Begin native rewrite without anchor

src/loaders.rs

@@ -0,0 +1,65 @@
+use solana_program::{
+    account_info::AccountInfo, program_error::ProgramError, pubkey::Pubkey, system_program,
+};
+
+pub fn load_signer<'a, 'info>(
+    info: &'a AccountInfo<'info>,
+) -> Result<&'a AccountInfo<'info>, ProgramError> {
+    if !info.is_signer {
+        return Err(ProgramError::MissingRequiredSignature);
+    }
+    Ok(info)
+}
+
+pub fn load_pda<'a, 'info>(
+    info: &'a AccountInfo<'info>,
+    seeds: &[&[u8]],
+    writable: bool,
+) -> Result<&'a AccountInfo<'info>, ProgramError> {
+    let key = Pubkey::create_program_address(seeds, &crate::id())?;
+    if !info.key.eq(&key) {
+        return Err(ProgramError::InvalidSeeds);
+    }
+    if !info.owner.eq(&crate::id()) {
+        return Err(ProgramError::InvalidAccountOwner);
+    }
+    if writable {
+        if !info.is_writable {
+            return Err(ProgramError::InvalidAccountData);
+        }
+    }
+    Ok(info)
+}
+
+pub fn load_uninitialized_pda<'a, 'info>(
+    info: &'a AccountInfo<'info>,
+    seeds: &[&[u8]],
+) -> Result<&'a AccountInfo<'info>, ProgramError> {
+    let key = Pubkey::create_program_address(seeds, &crate::id())?;
+    if !info.key.eq(&key) {
+        return Err(ProgramError::InvalidSeeds);
+    }
+    load_uninitialized_account(info)
+}
+
+pub fn load_uninitialized_account<'a, 'info>(
+    info: &'a AccountInfo<'info>,
+) -> Result<&'a AccountInfo<'info>, ProgramError> {
+    if !info.is_writable {
+        return Err(ProgramError::InvalidAccountData);
+    }
+    if !info.data_is_empty() || !info.owner.eq(&system_program::id()) {
+        return Err(ProgramError::AccountAlreadyInitialized);
+    }
+    Ok(info)
+}
+
+pub fn load_account<'a, 'info>(
+    info: &'a AccountInfo<'info>,
+    key: Pubkey,
+) -> Result<&'a AccountInfo<'info>, ProgramError> {
+    if !info.key.eq(&key) {
+        return Err(ProgramError::InvalidAccountData);
+    }
+    Ok(info)
+}