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Pair Addresses

Rails Network utilizes the tried and tested Uniswap V2 libraries. Below is information about the Uniswap V2 Smart Contracts directly from Uniswap:

getPair

The most obvious way to get the address for a pair is to call getPair on the factory. If the pair exists, this function will return its address, else address(0) (0x0000000000000000000000000000000000000000).

  • The "canonical" way to determine whether or not a pair exists.
  • Requires an on-chain lookup.

CREATE2

Thanks to some fancy footwork in the factory, we can also compute pair addresses without any on-chain lookups because of CREATE2. The following values are required for this technique:

addressThe factory address
saltkeccak256(abi.encodePacked(token0, token1))
keccak256(init_code)0x96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f
  • token0 must be strictly less than token1 by sort order.
  • Can be computed offline.
  • Requires the ability to perform keccak256.

Examples​

Solidity​

address factory = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
address token0 = 0xCAFE000000000000000000000000000000000000; // change me!
address token1 = 0xF00D000000000000000000000000000000000000; // change me!

address pair = address(uint(keccak256(abi.encodePacked(
  hex'ff',
  factory,
  keccak256(abi.encodePacked(token0, token1)),
  hex'96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f'
))));