ABI spec #194

digorithm · 2021-08-03T21:07:24Z

WIP

This is the initial draft for the Fuel's ABI specs. Heavily inspired by Solidity's ABI spec but directed toward Sway's canonical types.

This is tackling the following issue: #151

This is prerequisite to build an initial version of the Rust SDK for Sway, which is a prerequisite to enable users to write Sway tests in Rusts.

Having the ABI spec'd out will enable the tooling around the Sway compiler to craft ABI calls, enabling users to use other languages (such as Rust) to interact with Sway contracts.

This is a work in progress and we still have to discuss some implementation details, such as padding direction, encoding Sway custom types (structs, enums), and more. So feel free to discuss everything related to it in this space.

There's also an accompanying PR for this PR: FuelLabs/sway#131 where I'm writing some code to test the encoding of this ABI being spec'd here.

specs/protocol/abi.md

sezna · 2021-08-04T00:26:14Z

specs/protocol/abi.md

+To select which function you want to call, first, this function must be a _public_ function in a _contract_ type of a Sway program. For instance:
+
+```rust
+contract;


This is actually not entirely true anymore, and this may be my fault for not making this clear. There are examples here. A function must be in an abi for it to be included here.

specs/protocol/abi.md

adlerjohn · 2021-08-04T02:08:13Z

specs/protocol/abi.md

+## Function selector 
+To select which function you want to call, first, this function must be a _public_ function in a _contract_ type of a Sway program. For instance:
+
+```rust


Is now a good time to migrate to mdBook and make use of FuelLabs/sway#129?

cc @leviathanbeak. Would a sway codeblock work with just the changes to highlight.js, or is it also required to modify mdBook somehow?

specs/protocol/abi.md

digorithm · 2021-08-23T16:23:09Z

specs/protocol/abi.md

+000000000000002a // `42` encoded as u64
+```
+
+TODO: I'm assuming the encoder/decoder can infer which variant is being passed by the call arguments (e.g `MySumType::x(42)` being passed to the call, so it knows it's the variant `x`). We could also encode the enum variant's numeric representation (e.g 0, 1, 2, ...) in the ABI. Thoughts?


@adlerjohn @sezna Can I get some thoughts on this last TODO here?

ABI encoded data should be able to be decoded knowing only the ABI definition (and the encoded data ofc). So you shouldn't need access to how the encoding happened.

sezna · 2021-08-25T23:31:20Z

This is looking really good upon cursory skimming. I'll comb through it again soon.

specs/protocol/abi.md

sezna · 2021-08-27T18:10:53Z

specs/protocol/abi.md

+
+Then, each receipt type will have its own properties. Some of these properties are related to the FuelVM's registers, as specified in more detail [here](https://github.com/FuelLabs/fuel-specs/blob/master/specs/vm/opcodes.md).
+
+_Important note:_ For the JSON representation of the receipts, we represent 64-bit unsigned integers as a JSON's `String` due to limitation around the type `Number` in the JSON specification, which only supports numbers up to `2^{53-1}`, whereas the FuelVM's registers hold values up to `2^64`.


Suggested change

_Important note:_ For the JSON representation of the receipts, we represent 64-bit unsigned integers as a JSON's `String` due to limitation around the type `Number` in the JSON specification, which only supports numbers up to `2^{53-1}`, whereas the FuelVM's registers hold values up to `2^64`.

_Important note:_ For the JSON representation of receipts, we represent 64-bit unsigned integers as a JSON `String` due to limitations around the type `Number` in the JSON specification, which only supports numbers up to `2^{53-1}`, while the FuelVM's registers hold values up to `2^64`.

sezna · 2021-08-27T18:11:10Z

specs/protocol/abi.md

+#### Panic receipt
+
+- `type`: `Panic`.
+- `id`: Hexadecimal string representation of the 256-bit (32 bytes) contract ID of the current context if in an internal context. `null` otherwise.


Suggested change

- `id`: Hexadecimal string representation of the 256-bit (32 bytes) contract ID of the current context if in an internal context. `null` otherwise.

- `id`: Hexadecimal string representation of the 256-bit (32-byte) contract ID of the current context if in an internal context. `null` otherwise.

sezna · 2021-08-27T18:11:22Z

specs/protocol/abi.md

+#### Return receipt
+
+- `type`: `Return`.
+- `id`: Hexadecimal string representation of the 256-bit (32 bytes) contract ID of the current context if in an internal context; `null` otherwise.


Suggested change

- `id`: Hexadecimal string representation of the 256-bit (32 bytes) contract ID of the current context if in an internal context; `null` otherwise.

- `id`: Hexadecimal string representation of the 256-bit (32-byte) contract ID of the current context if in an internal context; `null` otherwise.

sezna · 2021-08-27T18:11:52Z

specs/protocol/abi.md

+#### Call receipt
+
+- `type`: `Call`.
+- `from`: Hexadecimal string representation of the 256-bit (32 bytes) contract ID of the current context if in an internal context; `null` otherwise.


I'm not gonna do all of these but just find and replace 256-bit (32 bytes) with 256-bit (32-byte)

sezna · 2021-08-27T18:13:27Z

specs/protocol/abi.md

+- `color`: Hexadecimal string representation of the 256-bit (32 bytes) color of coins to forward.
+- `gas`: Decimal string representation of a 64-bit unsigned integer; amount gas to forward; value in register `$rD`.
+- `param1`: Hexadecimal string representation of a 64-bit unsigned integer; first parameter, holds the function selector.
+- `param2`: Hexadecimal string representation of a 64-bit unsigned integer; second parameter.


Do we want to say something like "second parameter, typically used for the user-specified input to the ABI function being selected"?

@adlerjohn for your wordsmithing

Sure, sounds about right.

sezna · 2021-08-27T18:14:13Z

specs/protocol/abi.md

+
+The signature is composed of the function name with the parenthesized list of comma-separated parameter types without spaces. All strings encoded with UTF-8.
+
+For instance, in the case of the function `entry_one` above, we would pass the string `"entry_one(u64)"` to the `sha256()` hashing algorithm, the full digest would be:


Suggested change

For instance, in the case of the function `entry_one` above, we would pass the string `"entry_one(u64)"` to the `sha256()` hashing algorithm, the full digest would be:

For instance, in the case of the function `entry_one` above, we would pass the string `"entry_one(u64)"` to the `sha256()` hashing algorithm. The full digest would be:

sezna · 2021-08-27T18:14:29Z

specs/protocol/abi.md

+0x0c36cb9cb766ff60422db243c4fff06d342949da3c64a3c6ac564941f84b6f06
+```
+
+Then we would get only the first 4 bytes of this digest and left pad it to 8 bytes:


Suggested change

Then we would get only the first 4 bytes of this digest and left pad it to 8 bytes:

Then we would get only the first 4 bytes of this digest and left-pad it to 8 bytes:

sezna · 2021-08-27T18:14:45Z

specs/protocol/abi.md

+
+## Argument Encoding
+
+When crafting a transaction script data, you must encode the arguments you wish to pass to the script.


Suggested change

When crafting a transaction script data, you must encode the arguments you wish to pass to the script.

When crafting transaction script data, you must encode the arguments you wish to pass to the script.

sezna · 2021-08-27T18:15:46Z

specs/protocol/abi.md

+
+### Address
+
+A 256 bits (32 bytes) address, encoded in the same way as a `B256` argument: encoded as-is.


Suggested change

A 256 bits (32 bytes) address, encoded in the same way as a `B256` argument: encoded as-is.

A 256-bit (32-byte) address, encoded in the same way as a `b256` argument: encoded as-is.

sezna · 2021-08-27T18:17:12Z

specs/protocol/abi.md

+
+An array of a certain type `T`, `T[n]`, where `n` is the length of the array.
+
+Arrays in Sway have fixed-length known at compile time, this means the ABI encoding for arrays also happens in-place.  


Suggested change

Arrays in Sway have fixed-length known at compile time, this means the ABI encoding for arrays also happens in-place.

Arrays in Sway have a fixed-length which is known at compile time. This means the ABI encoding for arrays also happens in-place, with no need to account for dynamic sizing.

sezna · 2021-08-27T18:18:39Z

specs/protocol/abi.md

+
+### Structs
+
+Encoding ABIs that contain custom types, such as structs, is similar to encoding a set of primitive types. The encoding will proceed in the order that the inner types of a custom type are declared and _recursively_ just like encoding any other type. This way you can encode structs with primitive types or structs with more complex types in it, such as other structs, arrays, strings, and enums.


Suggested change

Encoding ABIs that contain custom types, such as structs, is similar to encoding a set of primitive types. The encoding will proceed in the order that the inner types of a custom type are declared and _recursively_ just like encoding any other type. This way you can encode structs with primitive types or structs with more complex types in it, such as other structs, arrays, strings, and enums.

Encoding ABIs that contain custom types, such as structs, is similar to encoding a set of primitive types. The encoding will proceed in the order that the inner types of a custom type are declared and _recursively_ just like encoding any other type. This way you can encode structs with primitive types or structs with more complex types in them such as other structs, arrays, strings, and enums.

sezna · 2021-08-27T18:20:47Z

specs/protocol/abi.md

+
+### Sum types (Enums)
+
+ABI calls containing sum types (enums) are encoded identically to structs: encode the offset first, then recursively encode the type of the enum variant being passed to the function being called.


Suggested change

ABI calls containing sum types (enums) are encoded identically to structs: encode the offset first, then recursively encode the type of the enum variant being passed to the function being called.

ABI calls containing sum types (enums) are encoded similarly to structs: encode the discriminant first, then recursively encode the type of the enum variant being passed to the function being called.

I don't think it is fair to say identically, because we encode a discriminant where for structs do not.

Damn, that whole paragraph was actually outdated, it was when we were going with the dynamic encoding approach (encoding offset first and wasn't encoding the Enum's discriminant).

But this change you suggest makes it 100% correct 😁

sezna · 2021-08-27T18:20:57Z

specs/protocol/abi.md

+0000000000000005 // `5` encoded as u8
+```
+
+More complex scenario


Suggested change

More complex scenario

A more complex scenario:

sezna

sezna

L
G
T
M
🎊

Add initial specs for the ABI

18f0b8e

digorithm changed the title ~~Add initial specs for the ABI~~ ABI spec Aug 3, 2021

digorithm linked an issue Aug 3, 2021 that may be closed by this pull request

Contract ABI Specification Format #151

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digorithm mentioned this pull request Aug 3, 2021

ABI encoder and decoder FuelLabs/sway#131

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digorithm added 2 commits August 3, 2021 17:50

Fix JSON formatting

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Improve wording/phrasing

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digorithm added 3 commits August 7, 2021 18:54

Add initial specs for arrays and strings

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Fix word alignment mistakes

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Remove need for array/string length encoded in the ABI

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Add specs for structs and enums

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Add receipts specs and other small fixes

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digorithm marked this pull request as ready for review August 23, 2021 16:23

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Add more info to string representation and other improvements

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Reason now a string type and string enc word alignment

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ABI spec #194

ABI spec #194

digorithm commented Aug 3, 2021 •

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		Then, each receipt type will have its own properties. Some of these properties are related to the FuelVM's registers, as specified in more detail [here](https://github.com/FuelLabs/fuel-specs/blob/master/specs/vm/opcodes.md).

		_Important note:_ For the JSON representation of the receipts, we represent 64-bit unsigned integers as a JSON's `String` due to limitation around the type `Number` in the JSON specification, which only supports numbers up to `2^{53-1}`, whereas the FuelVM's registers hold values up to `2^64`.

	- `id`: Hexadecimal string representation of the 256-bit (32 bytes) contract ID of the current context if in an internal context. `null` otherwise.
	- `id`: Hexadecimal string representation of the 256-bit (32-byte) contract ID of the current context if in an internal context. `null` otherwise.


		The signature is composed of the function name with the parenthesized list of comma-separated parameter types without spaces. All strings encoded with UTF-8.

		For instance, in the case of the function `entry_one` above, we would pass the string `"entry_one(u64)"` to the `sha256()` hashing algorithm, the full digest would be:

	Then we would get only the first 4 bytes of this digest and left pad it to 8 bytes:
	Then we would get only the first 4 bytes of this digest and left-pad it to 8 bytes:


		## Argument Encoding

		When crafting a transaction script data, you must encode the arguments you wish to pass to the script.

	When crafting a transaction script data, you must encode the arguments you wish to pass to the script.
	When crafting transaction script data, you must encode the arguments you wish to pass to the script.


		### Address

		A 256 bits (32 bytes) address, encoded in the same way as a `B256` argument: encoded as-is.

	A 256 bits (32 bytes) address, encoded in the same way as a `B256` argument: encoded as-is.
	A 256-bit (32-byte) address, encoded in the same way as a `b256` argument: encoded as-is.


		An array of a certain type `T`, `T[n]`, where `n` is the length of the array.

		Arrays in Sway have fixed-length known at compile time, this means the ABI encoding for arrays also happens in-place.

	Arrays in Sway have fixed-length known at compile time, this means the ABI encoding for arrays also happens in-place.
	Arrays in Sway have a fixed-length which is known at compile time. This means the ABI encoding for arrays also happens in-place, with no need to account for dynamic sizing.


		### Structs

		Encoding ABIs that contain custom types, such as structs, is similar to encoding a set of primitive types. The encoding will proceed in the order that the inner types of a custom type are declared and _recursively_ just like encoding any other type. This way you can encode structs with primitive types or structs with more complex types in it, such as other structs, arrays, strings, and enums.


		### Sum types (Enums)

		ABI calls containing sum types (enums) are encoded identically to structs: encode the offset first, then recursively encode the type of the enum variant being passed to the function being called.

ABI spec #194

ABI spec #194

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digorithm commented Aug 3, 2021 •

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