func (f *bitFiler) ReadAt(b []byte, off int64) (n int, err error) {
avail := f.size - off
pgI := off >> bfBits
pgO := int(off & bfMask)
rem := len(b)
if int64(rem) >= avail {
rem = int(avail)
err = io.EOF
}
for rem != 0 && avail > 0 {
pg := f.m[pgI]
if pg == nil {
pg = &bitPage{}
if f.parent != nil {
_, err = f.parent.ReadAt(pg.data[:], off&^bfMask)
if err != nil && !fileutil.IsEOF(err) {
return
}
err = nil
}
f.m[pgI] = pg
}
nc := copy(b[:mathutil.Min(rem, bfSize)], pg.data[pgO:])
pgI++
pgO = 0
rem -= nc
n += nc
b = b[nc:]
off += int64(nc)
}
return
}
func (t *treeCache) getTree(db *DB, prefix int, name string, canCreate bool, cacheSize int) (r *lldb.BTree, err error) {
m := t.get()
r, ok := m[name]
if ok {
return
}
root, err := db.root()
if err != nil {
return
}
val, err := root.get(prefix, name)
if err != nil {
return
}
switch x := val.(type) {
case nil:
if !canCreate {
return
}
var h int64
r, h, err = lldb.CreateBTree(db.alloc, collate)
if err != nil {
return nil, err
}
if err = root.set(h, prefix, name); err != nil {
return nil, err
}
case int64:
if r, err = lldb.OpenBTree(db.alloc, collate, x); err != nil {
return nil, err
}
default:
return nil, &lldb.ErrINVAL{Src: "corrupted root directory value for", Val: fmt.Sprintf("%q, %q", prefix, name)}
}
if len(m) > cacheSize {
i, j, n := 0, cacheSize/2, mathutil.Min(cacheSize/20, 10)
loop:
for k := range m {
if i++; i >= j {
delete(m, k)
if n == 0 {
break loop
}
n--
}
}
}
m[name] = r
return
}
func (c *cache) get2(n int) (r *node, isZeroed bool) {
s := *c
lens := len(s)
if lens == 0 {
return &node{b: make([]byte, n, mathutil.Min(2*n, maxBuf))}, true
}
i := sort.Search(lens, func(x int) bool { return len(s[x].b) >= n })
if i == lens {
i--
s[i].b, isZeroed = make([]byte, n, mathutil.Min(2*n, maxBuf)), true
}
r = s[i]
r.b = r.b[:n]
copy(s[i:], s[i+1:])
s = s[:lens-1]
*c = s
return
}
func BenchmarkRollbackFiler(b *testing.B) {
rng := rand.New(rand.NewSource(42))
type t struct {
off int64
b []byte
}
a := []t{}
for rem := b.N; rem > 0; {
off := rng.Int63()
n := mathutil.Min(rng.Intn(1e3)+1, rem)
a = append(a, t{off, rndBytes(rng, n)})
rem -= n
}
var r *RollbackFiler
f := NewMemFiler()
checkpoint := func(sz int64) (err error) {
return f.Truncate(sz)
}
r, err := NewRollbackFiler(f, checkpoint, f)
if err != nil {
b.Fatal(err)
}
if err := r.BeginUpdate(); err != nil {
b.Fatal(err)
}
b.SetBytes(1)
b.ResetTimer()
for _, v := range a {
if _, err := r.WriteAt(v.b, v.off); err != nil {
b.Fatal(err)
}
}
}
// ReadAt implements Filer.
func (f *MemFiler) ReadAt(b []byte, off int64) (n int, err error) {
avail := f.size - off
pgI := off >> pgBits
pgO := int(off & pgMask)
rem := len(b)
if int64(rem) >= avail {
rem = int(avail)
err = io.EOF
}
for rem != 0 && avail > 0 {
pg := f.m[pgI]
if pg == nil {
pg = &zeroPage
}
nc := copy(b[:mathutil.Min(rem, pgSize)], pg[pgO:])
pgI++
pgO = 0
rem -= nc
n += nc
b = b[nc:]
}
return
}
func (f *File) readAt(b []byte, off int64, bits bool) (n int, err error) {
var fsize int64
if !bits {
fsize, err = f.Size()
if err != nil {
return
}
}
avail := fsize - off
pgI := off >> pgBits
pgO := int(off & pgMask)
rem := len(b)
if !bits && int64(rem) >= avail {
rem = int(avail)
err = io.EOF
}
for rem != 0 && (bits || avail > 0) {
v, err := (*Array)(f).Get(pgI)
if err != nil {
return n, err
}
pg, _ := v.([]byte)
if len(pg) == 0 {
pg = zeroPage[:]
}
nc := copy(b[:mathutil.Min(rem, pgSize)], pg[pgO:])
pgI++
pgO = 0
rem -= nc
n += nc
b = b[nc:]
}
return
}