init

.gitignore

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+/target
+/Cargo.lock
+.idea

Cargo.toml

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+[package]
+name = "solana-sandwich"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+solana-program = "1.11.10"

src/lib.rs

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+mod errors;
+mod structs;
+mod utils;
+
+use crate::structs::{AllowedRules, InstructionsData};
+use crate::utils::load_instruction_data;
+use solana_program::account_info::AccountInfo;
+use solana_program::program_error::ProgramError;
+use solana_program::sysvar::instructions::load_instruction_at_checked;
+
+pub fn allowed_only<'a>(
+    instruction_sysvar_account: &'a AccountInfo<'a>,
+    rules: Vec<AllowedRules>,
+) -> Result<bool, ProgramError> {
+    let instruction_data = load_instruction_data(instruction_sysvar_account)?;
+
+    for index in 0..instruction_data.num_of_instructions {
+        let instruction = load_instruction_at_checked(index as usize, instruction_sysvar_account)?;
+        let rule: &AllowedRules = match rules
+            .iter()
+            .find(|rule| rule.program == instruction.program_id)
+        {
+            Some(r) => r,
+            None => {
+                return Ok(false);
+            }
+        };
+
+        if !rule.before && index > instruction_data.current_index {
+            return Ok(false);
+        }
+        if !rule.after && index < instruction_data.current_index {
+            return Ok(false);
+        }
+    }
+
+    Ok(true)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        let result = 2 + 2;
+        assert_eq!(result, 4);
+    }
+}

src/structs.rs

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+use solana_program::account_info::AccountInfo;
+use solana_program::pubkey::Pubkey;
+
+pub struct AllowedRules {
+    pub program: Pubkey,
+    pub before: bool,
+    pub after: bool,
+}
+
+pub struct InstructionsData<'a> {
+    pub current_program: Pubkey,
+    pub current_index: u16,
+    pub num_of_instructions: u16,
+    pub instruction_sysvar_account: &'a AccountInfo<'a>,
+}

src/utils.rs

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+use crate::InstructionsData;
+use solana_program::account_info::AccountInfo;
+use solana_program::program_error::ProgramError;
+use solana_program::serialize_utils::read_u16;
+use solana_program::sysvar::instructions::{
+    load_current_index_checked, load_instruction_at_checked,
+};
+
+pub fn load_instruction_data<'a>(
+    instruction_sysvar_account: &'a AccountInfo<'a>,
+) -> Result<InstructionsData<'a>, ProgramError> {
+    let data = instruction_sysvar_account.try_borrow_data()?;
+    let current_index = load_current_index_checked(instruction_sysvar_account)?;
+    let instruction =
+        load_instruction_at_checked(current_index as usize, instruction_sysvar_account)?;
+    let mut current = 0;
+    let num_of_instructions= match read_u16(&mut current, &**data) {
+        Ok(index) => {
+            index
+        }
+        Err(_) => {
+            return Err(ProgramError::InvalidArgument);
+            // return Err(ReadingNumInstructionsError);
+        }
+    };
+
+    Ok(InstructionsData {
+        current_program: instruction.program_id,
+        current_index,
+        num_of_instructions,
+        instruction_sysvar_account,
+    })
+}