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// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package vm
import (
"math/big"
"sync"
)
var checkVal = big.NewInt(-42)
const poolLimit = 256
// intPool is a pool of big integers that
// can be reused for all big.Int operations.
type intPool struct {
pool *Stack
}
func newIntPool() *intPool {
return &intPool{pool: newstack()}
}
// get retrieves a big int from the pool, allocating one if the pool is empty.
// Note, the returned int's value is arbitrary and will not be zeroed!
func (p *intPool) get() *big.Int {
if p.pool.len() > 0 {
return p.pool.pop()
}
return new(big.Int)
}
// getZero retrieves a big int from the pool, setting it to zero or allocating
// a new one if the pool is empty.
func (p *intPool) getZero() *big.Int {
if p.pool.len() > 0 {
return p.pool.pop().SetUint64(0)
}
return new(big.Int)
}
// put returns an allocated big int to the pool to be later reused by get calls.
// Note, the values as saved as is; neither put nor get zeroes the ints out!
func (p *intPool) put(is ...*big.Int) {
if len(p.pool.data) > poolLimit {
return
}
for _, i := range is {
// verifyPool is a build flag. Pool verification makes sure the integrity
// of the integer pool by comparing values to a default value.
if verifyPool {
i.Set(checkVal)
}
p.pool.push(i)
}
}
// The intPool pool's default capacity
const poolDefaultCap = 25
// intPoolPool manages a pool of intPools.
type intPoolPool struct {
pools []*intPool
lock sync.Mutex
}
var poolOfIntPools = &intPoolPool{
pools: make([]*intPool, 0, poolDefaultCap),
}
// get is looking for an available pool to return.
func (ipp *intPoolPool) get() *intPool {
ipp.lock.Lock()
defer ipp.lock.Unlock()
if len(poolOfIntPools.pools) > 0 {
ip := ipp.pools[len(ipp.pools)-1]
ipp.pools = ipp.pools[:len(ipp.pools)-1]
return ip
}
return newIntPool()
}
// put a pool that has been allocated with get.
func (ipp *intPoolPool) put(ip *intPool) {
ipp.lock.Lock()
defer ipp.lock.Unlock()
if len(ipp.pools) < cap(ipp.pools) {
ipp.pools = append(ipp.pools, ip)
}
}
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