Minor cleanup

core/src/runtime/mod.rs

@@ -34,8 +34,7 @@ use athena_interface::{AthenaContext, HostInterface, HostProvider, StatusCode};
 
 /// An implementation of a runtime for the Athena RISC-V VM.
 ///
-/// The runtime is responsible for executing a user program and tracing important events which occur
-/// during execution (i.e., memory reads, alu operations, etc).
+/// The runtime is responsible for executing a user program.
 ///
 /// For more information on the RV32IM instruction set, see the following:
 /// https://www.cs.sfu.ca/~ashriram/Courses/CS295/assets/notebooks/RISCV/RISCV_CARD.pdf
@@ -67,7 +66,7 @@ pub struct Runtime<T: HostInterface> {
   /// the unconstrained block. The only thing preserved is writes to the input stream.
   pub unconstrained: bool,
 
-  /// Max gas for the runtime. If gas is set to 0, the runtime will not meter gas.
+  /// Max gas for the runtime.
   pub max_gas: Option<u32>,
 
   pub(crate) unconstrained_state: ForkState,
@@ -831,6 +830,7 @@ pub mod tests {
     },
   };
 
+  use super::syscall::SyscallCode;
   use super::{Instruction, Opcode, Program, Runtime};
 
   pub fn simple_program() -> Program {
@@ -900,7 +900,7 @@ pub mod tests {
       Arc::new(RefCell::new(HostProvider::new(MockHost::new())))
     }
 
-    // program should cost 4332 gas units
+    // program should cost 11237 gas units
 
     // failure
     let mut runtime = Runtime::<MockHost>::new(
@@ -957,8 +957,15 @@ pub mod tests {
       // X12 is arg3 (input len)
       // no input
       Instruction::new(Opcode::ADD, Register::X12 as u32, 0, 0, false, true),
-      // X5 is syscall ID: 0xA2 (HOST_CALL)
-      Instruction::new(Opcode::ADD, Register::X5 as u32, 0, 0xA2, false, true),
+      // X5 is syscall ID
+      Instruction::new(
+        Opcode::ADD,
+        Register::X5 as u32,
+        0,
+        SyscallCode::HOST_CALL as u32,
+        false,
+        true,
+      ),
       Instruction::new(Opcode::ECALL, 0, 0, 0, false, false),
     ];
     let program = Program::new(instructions, 0, 0);

ffi/vmlib/src/lib.rs

@@ -8,10 +8,11 @@ use athcon_vm::{
   SetOptionError,
 };
 use athena_interface::{
-  Address, AthenaMessage, AthenaRevision, Balance, Bytes32, ExecutionResult, HostInterface,
-  HostProvider, MessageKind, StatusCode, StorageStatus, TransactionContext, VmInterface,
+  Address, AthenaMessage, AthenaRevision, Balance, Bytes32, Bytes32AsU64, ExecutionResult,
+  HostInterface, HostProvider, MessageKind, StatusCode, StorageStatus, TransactionContext,
+  VmInterface,
 };
-use athena_runner::{AthenaVm, Bytes32AsU64};
+use athena_runner::AthenaVm;
 
 #[athcon_declare_vm("Athena", "athena1", "0.1.0")]
 pub struct AthenaVMWrapper {

interface/src/lib.rs

@@ -21,6 +21,37 @@ pub type Balance = u64;
 pub type Bytes32 = [u8; BYTES32_LENGTH];
 pub type Bytes = [u8];
 
+pub struct Bytes32AsU64(Bytes32);
+
+impl Bytes32AsU64 {
+  pub fn new(bytes: Bytes32) -> Self {
+    Bytes32AsU64(bytes)
+  }
+}
+
+impl From<Bytes32AsU64> for u64 {
+  fn from(bytes: Bytes32AsU64) -> Self {
+    // take most significant 8 bytes, assume little-endian
+    let slice = &bytes.0[..8];
+    u64::from_le_bytes(slice.try_into().expect("slice with incorrect length"))
+  }
+}
+
+impl From<Bytes32AsU64> for Bytes32 {
+  fn from(bytes: Bytes32AsU64) -> Self {
+    bytes.0
+  }
+}
+
+impl From<u64> for Bytes32AsU64 {
+  fn from(value: u64) -> Self {
+    let mut bytes = [0u8; 32];
+    let value_bytes = value.to_le_bytes();
+    bytes[..8].copy_from_slice(&value_bytes);
+    Bytes32AsU64(bytes)
+  }
+}
+
 pub struct AddressWrapper(Address);
 
 impl From<Vec<u32>> for AddressWrapper {

runner/src/lib.rs

@@ -1,5 +1,3 @@
-pub mod host;
 pub mod vm;
 
-pub use host::Bytes32AsU64;
 pub use vm::AthenaVm;