Cleanup magic numbers

Rename `num_signatures` to `num_required_signatures` to
disambiguate it from `tx.signatures.len()`.

core/src/sigverify.rs

@@ -16,6 +16,9 @@ use std::mem::size_of;
 
 type TxOffsets = (Vec<u32>, Vec<u32>, Vec<u32>, Vec<u32>, Vec<Vec<u32>>);
 
+// The serialized size of Message::num_required_signatures.
+const NUM_REQUIRED_SIGNATURES_SIZE: usize = 1;
+
 #[cfg(feature = "cuda")]
 #[repr(C)]
 struct Elems {
@@ -128,7 +131,7 @@ pub fn get_packet_offsets(packet: &Packet, current_offset: u32) -> (u32, u32, u3
 
     let sig_start = current_offset as usize + sig_size;
     let msg_start = current_offset as usize + msg_start_offset;
-    let pubkey_start = msg_start + 1 + pubkey_size;
+    let pubkey_start = msg_start + NUM_REQUIRED_SIGNATURES_SIZE + pubkey_size;
 
     (
         sig_len as u32,

runtime/src/runtime.rs

@@ -129,7 +129,7 @@ impl Runtime {
             .map(|&index| {
                 let index = index as usize;
                 let key = &message.account_keys[index];
-                (key, index < message.num_signatures as usize)
+                (key, index < message.num_required_signatures as usize)
             })
             .zip(program_accounts.iter_mut())
             .map(|((key, is_signer), account)| KeyedAccount::new(key, is_signer, account))

sdk/src/message.rs

@@ -70,7 +70,9 @@ fn get_program_ids(instructions: &[Instruction]) -> Vec<Pubkey> {
 
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub struct Message {
-    pub num_signatures: u8,
+    /// The number of signatures required for this message to be considered valid. The
+    /// signatures must match the first `num_required_signatures` of `account_keys`.
+    pub num_required_signatures: u8,
 
     /// All the account keys used by this transaction
     #[serde(with = "short_vec")]
@@ -94,7 +96,7 @@ pub struct Message {
 
 impl Message {
     pub fn new_with_compiled_instructions(
-        num_signatures: u8,
+        num_required_signatures: u8,
         account_keys: Vec<Pubkey>,
         recent_blockhash: Hash,
         fee: u64,
@@ -102,7 +104,7 @@ impl Message {
         instructions: Vec<CompiledInstruction>,
     ) -> Self {
         Self {
-            num_signatures,
+            num_required_signatures,
             account_keys,
             recent_blockhash,
             fee,
@@ -111,15 +113,14 @@ impl Message {
         }
     }
 
-    /// Return an unsigned transaction with space for requires signatures.
     pub fn new(instructions: Vec<Instruction>) -> Self {
         let program_ids = get_program_ids(&instructions);
         let (mut signed_keys, unsigned_keys) = get_keys(&instructions);
-        let num_signatures = signed_keys.len() as u8;
+        let num_required_signatures = signed_keys.len() as u8;
         signed_keys.extend(&unsigned_keys);
         let instructions = compile_instructions(instructions, &signed_keys, &program_ids);
         Self::new_with_compiled_instructions(
-            num_signatures,
+            num_required_signatures,
             signed_keys,
             Hash::default(),
             0,
@@ -240,11 +241,11 @@ mod tests {
         let id0 = Pubkey::default();
         let ix = Instruction::new(program_id, &0, vec![AccountMeta::new(id0, false)]);
         let message = Message::new(vec![ix]);
-        assert_eq!(message.num_signatures, 0);
+        assert_eq!(message.num_required_signatures, 0);
 
         let ix = Instruction::new(program_id, &0, vec![AccountMeta::new(id0, true)]);
         let message = Message::new(vec![ix]);
-        assert_eq!(message.num_signatures, 1);
+        assert_eq!(message.num_required_signatures, 1);
     }
 
     #[test]

sdk/src/transaction.rs

@@ -61,7 +61,7 @@ pub struct Transaction {
 impl Transaction {
     pub fn new_unsigned(message: Message) -> Self {
         Self {
-            signatures: Vec::with_capacity(message.num_signatures as usize),
+            signatures: Vec::with_capacity(message.num_required_signatures as usize),
             message,
         }
     }
@@ -176,7 +176,8 @@ impl Transaction {
 
     /// Check keys and keypair lengths, then sign this transaction.
     pub fn sign<T: KeypairUtil>(&mut self, keypairs: &[&T], recent_blockhash: Hash) {
-        let signed_keys = &self.message.account_keys[0..self.message.num_signatures as usize];
+        let signed_keys =
+            &self.message.account_keys[0..self.message.num_required_signatures as usize];
         for (i, keypair) in keypairs.iter().enumerate() {
             assert_eq!(keypair.pubkey(), signed_keys[i], "keypair-pubkey mismatch");
         }
@@ -348,16 +349,20 @@ mod tests {
 
         let tx = Transaction::new(&[&alice_keypair], message, Hash::default());
 
-        let expected_transaction_size = 1
+        let len_size = 1;
+        let num_required_sigs_size = 1;
+        let blockhash_size = size_of::<Hash>();
+        let fee_size = size_of::<u64>();
+        let expected_transaction_size = len_size
             + (tx.signatures.len() * size_of::<Signature>())
-            + 1
-            + 1
+            + num_required_sigs_size
+            + len_size
             + (tx.message.account_keys.len() * size_of::<Pubkey>())
-            + size_of::<Hash>()
-            + size_of::<u64>()
-            + 1
+            + blockhash_size
+            + fee_size
+            + len_size
             + (tx.message.program_ids.len() * size_of::<Pubkey>())
-            + 1
+            + len_size
             + expected_instruction_size;
         assert_eq!(expected_transaction_size, 222);