no_std support

[orsinium]

Thank you for the project! We're looking into using wasm-coredump in wasmi for generating coredumps. The problem is that wasmi is designed for no_std environments and wasm-coredump depends on leb128 which requires std. Would you be interested in leb128 having no_std support?

Making leb128 no_std is quite easy. The only problem is that there is no io::Read and io::Write in core yet. The solution is to use embedded-io which provides no_std io traits and can also automatically convert everything implementing std::io traits. Would you be ok with leb128 having a dependency on embedded-io?

[fitzgen]

Would you be ok with leb128 having a dependency on embedded-io?

I think this is fine, if we do the following approach

• always #![no_std]
• optional dep on embedded-io
• feature for nostd that enables dep:embedded-io and associated code paths
• feature for std that enables extern crate std; and associated code paths
• std is enabled by default

[fitzgen]

This way, std usage doesn't need embedded-io