-// splitBlockGroup(bd,B) splits bd in two. Afterward, bd will have B
-// blocks, and a new block descriptor pointing to the remainder is
-// returned.
-bdescr *
-splitBlockGroup (bdescr *bd, nat blocks)
-{
- bdescr *new_bd;
-
- if (bd->blocks <= blocks) {
- barf("splitLargeBlock: too small");
- }
-
- if (bd->blocks > BLOCKS_PER_MBLOCK) {
- nat low_mblocks, high_mblocks;
- void *new_mblock;
- if ((blocks - BLOCKS_PER_MBLOCK) % (MBLOCK_SIZE / BLOCK_SIZE) != 0) {
- barf("splitLargeBlock: not a multiple of a megablock");
- }
- low_mblocks = 1 + (blocks - BLOCKS_PER_MBLOCK) / (MBLOCK_SIZE / BLOCK_SIZE);
- high_mblocks = (bd->blocks - blocks) / (MBLOCK_SIZE / BLOCK_SIZE);
-
- new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + (W_)low_mblocks * MBLOCK_SIZE_W);
- initMBlock(new_mblock);
- new_bd = FIRST_BDESCR(new_mblock);
- new_bd->blocks = MBLOCK_GROUP_BLOCKS(high_mblocks);
-
- ASSERT(blocks + new_bd->blocks ==
- bd->blocks + BLOCKS_PER_MBLOCK - MBLOCK_SIZE/BLOCK_SIZE);
- }
- else
- {
- // NB. we're not updating all the bdescrs in the split groups to
- // point to the new heads, so this can only be used for large
- // objects which do not start in the non-head block.
- new_bd = bd + blocks;
- new_bd->blocks = bd->blocks - blocks;
- }
- bd->blocks = blocks;
-
- return new_bd;
-}
-