Burn functionality

[hoffmannjan]

Implements casper-network/ceps#92

[EdHastingsCasperAssociation]

optimistic approval assuming asked for changes are made.

[mpapierski]

Looking good, few tweaks

[mpapierski]

I found an existing method that does the same thing in other test contracts, perhaps you can just copy and paste it from there:

casper-node/smart_contracts/contracts/client/non-standard-payment/src/main.rs

Lines 49 to 88 in 79f4f34

	fn get_named_arg_if_exists<T: FromBytes>(name: &str) -> Option<T> {
	let arg_size = {
	let mut arg_size: usize = 0;
	let ret = unsafe {
	ext_ffi::casper_get_named_arg_size(
	name.as_bytes().as_ptr(),
	name.len(),
	&mut arg_size as *mut usize,
	)
	};
	match api_error::result_from(ret) {
	Ok(_) => Some(arg_size),
	Err(ApiError::MissingArgument) => None,
	Err(e) => runtime::revert(e),
	}
	}?;
	let arg_bytes = if arg_size > 0 {
	let res = {
	let data_non_null_ptr = contract_api::alloc_bytes(arg_size);
	let ret = unsafe {
	ext_ffi::casper_get_named_arg(
	name.as_bytes().as_ptr(),
	name.len(),
	data_non_null_ptr.as_ptr(),
	arg_size,
	)
	};
	let data =
	unsafe { Vec::from_raw_parts(data_non_null_ptr.as_ptr(), arg_size, arg_size) };
	api_error::result_from(ret).map(|_| data)
	};
	// Assumed to be safe as `get_named_arg_size` checks the argument already
	res.unwrap_or_revert()
	} else {
	// Avoids allocation with 0 bytes and a call to get_named_arg
	Vec::new()
	};
	let value = bytesrepr::deserialize(arg_bytes).unwrap_or_revert_with(ApiError::InvalidArgument);
	Some(value)
	}

[EdHastingsCasperAssociation]

yes...that's the one i was looking for a couple of weeks ago...couldn't remember which contract it was in

we should just add this to contract api...it's come up various times.

[mpapierski]

LGTM

[marc-casperlabs]

The networking related changes LGTM, too.