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path: root/core/block_cache.go
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package core

import (
    "sync"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
)

// BlockCache implements a caching mechanism specifically for blocks and uses FILO to pop
type BlockCache struct {
    size int

    hashes []common.Hash
    blocks map[common.Hash]*types.Block

    mu sync.RWMutex
}

// Creates and returns a `BlockCache` with `size`. If `size` is smaller than 1 it will panic
func NewBlockCache(size int) *BlockCache {
    if size < 1 {
        panic("block cache size not allowed to be smaller than 1")
    }

    bc := &BlockCache{size: size}
    bc.Clear()
    return bc
}

func (bc *BlockCache) Clear() {
    bc.blocks = make(map[common.Hash]*types.Block)
    bc.hashes = nil

}

func (bc *BlockCache) Push(block *types.Block) {
    bc.mu.Lock()
    defer bc.mu.Unlock()

    if len(bc.hashes) == bc.size {
        delete(bc.blocks, bc.hashes[0])

        // XXX There are a few other options on solving this
        // 1) use a poller / GC like mechanism to clean up untracked objects
        // 2) copy as below
        // re-use the slice and remove the reference to bc.hashes[0]
        // this will allow the element to be garbage collected.
        copy(bc.hashes, bc.hashes[1:])
    } else {
        bc.hashes = append(bc.hashes, common.Hash{})
    }

    hash := block.Hash()
    bc.blocks[hash] = block
    bc.hashes[len(bc.hashes)-1] = hash
}

func (bc *BlockCache) Get(hash common.Hash) *types.Block {
    bc.mu.RLock()
    defer bc.mu.RUnlock()

    if block, haz := bc.blocks[hash]; haz {
        return block
    }

    return nil
}