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array.go
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array.go
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// Copyright 2014 The dbm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package dbm
import (
"fmt"
"io"
"camlistore.org/third_party/github.com/cznic/exp/lldb"
)
// Array is a reference to a subtree of an array.
type Array struct {
db *DB
tree *lldb.BTree
prefix []byte
name string
namespace byte
}
// MemArray returns an Array associated with a subtree of an anonymous array,
// determined by subscripts. MemArrays are resource limited as they are
// completely held in memory and are not automatically persisted.
func MemArray(subscripts ...interface{}) (a Array, err error) {
a.db = &DB{}
if a, err = a.Array(subscripts...); err != nil {
return a, err
}
a.tree = lldb.NewBTree(collate)
return
}
func bpack(a []byte) []byte {
if cap(a) > len(a) {
return append([]byte(nil), a...)
}
return a
}
// Named trees (arrays) can get removed, but references to them (Arrays) may
// outlive that. db.bkl locked is assumed. ok => a.tree != nil && err == nil.
func (a *Array) validate(canCreate bool) (ok bool, err error) {
if a.tree != nil && (a.tree.Handle() == 1 || a.tree.IsMem()) {
return true, nil
}
switch a.namespace {
case arraysPrefix:
a.tree, err = a.db.acache.getTree(a.db, arraysPrefix, a.name, canCreate, aCacheSize)
case filesPrefix:
a.tree, err = a.db.fcache.getTree(a.db, filesPrefix, a.name, canCreate, fCacheSize)
case systemPrefix:
a.tree, err = a.db.scache.getTree(a.db, systemPrefix, a.name, canCreate, sCacheSize)
default:
panic("internal error")
}
switch {
case a.tree == nil && err == nil:
return false, nil
case a.tree == nil && err != nil:
return false, err
case a.tree != nil && err == nil:
return true, nil
//case a.tree != nil && err != nil:
}
panic("internal error")
}
// Array returns an object associated with a subtree of array 'a', determined
// by subscripts.
func (a *Array) Array(subscripts ...interface{}) (r Array, err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
return a.array(subscripts...)
}
func (a *Array) array(subscripts ...interface{}) (r Array, err error) {
r = *a
prefix, err := lldb.EncodeScalars(subscripts...)
if err != nil {
return
}
r.prefix = append(bpack(r.prefix), prefix...)
return
}
func (a *Array) bset(val, key []byte) (err error) {
err = a.tree.Set(append(a.prefix, key...), val)
return
}
func (a *Array) binc(delta int64, key []byte) (r int64, err error) {
_, _, err = a.tree.Put(
nil, //TODO buffers
append(a.prefix, key...),
func(key []byte, old []byte) (new []byte, write bool, err error) {
write = true
if len(old) != 0 {
decoded, err := lldb.DecodeScalars(old)
switch {
case err != nil:
// nop
case len(decoded) != 1:
// nop
default:
r, _ = decoded[0].(int64)
}
}
r += delta
new, err = lldb.EncodeScalars(r)
return
},
)
return
}
func (a *Array) bget(key []byte) (value []byte, err error) {
return a.tree.Get(nil, append(a.prefix, key...))
}
func (a *Array) bdelete(key []byte) (err error) {
return a.tree.Delete(append(a.prefix, key...))
}
// Set sets the value at subscripts in subtree 'a'. Any previous value, if
// existed, is overwritten by the new one.
func (a *Array) Set(value interface{}, subscripts ...interface{}) (err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
if t := a.tree; t != nil && !t.IsMem() && a.tree.Handle() == 1 {
return &lldb.ErrPERM{Src: "dbm.Array.Set"}
}
if ok, err := a.validate(true); !ok {
return err
}
return a.set(value, subscripts...)
}
func (a *Array) set(value interface{}, subscripts ...interface{}) (err error) {
val, err := encVal(value)
if err != nil {
return
}
key, err := lldb.EncodeScalars(subscripts...)
if err != nil {
return
}
return a.bset(val, key)
}
// Inc atomically increments the value at subscripts by delta and returns the
// new value. If the value doesn't exists before calling Inc or if the value is
// not an integer then the value is considered to be zero.
func (a *Array) Inc(delta int64, subscripts ...interface{}) (val int64, err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
if t := a.tree; t != nil && !t.IsMem() && a.tree.Handle() == 1 {
return 0, &lldb.ErrPERM{Src: "dbm.Array.Inc"}
}
if ok, err := a.validate(true); !ok {
return 0, err
}
return a.inc(delta, subscripts...)
}
func (a *Array) inc(delta int64, subscripts ...interface{}) (val int64, err error) {
key, err := lldb.EncodeScalars(subscripts...)
if err != nil {
return
}
return a.binc(delta, key)
}
// Get returns the value at subscripts in subtree 'a', or nil if no such value
// exists.
func (a *Array) Get(subscripts ...interface{}) (value interface{}, err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
if ok, e := a.validate(false); !ok || err != nil {
err = e
return
}
value, err = a.get(subscripts...)
if value == nil {
return
}
if t := a.tree; t != nil && !t.IsMem() && t.Handle() == 1 {
value = 0
}
return
}
func (a *Array) get(subscripts ...interface{}) (value interface{}, err error) {
key, err := lldb.EncodeScalars(subscripts...)
if err != nil {
return
}
val, err := a.bget(key)
if err != nil {
return
}
if val == nil {
return
}
va, err := lldb.DecodeScalars(val)
if err != nil {
return nil, err
}
value = va
if len(va) == 1 {
value = va[0]
}
return
}
// Delete deletes the value at subscripts in array.
func (a *Array) Delete(subscripts ...interface{}) (err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
if t := a.tree; t != nil && !t.IsMem() && a.tree.Handle() == 1 {
return &lldb.ErrPERM{Src: "dbm.Array.Delete"}
}
if ok, err := a.validate(false); !ok {
return err
}
return a.delete(subscripts...)
}
func (a *Array) delete(subscripts ...interface{}) (err error) {
key, err := lldb.EncodeScalars(subscripts...)
if err != nil {
return
}
return a.bdelete(key)
}
// Clear empties the subtree at subscripts in 'a'.
func (a *Array) Clear(subscripts ...interface{}) (err error) {
//TODO optimize for clear "everything"
if err = a.db.enter(); err != nil {
return
}
doLeave := true
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
if doLeave {
a.db.leave(&err)
}
}()
if t := a.tree; t != nil && !t.IsMem() && a.tree.Handle() == 1 {
return &lldb.ErrPERM{Src: "dbm.Array.Clear"}
}
if ok, err := a.validate(false); !ok {
return err
}
doLeave = false
if a.db.leave(&err) != nil {
return
}
a0 := *a
a0.prefix = nil
prefix, err := lldb.DecodeScalars(a.prefix)
if err != nil {
panic("internal error")
}
subscripts = append(prefix, subscripts...)
n := len(subscripts)
bSubscripts, err := lldb.EncodeScalars(subscripts...)
if err != nil {
panic("internal error")
}
s, err := a0.Slice(nil, nil)
if err != nil {
return
}
return s.Do(func(actualSubscripts, value []interface{}) (more bool, err error) {
if len(actualSubscripts) < n {
return
}
common := actualSubscripts[:n]
bcommon, err := lldb.EncodeScalars(common...)
if err != nil {
panic("internal error")
}
switch collate(bcommon, bSubscripts) {
case -1:
return true, nil
case 0:
return true, a0.Delete(actualSubscripts...)
}
// case 1:
return false, nil
})
}
// Slice returns a new Slice from Array, with a subscripts range of [from, to].
// If from is nil it works as 'from lowest existing key'. If to is nil it
// works as 'to highest existing key'.
func (a *Array) Slice(from, to []interface{}) (s *Slice, err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
prefix, err := lldb.DecodeScalars(a.prefix)
if err != nil {
return
}
return &Slice{
a: a,
prefix: prefix,
from: from,
to: to,
}, nil
}
// Dump outputs a human readable dump of a to w. Intended use is only for
// examples or debugging. Some type information is lost in the rendering, for
// example a float value '17.' and an integer value '17' may both output as
// '17'.
//
// Note: Dump will lock the database until finished.
func (a *Array) Dump(w io.Writer) (err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
err = fmt.Errorf("%v", e)
}
a.db.leave(&err)
}()
return a.tree.Dump(w)
}
func (a *Array) Tree() (tr *lldb.BTree, err error) {
_, err = a.validate(false)
if err != nil {
return
}
return a.tree, nil
}
// Enumerator returns a "raw" enumerator of the whole array. It's initially
// positioned on the first (asc is true) or last (asc is false)
// subscripts/value pair in the array.
//
// This method is safe for concurrent use by multiple goroutines.
func (a *Array) Enumerator(asc bool) (en *Enumerator, err error) {
if err = a.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
switch x := e.(type) {
case error:
err = x
default:
err = fmt.Errorf("%v", e)
}
}
a.db.leave(&err)
}()
var e Enumerator
switch asc {
case true:
e.en, err = a.tree.SeekFirst()
default:
e.en, err = a.tree.SeekLast()
}
if err != nil {
return
}
e.db = a.db
return &e, nil
}
// Enumerator provides visiting all K/V pairs in a DB/range.
type Enumerator struct {
db *DB
en *lldb.BTreeEnumerator
}
// Next returns the currently enumerated raw KV pair, if it exists and moves to
// the next KV in the key collation order. If there is no KV pair to return,
// err == io.EOF is returned.
//
// This method is safe for concurrent use by multiple goroutines.
func (e *Enumerator) Next() (key, value []interface{}, err error) {
if err = e.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
switch x := e.(type) {
case error:
err = x
default:
err = fmt.Errorf("%v", e)
}
}
e.db.leave(&err)
}()
k, v, err := e.en.Next()
if err != nil {
return
}
if key, err = lldb.DecodeScalars(k); err != nil {
return
}
value, err = lldb.DecodeScalars(v)
return
}
// Prev returns the currently enumerated raw KV pair, if it exists and moves to
// the previous KV in the key collation order. If there is no KV pair to
// return, err == io.EOF is returned.
//
// This method is safe for concurrent use by multiple goroutines.
func (e *Enumerator) Prev() (key, value []interface{}, err error) {
if err = e.db.enter(); err != nil {
return
}
defer func() {
if e := recover(); e != nil {
switch x := e.(type) {
case error:
err = x
default:
err = fmt.Errorf("%v", e)
}
}
e.db.leave(&err)
}()
k, v, err := e.en.Prev()
if err != nil {
return
}
if key, err = lldb.DecodeScalars(k); err != nil {
return
}
value, err = lldb.DecodeScalars(v)
return
}