github.com/Goplush/go-ethereum@v0.0.0-20191031044858-21506be82b68/core/vm/intpool.go (about)

     1  // Copyright 2017 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"math/big"
    21  	"sync"
    22  )
    23  
    24  var checkVal = big.NewInt(-42)
    25  
    26  const poolLimit = 256
    27  
    28  // intPool is a pool of big integers that
    29  // can be reused for all big.Int operations.
    30  type intPool struct {
    31  	pool *Stack
    32  }
    33  
    34  func newIntPool() *intPool {
    35  	return &intPool{pool: newstack()}
    36  }
    37  
    38  // get retrieves a big int from the pool, allocating one if the pool is empty.
    39  // Note, the returned int's value is arbitrary and will not be zeroed!
    40  func (p *intPool) get() *big.Int {
    41  	if p.pool.len() > 0 {
    42  		return p.pool.pop()
    43  	}
    44  	return new(big.Int)
    45  }
    46  
    47  // getZero retrieves a big int from the pool, setting it to zero or allocating
    48  // a new one if the pool is empty.
    49  func (p *intPool) getZero() *big.Int {
    50  	if p.pool.len() > 0 {
    51  		return p.pool.pop().SetUint64(0)
    52  	}
    53  	return new(big.Int)
    54  }
    55  
    56  // put returns an allocated big int to the pool to be later reused by get calls.
    57  // Note, the values as saved as is; neither put nor get zeroes the ints out!
    58  func (p *intPool) put(is ...*big.Int) {
    59  	if len(p.pool.data) > poolLimit {
    60  		return
    61  	}
    62  	for _, i := range is {
    63  		// verifyPool is a build flag. Pool verification makes sure the integrity
    64  		// of the integer pool by comparing values to a default value.
    65  		if verifyPool {
    66  			i.Set(checkVal)
    67  		}
    68  		p.pool.push(i)
    69  	}
    70  }
    71  
    72  // The intPool pool's default capacity
    73  const poolDefaultCap = 25
    74  
    75  // intPoolPool manages a pool of intPools.
    76  type intPoolPool struct {
    77  	pools []*intPool
    78  	lock  sync.Mutex
    79  }
    80  
    81  var poolOfIntPools = &intPoolPool{
    82  	pools: make([]*intPool, 0, poolDefaultCap),
    83  }
    84  
    85  // get is looking for an available pool to return.
    86  func (ipp *intPoolPool) get() *intPool {
    87  	ipp.lock.Lock()
    88  	defer ipp.lock.Unlock()
    89  
    90  	if len(poolOfIntPools.pools) > 0 {
    91  		ip := ipp.pools[len(ipp.pools)-1]
    92  		ipp.pools = ipp.pools[:len(ipp.pools)-1]
    93  		return ip
    94  	}
    95  	return newIntPool()
    96  }
    97  
    98  // put a pool that has been allocated with get.
    99  func (ipp *intPoolPool) put(ip *intPool) {
   100  	ipp.lock.Lock()
   101  	defer ipp.lock.Unlock()
   102  
   103  	if len(ipp.pools) < cap(ipp.pools) {
   104  		ipp.pools = append(ipp.pools, ip)
   105  	}
   106  }