> For the complete documentation index, see [llms.txt](https://docs.fly.trade/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fly.trade/developers/deprecated-magpie-contracts/magpierouterv2/router/libuniswapv3.md).

# LibUniswapV3

This is a Solidity library called LibUniswapV3 that provides functions for swapping assets on Uniswap v3. 

### swapUniswapV3():

The `swapUniswapV3` function is tailored for executing token swaps on Uniswap V3, a more advanced and flexible version of the Uniswap protocol. It begins by extracting key parameters from the `input` byte array using assembly for efficiency, including the amount of the input token (`amountIn`), recipient's address, pool address (`poolAddress`), input and output token addresses (`assetIn` and `assetOut`), and the swap fee (`fee`). A special `data` byte array is prepared, embedding the `assetIn` address, to be used in the swap call. The function then determines the swap direction (`zeroForOne`) based on the order of the input and output assets. It executes the swap by calling the `swap` method on the Uniswap V3 pool contract, passing parameters like the recipient, swap direction, input amount, and a price limit determined by the constants `MIN_SQRT_RATIO` and `MAX_SQRT_RATIO`. Finally, it calculates the output amount (`amountOut`) based on the returned values from the swap, ensuring the correct output amount is obtained whether swapping for token 0 or token 1 in the pool.

**Input**

<table><thead><tr><th width="216.99999999999997">Field</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td>input</td><td>bytes memory </td><td>A byte array containing necessary swapping parameters.</td></tr></tbody></table>

**Output**

<table><thead><tr><th>Field</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td><p></p><pre class="language-solidity"><code class="lang-solidity">amountOut
</code></pre></td><td><p></p><pre class="language-solidity"><code class="lang-solidity">uint256
</code></pre></td><td>The amount received after swapping.</td></tr></tbody></table>

### uniswapV3SwapCallback():

\
The `uniswapV3SwapCallback` function is an internal callback function used in Uniswap V3 swaps, typically called by the Uniswap V3 pool contract during a swap operation. The function first checks if both `amount0Delta` and `amount1Delta` are non-positive, in which case it reverts the transaction as this indicates an invalid state. Then, it extracts the `assetIn` address from the `data` byte array using assembly for efficient memory access. Finally, the function transfers the appropriate amount of `assetIn` (determined by whether `amount0Delta` or `amount1Delta` is positive) to the sender of the transaction (`msg.sender`), fulfilling the liquidity requirements of the swap on Uniswap V3.

**input**

| Field        | Type         | Description                                                             |
| ------------ | ------------ | ----------------------------------------------------------------------- |
| amount0Delta | int256       | the changes in the amount of the first token involved in the swap       |
| amount1Delta | int256       | the changes in the amount of the second token involved in the swap      |
| data         | bytes memory | a byte array containing additional information needed for the callback. |