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

use crate::{encode_section, encoding_size, Encode, Instruction, Section, SectionId};

/// An encoder for the data section.
///
/// Data sections are only supported for modules.
///
/// # Example
///
/// ```
/// use wasm_encoder::{
///     DataSection, Instruction, MemorySection, MemoryType,
///     Module,
/// };
///
/// let mut memory = MemorySection::new();
/// memory.memory(MemoryType {
///     minimum: 1,
///     maximum: None,
///     memory64: false,
///     shared: false,
/// });
///
/// let mut data = DataSection::new();
/// let memory_index = 0;
/// let offset = Instruction::I32Const(42);
/// let segment_data = b"hello";
/// data.active(memory_index, &offset, segment_data.iter().copied());
///
/// let mut module = Module::new();
/// module
///     .section(&memory)
///     .section(&data);
///
/// let wasm_bytes = module.finish();
/// ```
#[derive(Clone, Default, Debug)]
pub struct DataSection {
    bytes: Vec<u8>,
    num_added: u32,
}

/// A segment in the data section.
#[derive(Clone, Debug)]
pub struct DataSegment<'a, D> {
    /// This data segment's mode.
    pub mode: DataSegmentMode<'a>,
    /// This data segment's data.
    pub data: D,
}

/// A data segment's mode.
#[derive(Clone, Debug)]
pub enum DataSegmentMode<'a> {
    /// An active data segment.
    Active {
        /// The memory this segment applies to.
        memory_index: u32,
        /// The offset where this segment's data is initialized at.
        offset: &'a Instruction<'a>,
    },
    /// A passive data segment.
    ///
    /// Passive data segments are part of the bulk memory proposal.
    Passive,
}

impl DataSection {
    /// Create a new data section encoder.
    pub fn new() -> Self {
        Self::default()
    }

    /// The number of data segments in the section.
    pub fn len(&self) -> u32 {
        self.num_added
    }

    /// Determines if the section is empty.
    pub fn is_empty(&self) -> bool {
        self.num_added == 0
    }

    /// Define a data segment.
    pub fn segment<D>(&mut self, segment: DataSegment<D>) -> &mut Self
    where
        D: IntoIterator<Item = u8>,
        D::IntoIter: ExactSizeIterator,
    {
        match segment.mode {
            DataSegmentMode::Passive => {
                self.bytes.push(0x01);
            }
            DataSegmentMode::Active {
                memory_index: 0,
                offset,
            } => {
                self.bytes.push(0x00);
                offset.encode(&mut self.bytes);
                Instruction::End.encode(&mut self.bytes);
            }
            DataSegmentMode::Active {
                memory_index,
                offset,
            } => {
                self.bytes.push(0x02);
                memory_index.encode(&mut self.bytes);
                offset.encode(&mut self.bytes);
                Instruction::End.encode(&mut self.bytes);
            }
        }

        let data = segment.data.into_iter();
        data.len().encode(&mut self.bytes);
        self.bytes.extend(data);

        self.num_added += 1;
        self
    }

    /// Define an active data segment.
    pub fn active<D>(&mut self, memory_index: u32, offset: &Instruction, data: D) -> &mut Self
    where
        D: IntoIterator<Item = u8>,
        D::IntoIter: ExactSizeIterator,
    {
        self.segment(DataSegment {
            mode: DataSegmentMode::Active {
                memory_index,
                offset,
            },
            data,
        })
    }

    /// Define a passive data segment.
    ///
    /// Passive data segments are part of the bulk memory proposal.
    pub fn passive<D>(&mut self, data: D) -> &mut Self
    where
        D: IntoIterator<Item = u8>,
        D::IntoIter: ExactSizeIterator,
    {
        self.segment(DataSegment {
            mode: DataSegmentMode::Passive,
            data,
        })
    }

    /// Copy an already-encoded data segment into this data section.
    pub fn raw(&mut self, already_encoded_data_segment: &[u8]) -> &mut Self {
        self.bytes.extend_from_slice(already_encoded_data_segment);
        self.num_added += 1;
        self
    }
}

impl Encode for DataSection {
    fn encode(&self, sink: &mut Vec<u8>) {
        encode_section(sink, self.num_added, &self.bytes);
    }
}

impl Section for DataSection {
    fn id(&self) -> u8 {
        SectionId::Data.into()
    }
}

/// An encoder for the data count section.
#[derive(Clone, Copy, Debug)]
pub struct DataCountSection {
    /// The number of segments in the data section.
    pub count: u32,
}

impl Encode for DataCountSection {
    fn encode(&self, sink: &mut Vec<u8>) {
        encoding_size(self.count).encode(sink);
        self.count.encode(sink);
    }
}

impl Section for DataCountSection {
    fn id(&self) -> u8 {
        SectionId::DataCount.into()
    }
}