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f2ca499c97
Introduce shadow tickets for export replay protection: - ltSHADOW_TICKET ledger entry: account-owned, keyed by account + ticket sequence. Fields: sfAccount, sfTicketSequence, sfTransactionHash, sfLedgerSequence, sfOwnerNode. - ExportLedgerOps::createShadowTicket(): creates shadow ticket when exported tx has sfTicketSequence. Charges owner reserve. Called from both hook xport() path and Export transactor. - ExportLedgerOps::cancelShadowTicket(): deletes shadow ticket, frees reserve. Used by xport_cancel hook API. - xport_cancel(ticket_seq) hook API: allows hooks to cancel shadow tickets for exports that will never get a callback. - InvariantCheck: add ltSHADOW_TICKET to valid entry types. - Test: verify shadow ticket creation with correct fields and owner count bump via ttEXPORT with TicketSequence.
protocol
Classes and functions for handling data and values associated with the XRP Ledger protocol.
Serialized Objects
Objects transmitted over the network must be serialized into a canonical format. The prefix "ST" refers to classes that deal with the serialized format.
The term "Tx" or "tx" is an abbreviation for "Transaction", a commonly occurring object type.
Optional Fields
Our serialized fields have some "type magic" to make optional fields easier to read:
- The operation
x[sfFoo]means "return the value of 'Foo' if it exists, or the default value if it doesn't." - The operation
x[~sfFoo]means "return the value of 'Foo' if it exists, or nothing if it doesn't." This usage of the tilde/bitwise NOT operator is not standard outside of therippledcodebase.- As a consequence of this,
x[~sfFoo] = y[~sfFoo]assigns the value of Foo from y to x, including omitting Foo from x if it doesn't exist in y.
- As a consequence of this,
Typically, for things that are guaranteed to exist, you use
x[sfFoo] and avoid having to deal with a container that may
or may not hold a value. For things not guaranteed to exist,
you use x[~sfFoo] because you want such a container. It
avoids having to look something up twice, once just to see if
it exists and a second time to get/set its value.
(Real example)
The source of this "type magic" is in SField.h.