Ethereum (ETH) Exchange Wallet Development: Withdrawal Request Process

Overview

The withdrawal process in an Ethereum exchange wallet follows a specific sequence. This guide builds upon the previous installment, "Ethereum (ETH) Exchange Wallet Development: Deposit Address Generation", which covered API request validation. The same validation middleware (using Gin framework) applies here.

Withdrawal Request Parameters

Key Considerations

1. OutSerial Field:

   • Database enforces uniqueness via index
   • Prevents duplicate processing of identical withdrawal requests

Validation Process

1. Address Validation

req.Address = strings.ToLower(req.Address)
re := regexp.MustCompile("^0x[0-9a-fA-F]{40}$")
if !re.MatchString(req.Address) {
    c.JSON(http.StatusOK, gin.H{
        "error":   hcommon.ErrorAddressWrong,
        "err_msg": hcommon.ErrorAddressWrongMsg,
    })
    return
}

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2. Amount Validation

balanceObj, err := decimal.NewFromString(req.Balance)
if err != nil {
    hcommon.Log.Errorf("err: [%T] %s", err, err.Error())
    c.JSON(http.StatusOK, gin.H{
        "error":   hcommon.ErrorBalanceFormat,
        "err_msg": hcommon.ErrorBalanceFormatMsg,
    })
    return
}

if balanceObj.LessThanOrEqual(decimal.NewFromInt(0)) {
    c.JSON(http.StatusOK, gin.H{
        "error":   hcommon.ErrorBalanceFormat,
        "err_msg": hcommon.ErrorBalanceFormatMsg,
    })
    return
}

if balanceObj.Exponent() < -18 {
    c.JSON(http.StatusOK, gin.H{
        "error":   hcommon.ErrorBalanceFormat,
        "err_msg": hcommon.ErrorBalanceFormatMsg,
    })
    return
}

Post-Validation Process

After successful validation:

1. Data gets inserted into the database
2. The withdrawal processing system takes over (as described in "Ethereum (ETH) Exchange Wallet Development: Withdrawal Processing")

Implementation Details

The complete implementation is available on GitHub:
https://github.com/moremorefun/go-dc-wallet

Main functionality entry point: cmd/api/main.go

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FAQ

Q: Why is address case conversion necessary?

A: Ethereum addresses are case-insensitive. Converting to lowercase ensures consistent validation and storage.

Q: What happens if duplicate OutSerial is submitted?

A: The database uniqueness constraint will reject the transaction, preventing duplicate withdrawals.

Q: What's the maximum decimal precision for ETH?

A: Ethereum supports up to 18 decimal places (1 Wei = 10^-18 ETH).

Q: How are negative withdrawal amounts prevented?

A: The validation explicitly checks that the amount is greater than zero.

Q: Where does the process go after successful validation?

A: The withdrawal gets queued for processing by the system described in part 4 of this series.