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70 lines
1.7 KiB
70 lines
1.7 KiB
/* freemem.c - freemem */ |
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#include <xinu.h> |
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/*------------------------------------------------------------------------ |
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* freemem - Free a memory block, returning the block to the free list |
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*------------------------------------------------------------------------ |
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*/ |
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syscall freemem( |
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char *blkaddr, /* Pointer to memory block */ |
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uint32 nbytes /* Size of block in bytes */ |
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) |
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{ |
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intmask mask; /* Saved interrupt mask */ |
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struct memblk *next, *prev, *block; |
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uint32 top; |
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mask = disable(); |
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if ((nbytes == 0) || ((uint32) blkaddr < (uint32) minheap) |
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|| ((uint32) blkaddr > (uint32) maxheap)) { |
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restore(mask); |
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return SYSERR; |
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} |
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nbytes = (uint32) roundmb(nbytes); /* Use memblk multiples */ |
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block = (struct memblk *)blkaddr; |
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prev = &memlist; /* Walk along free list */ |
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next = memlist.mnext; |
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while ((next != NULL) && (next < block)) { |
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prev = next; |
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next = next->mnext; |
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} |
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if (prev == &memlist) { /* Compute top of previous block*/ |
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top = (uint32) NULL; |
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} else { |
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top = (uint32) prev + prev->mlength; |
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} |
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/* Ensure new block does not overlap previous or next blocks */ |
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if (((prev != &memlist) && (uint32) block < top) |
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|| ((next != NULL) && (uint32) block+nbytes>(uint32)next)) { |
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restore(mask); |
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return SYSERR; |
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} |
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memlist.mlength += nbytes; |
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/* Either coalesce with previous block or add to free list */ |
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if (top == (uint32) block) { /* Coalesce with previous block */ |
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prev->mlength += nbytes; |
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block = prev; |
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} else { /* Link into list as new node */ |
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block->mnext = next; |
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block->mlength = nbytes; |
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prev->mnext = block; |
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} |
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/* Coalesce with next block if adjacent */ |
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if (((uint32) block + block->mlength) == (uint32) next) { |
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block->mlength += next->mlength; |
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block->mnext = next->mnext; |
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} |
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restore(mask); |
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return OK; |
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}
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