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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "runtime.h"
#include "arch.h"
#include "malloc.h"
enum { debug = 0 };
typedef struct Fin Fin;
struct Fin
{
void (*fn)(void*);
const struct __go_func_type *ft;
};
// Finalizer hash table. Direct hash, linear scan, at most 3/4 full.
// Table size is power of 3 so that hash can be key % max.
// Key[i] == (void*)-1 denotes free but formerly occupied entry
// (doesn't stop the linear scan).
// Key and val are separate tables because the garbage collector
// must be instructed to ignore the pointers in key but follow the
// pointers in val.
typedef struct Fintab Fintab;
struct Fintab
{
Lock;
void **fkey;
Fin *val;
int32 nkey; // number of non-nil entries in key
int32 ndead; // number of dead (-1) entries in key
int32 max; // size of key, val allocations
};
#define TABSZ 17
#define TAB(p) (&fintab[((uintptr)(p)>>3)%TABSZ])
static struct {
Fintab;
uint8 pad[0 /* CacheLineSize - sizeof(Fintab) */];
} fintab[TABSZ];
static void
addfintab(Fintab *t, void *k, void (*fn)(void*), const struct __go_func_type *ft)
{
int32 i, j;
i = (uintptr)k % (uintptr)t->max;
for(j=0; j<t->max; j++) {
if(t->fkey[i] == nil) {
t->nkey++;
goto ret;
}
if(t->fkey[i] == (void*)-1) {
t->ndead--;
goto ret;
}
if(++i == t->max)
i = 0;
}
// cannot happen - table is known to be non-full
runtime_throw("finalizer table inconsistent");
ret:
t->fkey[i] = k;
t->val[i].fn = fn;
t->val[i].ft = ft;
}
static bool
lookfintab(Fintab *t, void *k, bool del, Fin *f)
{
int32 i, j;
if(t->max == 0)
return false;
i = (uintptr)k % (uintptr)t->max;
for(j=0; j<t->max; j++) {
if(t->fkey[i] == nil)
return false;
if(t->fkey[i] == k) {
if(f)
*f = t->val[i];
if(del) {
t->fkey[i] = (void*)-1;
t->val[i].fn = nil;
t->val[i].ft = nil;
t->ndead++;
}
return true;
}
if(++i == t->max)
i = 0;
}
// cannot happen - table is known to be non-full
runtime_throw("finalizer table inconsistent");
return false;
}
static void
resizefintab(Fintab *tab)
{
Fintab newtab;
void *k;
int32 i;
runtime_memclr((byte*)&newtab, sizeof newtab);
newtab.max = tab->max;
if(newtab.max == 0)
newtab.max = 3*3*3;
else if(tab->ndead < tab->nkey/2) {
// grow table if not many dead values.
// otherwise just rehash into table of same size.
newtab.max *= 3;
}
newtab.fkey = runtime_mallocgc(newtab.max*sizeof newtab.fkey[0], FlagNoPointers, 0, 1);
newtab.val = runtime_mallocgc(newtab.max*sizeof newtab.val[0], 0, 0, 1);
for(i=0; i<tab->max; i++) {
k = tab->fkey[i];
if(k != nil && k != (void*)-1)
addfintab(&newtab, k, tab->val[i].fn, tab->val[i].ft);
}
runtime_free(tab->fkey);
runtime_free(tab->val);
tab->fkey = newtab.fkey;
tab->val = newtab.val;
tab->nkey = newtab.nkey;
tab->ndead = newtab.ndead;
tab->max = newtab.max;
}
bool
runtime_addfinalizer(void *p, void (*f)(void*), const struct __go_func_type *ft)
{
Fintab *tab;
byte *base;
if(debug) {
if(!runtime_mlookup(p, &base, nil, nil) || p != base)
runtime_throw("addfinalizer on invalid pointer");
}
tab = TAB(p);
runtime_lock(tab);
if(f == nil) {
lookfintab(tab, p, true, nil);
runtime_unlock(tab);
return true;
}
if(lookfintab(tab, p, false, nil)) {
runtime_unlock(tab);
return false;
}
if(tab->nkey >= tab->max/2+tab->max/4) {
// keep table at most 3/4 full:
// allocate new table and rehash.
resizefintab(tab);
}
addfintab(tab, p, f, ft);
runtime_setblockspecial(p, true);
runtime_unlock(tab);
return true;
}
// get finalizer; if del, delete finalizer.
// caller is responsible for updating RefHasFinalizer (special) bit.
bool
runtime_getfinalizer(void *p, bool del, void (**fn)(void*), const struct __go_func_type **ft)
{
Fintab *tab;
bool res;
Fin f;
tab = TAB(p);
runtime_lock(tab);
res = lookfintab(tab, p, del, &f);
runtime_unlock(tab);
if(res==false)
return false;
*fn = f.fn;
*ft = f.ft;
return true;
}
void
runtime_walkfintab(void (*fn)(void*), void (*scan)(byte *, int64))
{
void **key;
void **ekey;
int32 i;
for(i=0; i<TABSZ; i++) {
runtime_lock(&fintab[i]);
key = fintab[i].fkey;
ekey = key + fintab[i].max;
for(; key < ekey; key++)
if(*key != nil && *key != ((void*)-1))
fn(*key);
scan((byte*)&fintab[i].fkey, sizeof(void*));
scan((byte*)&fintab[i].val, sizeof(void*));
runtime_unlock(&fintab[i]);
}
}
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