HDR_BLOCK
block->size += block2->size + HDR_BLOCK;
((char *)block + HDR_BLOCK + size);
newblock->size = block->size - size - HDR_BLOCK;
block = (struct block *)((char *)ptr - HDR_BLOCK);
block->size += block->next->size + HDR_BLOCK;
block = (struct block *)((char *)ptr - HDR_BLOCK);
block = (struct block *)((char *)ptr - HDR_BLOCK);
block->size += block->next->size + HDR_BLOCK;
block = (struct block *)((char *)ptr - HDR_BLOCK);
newblock = (struct block *)((char *)block + HDR_BLOCK + size);
newblock->size = block->size - size - HDR_BLOCK;
block->size += block2->size + HDR_BLOCK;