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core/vm: metropolis precompiles #14959

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Aug 15, 2017
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core/vm: metropolis precompiles #14959

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7bbdf3e
core: add Metropolis pre-compiles (EIP 197, 198 and 213)
obscuren Aug 10, 2017
6131dd5
core/vm: polish precompile contract code, add tests and benches
karalabe Aug 10, 2017
d8aaa3a
core/vm: benchmarking of metro precompiles
holiman Aug 14, 2017
f8d8b56
core/vm: optimize copy-less data retrievals
karalabe Aug 14, 2017
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16 changes: 15 additions & 1 deletion core/vm/common.go
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,21 @@ func calcMemSize(off, l *big.Int) *big.Int {

// getData returns a slice from the data based on the start and size and pads
// up to size with zero's. This function is overflow safe.
func getData(data []byte, start, size *big.Int) []byte {
func getData(data []byte, start uint64, size uint64) []byte {
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Comment says this function is overflow safe. It's not..

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Overflow safe as in you can index outside of the bounds.

length := uint64(len(data))
if start > length {
start = length
}
end := start + size
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Though, I guess it would be overflow safe if you ensured that end >= start ?

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Well, if start + size can overflow a uint64, the big version of this method should be used.

if end > length {
end = length
}
return common.RightPadBytes(data[start:end], int(size))
}

// getDataBig returns a slice from the data based on the start and size and pads
// up to size with zero's. This function is overflow safe.
func getDataBig(data []byte, start *big.Int, size *big.Int) []byte {
dlen := big.NewInt(int64(len(data)))

s := math.BigMin(start, dlen)
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