dfir_lang/graph/ops/
source_json.rs

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1use quote::quote_spanned;
2
3use super::{
4    FloType, OpInstGenerics, OperatorCategory, OperatorConstraints, OperatorInstance,
5    OperatorWriteOutput, WriteContextArgs, RANGE_0, RANGE_1,
6};
7
8/// > 0 input streams, 1 output stream
9///
10/// > Arguments: An [`AsRef`](https://doc.rust-lang.org/std/convert/trait.AsRef.html)`<`[`Path`](https://doc.rust-lang.org/nightly/std/path/struct.Path.html)`>`
11/// > for a file to read as json. This will emit the parsed value one time.
12///
13/// `source_json` may take one generic type argument, the type of the value to be parsed, which must implement [`Deserialize`](https://docs.rs/serde/latest/serde/de/trait.Deserialize.html).
14///
15/// ```dfir
16/// source_json("example.json") -> for_each(|json: dfir_rs::serde_json::Value| println!("{:#?}", json));
17/// ```
18pub const SOURCE_JSON: OperatorConstraints = OperatorConstraints {
19    name: "source_json",
20    categories: &[OperatorCategory::Source],
21    hard_range_inn: RANGE_0,
22    soft_range_inn: RANGE_0,
23    hard_range_out: RANGE_1,
24    soft_range_out: RANGE_1,
25    num_args: 1,
26    persistence_args: RANGE_0,
27    type_args: &(0..=1),
28    is_external_input: true,
29    has_singleton_output: false,
30    flo_type: Some(FloType::Source),
31    ports_inn: None,
32    ports_out: None,
33    input_delaytype_fn: |_| None,
34    write_fn: |wc @ &WriteContextArgs {
35                   root,
36                   op_span,
37                   ident,
38                   op_inst:
39                       OperatorInstance {
40                           generics: OpInstGenerics { type_args, .. },
41                           ..
42                       },
43                   arguments,
44                   ..
45               },
46               _| {
47        let generic_type = type_args.first().map(|ty| quote_spanned!(op_span=> : #ty));
48
49        let ident_jsonread = wc.make_ident("jsonread");
50        let write_prologue = quote_spanned! {op_span=>
51            // Note that reading the entire file to memory is (probably still) faster than using a
52            // reader: https://github.com/serde-rs/json/issues/160
53            let mut #ident_jsonread = {
54                let string = ::std::fs::read_to_string(#arguments).unwrap();
55                let value #generic_type = #root::serde_json::from_str(&string).unwrap();
56                ::std::iter::once(value)
57            };
58        };
59        let write_iterator = quote_spanned! {op_span=>
60            let #ident = #ident_jsonread.by_ref();
61        };
62        Ok(OperatorWriteOutput {
63            write_prologue,
64            write_iterator,
65            ..Default::default()
66        })
67    },
68};
dfir_lang/graph/ops/source_json.rs

dfir_lang/graph/ops/
source_json.rs
