feat(libraries): add byte slicing and multi-hop path encoding

src/libraries/BytesLib.sol

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+/// @title Slicing and word reads over tightly packed calldata paths.
+library BytesLib {
+    function slice(bytes memory source, uint256 start, uint256 length) internal pure returns (bytes memory) {
+        require(length + 31 >= length, "BytesLib: SLICE_OVERFLOW");
+        require(source.length >= start + length, "BytesLib: SLICE_OOB");
+
+        bytes memory result;
+        assembly {
+            switch iszero(length)
+            case 0 {
+                result := mload(0x40)
+                let lengthmod := and(length, 31)
+                let mc := add(add(result, lengthmod), mul(0x20, iszero(lengthmod)))
+                let end := add(mc, length)
+                for {
+                    let cc := add(add(add(source, lengthmod), mul(0x20, iszero(lengthmod))), start)
+                } lt(mc, end) {
+                    mc := add(mc, 0x20)
+                    cc := add(cc, 0x20)
+                } { mstore(mc, mload(cc)) }
+                mstore(result, length)
+                mstore(0x40, and(add(mc, 31), not(31)))
+            }
+            default {
+                result := mload(0x40)
+                mstore(result, 0)
+                mstore(0x40, add(result, 0x20))
+            }
+        }
+        return result;
+    }
+
+    function toAddress(bytes memory source, uint256 start) internal pure returns (address) {
+        require(source.length >= start + 20, "BytesLib: ADDRESS_OOB");
+        address result;
+        assembly {
+            result := div(mload(add(add(source, 0x20), start)), 0x1000000000000000000000000)
+        }
+        return result;
+    }
+
+    function toUint24(bytes memory source, uint256 start) internal pure returns (uint24) {
+        require(source.length >= start + 3, "BytesLib: UINT24_OOB");
+        uint24 result;
+        assembly {
+            result := mload(add(add(source, 0x3), start))
+        }
+        return result;
+    }
+}

src/libraries/Path.sol

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.36;
+
+import {BytesLib} from "./BytesLib.sol";
+
+/// @title Encoding of multi-hop swap paths as packed token/fee/token sequences.
+library Path {
+    using BytesLib for bytes;
+
+    uint256 private constant addrSize = 20;
+    uint256 private constant feeSize = 3;
+    uint256 private constant nextOffset = addrSize + feeSize;
+    uint256 private constant popOffset = nextOffset + addrSize;
+    uint256 private constant multiplePoolsMinLength = popOffset + nextOffset;
+
+    function hasMultiplePools(bytes memory path) internal pure returns (bool) {
+        return path.length >= multiplePoolsMinLength;
+    }
+
+    function numPools(bytes memory path) internal pure returns (uint256) {
+        return (path.length - addrSize) / nextOffset;
+    }
+
+    function decodeFirstPool(bytes memory path) internal pure returns (address tokenA, address tokenB, uint24 fee) {
+        tokenA = path.toAddress(0);
+        fee = path.toUint24(addrSize);
+        tokenB = path.toAddress(nextOffset);
+    }
+
+    function getFirstPool(bytes memory path) internal pure returns (bytes memory) {
+        return path.slice(0, popOffset);
+    }
+
+    function skipToken(bytes memory path) internal pure returns (bytes memory) {
+        return path.slice(nextOffset, path.length - nextOffset);
+    }
+}