45 lines
1.1 KiB
Go
45 lines
1.1 KiB
Go
package vm
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import (
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"math/big"
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)
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const (
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gasOveruseNum = 11
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gasOveruseDenom = 10
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)
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// ComputeGasOutputs computes amount of gas to be refunded and amount of gas to be burned
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// Result is (refund, burn)
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func ComputeGasOutputs(gasUsed, gasLimit int64) (int64, int64) {
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if gasUsed == 0 {
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return 0, gasLimit
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}
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// over = gasLimit/gasUsed - 1 - 0.3
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// over = min(over, 1)
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// gasToBurn = (gasLimit - gasUsed) * over
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// so to factor out division from `over`
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// over*gasUsed = min(gasLimit - (13*gasUsed)/10, gasUsed)
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// gasToBurn = ((gasLimit - gasUsed)*over*gasUsed) / gasUsed
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over := gasLimit - (gasOveruseNum*gasUsed)/gasOveruseDenom
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if over < 0 {
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return gasLimit - gasUsed, 0
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}
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// if we want sharper scaling it goes here:
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// over *= 2
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if over > gasUsed {
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over = gasUsed
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}
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// needs bigint, as it overflows in pathological case gasLimit > 2^32 gasUsed = gasLimit / 2
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gasToBurn := big.NewInt(gasLimit - gasUsed)
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gasToBurn = gasToBurn.Mul(gasToBurn, big.NewInt(over))
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gasToBurn = gasToBurn.Div(gasToBurn, big.NewInt(gasUsed))
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return gasLimit - gasUsed - gasToBurn.Int64(), gasToBurn.Int64()
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}
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