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

// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

use crate::blob_schema::{BlobSchema, BlobSchemaV1};
use alloc::boxed::Box;
use icu_provider::buf::BufferFormat;
use icu_provider::prelude::*;
use icu_provider::Cart;
use yoke::*;

/// A data provider that reads from serialized blobs of data.
///
/// This enables data blobs to be read from arbitrary sources at runtime, allowing code and data
/// to be separated. Alternatively, blobs can also be statically included at compile time.
///
/// [`BlobDataProvider`] implements [`BufferProvider`], so it can be used in
/// `*_with_buffer_provider` constructors across ICU4X.
///
/// # `Sync + Send`
///
/// This provider uses reference counting internally. When the `sync` Cargo feature on the [`icu_provider`]
/// crate is enabled, it uses [`Arc`](alloc::sync::Arc) instead of [`Rc`](alloc::rc::Rc), making
/// it `Sync + Send`.
///
/// # Examples
///
/// ## Dynamic loading
///
/// Load "hello world" data from a postcard blob loaded at runtime:
///
/// ```
/// use icu_locid::locale;
/// use icu_provider::hello_world::HelloWorldFormatter;
/// use icu_provider_blob::BlobDataProvider;
/// use writeable::assert_writeable_eq;
///
/// // Read an ICU4X data blob dynamically:
/// let blob = std::fs::read(concat!(
///     env!("CARGO_MANIFEST_DIR"),
///     "/tests/data/hello_world.postcard",
/// ))
/// .expect("Reading pre-computed postcard buffer");
///
/// // Create a DataProvider from it:
/// let provider = BlobDataProvider::try_new_from_blob(blob.into_boxed_slice())
///     .expect("Deserialization should succeed");
///
/// // Check that it works:
/// let formatter = HelloWorldFormatter::try_new_with_buffer_provider(
///     &provider,
///     &locale!("la").into(),
/// )
/// .expect("locale exists");
///
/// assert_writeable_eq!(formatter.format(), "Ave, munde");
/// ```
///
/// ## Static loading
///
/// Load "hello world" data from a postcard blob statically linked at compile time:
///
/// ```
/// use icu_locid::locale;
/// use icu_provider::hello_world::HelloWorldFormatter;
/// use icu_provider_blob::BlobDataProvider;
/// use writeable::assert_writeable_eq;
///
/// // Read an ICU4X data blob statically:
/// const HELLO_WORLD_BLOB: &[u8] = include_bytes!(concat!(
///     env!("CARGO_MANIFEST_DIR"),
///     "/tests/data/hello_world.postcard"
/// ));
///
/// // Create a DataProvider from it:
/// let provider = BlobDataProvider::try_new_from_static_blob(HELLO_WORLD_BLOB)
///     .expect("Deserialization should succeed");
///
/// // Check that it works:
/// let formatter = HelloWorldFormatter::try_new_with_buffer_provider(
///     &provider,
///     &locale!("la").into(),
/// )
/// .expect("locale exists");
///
/// assert_writeable_eq!(formatter.format(), "Ave, munde");
/// ```
#[derive(Clone)]
pub struct BlobDataProvider {
    data: Yoke<BlobSchemaV1<'static>, Option<Cart>>,
}

impl BlobDataProvider {
    /// Create a [`BlobDataProvider`] from a blob of ICU4X data.
    pub fn try_new_from_blob(blob: Box<[u8]>) -> Result<Self, DataError> {
        Ok(Self {
            data: Cart::try_make_yoke(blob, |bytes| {
                BlobSchema::deserialize_v1(&mut postcard::Deserializer::from_bytes(bytes))
            })?,
        })
    }

    /// Create a [`BlobDataProvider`] from a static blob. This is a special case of
    /// [`try_new_from_blob`](BlobDataProvider::try_new_from_blob) and is allocation-free.
    pub fn try_new_from_static_blob(blob: &'static [u8]) -> Result<Self, DataError> {
        Ok(Self {
            data: Yoke::new_owned(BlobSchema::deserialize_v1(
                &mut postcard::Deserializer::from_bytes(blob),
            )?),
        })
    }
}

impl BufferProvider for BlobDataProvider {
    fn load_buffer(
        &self,
        key: DataKey,
        req: DataRequest,
    ) -> Result<DataResponse<BufferMarker>, DataError> {
        let mut metadata = DataResponseMetadata::default();
        metadata.buffer_format = Some(BufferFormat::Postcard1);
        Ok(DataResponse {
            metadata,
            payload: Some(DataPayload::from_yoked_buffer(
                self.data
                    .try_map_project_cloned(|blob, _| blob.load(key, req))?,
            )),
        })
    }
}