1use crate::{encode_section, Encode, Section, SectionId};
2
3/// An encoder for the memory section.
4///
5/// Memory sections are only supported for modules.
6///
7/// # Example
8///
9/// ```
10/// use wasm_encoder::{Module, MemorySection, MemoryType};
11///
12/// let mut memories = MemorySection::new();
13/// memories.memory(MemoryType {
14/// minimum: 1,
15/// maximum: None,
16/// memory64: false,
17/// shared: false,
18/// page_size_log2: None,
19/// });
20///
21/// let mut module = Module::new();
22/// module.section(&memories);
23///
24/// let wasm_bytes = module.finish();
25/// ```
26#[derive(Clone, Default, Debug)]
27pub struct MemorySection {
28 bytes: Vec<u8>,
29 num_added: u32,
30}
31
32impl MemorySection {
33 /// Create a new memory section encoder.
34 pub fn new() -> Self {
35 Self::default()
36 }
37
38 /// The number of memories in the section.
39 pub fn len(&self) -> u32 {
40 self.num_added
41 }
42
43 /// Determines if the section is empty.
44 pub fn is_empty(&self) -> bool {
45 self.num_added == 0
46 }
47
48 /// Define a memory.
49 pub fn memory(&mut self, memory_type: MemoryType) -> &mut Self {
50 memory_type.encode(&mut self.bytes);
51 self.num_added += 1;
52 self
53 }
54}
55
56impl Encode for MemorySection {
57 fn encode(&self, sink: &mut Vec<u8>) {
58 encode_section(sink, self.num_added, &self.bytes);
59 }
60}
61
62impl Section for MemorySection {
63 fn id(&self) -> u8 {
64 SectionId::Memory.into()
65 }
66}
67
68/// A memory's type.
69#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
70pub struct MemoryType {
71 /// Minimum size, in pages, of this memory
72 pub minimum: u64,
73 /// Maximum size, in pages, of this memory
74 pub maximum: Option<u64>,
75 /// Whether or not this is a 64-bit memory.
76 pub memory64: bool,
77 /// Whether or not this memory is shared.
78 pub shared: bool,
79 /// The log base 2 of a custom page size for this memory.
80 ///
81 /// The default page size for Wasm memories is 64KiB, i.e. 2<sup>16</sup> or
82 /// `65536`.
83 ///
84 /// After the introduction of [the custom-page-sizes
85 /// proposal](https://github.com/WebAssembly/custom-page-sizes), Wasm can
86 /// customize the page size. It must be a power of two that is less than or
87 /// equal to 64KiB. Attempting to encode an invalid page size may panic.
88 pub page_size_log2: Option<u32>,
89}
90
91impl Encode for MemoryType {
92 fn encode(&self, sink: &mut Vec<u8>) {
93 let mut flags = 0;
94 if self.maximum.is_some() {
95 flags |= 0b0001;
96 }
97 if self.shared {
98 flags |= 0b0010;
99 }
100 if self.memory64 {
101 flags |= 0b0100;
102 }
103 if self.page_size_log2.is_some() {
104 flags |= 0b1000;
105 }
106 sink.push(flags);
107 self.minimum.encode(sink);
108 if let Some(max) = self.maximum {
109 max.encode(sink);
110 }
111 if let Some(p) = self.page_size_log2 {
112 p.encode(sink);
113 }
114 }
115}
116