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Overview

TransferHelper is a utility library that provides safe wrapper functions for ERC20 token transfers. It uses Solmate’s SafeTransferLib to ensure secure token operations. Source: src/libraries/TransferHelper.sol

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Dependencies

import { SafeTransferLib, ERC20 } from "lib/solmate/src/utils/SafeTransferLib.sol";
This library wraps Solmate’s SafeTransferLib for safe ERC20 operations.

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Functions

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_transferFromERC20

function _transferFromERC20(
    address token,
    address from,
    address to,
    uint256 amount
) internal
Transfers tokens from a specified address to a destination address. Parameters:
  • token (address): The contract address of the ERC20 token to transfer
  • from (address): The originating address from which tokens will be transferred
  • to (address): The destination address for the transfer
  • amount (uint256): The amount of tokens to transfer
Requirements:
  • The caller must have approval to spend amount tokens from the from address
  • The from address must have sufficient balance
Safety Features:
  • Automatically handles tokens with non-standard return values
  • Reverts on failed transfers
  • Gas-optimized implementation via Solmate

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_transfer

function _transfer(
    address token,
    address to,
    uint256 amount
) internal
Transfers tokens from the current contract to a destination address. Parameters:
  • token (address): The contract address of the ERC20 token to transfer
  • to (address): The destination address for the transfer
  • amount (uint256): The amount of tokens to transfer
Requirements:
  • The contract must have sufficient balance of the token
Safety Features:
  • Automatically handles tokens with non-standard return values
  • Reverts on failed transfers
  • Gas-optimized implementation via Solmate

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Usage Example

import { TransferHelper } from "./libraries/TransferHelper.sol";

contract Example {
    using TransferHelper for *;
    
    // Transfer tokens from a user to this contract
    function depositTokens(
        address token,
        address user,
        uint256 amount
    ) external {
        TransferHelper._transferFromERC20(
            token,
            user,
            address(this),
            amount
        );
    }
    
    // Transfer tokens from this contract to a user
    function withdrawTokens(
        address token,
        address user,
        uint256 amount
    ) external {
        TransferHelper._transfer(
            token,
            user,
            amount
        );
    }
}

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Why Use TransferHelper?

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Handles Non-Standard ERC20 Tokens

Some ERC20 tokens don’t follow the standard specification:
  • Tokens that don’t return a boolean on transfer or transferFrom
  • Tokens that revert on failure instead of returning false
  • Tokens with missing return values
TransferHelper (via SafeTransferLib) handles all these cases safely.

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Gas Optimization

Solmate’s SafeTransferLib is highly gas-optimized compared to OpenZeppelin’s SafeERC20, making it ideal for production use.

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Consistent Interface

Provides a uniform interface for token transfers across the UMA CTF Adapter codebase.

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Security Considerations

Always ensure proper access control when using these transfer functions. They should typically be called from protected functions to prevent unauthorized token transfers.
These functions will revert if the transfer fails for any reason (insufficient balance, insufficient allowance, etc.). Always handle these cases appropriately in your calling code.

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