ลองเขียน Hello World Solana ด้วยการใช้ Solana Playground

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use borsh::{BorshDeserialize, BorshSerialize};
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use solana_program::{
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    account_info::{next_account_info, AccountInfo},
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    entrypoint,
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    entrypoint::ProgramResult,
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    msg,
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    program_error::ProgramError,
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    pubkey::Pubkey,
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};
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/// Define the type of state stored in accounts
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#[derive(BorshSerialize, BorshDeserialize, Debug)]
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pub struct GreetingAccount {
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    /// number of greetings
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    pub counter: u32,
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}
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// Declare and export the program's entrypoint
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entrypoint!(process_instruction);
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// Program entrypoint's implementation
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pub fn process_instruction(
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    program_id: &Pubkey, // Public key of the account the hello world program was loaded into
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    accounts: &[AccountInfo], // The account to say hello to
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    _instruction_data: &[u8], // Ignored, all helloworld instructions are hellos
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) -> ProgramResult {
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    msg!("Hello World Rust program entrypoint");
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    // Iterating accounts is safer than indexing
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    let accounts_iter = &mut accounts.iter();
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    // Get the account to say hello to
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    let account = next_account_info(accounts_iter)?;
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    // The account must be owned by the program in order to modify its data
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    if account.owner != program_id {
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        msg!("Greeted account does not have the correct program id");
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        return Err(ProgramError::IncorrectProgramId);
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    }
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    // Increment and store the number of times the account has been greeted
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    let mut greeting_account = GreetingAccount::try_from_slice(&account.data.borrow())?;
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    greeting_account.counter += 1;
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    greeting_account.serialize(&mut &mut account.data.borrow_mut()[..])?;
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    msg!("Greeted {} time(s)!", greeting_account.counter);
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    Ok(())
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}

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Deployment successful. Completed in 14s.