forked from cayleygraph/cayley
/
kv.go
225 lines (196 loc) · 4.21 KB
/
kv.go
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package kv
import (
"bytes"
"context"
"errors"
"fmt"
)
var (
ErrNotFound = errors.New("kv: not found")
ErrNoBucket = errors.New("kv: bucket is missing")
ErrBucketExists = errors.New("kv: bucket already exists")
)
type Tx interface {
Commit(ctx context.Context) error
Rollback() error
}
type Bucket interface {
Get(ctx context.Context, keys [][]byte) ([][]byte, error)
Put(k, v []byte) error
Del(k []byte) error
Scan(pref []byte) KVIterator
}
func GetOne(ctx context.Context, b Bucket, key []byte) ([]byte, error) {
out, err := b.Get(ctx, [][]byte{key})
if err != nil {
return nil, err
} else if len(out) == 0 || out[0] == nil {
return nil, ErrNotFound
}
return out[0], nil
}
type KVIterator interface {
Next(ctx context.Context) bool
Err() error
Close() error
Key() []byte
Val() []byte
}
type BucketKey struct {
Bucket, Key []byte
}
type BucketTx interface {
Tx
Bucket(name []byte) Bucket
Get(ctx context.Context, keys []BucketKey) ([][]byte, error)
}
type FlatTx interface {
Tx
Bucket
}
type Base interface {
Type() string
Close() error
}
type BucketKV interface {
Base
Tx(update bool) (BucketTx, error)
}
type FlatKV interface {
Base
Tx(update bool) (FlatTx, error)
}
func Update(ctx context.Context, kv BucketKV, update func(tx BucketTx) error) error {
tx, err := kv.Tx(true)
if err != nil {
return err
}
defer tx.Rollback()
if err = update(tx); err != nil {
return err
}
return tx.Commit(ctx)
}
func View(kv BucketKV, view func(tx BucketTx) error) error {
tx, err := kv.Tx(false)
if err != nil {
return err
}
defer tx.Rollback()
err = view(tx)
if err == nil {
err = tx.Rollback()
}
return err
}
func Each(ctx context.Context, b Bucket, pref []byte, fnc func(k, v []byte) error) error {
it := b.Scan(pref)
defer it.Close()
for it.Next(ctx) {
if err := fnc(it.Key(), it.Val()); err != nil {
return err
}
}
return it.Err()
}
var _ BucketKV = (*flatKV)(nil)
func FromFlat(flat FlatKV) BucketKV {
return &flatKV{flat: flat}
}
type flatKV struct {
flat FlatKV
}
func (kv *flatKV) Type() string { return kv.flat.Type() }
func (kv *flatKV) Close() error { return kv.flat.Close() }
func (kv *flatKV) Tx(update bool) (BucketTx, error) {
tx, err := kv.flat.Tx(update)
if err != nil {
return nil, err
}
return &flatTx{kv: kv.flat, tx: tx, ro: !update}, nil
}
type flatTx struct {
kv FlatKV
tx FlatTx
ro bool
buckets map[string]*flatBucket
}
func (v *flatTx) Get(ctx context.Context, keys []BucketKey) ([][]byte, error) {
ks := make([][]byte, len(keys))
for i, k := range keys {
ks[i] = v.bucketKey(k.Bucket, k.Key)
}
return v.tx.Get(ctx, ks)
}
func (v *flatTx) Commit(ctx context.Context) error {
return v.tx.Commit(ctx)
}
func (v *flatTx) Rollback() error {
return v.tx.Rollback()
}
const bucketSep = '/'
func (v *flatTx) bucketKey(name, key []byte) []byte {
p := make([]byte, len(name)+1+len(key))
n := copy(p, name)
p[n] = bucketSep
n++
copy(p[n:], key)
return p
}
func (v *flatTx) Bucket(name []byte) Bucket {
if b := v.buckets[string(name)]; b != nil {
return b
}
if v.buckets == nil {
v.buckets = make(map[string]*flatBucket)
}
pref := v.bucketKey(name, nil)
b := &flatBucket{flatTx: v, pref: pref}
v.buckets[string(name)] = b
return b
}
type flatBucket struct {
*flatTx
pref []byte
}
func (b *flatBucket) key(k []byte) []byte {
key := make([]byte, len(b.pref)+len(k))
n := copy(key, b.pref)
copy(key[n:], k)
return key
}
func (b *flatBucket) Get(ctx context.Context, keys [][]byte) ([][]byte, error) {
if len(keys) == 0 {
return nil, nil
} else if len(keys) == 1 {
return b.tx.Get(ctx, [][]byte{b.key(keys[0])})
}
nk := make([][]byte, len(keys))
for i, k := range keys {
nk[i] = b.key(k)
}
return b.tx.Get(ctx, nk)
}
func (b *flatBucket) Put(k, v []byte) error {
if b.ro {
return fmt.Errorf("put in ro tx")
}
return b.tx.Put(b.key(k), v)
}
func (b *flatBucket) Del(k []byte) error {
if b.ro {
return fmt.Errorf("del in ro tx")
}
return b.tx.Del(b.key(k))
}
type prefIter struct {
KVIterator
trim []byte
}
func (it *prefIter) Key() []byte {
return bytes.TrimPrefix(it.KVIterator.Key(), it.trim)
}
func (b *flatBucket) Scan(pref []byte) KVIterator {
pref = b.key(pref)
return &prefIter{KVIterator: b.tx.Scan(pref), trim: b.pref}
}