This module provides low-level decoding and encoding functionality for Solidity and the Solidity ABI. Many parts of this module are intended primarily for internal use by Truffle and so remain largely undocumented, but some of its types are also output by @truffle/decoder, which provides a higher-level interface to much of this module's functionality.

If you're here from Truffle Decoder

If you're coming here from @truffle/decoder, you probably just want to know about the parts that are relevant to you. These are:

• The "data" category (specifically Format)
• The "output" and "enumerations" categories (CalldataDecoding, LogDecoding, et al., see below)
• The "errors" category (specifically UnknownUserDefinedTypeError)

Note that the data category is largely scarce in documentation, although that's because it's largely self-explanatory.

If you're not just here from Truffle Decoder, but are actually interested in the lower-level workings, read on.

How this module differs from Truffle Decoder

Unlike Truffle Decoder, this library makes no network connections and avoids dependencies that do. Instead, its decoding functionality is generator-based; calling one of the decoding functions returns a generator. This generator's next() function may return a finished result, or it may return a request for more information. It is up to the caller to fulfill these requests -- say, by making a network connection of its own. This is how @truffle/decoder works; @truffle/codec makes requests, and @truffle/decoder fulfills them by looking up the necessary information on the blockchain.

This library also provides additional functionality beyond what's used by Truffle Decoder. In particular, this library also exists to support Truffle Debugger, and so it provides encoding functionality not just for transactions, logs, and state variables, but also for Solidity variables during transaction execution. It provides functionality for decoding Solidity's internal function pointers, which the debugger uses, even though Truffle Decoder does not.

(Note that circularity detection for memory structures has yet to be implemented, but is coming soon.)

There is also some rudimentary encoding functionality, although currently that's just used internally. A better interface for the encoding functionality is intended for the future.

How to use

You should probably use @truffle/decoder instead, if your use case doesn't preclude it. This module has little documentation, where it has any at all, and it's likely that parts of its interface may change (particularly regarding allocation). That said, if you truly need the functionality here, Truffle Decoder can perhaps serve as something of a reference implementation (and perhaps Truffle Debugger as well, though that code is much harder to read or copy).