24 bytes 1 byte 48 bytes 576 bytes

3. H=24, current header offset=0, capacity=40, arena end=80. How many bytes remain after the block?

4. For that 16-byte suffix, what does block_next_in_memory return? Select one.

Select one answer.

The stored next pointer regardless of geometry A pointer to offset 80 NULL because the complete next header does not fit A pointer to offset 64 because it is below 80

5. A header at 4096 has H=24. Is its payload necessarily 16-byte aligned? Select one.

Select one answer.

No; payload pointers can never be aligned No; 4120 is eight bytes past a 16-byte boundary Yes; every struct size is a multiple of 16 Yes; pointer casts automatically realign addresses

6. What precondition makes reading a header magic field meaningful? Select one.

Select one answer.

The payload has at least one nonzero byte A matching magic value can be assumed before reading it The pointer already names a trusted readable header Any non-NULL integer can be converted into a valid header

7. The physical candidate is offset 136, but block->next stores another valid header address. Which does physical walking use? Select one.

Select one answer.

Whichever address is smaller The list head Offset 136, after checking arena bounds Always the stored next pointer

8. block_init reuses dirty storage. Which fields must it initialize? Select one.

Select one answer.

Only magic; it defines all other fields Capacity and free flag; magic is optional Capacity, free flag, magic, and next=NULL Only capacity; old links remain useful

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