transfer-lamports: Also read instruction data (#11)

#### Problem

The transfer-lamports example is limited in usefulness since it doesn't
read instruction data. This means it only tests a portion of the program
entrypoint.

#### Summary of changes

Add instruction data! Programs interpet 8 bytes of instruction data as a
little-endian u64. Also, update the numbers for the test.

Author: joncinque

README.md

@@ -157,22 +157,20 @@ Since this is just doing a syscall, all the languages behave the same. The only
 difference is that the Assembly version *doesn't* set the return code to 0, and
 lets the VM assume it worked.
 
-* Transfer-Lamports: moves 5 lamports from a source account to a destination
+* Transfer-Lamports: moves lamports from a source account to a destination, with
+the amount given by a little-endian u64 in instruction data.
 
 | Language | CU Usage |
 | --- | --- |
-| Rust | 464 |
-| Zig | 43 |
-| C | 103 |
-| Assembly | 22 |
-| Rust (pinocchio) | 23 |
+| Rust | 459 |
+| Zig | 44 |
+| C | 104 |
+| Assembly | 31 |
+| Rust (pinocchio) | 32 |
 
 This one starts to get interesting since it requires parsing the instruction
 input. Since the assembly version knows exactly where to find everything, it can
-be hyper-optimized. The C version is also very performant.
-
-Zig's version should perform the same as C, but there are some inefficiencies that
-are currently being fixed.
+be hyper-optimized.
 
 * CPI: allocates a PDA given by the seed "You pass butter" and a bump seed in
 the instruction data. This requires a call to `create_program_address` to check

transfer-lamports/asm/main.s

@@ -2,23 +2,38 @@
 entrypoint:
 	ldxdw r2, [r1 + 0] # get number of accounts
 	jne r2, 2, error # error if not 2 accounts
+
 	ldxb r2, [r1 + 8] # get first account
-	jne r2, 0xff, error # shouldn't be a duplicate, but check
+	# can check this, but isn't necessary
+	# jne r2, 0xff, error
 	ldxdw r2, [r1 + 8 + 8 + 32 + 32] # get source lamports
 	ldxdw r3, [r1 + 8 + 8 + 32 + 32 + 8] # get account data size
 	mov64 r4, r1
 	add64 r4, 8 + 8 + 32 + 32 + 8 + 8 + 10240 + 8 # calculate end of account data
 	add64 r4, r3
 	mov64 r5, r4 # check how much padding we need to add
-	and64 r5, 7 # clear high bits
-	jeq r5, 0, 1 # no low bits set, jump ahead
+	and64 r5, -8 # clear low bits
+	jeq r5, r4, 1 # no low bits set, jump ahead
 	add64 r4, 8 # add 8 for truncation if needed
 	and64 r4, -8 # clear low bits
+
 	ldxb r5, [r4 + 0] # get second account
 	jne r5, 0xff, error # we don't allow duplicates
 	ldxdw r5, [r4 + 8 + 32 + 32] # get destination lamports
-	sub64 r2, 5 # subtract lamports
-	add64 r5, 5 # add lamports
+	ldxdw r6, [r4 + 8 + 32 + 32 + 8] # get account data size
+	mov64 r7, r4
+	add64 r7, 8 + 32 + 32 + 8 + 8 + 10240 + 8 # calculate end of account data
+	add64 r7, r6
+	mov64 r8, r7 # check how much padding we need to add
+	and64 r8, -8 # clear low bits
+	jeq r8, r7, 1 # no low bits set, jump ahead
+	add64 r7, 8 # add 8 for truncation if low bits are set
+	ldxdw r8, [r7 + 0] # get instruction data size
+	jne r8, 0x08, error # need 8 bytes of instruction data
+	ldxdw r8, [r7 + 8] # get instruction data as little-endian u64
+
+	sub64 r2, r8 # subtract lamports
+	add64 r5, r8 # add lamports
 	stxdw [r1 + 8 + 8 + 32 + 32], r2 # write the new values back
 	stxdw [r4 + 8 + 32 + 32], r5
 	exit

transfer-lamports/c/src/main.c

@@ -11,10 +11,11 @@ extern uint64_t entrypoint(const uint8_t *input) {
     return ERROR_INVALID_ARGUMENT;
   }
 
+  uint64_t transfer_amount = *(uint64_t *) params.data;
   SolAccountInfo source_account = params.ka[0];
   SolAccountInfo destination_account = params.ka[1];
-  *source_account.lamports -= 5;
-  *destination_account.lamports += 5;
+  *source_account.lamports -= transfer_amount;
+  *destination_account.lamports += transfer_amount;
 
   return 0;
 }

transfer-lamports/pinocchio/src/entrypoint.rs

@@ -38,10 +38,12 @@ fn process_instruction(mut context: InstructionContext) -> ProgramResult {
         // accounts are different, so we can safely ignore the case when the account is
         // duplicated.
         if let MaybeAccount::Account(destination_info) = context.next_account_unchecked() {
+            let (instruction_data, _) = context.instruction_data_unchecked();
+            let transfer_amount = u64::from_le_bytes(instruction_data.try_into().unwrap());
             // withdraw five lamports
-            *source_info.borrow_mut_lamports_unchecked() -= 5;
+            *source_info.borrow_mut_lamports_unchecked() -= transfer_amount;
             // deposit five lamports
-            *destination_info.borrow_mut_lamports_unchecked() += 5;
+            *destination_info.borrow_mut_lamports_unchecked() += transfer_amount;
         }
     }
 

transfer-lamports/src/processor.rs

@@ -11,20 +11,21 @@ use solana_program::{
 pub fn process_instruction(
     _program_id: &Pubkey,
     accounts: &[AccountInfo],
-    _instruction_data: &[u8],
+    instruction_data: &[u8],
 ) -> ProgramResult {
     // Create an iterator to safely reference accounts in the slice
     let account_info_iter = &mut accounts.iter();
+    let transfer_amount = u64::from_le_bytes(instruction_data.try_into().unwrap());
 
     // As part of the program specification the first account is the source
     // account and the second is the destination account
     let source_info = next_account_info(account_info_iter)?;
     let destination_info = next_account_info(account_info_iter)?;
 
     // Withdraw five lamports from the source
-    **source_info.try_borrow_mut_lamports()? -= 5;
+    **source_info.try_borrow_mut_lamports()? -= transfer_amount;
     // Deposit five lamports into the destination
-    **destination_info.try_borrow_mut_lamports()? += 5;
+    **destination_info.try_borrow_mut_lamports()? += transfer_amount;
 
     Ok(())
 }

transfer-lamports/tests/functional.rs

@@ -20,7 +20,7 @@ async fn test_lamport_transfer() {
         None,
     );
 
-    let source_lamports = 5;
+    let source_lamports = 555_555;
     let destination_lamports = 890_875;
     program_test.add_account(
         source_pubkey,
@@ -43,7 +43,7 @@ async fn test_lamport_transfer() {
     let mut transaction = Transaction::new_with_payer(
         &[Instruction::new_with_bincode(
             program_id,
-            &(),
+            &source_lamports.to_le_bytes(),
             vec![
                 AccountMeta::new(source_pubkey, false),
                 AccountMeta::new(destination_pubkey, false),

transfer-lamports/zig/main.zig

@@ -1,10 +1,12 @@
+const std = @import("std");
 const sol = @import("solana-program-sdk");
 
 export fn entrypoint(input: [*]u8) u64 {
     const context = sol.Context.load(input) catch return 1;
     const source = context.accounts[0];
     const destination = context.accounts[1];
-    source.lamports().* -= 5;
-    destination.lamports().* += 5;
+    const transfer_amount = std.mem.bytesToValue(u64, context.data[0..@sizeOf(u64)]);
+    source.lamports().* -= transfer_amount;
+    destination.lamports().* += transfer_amount;
     return 0;
 }