Struct MemoryTypeBuilder

pub struct MemoryTypeBuilder { /* private fields */ }

Available on crate feature runtime only.

A builder for MemoryTypes.

A new builder can be constructed via its Default implementation.

When you’re done configuring, get the underlying MemoryType by calling the build method.

Example

use wasmtime::MemoryTypeBuilder;

let memory_type = MemoryTypeBuilder::new()
    // Set the minimum size, in pages.
    .min(4096)
    // Set the maximum size, in pages.
    .max(Some(4096))
    // Set the page size to 1 byte (aka 2**0).
    .page_size_log2(0)
    // Get the underlying memory type.
    .build()?;

Implementations

impl MemoryTypeBuilder

pub fn new() -> MemoryTypeBuilder

Create a new builder for a MemoryType with the default settings.

By default memory types have the following properties:

• The minimum memory size is 0 pages.
• The maximum memory size is unspecified.
• Memories use 32-bit indexes.
• The page size is 64KiB.

Each option can be configued through the methods on the returned builder.

pub fn min(&mut self, minimum: u64) -> &mut Self

Set the minimum size, in units of pages, for the memory type being built.

The default minimum is 0.

pub fn max(&mut self, maximum: Option<u64>) -> &mut Self

Set the maximum size, in units of pages, for the memory type being built.

The default maximum is None.

pub fn memory64(&mut self, memory64: bool) -> &mut Self

Set whether this is a 64-bit memory or not.

If a memory is not a 64-bit memory, then it is a 32-bit memory.

The default is false, aka 32-bit memories.

Note that 64-bit memories are part of the memory64 proposal for WebAssembly which is not fully standardized yet.

pub fn shared(&mut self, shared: bool) -> &mut Self

Set the sharedness for the memory type being built.

The default is false, aka unshared.

Note that shared memories are part of the threads proposal for WebAssembly which is not fully standardized yet.

pub fn page_size_log2(&mut self, page_size_log2: u8) -> &mut Self

Set the log base 2 of the page size, in bytes, for the memory type being built.

The default value is 16, which results in the default Wasm page size of 64KiB (aka 2¹⁶ or 65536).

Other than 16, the only valid value is 0, which results in a page size of one byte (aka 2⁰). Single-byte page sizes can be used to get fine-grained control over a Wasm memory’s resource consumption and run Wasm in embedded environments with less than 64KiB of RAM, for example.

Future extensions to the core WebAssembly language might relax these constraints and introduce more valid page sizes, such as any power of two between 1 and 65536 inclusive.

Note that non-default page sizes are part of the custom-page-sizes proposal for WebAssembly which is not fully standardized yet.

pub fn build(&self) -> Result<MemoryType>

Get the underlying memory type that this builder has been building.

Errors

Returns an error if the configured memory type is invalid, for example if the maximum size is smaller than the minimum size.

Trait Implementations

impl Default for MemoryTypeBuilder

fn default() -> Self

Returns the “default value” for a type.