Add way to look at tx instructions (#11943)

sdk/src/sysvar/instructions.rs

@@ -0,0 +1,51 @@
+//! This account contains the serialized transaction instructions
+//!
+
+use crate::instruction::Instruction;
+use crate::sanitize::SanitizeError;
+use crate::sysvar::Sysvar;
+
+pub type Instructions = Vec<Instruction>;
+
+crate::declare_sysvar_id!("instructions1111111111111111111111111111111", Instructions);
+
+impl Sysvar for Instructions {}
+
+#[cfg(not(feature = "program"))]
+use crate::clock::Epoch;
+#[cfg(not(feature = "program"))]
+use crate::genesis_config::ClusterType;
+
+#[cfg(not(feature = "program"))]
+pub fn is_enabled(_epoch: Epoch, cluster_type: ClusterType) -> bool {
+    cluster_type == ClusterType::Development
+}
+
+pub fn get_current_instruction(data: &[u8]) -> u16 {
+    let mut instr_fixed_data = [0u8; 2];
+    let len = data.len();
+    instr_fixed_data.copy_from_slice(&data[len - 2..len]);
+    u16::from_le_bytes(instr_fixed_data)
+}
+
+pub fn store_current_instruction(data: &mut [u8], instruction_index: u16) {
+    let last_index = data.len() - 2;
+    data[last_index..last_index + 2].copy_from_slice(&instruction_index.to_le_bytes());
+}
+
+pub fn get_instruction(index: usize, data: &[u8]) -> Result<Instruction, SanitizeError> {
+    solana_sdk::message::Message::deserialize_instruction(index, data)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_store_instruction() {
+        let mut data = [4u8; 10];
+        store_current_instruction(&mut data, 3);
+        assert_eq!(get_current_instruction(&data), 3);
+        assert_eq!([4u8; 8], data[0..8]);
+    }
+}

sdk/src/sysvar/mod.rs

@@ -11,6 +11,7 @@ use crate::{
 pub mod clock;
 pub mod epoch_schedule;
 pub mod fees;
+pub mod instructions;
 pub mod recent_blockhashes;
 pub mod rent;
 pub mod rewards;
@@ -28,6 +29,7 @@ pub fn is_sysvar_id(id: &Pubkey) -> bool {
         || slot_hashes::check_id(id)
         || slot_history::check_id(id)
         || stake_history::check_id(id)
+        || instructions::check_id(id)
 }
 
 #[macro_export]