database/leveldb/cache.go

   1 package leveldb
   2
   3 import (
   4         "fmt"
   5         "sync"
   6
   7         "github.com/golang/groupcache/lru"
   8         "github.com/golang/groupcache/singleflight"
   9
  10         "github.com/vapor/protocol/bc"
  11         "github.com/vapor/protocol/bc/types"
  12 )
  13
  14 const maxCachedBlocks = 30
  15
  16 func newBlockCache(fillFn func(hash *bc.Hash) *types.Block) blockCache {
  17         return blockCache{
  18                 lru:    lru.New(maxCachedBlocks),
  19                 fillFn: fillFn,
  20         }
  21 }
  22
  23 type blockCache struct {
  24         mu     sync.Mutex
  25         lru    *lru.Cache
  26         fillFn func(hash *bc.Hash) *types.Block
  27         single singleflight.Group
  28 }
  29
  30 func (c *blockCache) lookup(hash *bc.Hash) (*types.Block, error) {
  31         if b, ok := c.get(hash); ok {
  32                 return b, nil
  33         }
  34
  35         block, err := c.single.Do(hash.String(), func() (interface{}, error) {
  36                 b := c.fillFn(hash)
  37                 if b == nil {
  38                         return nil, fmt.Errorf("There are no block with given hash %s", hash.String())
  39                 }
  40
  41                 c.add(b)
  42                 return b, nil
  43         })
  44         if err != nil {
  45                 return nil, err
  46         }
  47         return block.(*types.Block), nil
  48 }
  49
  50 func (c *blockCache) get(hash *bc.Hash) (*types.Block, bool) {
  51         c.mu.Lock()
  52         block, ok := c.lru.Get(*hash)
  53         c.mu.Unlock()
  54         if block == nil {
  55                 return nil, ok
  56         }
  57         return block.(*types.Block), ok
  58 }
  59
  60 func (c *blockCache) add(block *types.Block) {
  61         c.mu.Lock()
  62         c.lru.Add(block.Hash(), block)
  63         c.mu.Unlock()
  64 }