NAME

Wasm::Global - Interface to WebAssembly global variables

VERSION

version 0.21

SYNOPSIS

Import globals into Perl from WebAssembly

 use Wasm
   -api => 0,
   -wat => q{
     (module
       (global (export "global") (mut i32) (i32.const 42))
     )
   }
 ;
 
 print "$global\n";  # 42
 $global = 99;
 print "$global\n";  # 99

Import globals from Perl into WebAssembly

 package Foo;
 
 use Wasm
   -api    => 0,
   -global => [
     'foo',  # name
     'i32',  # type
     'var',  # mutability
     42,     # initial value
   ]
 ;
 
 package Bar;
 
 use Wasm
   -api      => 0,
   -wat      => q{
     (module
       (global $foo (import "Foo" "foo") (mut i32))
       (func (export "get_foo") (result i32)
         (global.get $foo))
       (func (export "inc_foo")
         (global.set $foo
           (i32.add (global.get $foo) (i32.const 1))))
     )
   }
 ;
 
 package main;
 
 print Bar::get_foo(), "\n";   # 42
 Bar::inc_foo();
 print Bar::get_foo(), "\n";   # 43
 $Foo::foo = 0;
 print Bar::get_foo(), "\n";   # 0

DESCRIPTION

WARNING: WebAssembly and Wasmtime are a moving target and the interface for these modules is under active development. Use with caution.

This documents the interface to global variables for Wasm. Each global variable exported from WebAssembly is automatically imported into Perl space as a tied scalar, which allows you to get and set the variable easily from Perl. Going the other way requires a bit more boilerplate, but is almost as easy. Using the -global option on the Wasm module, you can define global variables in Pure Perl modules that can be imported into WebAssembly from Perl.

CAVEATS

Note that depending on the storage of the global variable setting might be lossy and round-trip isn't guaranteed. For example for integer types, if you set a string value it will be converted to an integer using the normal Perl string to integer conversion, and when it comes back you will just have the integer value.

SEE ALSO

Wasm

AUTHOR

Graham Ollis <plicease@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2020 by Graham Ollis.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.