smugfs(4): new program

src/cmd/smugfs/cache.c

@@ -0,0 +1,149 @@
+#include "a.h"
+
+struct Cache
+{
+	CEntry **hash;
+	int nhash;
+	CEntry *head;
+	CEntry *tail;
+	int nentry;
+	int maxentry;
+	int sizeofentry;
+	void (*cefree)(CEntry*);
+};
+
+static void
+nop(CEntry *ce)
+{
+}
+
+static uint
+hash(const char *s)
+{
+	uint h;
+	uchar *p;
+
+	h = 0;
+	for(p=(uchar*)s; *p; p++)
+		h = h*37 + *p;
+	return h;
+}
+
+Cache*
+newcache(int sizeofentry, int maxentry, void (*cefree)(CEntry*))
+{
+	Cache *c;
+	int i;
+
+	assert(sizeofentry >= sizeof(CEntry));
+	c = emalloc(sizeof *c);
+	c->sizeofentry = sizeofentry;
+	c->maxentry = maxentry;
+	c->nentry = 0;
+	for(i=1; i<maxentry; i<<=1)
+		;
+	c->nhash = i;
+	c->hash = emalloc(c->nhash * sizeof c->hash[0]);
+	if(cefree == nil)
+		cefree = nop;
+	c->cefree = cefree;
+	return c;
+}
+
+static void
+popout(Cache *c, CEntry *e)
+{
+	if(e->list.prev)
+		e->list.prev->list.next = e->list.next;
+	else
+		c->head = e->list.next;
+	if(e->list.next)
+		e->list.next->list.prev = e->list.prev;
+	else
+		c->tail = e->list.prev;
+}
+
+static void
+insertfront(Cache *c, CEntry *e)
+{
+	e->list.next = c->head;
+	c->head = e;
+	if(e->list.next)
+		e->list.next->list.prev = e;
+	else
+		c->tail = e;
+}
+
+static void
+movetofront(Cache *c, CEntry *e)
+{
+	popout(c, e);
+	insertfront(c, e);	
+}
+
+static CEntry*
+evict(Cache *c)
+{
+	CEntry *e;
+	
+	e = c->tail;
+	popout(c, e);
+	c->cefree(e);
+	free(e->name);
+	e->name = nil;
+	memset(e, 0, c->sizeofentry);
+	insertfront(c, e);
+	return e;
+}
+
+CEntry*
+cachelookup(Cache *c, char *name, int create)
+{
+	int h;
+	CEntry *e;
+	
+	h = hash(name) % c->nhash;
+	for(e=c->hash[h]; e; e=e->hash.next){
+		if(strcmp(name, e->name) == 0){
+			movetofront(c, e);
+			return e;
+		}
+	}
+	
+	if(!create)
+		return nil;
+	
+	if(c->nentry >= c->maxentry)
+		e = evict(c);
+	else{
+		e = emalloc(c->sizeofentry);
+		insertfront(c, e);
+		c->nentry++;
+	}
+	e->name = estrdup(name);
+	h = hash(name) % c->nhash;
+	e->hash.next = c->hash[h];
+	c->hash[h] = e;
+	return e;	
+}
+
+void
+cacheflush(Cache *c, char *substr)
+{
+	CEntry **l, *e;
+	int i;
+	
+	for(i=0; i<c->nhash; i++){
+		for(l=&c->hash[i]; (e=*l); ){
+			if(substr == nil || strstr(e->name, substr)){
+				*l = e->hash.next;
+				c->nentry--;
+				popout(c, e);
+				c->cefree(e);
+				free(e->name);
+				free(e);
+			}else
+				l = &e->hash.next;
+		}
+	}
+}