github.com/xfond/eth-implementation@v1.8.9-0.20180514135602-f6bc65fc6811/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 "math/big"
    20  
    21  var checkVal = big.NewInt(-42)
    22  
    23  const poolLimit = 256
    24  
    25  // intPool is a pool of big integers that
    26  // can be reused for all big.Int operations.
    27  type intPool struct {
    28  	pool *Stack
    29  }
    30  
    31  func newIntPool() *intPool {
    32  	return &intPool{pool: newstack()}
    33  }
    34  
    35  // get retrieves a big int from the pool, allocating one if the pool is empty.
    36  // Note, the returned int's value is arbitrary and will not be zeroed!
    37  func (p *intPool) get() *big.Int {
    38  	if p.pool.len() > 0 {
    39  		return p.pool.pop()
    40  	}
    41  	return new(big.Int)
    42  }
    43  
    44  // getZero retrieves a big int from the pool, setting it to zero or allocating
    45  // a new one if the pool is empty.
    46  func (p *intPool) getZero() *big.Int {
    47  	if p.pool.len() > 0 {
    48  		return p.pool.pop().SetUint64(0)
    49  	}
    50  	return new(big.Int)
    51  }
    52  
    53  // put returns an allocated big int to the pool to be later reused by get calls.
    54  // Note, the values as saved as is; neither put nor get zeroes the ints out!
    55  func (p *intPool) put(is ...*big.Int) {
    56  	if len(p.pool.data) > poolLimit {
    57  		return
    58  	}
    59  	for _, i := range is {
    60  		// verifyPool is a build flag. Pool verification makes sure the integrity
    61  		// of the integer pool by comparing values to a default value.
    62  		if verifyPool {
    63  			i.Set(checkVal)
    64  		}
    65  		p.pool.push(i)
    66  	}
    67  }