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WebSVN – planix.SVN – Blame – /os/branches/feature_posix/sys/src/lib9p/intmap.c – Rev 2

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#include <u.h>
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#include <libc.h>
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#include <auth.h>
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#include <fcall.h>
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#include <thread.h>
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#include <9p.h>
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enum {
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	NHASH = 128
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};
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typedef struct Intlist	Intlist;
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struct Intlist
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{
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	ulong	id;
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	void*	aux;
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	Intlist*	link;
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};
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struct Intmap
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{
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	RWLock;
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	Intlist*	hash[NHASH];
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	void (*inc)(void*);
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};
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static ulong
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hashid(ulong id)
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{
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	return id%NHASH;
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}
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static void
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nop(void*)
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{
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}
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Intmap*
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allocmap(void (*inc)(void*))
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{
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	Intmap *m;
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	m = emalloc9p(sizeof(*m));
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	if(inc == nil)
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		inc = nop;
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	m->inc = inc;
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	return m;
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}
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void
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freemap(Intmap *map, void (*destroy)(void*))
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{
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	int i;
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	Intlist *p, *nlink;
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	if(destroy == nil)
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		destroy = nop;
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	for(i=0; i<NHASH; i++){
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		for(p=map->hash[i]; p; p=nlink){
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			nlink = p->link;
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			destroy(p->aux);
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			free(p);
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		}
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	}
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	free(map);
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}
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static Intlist**
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llookup(Intmap *map, ulong id)
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{
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	Intlist **lf;
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	for(lf=&map->hash[hashid(id)]; *lf; lf=&(*lf)->link)
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		if((*lf)->id == id)
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			break;
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	return lf;
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}
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/*
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 * The RWlock is used as expected except that we allow
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 * inc() to be called while holding it.  This is because we're
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 * locking changes to the tree structure, not to the references.
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 * Inc() is expected to have its own locking.
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 */
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void*
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lookupkey(Intmap *map, ulong id)
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{
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	Intlist *f;
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	void *v;
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	rlock(map);
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	if(f = *llookup(map, id)){
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		v = f->aux;
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		map->inc(v);
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	}else
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		v = nil;
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	runlock(map);
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	return v;
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}
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void*
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insertkey(Intmap *map, ulong id, void *v)
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{
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	Intlist *f;
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	void *ov;
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	ulong h;
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	wlock(map);
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	if(f = *llookup(map, id)){
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		/* no decrement for ov because we're returning it */
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		ov = f->aux;
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		f->aux = v;
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	}else{
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		f = emalloc9p(sizeof(*f));
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		f->id = id;
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		f->aux = v;
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		h = hashid(id);
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		f->link = map->hash[h];
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		map->hash[h] = f;
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		ov = nil;
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	}
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	wunlock(map);
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	return ov;
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}
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int
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caninsertkey(Intmap *map, ulong id, void *v)
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{
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	Intlist *f;
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	int rv;
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	ulong h;
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	wlock(map);
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	if(*llookup(map, id))
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		rv = 0;
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	else{
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		f = emalloc9p(sizeof *f);
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		f->id = id;
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		f->aux = v;
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		h = hashid(id);
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		f->link = map->hash[h];
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		map->hash[h] = f;
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		rv = 1;
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	}
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	wunlock(map);
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	return rv;
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}
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void*
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deletekey(Intmap *map, ulong id)
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{
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	Intlist **lf, *f;
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	void *ov;
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	wlock(map);
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	if(f = *(lf = llookup(map, id))){
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		ov = f->aux;
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		*lf = f->link;
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		free(f);
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	}else
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		ov = nil;
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	wunlock(map);
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	return ov;
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}