94 lines
2.1 KiB
C
94 lines
2.1 KiB
C
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#include "param.h"
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#include "impl.h"
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#include "check.h"
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#include "phys.h"
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/* Physical manipulations.
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The blocks concerned are not in any logical chain.
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*/
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public mallink *
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create_chunk(p, n)
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char *p;
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unsigned int n;
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{
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/* The newly acquired piece of memory at p, of length n,
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is turned into a free chunk, properly chained in the
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physical chain.
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The address of the chunk is returned.
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*/
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register mallink *ml;
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/* All of malloc memory is followed by a virtual chunk, the
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mallink of which starts mallink_size() bytes past the last
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byte in memory.
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Its use is prevented by testing for ml == ml_last first.
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*/
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register mallink *last = ml_last;
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assert(!last || p == (char *)phys_next_of(last) - mallink_size());
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ml = (mallink *)(p + mallink_size()); /* bump ml */
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started_working_on(ml);
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set_free(ml, 1);
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set_phys_prev(ml, last);
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ml_last = ml;
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set_phys_next(ml, (mallink *)((char *)ml + n));
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calc_checksum(ml);
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assert(size_of(ml) + mallink_size() == n);
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if (last && free_of(last)) {
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coalesce_backw(ml, last);
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ml = last;
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}
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check_mallinks("create_chunk, phys. linked");
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return ml;
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}
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public
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truncate(ml, size)
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register mallink *ml;
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unsigned int size;
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{
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/* The chunk ml is truncated.
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The chunk at ml is split in two.
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The remaining part is then freed.
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*/
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register mallink *new = (mallink *)((char *)ml + size);
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register mallink *ph_next = phys_next_of(ml);
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set_free(new, 1);
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set_phys_prev(new, ml);
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set_phys_next(new, ph_next);
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calc_checksum(new);
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if (! last_mallink(ml)) {
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set_phys_prev(ph_next, new);
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calc_checksum(ph_next);
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if (free_of(ph_next)) coalesce_forw(new, ph_next);
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}
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else ml_last = new;
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set_phys_next(ml, new);
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calc_checksum(ml);
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started_working_on(new);
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link_free_chunk(new);
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stopped_working_on(new);
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check_mallinks("truncate");
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}
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public
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combine_chunks(ml1, ml2)
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register mallink *ml1, *ml2;
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{
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/* The chunks ml1 and ml2 are combined.
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*/
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register mallink *ml3 = phys_next_of(ml2);
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set_phys_next(ml1, ml3);
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calc_checksum(ml1);
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if (!last_mallink(ml2)) {
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set_phys_prev(ml3, ml1);
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calc_checksum(ml3);
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}
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if (ml_last == ml2)
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ml_last = ml1;
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}
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