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01372a67a8
- spec: XRPLF/XRPL-Standards#220 - amendment: "DeepFreeze" - implemented deep freeze spec to allow token issuers to prevent currency holders from being able to acquire more of these tokens. - in combination with normal freeze, deep freeze effectively prevents any balance trust line balance change of a currency holder (except direct issuer <-> holder payments). - added 2 new invariant checks to verify that deep freeze cannot be enacted without normal freeze and transfer is not frozen. - made some fixes to existing freeze handling. Co-authored-by: Ed Hennis <ed@ripple.com> Co-authored-by: Howard Hinnant <howard.hinnant@gmail.com>
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.