FractalVM Specification

#![no_std]
#![no_main]

// Host function imports
extern "C" {
    fn storage_read(key_ptr: u32, key_len: u32, val_ptr: u32) -> i32;
    fn storage_write(key_ptr: u32, key_len: u32, val_ptr: u32, val_len: u32) -> i32;
    fn get_caller(ptr: u32);
}

const COUNTER_KEY: &[u8] = b"counter";
static mut BUFFER: [u8; 64] = [0u8; 64];

#[no_mangle]
pub extern "C" fn increment() {
    unsafe {
        // Read current value
        let bytes_read = storage_read(
            COUNTER_KEY.as_ptr() as u32,
            COUNTER_KEY.len() as u32,
            BUFFER.as_ptr() as u32,
        );

        let current: u64 = if bytes_read > 0 {
            u64::from_le_bytes(BUFFER[..8].try_into().unwrap())
        } else {
            0
        };

        // Increment and store
        let new_val = current + 1;
        let bytes = new_val.to_le_bytes();
        storage_write(
            COUNTER_KEY.as_ptr() as u32,
            COUNTER_KEY.len() as u32,
            bytes.as_ptr() as u32,
            8,
        );
    }
}

#[no_mangle]
pub extern "C" fn get_count() -> u64 {
    unsafe {
        let bytes_read = storage_read(
            COUNTER_KEY.as_ptr() as u32,
            COUNTER_KEY.len() as u32,
            BUFFER.as_ptr() as u32,
        );
        if bytes_read > 0 {
            u64::from_le_bytes(BUFFER[..8].try_into().unwrap())
        } else {
            0
        }
    }
}