_decimalsOffset()

• The _decimalsOffset() plays an important role in preventing the first deposit attack, in which an attacker could inflate the worth of each share by donating assets directly to the vault.

Introductory Questions

No deposits have been made on a Vault, decimalOffset is 9, and underlyingTokenDecimals are 6.

• How many shares will you receive for depositing 1 wei of underlying?
  • 1e9 shares
• How many assets are required to mint 1 wei of shares? and what about 1e9 shares?
  • 1 wei of underlying for any amount of shares between 1 wei - 1e9
• What about to mint 1e15 shares?
  • 1 full underlyingToken (1e6)
• How many shares will you receive if you deposit 1 full USDC (1e6)?
  • 1e15 (A full share)

decimalOffset is 9. How many shares will you receive for depositing:

• 1 fullToken if underlyingToken has 6 decimals?
  • 1e15
• And if underlyingToken has 8 decimals?
  • 1e17
• What about if underlyingToken has 18 decimals?
  • 1e27

Assume the shares-asset rate is the same as when it was initialized (no yield generated) && decimalOffset is 9.

• How many shares will you need to withdraw 1 fullToken:
  • if underlyingToken has 18 decimals?
    • 1e27
  • What about if it has 6 decimals?
    • 1e15

OZ explanation:

The _decimalsOffset() corresponds to an offset in the decimal representation between the underlying asset's decimals and the vault decimals. 
This offset also determines the rate of virtual shares to virtual assets in the vault, which itself determines the initial exchange rate