candid 0.7.18

Candid is an interface description language (IDL) for interacting with canisters running on the Internet Computer.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283

use crate::de::IDLDeserialize;
use crate::ser::IDLBuilder;
use crate::{check_prog, pretty_check_file, pretty_parse, types::Type, TypeEnv};
use crate::{CandidType, Error, Result};
use serde::de::Deserialize;
use std::path::Path;

pub enum CandidSource<'a> {
    File(&'a Path),
    Text(&'a str),
}
impl<'a> CandidSource<'a> {
    pub fn load(&self) -> Result<(TypeEnv, Option<Type>)> {
        Ok(match self {
            CandidSource::File(path) => pretty_check_file(path)?,
            CandidSource::Text(str) => {
                let ast = pretty_parse("", str)?;
                let mut env = TypeEnv::new();
                let actor = check_prog(&mut env, &ast)?;
                (env, actor)
            }
        })
    }
}

/// Check compatibility of two service types
pub fn service_compatible(new: CandidSource, old: CandidSource) -> Result<()> {
    let (mut env, t1) = new.load()?;
    let t1 = t1.ok_or_else(|| Error::msg("new interface has no main service type"))?;
    let (env2, t2) = old.load()?;
    let t2 = t2.ok_or_else(|| Error::msg("old interface has no main service type"))?;
    let mut gamma = std::collections::HashSet::new();
    let t2 = env.merge_type(env2, t2);
    crate::types::subtype::subtype(&mut gamma, &env, &t1, &t2)?;
    Ok(())
}

/// 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),*))
    }};
}

/// Decode a series of arguments, represented as a tuple. There is a maximum of 16 arguments
/// supported.
///
/// Example:
///
/// ```
/// # use candid::Encode;
/// # use candid::decode_args;
/// let golden1 = 123u64;
/// let golden2 = "456";
/// let bytes = Encode!(&golden1, &golden2).unwrap();
/// let (value1, value2): (u64, String) = decode_args(&bytes).unwrap();
///
/// assert_eq!(golden1, value1);
/// assert_eq!(golden2, value2);
/// ```
pub fn decode_args<'a, Tuple>(bytes: &'a [u8]) -> Result<Tuple>
where
    Tuple: ArgumentDecoder<'a>,
{
    let mut de = IDLDeserialize::new(bytes)?;
    let res = ArgumentDecoder::decode(&mut de)?;
    de.done()?;
    Ok(res)
}

/// Decode a single argument.
///
/// Example:
///
/// ```
/// # use candid::Encode;
/// # use candid::decode_one;
/// let golden1 = 123u64;
/// let bytes = Encode!(&golden1).unwrap();
/// let value1: u64 = decode_one(&bytes).unwrap();
///
/// assert_eq!(golden1, value1);
/// ```
pub fn decode_one<'a, T>(bytes: &'a [u8]) -> Result<T>
where
    T: Deserialize<'a> + CandidType,
{
    let (res,) = decode_args(bytes)?;
    Ok(res)
}

/// Serialize an encoding of a tuple and write it to a `Write` buffer.
///
/// ```
/// # use candid::Decode;
/// # use candid::write_args;
/// let golden1 = 1u64;
/// let golden2 = "hello";
/// let mut buffer = Vec::new();
/// write_args(&mut buffer, (golden1, golden2)).unwrap();
///
/// let (value1, value2) = Decode!(&buffer, u64, String).unwrap();
/// assert_eq!(golden1, value1);
/// assert_eq!(golden2, value2);
/// ```
pub fn write_args<Tuple: ArgumentEncoder, Writer: std::io::Write>(
    writer: &mut Writer,
    arguments: Tuple,
) -> Result<()> {
    let mut ser = IDLBuilder::new();
    arguments.encode(&mut ser)?;
    ser.serialize(writer)
}

/// Serialize an encoding of a tuple to a vector of bytes.
///
/// ```
/// # use candid::Decode;
/// # use candid::encode_args;
/// let golden1 = 1u64;
/// let golden2 = "hello";
/// let buffer = encode_args((golden1, golden2)).unwrap();
///
/// let (value1, value2) = Decode!(&buffer, u64, String).unwrap();
/// assert_eq!(golden1, value1);
/// assert_eq!(golden2, value2);
/// ```
pub fn encode_args<Tuple: ArgumentEncoder>(arguments: Tuple) -> Result<Vec<u8>> {
    let mut result = Vec::new();
    write_args(&mut result, arguments)?;
    Ok(result)
}

/// Serialize a single value to a vector of bytes.
///
/// ```
/// # use candid::Decode;
/// # use candid::encode_one;
/// let golden = "hello";
/// let buffer = encode_one(golden).unwrap();
///
/// let (value) = Decode!(&buffer, String).unwrap();
/// assert_eq!(golden, value);
/// ```
pub fn encode_one<T: CandidType>(argument: T) -> Result<Vec<u8>> {
    encode_args((argument,))
}

/// Allow decoding of any sized argument.
pub trait ArgumentDecoder<'a>: Sized {
    /// Decodes a value of type [Self], modifying the deserializer (values are consumed).
    fn decode(de: &mut IDLDeserialize<'a>) -> Result<Self>;
}

/// Decode an empty tuple.
impl<'a> ArgumentDecoder<'a> for () {
    fn decode(_de: &mut IDLDeserialize<'a>) -> Result<()> {
        Ok(())
    }
}

/// Allow encoding of any serializable value.
pub trait ArgumentEncoder {
    /// Encode a value of type [Self].
    fn encode(self, ser: &mut IDLBuilder) -> Result<()>;
}

/// Decode an empty tuple.
impl ArgumentEncoder for () {
    fn encode(self, _de: &mut IDLBuilder) -> Result<()> {
        Ok(())
    }
}

// Create implementation of [ArgumentDecoder] for up to 16 value tuples.
macro_rules! decode_impl {
    ( $($id: ident : $typename: ident),* ) => {
        impl<'a, $( $typename ),*> ArgumentDecoder<'a> for ($($typename,)*)
        where
            $( $typename: Deserialize<'a> + CandidType ),*
        {
            fn decode(de: &mut IDLDeserialize<'a>) -> Result<Self> {
                $(
                let $id: $typename = de.get_value()?;
                )*

                Ok(($( $id, )*))
            }
        }
    }
}

// Create implementation of [ArgumentEncoder] for up to 16 value tuples.
macro_rules! encode_impl {
    ( $($id: ident : $typename: ident),* ) => {
        impl<$( $typename ),*> ArgumentEncoder for ($($typename,)*)
        where
            $( $typename: CandidType ),*
        {
            fn encode(self, ser: &mut IDLBuilder) -> Result<()> {
                let ( $( $id, )* ) = self;
                $(
                ser.arg(&$id)?;
                )*

                Ok(())
            }
        }
    }
}

decode_impl!(a: A);
decode_impl!(a: A, b: B);
decode_impl!(a: A, b: B, c: C);
decode_impl!(a: A, b: B, c: C, d: D);
decode_impl!(a: A, b: B, c: C, d: D, e: E);
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F);
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G);
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H);
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I);
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J);
#[rustfmt::skip]
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K);
#[rustfmt::skip]
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L);
#[rustfmt::skip]
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M);
#[rustfmt::skip]
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M, n: N);
#[rustfmt::skip]
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M, n: N, o: O);
#[rustfmt::skip]
decode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M, n: N, o: O, p: P);

encode_impl!(a: A);
encode_impl!(a: A, b: B);
encode_impl!(a: A, b: B, c: C);
encode_impl!(a: A, b: B, c: C, d: D);
encode_impl!(a: A, b: B, c: C, d: D, e: E);
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F);
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G);
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H);
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I);
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J);
#[rustfmt::skip]
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K);
#[rustfmt::skip]
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L);
#[rustfmt::skip]
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M);
#[rustfmt::skip]
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M, n: N);
#[rustfmt::skip]
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M, n: N, o: O);
#[rustfmt::skip]
encode_impl!(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M, n: N, o: O, p: P);