@ethereumjs/evm
Version:
JavaScript Ethereum Virtual Machine (EVM) implementation
63 lines • 2.48 kB
JavaScript
import { equalsBytes } from '@ethereumjs/util';
const ZERO_BYTES_16 = new Uint8Array(16);
/**
* Calculates the gas used for the MSM precompiles based on the number of pairs and
* calculating in some discount in relation to the number of pairs.
*
* @param numPairs - Number of pairings provided to the precompile
* @param gasUsedPerPair - Base gas cost per pairing
* @param discountTable - Discount table (pair count -> multiplier)
* @returns Total gas to charge after applying the discount table
*/
export const msmGasUsed = (numPairs, gasUsedPerPair, discountTable) => {
const gasDiscountMax = discountTable[discountTable.length - 1][1];
let gasDiscountMultiplier;
if (numPairs <= discountTable.length) {
if (numPairs === 0) {
gasDiscountMultiplier = 0; // this implicitly sets gasUsed to 0 as per the EIP.
}
else {
gasDiscountMultiplier = discountTable[numPairs - 1][1];
}
}
else {
gasDiscountMultiplier = gasDiscountMax;
}
// (numPairs * multiplication_cost * discount) / multiplier
return (BigInt(numPairs) * gasUsedPerPair * BigInt(gasDiscountMultiplier)) / BigInt(1000);
};
/**
* BLS-specific zero check to check that the top 16 bytes of a 64 byte field element provided
* are always zero (see EIP notes on field element encoding).
*
* Zero byte ranges are expected to be passed in the following format (and so each referencing
* 16-byte ranges):
*
* ```ts
* const zeroByteRanges = [
* [0, 16],
* [64, 80],
* [128, 144]
*
* ]
* ```
*
* @param opts - Precompile input wrapper containing the data to inspect
* @param zeroByteRanges - Ranges (as [start, end]) within which bytes must be zero
* @param pName - Human readable precompile name for logging
* @param pairStart - Optional offset into the data when iterating through pairs
* @returns `true` if every specified range contains only zero bytes
*/
export const leading16ZeroBytesCheck = (opts, zeroByteRanges, pName, pairStart = 0) => {
for (const index in zeroByteRanges) {
const slicedBuffer = opts.data.subarray(zeroByteRanges[index][0] + pairStart, zeroByteRanges[index][1] + pairStart);
if (!(equalsBytes(slicedBuffer, ZERO_BYTES_16) === true)) {
if (opts._debug !== undefined) {
opts._debug(`${pName} failed: Point not on curve`);
}
return false;
}
}
return true;
};
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