From d235e2c6a5788ec4a6cff15a16f56b38a3876a0d Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Sun, 28 Jun 2020 14:47:41 -0400
Subject: ...

---
 core/vm/intpool.go | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 core/vm/intpool.go

(limited to 'core/vm/intpool.go')

diff --git a/core/vm/intpool.go b/core/vm/intpool.go
new file mode 100644
index 0000000..917a78d
--- /dev/null
+++ b/core/vm/intpool.go
@@ -0,0 +1,106 @@
+// 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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