darkfi/src/runtime/util.rs

use log::{error, warn};

use super::{memory::MemoryManipulation, vm_runtime::Env};

/// Serialize contract payload to format accepted by the runtime entrypoint.
/// We keep the same payload as a slice of bytes, and prepend it with a
/// little-endian u64 to tell the payload's length.
pub fn serialize_payload(payload: &[u8]) -> Vec<u8> {
    let mut out = vec![];

    let len = payload.len() as u64;
    out.extend_from_slice(&len.to_le_bytes());
    out.extend_from_slice(payload);

    out
}

/// Host function for logging strings.
/// This is injected into the runtime with wasmer's `imports!` macro.
pub(crate) fn drk_log(env: &Env, ptr: u32, len: u32) {
    if let Some(bytes) = env.memory.get_ref().unwrap().read(ptr, len as usize) {
        // Piece the string together
        let msg = match String::from_utf8(bytes.to_vec()) {
            Ok(v) => v,
            Err(e) => {
                warn!(target: "wasm-runtime", "Invalid UTF-8 string: {:?}", e);
                return
            }
        };

        let mut logs = env.logs.lock().unwrap();
        logs.push(msg);
        std::mem::drop(logs);
        return
    }

    error!(target: "wasm-runtime", "Failed to read any bytes from VM memory");
}