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rippled
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Classes and functions for handling data and values associated with the Ripple protocol.
In ripple objects transmitted over the network must be serialized into a canonical format. The prefix "ST" refers to classes that deal with the serialized format of ripple objects.
The term "Tx" or "tx" is an abbreviation for "Transaction", a commonly occurring object type.
Our serialized fields have some "type magic" to make optional fields easier to read:
x[sfFoo] means "return the value of 'Foo'
if it exists, or the default value if it doesn't."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 the rippled codebase.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.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.
1.8.17