TransactionView: InstructionsIterator (#2580)

transaction-view/Cargo.toml

@@ -11,6 +11,7 @@ edition = { workspace = true }
 
 [dependencies]
 solana-sdk = { workspace = true }
+solana-svm-transaction = { workspace = true }
 
 [dev-dependencies]
 # See order-crates-for-publishing.py for using this unusual `path = "."`

transaction-view/src/instructions_meta.rs

@@ -1,6 +1,11 @@
-use crate::{
-    bytes::{advance_offset_for_array, check_remaining, optimized_read_compressed_u16, read_byte},
-    result::Result,
+use {
+    crate::{
+        bytes::{
+            advance_offset_for_array, check_remaining, optimized_read_compressed_u16, read_byte,
+        },
+        result::Result,
+    },
+    solana_svm_transaction::instruction::SVMInstruction,
 };
 
 /// Contains metadata about the instructions in a transaction packet.
@@ -64,6 +69,68 @@ impl InstructionsMeta {
     }
 }
 
+pub struct InstructionsIterator<'a> {
+    pub(crate) bytes: &'a [u8],
+    pub(crate) offset: usize,
+    pub(crate) num_instructions: u16,
+    pub(crate) index: u16,
+}
+
+impl<'a> Iterator for InstructionsIterator<'a> {
+    type Item = SVMInstruction<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index < self.num_instructions {
+            // Each instruction has 3 pieces:
+            // 1. Program ID index (u8)
+            // 2. Accounts indexes ([u8])
+            // 3. Data ([u8])
+
+            // Read the program ID index.
+            let program_id_index = read_byte(self.bytes, &mut self.offset).ok()?;
+
+            // Read the number of account indexes, and then update the offset
+            // to skip over the account indexes.
+            let num_accounts = optimized_read_compressed_u16(self.bytes, &mut self.offset).ok()?;
+            // SAFETY: Only returned after we check that there are enough bytes.
+            let accounts = unsafe {
+                core::slice::from_raw_parts(
+                    self.bytes.as_ptr().add(self.offset),
+                    usize::from(num_accounts),
+                )
+            };
+            advance_offset_for_array::<u8>(self.bytes, &mut self.offset, num_accounts).ok()?;
+
+            // Read the length of the data, and then update the offset to skip
+            // over the data.
+            let data_len = optimized_read_compressed_u16(self.bytes, &mut self.offset).ok()?;
+            // SAFETY: Only returned after we check that there are enough bytes.
+            let data = unsafe {
+                core::slice::from_raw_parts(
+                    self.bytes.as_ptr().add(self.offset),
+                    usize::from(data_len),
+                )
+            };
+            advance_offset_for_array::<u8>(self.bytes, &mut self.offset, data_len).ok()?;
+            self.index = self.index.wrapping_add(1);
+
+            Some(SVMInstruction {
+                program_id_index,
+                accounts,
+                data,
+            })
+        } else {
+            None
+        }
+    }
+}
+
+impl ExactSizeIterator for InstructionsIterator<'_> {
+    fn len(&self) -> usize {
+        usize::from(self.num_instructions.wrapping_sub(self.index))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use {

transaction-view/src/transaction_meta.rs

@@ -2,7 +2,7 @@ use {
     crate::{
         address_table_lookup_meta::AddressTableLookupMeta,
         bytes::advance_offset_for_type,
-        instructions_meta::InstructionsMeta,
+        instructions_meta::{InstructionsIterator, InstructionsMeta},
         message_header_meta::{MessageHeaderMeta, TransactionVersion},
         result::{Result, TransactionParsingError},
         signature_meta::SignatureMeta,
@@ -142,6 +142,19 @@ impl TransactionMeta {
             .as_ptr()
             .add(usize::from(self.recent_blockhash_offset)) as *const Hash)
     }
+
+    /// Return an iterator over the instructions in the transaction.
+    /// # Safety
+    /// - This function must be called with the same `bytes` slice that was
+    ///   used to create the `TransactionMeta` instance.
+    pub unsafe fn instructions_iter<'a>(&self, bytes: &'a [u8]) -> InstructionsIterator<'a> {
+        InstructionsIterator {
+            bytes,
+            offset: usize::from(self.instructions.offset),
+            num_instructions: self.instructions.num_instructions,
+            index: 0,
+        }
+    }
 }
 
 #[cfg(test)]
@@ -153,7 +166,7 @@ mod tests {
             message::{v0, Message, MessageHeader, VersionedMessage},
             pubkey::Pubkey,
             signature::Signature,
-            system_instruction,
+            system_instruction::{self, SystemInstruction},
             transaction::VersionedTransaction,
         },
     };
@@ -391,4 +404,24 @@ mod tests {
             assert_eq!(recent_blockhash, tx.message.recent_blockhash());
         }
     }
+
+    #[test]
+    fn test_instructions_iter() {
+        let tx = simple_transfer();
+        let bytes = bincode::serialize(&tx).unwrap();
+        let meta = TransactionMeta::try_new(&bytes).unwrap();
+
+        // SAFETY: `bytes` is the same slice used to create `meta`.
+        unsafe {
+            let mut iter = meta.instructions_iter(&bytes);
+            let ix = iter.next().unwrap();
+            assert_eq!(ix.program_id_index, 2);
+            assert_eq!(ix.accounts, &[0, 1]);
+            assert_eq!(
+                ix.data,
+                &bincode::serialize(&SystemInstruction::Transfer { lamports: 1 }).unwrap()
+            );
+            assert!(iter.next().is_none());
+        }
+    }
 }