Demo self-modifying Lua program

Also, drop dependency on bincode.

programs/native/solua/Cargo.toml

@@ -4,10 +4,12 @@ version = "0.1.0"
 authors = ["Solana Maintainers <maintainers@solana.com>"]
 
 [dependencies]
-bincode = "1.0.0"
 rlua = "0.15.2"
 solana_program_interface = { path = "../../../common" }
 
+[dev-dependencies]
+bincode = "1.0.0"
+
 [lib]
 name = "solua"
 crate-type = ["dylib"]

programs/native/solua/src/lib.rs

@@ -1,10 +1,9 @@
-extern crate bincode;
 extern crate rlua;
 extern crate solana_program_interface;
 
-use bincode::deserialize;
 use rlua::{Lua, Result, Table};
 use solana_program_interface::account::KeyedAccount;
+use std::str;
 
 /// Make KeyAccount values available to Lua.
 fn set_accounts(lua: &Lua, name: &str, keyed_accounts: &[KeyedAccount]) -> Result<()> {
@@ -12,6 +11,8 @@ fn set_accounts(lua: &Lua, name: &str, keyed_accounts: &[KeyedAccount]) -> Resul
     for (i, keyed_account) in keyed_accounts.iter().enumerate() {
         let account = lua.create_table()?;
         account.set("tokens", keyed_account.account.tokens)?;
+        let data_str = lua.create_string(&keyed_account.account.userdata)?;
+        account.set("userdata", data_str)?;
         accounts.set(i + 1, account)?;
     }
     let globals = lua.globals();
@@ -25,6 +26,8 @@ fn update_accounts(lua: &Lua, name: &str, keyed_accounts: &mut Vec<KeyedAccount>
     for (i, keyed_account) in keyed_accounts.into_iter().enumerate() {
         let account: Table = accounts.get(i + 1)?;
         keyed_account.account.tokens = account.get("tokens")?;
+        let data_str: rlua::String = account.get("userdata")?;
+        keyed_account.account.userdata = data_str.as_bytes().to_vec();
     }
     Ok(())
 }
@@ -42,14 +45,17 @@ fn run_lua(keyed_accounts: &mut Vec<KeyedAccount>, code: &str, data: &[u8]) -> R
 
 #[no_mangle]
 pub extern "C" fn process(keyed_accounts: &mut Vec<KeyedAccount>, data: &[u8]) {
-    let code: String = deserialize(&keyed_accounts[0].account.userdata).unwrap();
+    let code_data = keyed_accounts[0].account.userdata.clone();
+    let code = str::from_utf8(&code_data).unwrap();
     run_lua(keyed_accounts, &code, data).unwrap();
 }
 
 #[cfg(test)]
 mod tests {
+    extern crate bincode;
+
+    use self::bincode::serialize;
     use super::*;
-    use bincode::serialize;
     use solana_program_interface::account::{create_keyed_accounts, Account};
     use solana_program_interface::pubkey::Pubkey;
 
@@ -60,6 +66,7 @@ mod tests {
         let lua = Lua::new();
         set_accounts(&lua, "xs", &keyed_accounts)?;
         keyed_accounts[0].account.tokens = 42;
+        keyed_accounts[0].account.userdata = vec![];
         update_accounts(&lua, "xs", &mut keyed_accounts)?;
 
         // Ensure update_accounts() overwrites the local value 42.
@@ -86,13 +93,47 @@ mod tests {
 
     #[test]
     fn test_move_funds_with_lua_via_process() {
-        let userdata: Vec<u8> = serialize(
+        let userdata = r#"
-            r#"
             local tokens, _ = string.unpack("I", data)
             accounts[1].tokens = accounts[1].tokens - tokens
             accounts[2].tokens = accounts[2].tokens + tokens
-        "#,
+        "#.as_bytes()
-        ).unwrap();
+        .to_vec();
+
+        let alice_pubkey = Pubkey::default();
+        let bob_pubkey = Pubkey::default();
+        let program_id = Pubkey::default();
+
+        let mut accounts = [
+            (
+                alice_pubkey,
+                Account {
+                    tokens: 100,
+                    userdata,
+                    program_id,
+                },
+            ),
+            (bob_pubkey, Account::new(1, 0, program_id)),
+        ];
+        let data = serialize(&10u64).unwrap();
+        process(&mut create_keyed_accounts(&mut accounts), &data);
+        assert_eq!(accounts[0].1.tokens, 90);
+        assert_eq!(accounts[1].1.tokens, 11);
+
+        process(&mut create_keyed_accounts(&mut accounts), &data);
+        assert_eq!(accounts[0].1.tokens, 80);
+        assert_eq!(accounts[1].1.tokens, 21);
+    }
+
+    #[test]
+    fn test_move_funds_with_lua_via_process_and_terminate() {
+        let userdata = r#"
+            local tokens, _ = string.unpack("I", data)
+            accounts[1].tokens = accounts[1].tokens - tokens
+            accounts[2].tokens = accounts[2].tokens + tokens
+            accounts[1].userdata = ""
+        "#.as_bytes()
+        .to_vec();
 
         let alice_pubkey = Pubkey::default();
         let bob_pubkey = Pubkey::default();
@@ -114,8 +155,9 @@ mod tests {
         assert_eq!(accounts[0].1.tokens, 90);
         assert_eq!(accounts[1].1.tokens, 11);
 
+        // Verify the program modified itself to a no-op.
         process(&mut create_keyed_accounts(&mut accounts), &data);
-        assert_eq!(accounts[0].1.tokens, 80);
+        assert_eq!(accounts[0].1.tokens, 90);
-        assert_eq!(accounts[1].1.tokens, 21);
+        assert_eq!(accounts[1].1.tokens, 11);
     }
 }