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docs: update spl token exchange integration (#19573) 

* docs: update spl token exchange integration

* Apply suggestions from code review

Co-authored-by: Michael Vines <mvines@gmail.com>

Co-authored-by: Michael Vines <mvines@gmail.com>
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Trent Nelson 2021-09-02 11:32:08 -06:00 committed by GitHub
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36
docs/src/integrations/exchange.md
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@ -694,35 +694,35 @@ Signature: 3R6tsog17QM8KfzbcbdP4aoMfwgo6hBggJDVy7dZPVmH2xbCWjEj31JKD53NzMrf25ChF
### Depositing ### Depositing
Since each `(user, mint)` pair requires a separate account on chain, it is Since each `(wallet, mint)` pair requires a separate account on chain. It is
recommended that an exchange create batches of token accounts in advance and assign them recommended that the addresses for these accounts be derived from SOL deposit
to users on request. These accounts should all be owned by exchange-controlled wallets using the
keypairs. [Associated Token Account](https://spl.solana.com/associated-token-account) (ATA)
scheme and that _only_ deposits from ATA addresses be accepted.
Monitoring for deposit transactions should follow the [block polling](#poll-for-blocks) Monitoring for deposit transactions should follow the [block polling](#poll-for-blocks)
method described above. Each new block should be scanned for successful transactions method described above. Each new block should be scanned for successful transactions
issuing SPL Token [Transfer](https://github.com/solana-labs/solana-program-library/blob/096d3d4da51a8f63db5160b126ebc56b26346fc8/token/program/src/instruction.rs#L92) issuing SPL Token [Transfer](https://github.com/solana-labs/solana-program-library/blob/fc0d6a2db79bd6499f04b9be7ead0c400283845e/token/program/src/instruction.rs#L105)
or [Transfer2](https://github.com/solana-labs/solana-program-library/blob/096d3d4da51a8f63db5160b126ebc56b26346fc8/token/program/src/instruction.rs#L252) or [TransferChecked](https://github.com/solana-labs/solana-program-library/blob/fc0d6a2db79bd6499f04b9be7ead0c400283845e/token/program/src/instruction.rs#L268)
instructions referencing user accounts, then querying the instructions referencing user accounts. It is possible that a transfer is initiated
[token account balance](developing/clients/jsonrpc-api.md#gettokenaccountbalance) by a smart contract via [Cross Program Invocation](/developing/programming-model/calling-between-programs#cross-program-invocations),
updates. so [inner instructions](/terminology#inner-instruction) must be checked as well.
The `preTokenBalance` and `postTokenBalance` fields from the transaction's metadata
[Considerations](https://github.com/solana-labs/solana/issues/12318) are being must then be used to determine the effective balance change.
made to exend the `preBalance` and `postBalance` transaction status metadata
fields to include SPL Token balance transfers.
### Withdrawing ### Withdrawing
The withdrawal address a user provides should be the same address used for The withdrawal address a user provides must be the that of their SOL wallet.
regular SOL withdrawal.
Before executing a withdrawal [transfer](#token-transfers), Before executing a withdrawal [transfer](#token-transfers),
the exchange should check the address as the exchange should check the address as
[described above](#validating-user-supplied-account-addresses-for-withdrawals). [described above](#validating-user-supplied-account-addresses-for-withdrawals).
Additionally this address must be owned by the System Program and have no account data. If the address has no SOL balance, user confirmation should be obtained before proceeding with the withdrawal. All other withdrawal addresses must be rejected.
From the withdrawal address, the associated token account for the correct mint From the withdrawal address, the [Associated Token Account](https://spl.solana.com/associated-token-account)
determined and the transfer issued to that account. Note that it's possible (ATA) for the correct mint is derived and the transfer issued to that account via a
that the associated token account does not yet exist, at which point the [TransferChecked](https://github.com/solana-labs/solana-program-library/blob/fc0d6a2db79bd6499f04b9be7ead0c400283845e/token/program/src/instruction.rs#L268)
instruction. Note that it is possible that the ATA address does not yet exist, at which point the
exchange should fund the account on behalf of the user. For SPL Token v2 exchange should fund the account on behalf of the user. For SPL Token v2
accounts, funding the withdrawal account will require 0.00203928 SOL (2,039,280 accounts, funding the withdrawal account will require 0.00203928 SOL (2,039,280
lamports). lamports).

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docs/src/terminology.md
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@ -139,7 +139,7 @@ An increase in token supply over time used to fund rewards for validation and to
## inner instruction ## inner instruction
See [cross-program invocation](terminology.md#cross-program-invocation). See [cross-program invocation](terminology.md#cross-program-invocation-cpi).
## instruction ## instruction