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- protocol/README.md: restore historical GitHub URL path (src/ripple/) - Config.cpp: restore configLegacyName as "rippled.cfg" (legacy name must remain as-is for backward compatibility) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
45 lines
1.7 KiB
Markdown
45 lines
1.7 KiB
Markdown
# protocol
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Classes and functions for handling data and
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values associated with the XRP Ledger protocol.
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## Serialized Objects
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Objects transmitted over the network must be
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serialized into a canonical format. The prefix "ST" refers
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to classes that deal with the serialized format.
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The term "Tx" or "tx" is an abbreviation for "Transaction",
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a commonly occurring object type.
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### Optional Fields
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Our serialized fields have some "type magic" to make
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optional fields easier to read:
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- The operation `x[sfFoo]` means "return the value of 'Foo'
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if it exists, or the default value if it doesn't."
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- The operation `x[~sfFoo]` means "return the value of 'Foo'
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if it exists, or nothing if it doesn't." This usage of the
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tilde/bitwise NOT operator is not standard outside of the
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`xrpld` codebase.
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- As a consequence of this, `x[~sfFoo] = y[~sfFoo]`
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assigns the value of Foo from y to x, including omitting
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Foo from x if it doesn't exist in y.
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Typically, for things that are guaranteed to exist, you use
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`x[sfFoo]` and avoid having to deal with a container that may
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or may not hold a value. For things not guaranteed to exist,
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you use `x[~sfFoo]` because you want such a container. It
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avoids having to look something up twice, once just to see if
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it exists and a second time to get/set its value.
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([Real example](https://github.com/XRPLF/rippled/blob/35f4698aed5dce02f771b34cfbb690495cb5efcc/src/ripple/app/tx/impl/PayChan.cpp#L229-L236))
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The source of this "type magic" is in
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[SField.h](./SField.h#L296-L302).
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### Related Resources
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- [ripple-binary-codec SField enums](https://github.com/XRPLF/xrpl.js/tree/main/packages/ripple-binary-codec/src/enums)
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- [SFCode Registry Tables](https://github.com/XRPLF/sFieldRegistry)
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