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//! # Candid //! //! Candid is an interface description language (IDL) for interacting with _canisters_ (also known as _services_ or _actors_) running on the Internet Computer. //! //! There are three common ways that you might find yourself needing to work with Candid in Rust. //! - As a typed Rust data strcuture. When you write canisters or frontend in Rust, you want to have a seamless way of converting data between Rust and Candid. //! - As an untyped Candid value. When you write generic tools for the Internet Computer without knowing the type of the Candid data. //! - As text data. When you get the data from CLI or read from a file, you can use the provided parser to send/receive messages. //! //! Candid provides efficient, flexible and safe ways of converting data between each of these representations. //! //! ## Operating on native Rust values //! We are using a builder pattern to encode/decode Candid messages, see [`candid::ser::IDLBuilder`](ser/struct.IDLBuilder.html) for serialization and [`candid::de::IDLDeserialize`](de/struct.IDLDeserialize.html) for deserialization. //! //! ``` //! // Serialize 10 numbers to Candid binary format //! let mut ser = candid::ser::IDLBuilder::new(); //! for i in 0..10 { //! ser.arg(&i)?; //! } //! let bytes: Vec<u8> = ser.serialize_to_vec()?; //! //! // Deserialize Candid message and verify the values match //! let mut de = candid::de::IDLDeserialize::new(&bytes)?; //! let mut i = 0; //! while !de.is_done() { //! let x = de.get_value::<i32>()?; //! assert_eq!(x, i); //! i += 1; //! } //! de.done()?; //! # Ok::<(), candid::Error>(()) //! ``` //! //! Candid provides functions for encoding/decoding a Candid message in a type-safe way. //! //! ``` //! use candid::{encode_args, decode_args}; //! // Serialize two values [(42, "text")] and (42u32, "text") //! let bytes: Vec<u8> = encode_args((&[(42, "text")], &(42u32, "text")))?; //! // Deserialize the first value as type Vec<(i32, &str)>, //! // and the second value as type (u32, String) //! let (a, b): (Vec<(i32, &str)>, (u32, String)) = decode_args(&bytes)?; //! //! assert_eq!(a, [(42, "text")]); //! assert_eq!(b, (42u32, "text".to_string())); //! # Ok::<(), candid::Error>(()) //! ``` //! //! We also provide macros for encoding/decoding Candid message in a convenient way. //! //! ``` //! use candid::{Encode, Decode}; //! // Serialize two values [(42, "text")] and (42u32, "text") //! let bytes: Vec<u8> = Encode!(&[(42, "text")], &(42u32, "text"))?; //! // Deserialize the first value as type Vec<(i32, &str)>, //! // and the second value as type (u32, String) //! let (a, b) = Decode!(&bytes, Vec<(i32, &str)>, (u32, String))?; //! //! assert_eq!(a, [(42, "text")]); //! assert_eq!(b, (42u32, "text".to_string())); //! # Ok::<(), candid::Error>(()) //! ``` //! //! The [`Encode!`](macro.Encode.html) macro takes a sequence of Rust values, and returns a binary format `Vec<u8>` that can be sent over the wire. //! The [`Decode!`](macro.Decode.html) macro takes the binary message and a sequence of Rust types that you want to decode into, and returns a tuple //! of Rust values of the given types. //! //! Note that a fixed Candid message may be decoded in multiple Rust types. For example, //! we can decode a Candid `text` type into either `String` or `&str` in Rust. //! //! ## Operating on user defined struct/enum //! We use trait [`CandidType`](types/trait.CandidType.html) for serialization, and Serde's [`Deserialize`](trait.Deserialize.html) trait for deserialization. //! Any type that implements these two traits can be used for serialization and deserialization respectively. //! This includes built-in Rust standard library types like `Vec<T>` and `Result<T, E>`, as well as any structs //! or enums annotated with `#[derive(CandidType, Deserialize)]`. //! //! We do not use Serde's `Serialize` trait because Candid requires serializing types along with the values. //! This is difficult to achieve in `Serialize`, especially for enum types. Besides serialization, [`CandidType`](types/trait.CandidType.html) //! trait also converts Rust type to Candid type defined as [`candid::types::Type`](types/internal/enum.Type.html). //! ``` //! use candid::{Encode, Decode, CandidType, Deserialize}; //! #[derive(CandidType, Deserialize)] //! # #[derive(Debug, PartialEq)] //! enum List { //! #[serde(rename = "nil")] //! Nil, //! Cons(i32, Box<List>), //! } //! let list = List::Cons(42, Box::new(List::Nil)); //! //! let bytes = Encode!(&list)?; //! let res = Decode!(&bytes, List)?; //! assert_eq!(res, list); //! # Ok::<(), candid::Error>(()) //! ``` //! We also support serde's rename attributes for each field, namely `#[serde(rename = "foo")]` //! and `#[serde(rename(serialize = "foo", deserialize = "foo"))]`. //! This is useful when interoperating between Rust and Motoko canisters involving variant types, because //! they use different naming conventions for field names. //! //! Note that if you are deriving `Deserialize` trait from Candid, you need to import `serde` as a dependency in //! your project, as the derived implementation will refer to the `serde` crate. //! //! ## Operating on big integers //! To support big integer types [`Candid::Int`](types/number/struct.Int.html) and [`Candid::Nat`](types/number/struct.Nat.html), //! we use the `num_bigint` crate. We provide interface to convert `i64`, `u64`, `&str` and `&[u8]` to big integers. //! ``` //! use candid::{Int, Nat, Encode, Decode}; //! let x = "-10000000000000000000".parse::<Int>()?; //! let bytes = Encode!(&Nat::from(1024), &x)?; //! let (a, b) = Decode!(&bytes, Nat, Int)?; //! assert_eq!(a + 1, 1025); //! assert_eq!(b, Int::parse(b"-10000000000000000000")?); //! # Ok::<(), candid::Error>(()) //! ``` //! //! ## Operating on untyped Candid values //! Any valid Candid value can be manipulated in an recursive enum representation [`candid::parser::value::IDLValue`](parser/value/enum.IDLValue.html). //! We use `ser.value_arg(v)` and `de.get_value::<IDLValue>()` for encoding and decoding the value. //! The use of Rust value and `IDLValue` can be intermixed. //! //! ``` //! use candid::parser::value::IDLValue; //! // Serialize Rust value Some(42u8) and IDLValue "hello" //! let bytes = candid::ser::IDLBuilder::new() //! .arg(&Some(42u8))? //! .value_arg(&IDLValue::Text("hello".to_string()))? //! .serialize_to_vec()?; //! //! // Deserialize the first Rust value into IDLValue, //! // and the second IDLValue into Rust value //! let mut de = candid::de::IDLDeserialize::new(&bytes)?; //! let x = de.get_value::<IDLValue>()?; //! let y = de.get_value::<&str>()?; //! de.done()?; //! //! assert_eq!(x, IDLValue::Opt(Box::new(IDLValue::Nat8(42)))); //! assert_eq!(y, "hello"); //! # Ok::<(), candid::Error>(()) //! ``` //! //! We provide a data structure [`candid::IDLArgs`](parser/value/struct.IDLArgs.html) to represent a sequence of `IDLValue`s, //! and use `to_bytes()` and `from_bytes()` to encode and decode Candid messages. //! We also provide a parser to parse Candid values in text format. //! //! ``` //! use candid::IDLArgs; //! // Candid values represented in text format //! let text_value = r#" //! (42, opt true, vec {1;2;3}, //! opt record {label="text"; 42="haha"}) //! "#; //! //! // Parse text format into IDLArgs for serialization //! let args: IDLArgs = text_value.parse()?; //! let encoded: Vec<u8> = args.to_bytes()?; //! //! // Deserialize into IDLArgs //! let decoded: IDLArgs = IDLArgs::from_bytes(&encoded)?; //! assert_eq!(encoded, decoded.to_bytes()?); //! //! // Convert IDLArgs to text format //! let output: String = decoded.to_string(); //! let parsed_args: IDLArgs = output.parse()?; //! assert_eq!(args, parsed_args); //! # Ok::<(), candid::Error>(()) //! ``` //! Note that when parsing Candid values, we assume the number literals are always of type `Int`. //! This can be changed by providing the type of the method arguments, which can usually be obtained //! by parsing a Candid file in the following section. //! //! ## Operating on Candid AST //! We provide a parser and type checker for Candid files specifying the service interface. //! //! ``` //! use candid::{IDLProg, TypeEnv, check_prog, types::Type}; //! let did_file = r#" //! type List = opt record { head: int; tail: List }; //! type byte = nat8; //! service : { //! f : (byte, int, nat, int8) -> (List); //! g : (List) -> (int) query; //! } //! "#; //! //! // Parse did file into an AST //! let ast: IDLProg = did_file.parse()?; //! //! // Pretty-print AST //! let pretty: String = candid::parser::types::to_pretty(&ast, 80); //! //! // Type checking //! let mut env = TypeEnv::new(); //! let actor: Type = check_prog(&mut env, &ast)?.unwrap(); //! let method = env.get_method(&actor, "g").unwrap(); //! assert_eq!(method.is_query(), true); //! assert_eq!(method.args, vec![Type::Var("List".to_string())]); //! # Ok::<(), candid::Error>(()) //! ``` //! //! ## Serializing untyped Candid values with type annotations. //! With type signatures from the Candid file, [`candid::IDLArgs`](parser/value/struct.IDLArgs.html) //! uses `to_bytes_with_types` function to serialize arguments directed by the Candid types. //! This is useful when serializing different number types and recursive types. //! There is no need to use types for deserialization as the types are available in the Candid message. //! //! ``` //! use candid::{IDLArgs, parser::value::IDLValue}; //! # use candid::{IDLProg, TypeEnv, check_prog}; //! # let did_file = r#" //! # type List = opt record { head: int; tail: List }; //! # type byte = nat8; //! # service : { //! # f : (byte, int, nat, int8) -> (List); //! # g : (List) -> (int) query; //! # } //! # "#; //! # let ast = did_file.parse::<IDLProg>()?; //! # let mut env = TypeEnv::new(); //! # let actor = check_prog(&mut env, &ast)?.unwrap(); //! // Get method type f : (byte, int, nat, int8) -> (List) //! let method = env.get_method(&actor, "f").unwrap(); //! let args = "(42, 42, 42, 42)".parse::<IDLArgs>()?; //! // Serialize arguments with candid types //! let encoded = args.to_bytes_with_types(&env, &method.args)?; //! let decoded = IDLArgs::from_bytes(&encoded)?; //! assert_eq!(decoded.args, //! vec![IDLValue::Nat8(42), //! IDLValue::Int(42.into()), //! IDLValue::Nat(42.into()), //! IDLValue::Int8(42) //! ]); //! # Ok::<(), candid::Error>(()) //! ``` //! pub use candid_derive::{candid_method, export_service, CandidType}; pub use serde::Deserialize; pub mod codegen; pub use codegen::generate_code; pub mod bindings; pub mod error; pub use error::{pretty_parse, Error, Result}; pub mod types; pub use types::CandidType; pub use types::{ number::{Int, Nat}, principal::Principal, reserved::{Empty, Reserved}, }; pub mod parser; pub use parser::types::IDLProg; pub use parser::typing::{check_prog, TypeEnv}; pub use parser::value::IDLArgs; pub mod de; pub use de::{decode_args, decode_one}; pub mod ser; pub use ser::{encode_args, encode_one}; pub mod pretty; // Candid hash function comes from // https://caml.inria.fr/pub/papers/garrigue-polymorphic_variants-ml98.pdf // Not public API. Only used by tests. // Remember to update the same function in candid_derive if you change this function. #[doc(hidden)] #[inline] pub fn idl_hash(id: &str) -> u32 { let mut s: u32 = 0; for c in id.as_bytes().iter() { s = s.wrapping_mul(223).wrapping_add(*c as u32); } s } /// Encode sequence of Rust values into Candid message of type `candid::Result<Vec<u8>>`. #[macro_export] macro_rules! Encode { ( $($x:expr),* ) => {{ let mut builder = $crate::ser::IDLBuilder::new(); Encode!(@PutValue builder $($x,)*) }}; ( @PutValue $builder:ident $x:expr, $($tail:expr,)* ) => {{ $builder.arg($x).and_then(|builder| Encode!(@PutValue builder $($tail,)*)) }}; ( @PutValue $builder:ident ) => {{ $builder.serialize_to_vec() }}; } /// Decode Candid message into a tuple of Rust values of the given types. /// Produces `Err` if the message fails to decode at any given types. /// If the message contains only one value, it returns the value directly instead of a tuple. #[macro_export] macro_rules! Decode { ( $hex:expr $(,$ty:ty)* ) => {{ $crate::de::IDLDeserialize::new($hex) .and_then(|mut de| Decode!(@GetValue [] de $($ty,)*) .and_then(|res| de.done().and(Ok(res)))) }}; (@GetValue [$($ans:ident)*] $de:ident $ty:ty, $($tail:ty,)* ) => {{ $de.get_value::<$ty>() .and_then(|val| Decode!(@GetValue [$($ans)* val] $de $($tail,)* )) }}; (@GetValue [$($ans:ident)*] $de:ident) => {{ Ok(($($ans),*)) }}; }