Layout

Dropset assembly source files are in program/src/dropset/. The program is built using multi-file assembly, which allows splitting a single program across multiple .s files that are joined at build time via .include directives. See build scaffolding for details on how assembly constants are generated from Rust crates.

program/src/dropset/
├── dropset.s              # Top-level file
├── entrypoint.s           # Entrypoint dispatcher
├── common/
│   ├── discriminant.s     # Instruction discriminants
│   ├── error.s            # Error codes and subroutines
│   ├── memory.s           # Memory layout constants
│   ├── pubkey.s           # Pubkey chunk offsets and known addresses
│   └── token.s            # SPL Token constants
└── market/
    ├── init_market_pda.s  # Market PDA initialization
    ├── init_vault.s       # Vault initialization
    └── register.s         # RegisterMarket handler

Algorithm conventions

• procedure: a label that does not return (no stack push); control flow exits via exit or jumps to another procedure.
• function: a label that pushes onto the call stack and returns to the caller.
• Store(var): saves var to a callee-saved register before a call that would clobber caller-saved registers. The stored value is available after the call returns.

Top-level file

dropset.s file declares the global entrypoint and includes all other files.

Common

common/ houses several general constants and subroutines.

Discriminants

Instruction discriminant constants are injected from the interface crate's #[discriminant_enum] macro:

Errors

Error codes and subroutines injected via #[error_enum]. Each error label sets r0 to the corresponding error code and exits:

Memory

Data-related constants and input buffer offset constants are in memory.s:

Pubkeys

Pubkey operations in SBPF work on 32-byte addresses split into four 8-byte chunks. The pubkey module defines chunk offsets and known address immediates injected via constant_group!.

Each 32-byte pubkey is accessed as four 8-byte (u64) chunks at offsets 0, 8, 16, and 24. These are emitted as PUBKEY_CHUNK_{0..3}_OFF immediates.

Known addresses (such as the rent sysvar ID) are split into full 64-bit _CHUNK_{0..3} constants (loadable with a single lddw) and _CHUNK_{0..3}_LO / _CHUNK_{0..3}_HI i32 immediates (loadable with mov32 / lsh64 pairs) using pubkey!. The lddw form costs 2 CUs but uses one instruction; the mov32 / lsh64 pair also costs 2 CUs but can be optimized to 1 CU with mov32 alone when the high bits are zero.

When a struct field holds a 32-byte pubkey that needs per-chunk access, pubkey_offsets! generates a base _OFF plus four _CHUNK_{0..3}_OFF constants. This is used for input buffer fields (e.g. IB_MARKET_PUBKEY_CHUNK_{0..3}_OFF) and frame-relative fields (e.g. RM_FM_PDA_CHUNK_{0..3}_OFF). For frame fields that are not aligned to BPF_ALIGN_OF_U128, unaligned_pubkey_offsets! emits the same set of constants with a _UOFF suffix instead of _OFF.

Token

SPL Token constants (account size, instruction discriminants) are injected from the token module via constant_group!: