Wasm

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Wasm stays off until you ask for it. F3.inspect/2, F3.schema/1, and F3.metadata/1 never execute a module. A Wasm section in the footer is an offset and a size.

{:ok, batches} = F3.read(file, wasm: :sandbox)

wasm: :off is the default. A CUSTOM_WASM unit then returns :unsupported_encoding and the module bytes are not read. wasm: :sandbox is the only other accepted value. It runs that module for the encoding unit that names it.

The host limits are fixed:

  • fuel is 5_000_000 instructions
  • linear memory is 8 MiB
  • a module is at most 1 MiB unless you raise wasm_module_bytes:
  • wasm_module_bytes: cannot exceed 16 MiB

An omitted wasm_id selects module 0. Fuel exhaustion and the memory cap return :resource_limit. A module above the cap returns the same category. A panic or a corrupt unit returns :corrupt. These limits apply only after you opt in, and only when the native decoder is compiled.

This library does not fetch lib_urls. It does not generate Wasm, and the writer does not embed a module. If you would rather decode that unit in Elixir, register an F3.Extension and pass extensions: as described in Decoders. An extension that matches does not fall through into the sandbox.