Add ui amount conversion helpers

token/src/lib.rs

@@ -14,4 +14,15 @@ pub mod state;
 // solana-sdk version
 pub use solana_sdk;
 
+/// Convert the UI representation of a token amount (using the decimals field defined in its mint)
+/// to the raw amount
+pub fn ui_amount_to_amount(ui_amount: f64, decimals: u8) -> u64 {
+    (ui_amount * 10_usize.pow(decimals as u32) as f64) as u64
+}
+
+/// Convert a raw amount to its UI representation (using the decimals field defined in its mint)
+pub fn amount_to_ui_amount(amount: u64, decimals: u8) -> f64 {
+    amount as f64 / 10_usize.pow(decimals as u32) as f64
+}
+
 solana_sdk::declare_id!("TokenSVp5gheXUvJ6jGWGeCsgPKgnE3YgdGKRVCMY9o");

token/src/native_mint.rs

@@ -5,3 +5,21 @@ pub const DECIMALS: u8 = 9;
 
 // The Mint for native SOL Token accounts
 solana_sdk::declare_id!("So11111111111111111111111111111111111111111");
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use solana_sdk::native_token::*;
+
+    #[test]
+    fn test_decimals() {
+        assert_eq!(
+            lamports_to_sol(42),
+            crate::amount_to_ui_amount(42, DECIMALS)
+        );
+        assert_eq!(
+            sol_to_lamports(42.),
+            crate::ui_amount_to_amount(42., DECIMALS)
+        );
+    }
+}