solana-input-serialization.md

The latest loader serializes the program input parameters as follows (all encoding is little endian):

• 8 bytes unsigned number of accounts
• For each account
  • 1 byte indicating if this is a duplicate account, if not a duplicate then the value is 0xff, otherwise the value is the index of the account it is a duplicate of.
  • If duplicate: 7 bytes of padding
  • If not duplicate:
    • 1 byte boolean, true if account is a signer
    • 1 byte boolean, true if account is writable
    • 1 byte boolean, true if account is executable
    • 4 bytes of padding
    • 32 bytes of the account public key
    • 32 bytes of the account's owner public key
    • 8 bytes unsigned number of lamports owned by the account
    • 8 bytes unsigned number of bytes of account data
    • x bytes of account data
    • 10k bytes of padding, used for realloc
    • enough padding to align the offset to 8 bytes.
    • 8 bytes rent epoch
• 8 bytes of unsigned number of instruction data
• x bytes of instruction data
• 32 bytes of the program id