Path

Functions for encoding and decoding multi-hop swap paths.

Source: contracts/periphery/libraries/Path.sol

Path Format

Paths encode token addresses and fee tiers as packed bytes:

[token0][fee0][token1][fee1][token2]...
  20       3     20      3     20    bytes

Functions

hasMultiplePools

function hasMultiplePools(bytes memory path) internal pure returns (bool)

Returns true if the path contains more than one pool (multi-hop).

numPools

function numPools(bytes memory path) internal pure returns (uint256)

Returns the number of pools in the path.

decodeFirstPool

function decodeFirstPool(bytes memory path)
    internal
    pure
    returns (address tokenA, address tokenB, uint24 fee)

Decodes the first pool's tokens and fee from the path.

getFirstPool

function getFirstPool(bytes memory path) internal pure returns (bytes memory)

Returns the first pool's encoded bytes.

skipToken

function skipToken(bytes memory path) internal pure returns (bytes memory)

Skips the first token in the path, returning the remaining path.

JavaScript Implementation

function encodePath(tokens, fees) {
    if (tokens.length !== fees.length + 1) {
        throw new Error('Invalid path lengths');
    }

    let path = '0x';
    for (let i = 0; i < fees.length; i++) {
        // Token address (20 bytes)
        path += tokens[i].slice(2).toLowerCase();
        // Fee (3 bytes = 24 bits)
        path += fees[i].toString(16).padStart(6, '0');
    }
    // Final token
    path += tokens[tokens.length - 1].slice(2).toLowerCase();

    return path;
}

function decodePath(path) {
    const tokens = [];
    const fees = [];

    // Remove 0x prefix
    let data = path.slice(2);

    while (data.length > 0) {
        // Token (20 bytes = 40 hex chars)
        tokens.push('0x' + data.slice(0, 40));
        data = data.slice(40);

        if (data.length > 0) {
            // Fee (3 bytes = 6 hex chars)
            fees.push(parseInt(data.slice(0, 6), 16));
            data = data.slice(6);
        }
    }

    return { tokens, fees };
}

Usage Example

// Encode: WVC → USDT → TOKEN_C
const path = encodePath(
    [WVC, USDT, TOKEN_C],
    [3000, 500]  // 0.3%, 0.05%
);
// path = 0x[WVC]000bb8[USDT]0001f4[TOKEN_C]

// Decode
const { tokens, fees } = decodePath(path);
// tokens = [WVC, USDT, TOKEN_C]
// fees = [3000, 500]

Related

• SwapRouter

• VinuSwapQuoter